Energy & Power

Nier Mass Spectrograph

Description: Background on Nier Mass Spectrograph; object id no. 1990.0446.01; catalog no. N-09567; This object consists of the following three components: ion source with oven and acceleration electrode; semicircular glass vacuum chamber; ion collector with two plates. The original device included an electromagnet, which is not part of this accession.; In 1939, as political tensions in Europe increased, American physicists learned of an astonishing discovery: the nucleus of the uranium atom can be split, causing the release of an immense amount of energy. Given the prospects of war, the discovery was just as worrying as it was intellectually exciting. Could the Germans use it to develop an atomic bomb?; The Americans realized that they had to determine whether a bomb was physically possible. Uranium consists mostly of the isotope U-238, with less than 1% of U-235. Theoreticians predicted that it was the nuclei of the rare U-235 isotope that undergo fission, the U-238 being inactive. To test this prediction, it was necessary to separate the two isotopes, but it would be difficult to do this since they are chemically identical.; Alfred Nier, a young physicist at the University of Minnesota, was one of the few people in the world with the expertise to carry out the separation. He used a physical technique that took advantage of the small difference in mass of the two isotopes. To separate and collect small quantities of them, he employed a mass spectrometer technique that he first developed starting in about 1937 for measurement of relative abundance of isotopes throughout the periodic table. (The basic principles of the mass spectrometer are described below.); As a measure of the great importance of his work, in October 1939, Nier received a letter from eminent physicist Enrico Fermi, then at Columbia University, expressing great interest in whether, and how, the separation was progressing. Motivated by such urging, by late February 1940, Nier was able to produce two tiny samples of separated U-235 and U-238, which he provided to his collaborators at Columbia University, a team headed by John R. Dunning of Columbia. The Dunning team was using the cyclotron at the University in numerous studies to follow up on the news from Europe the year before on the fission of the uranium atom. In March 1940, with the samples provided by Nier, the team used neutrons produced by a proton beam from the cyclotron to show that it was the comparatively rare uranium-235 isotope that was the most readily fissile component, and not the abundant uranium-238.; The fission prediction was verified. The Nier-Dunning group remarked, "These experiments emphasize the importance of uranium isotope separation on a larger scale for the investigation of chain reaction possibilities in uranium" (reference: A.O. Nier et. al., Phys. Rev. 57, 546 (1940)). This proof that U-235 was the fissile uranium isotope opened the way to the intense U.S. efforts under the Manhattan Project to develop an atomic bomb. (For details, see Nier’s reminiscences of mass spectrometry and The Manhattan Project at: http://pubs.acs.org/doi/pdf/10.1021/ed066p385).; The Dunning cyclotron is also in the Modern Physics Collection (object id no. 1978.1074.01; catalog no. N-09130), and it will be presented on the SI collections website in 2015. (Search for “Dunning Cyclotron” at http://collections.si.edu/search/); The Nier mass spectrometer used to collect samples of U-235 and U-238 (object id no. 1990.0446.01); Nier designed an apparatus based on the principle of the mass spectrometer, an instrument that he had been using to measure isotopic abundance ratios throughout the entire periodic table. As in most mass spectrometers of the time, his apparatus produced positive ions by the controlled bombardment of a gas (UBr˅4, generated in a tiny oven) by an electron beam. The ions were drawn from the ionizing region and moved into an analyzer, which used an electromagnet for the separation of the various masses. Usually, the ion currents of the separated masses were measured by means of an electrometer tube amplifier, but in this case the ions simply accumulated on two small metal plates set at the appropriate positions. Nier’s mass spectrometer required that the ions move in a semicircular path in a uniform magnetic field. The mass analyzer tube was accordingly mounted between the poles of an electromagnet that weighed two tons, and required a 5 kW generator with a stabilized output voltage to power it. (The magnet and generator were not collected by the Smithsonian.) The ion source oven, 180-degree analyzer tube, and isotope collection plates are seen in the photos of the Nier apparatus (see accompanying media file images for this object).; Basic principles of the mass spectrometer; When a charged particle, such as an ion, moves in a plane perpendicular to a magnetic field, it follows a circular path. The radius of the particle’s path is proportional to the product of its mass and velocity, and is inversely proportional to the product of its electrical charge and the magnetic field strength. A mass spectrometer consists of three components: an ion source, a mass analyzer, and a detector. The ion source converts a portion of the sample into ions. There is a wide variety of ionization techniques, depending on the phase (solid, liquid, gas) of the sample and the efficiency of various ionization mechanisms for the unknown species. An extraction system removes ions from the sample and gives them a selected velocity. They then pass through the magnetic field (created by an electromagnet) of the mass analyzer. For a given magnetic field strength, the differences in mass-to-charge ratio of the ions result in corresponding differences in the curvature of their circular paths through the mass analyzer. This results in a spatial sorting of the ions exiting the analyzer. The detector records either the charge induced or the current produced when an ion passes by or hits a surface, thus providing data for calculating the abundance and mass of each isotope present in the sample. For a full description with a schematic diagram of a typical mass spectrometer, go to: http://www.chemguide.co.uk/analysis/masspec/howitworks.html; The Nier sector magnet mass spectrometer (not in Smithsonian Modern Physics Collection); In 1940, during the time that Nier separated the uranium isotopes, he developed a mass spectrometer for routine isotope and gas analysis. An instrument was needed that did not use a 2-ton magnet, or required a 5 kW voltage-stabilized generator for providing the current in the magnet coils. Nier therefore developed the sector magnet spectrometer, in which a 60-degree sector magnet took the place of the much larger one needed to give a 180-degree deflection. The result was that a magnet weighing a few hundred pounds, and powered by several automobile storage batteries, took the place of the significantly larger and heavier magnet which required a multi-kW generator. Quoting Nier, “The analyzer makes use of the well-known theorem that if ions are sent into a homogeneous magnetic field between two V-shaped poles there is a focusing action, provided the source, apex of the V, and the collector lie along a straight line” (reference: A.O. Nier, Rev. Sci. Instr., 11, 212, (1940)). This design was to become the prototype for all subsequent magnetic deflection instruments, including hundreds used in the Manhattan Project.
Location: Currently not on view

Date made: ca 1940-02

associated person: Nier, Alfred O.
maker: Nier, Alfred O.

ID Number: 1990.0446.01
accession number: 1990.0446
catalog number: 1990.0446.01

Data Source: National Museum of American History

Telegdi digital wire spark chamber spectrometer

Description: Three disjoint parts comprise the spectrometer assembly, 1977.0532.01, as follows: 01.1, the spectrometer proper - a rectangular aluminum base on which are mounted four sets of wire spark chambers (7 total), each ca. 0.4 x 0.4 x 0.03 m; 01.2, an individual core memory plane; 01.3, three light aluminum tanks that in the spectrometer assembly are placed between the 4 sets of spark chambers. The whole object includes a fraction of the associated assembly wiring.; The spectrometer proper (.01.1) consists of seven spark chambers, square planes mounted on edge on the surface of a rectangular metal base. Both the pulsed and read planes are made of 4 mil aluminum wires spaced 1 mm apart and enclosed in 1/2 mil Mylar windows. Four of the spark chambers have vertical wires and three have horizontal wires. The individual chambers are positioned on the base in order to measure the coordinates of charged particles as they trace helical orbits in a uniform perpendicular magnetic field. This data allows the energy and momentum of each particle to be determined.; Basic Principles and History; The complete Telegdi spectrometer system consists of a homogeneous magnet containing wire spark chambers with magnetic core readout. The spark chambers were covered with 0.5 mil Mylar, and a 9 to 1 neon-helium mixture flowed through them during operation. Within the spectrometer assembly, each wire chamber is connected to a corresponding memory plane containing ferrite cores. The ferrite core memory planes are located outside the spectrometer magnet in order to avoid interference from the magnetic field. Three aluminum tanks, with 5x10E-4 in. Mylar windows, serve as "helium boxes" placed between the 4 sets of spark chambers to reduce multiple scattering of charged particles (electrons) orbiting through the spectrometer.; Wire spark chambers with magnetic-core readout differ from ordinary visual spark chambers in that one of the plane electrodes (the “write plane”) is divided into wires, each of which is grounded through a ferrite core. Plug-in cables make the connection between the wire chamber and a memory plane. When a spark strikes a write wire, current flows through the core and “sets” it, thus digitizing the spark location. This information may then be transmitted conveniently to an online computer or stored on magnetic tape. For technical details see B. A. Sherwood, Phys. Rev. 156, 1475 (1967).; Between 1958 and 1965 bubble chambers dominated among particle detectors used in particle physics experiments. Bubble chambers enabled allowed photographs to be taken of the particle tracks in a three-dimensional volume and later analyzed exactly as to energy and momentum of each particle. However, accelerators soon provided such copious streams of particles that human scanning of bubble chamber photographs in search of events of interest became the most time-consuming part of the experiment.; The wire spark chamber provided electronic information of the path of a charge particle and was immediately mated with a digital computer programmed to analyze each track for distinct characteristics of interest. The Telegdi wire spark chamber spectrometer, one of the earliest applications of electronic readout spark chambers and on-line computer analysis, was developed in 1964 by V. L. Telegdi and his students at the University of Chicago to measure the energy distribution of positrons in the decay of muons. For detailed information on this experiment, see B. A. Sherwood, ibid.
Location: Currently not on view

date made: 1963-1964

maker: Telegdi, V. L.; Sherwood, B. A.; Fryberger, D.

ID Number: 1977.0532.01.1
catalog number: 1977.0532.01.1
accession number: 1977.0532

Data Source: National Museum of American History

Preampliier for multiwire proportional chamber from J-particle experiment of S. Ting at Brookhaven

Description: One signal amplifier on rectangular plastic circuit board. Apparently one of these preamplifiers would have been plugged into one corresponding socket of Mulitwire Proportional Chamber 1989.0050.01.1. A sticker accompanying this object reads "8 wire signals [from associated socket on chamber] get amplified .0002V to .8V" (to output to the computer). Similarly for all sockets of all four chambers in each of the two arms of the spectrometer setup at the Brookhaven Alternating Gradient Synchrotron, which was used to measure electrons and positrons resulting from decay of a hypothesized massive "J" particle.; Rectangular green plastic circuit board, with electronic components soldered on upper surface. As viewed from front of board: at left end of bottom edge are 12 contact strips, only 8 of which are connected to the circuits. Near the right end of the bottom edge are 10 such contact strips. Protruding from right edge are 10 pairs of short wires, which are inserted into a green plastic connector fitting, which has 9 contact sockets on the other side.; For background on the multiwire proportional chamber from J-particle experiment of S. Ting at Brookhaven see description for object ID no. 1989.0050.01.1
Location: Currently not on view

date made: 1972-1973

designer: Becker, Ulrich

ID Number: 1989.0050.01.2
accession number: 1989.0050
catalog number: 1989.0050.01.2

Data Source: National Museum of American History

Ceremonial trowel - one of three fabricated for use by President Eisenhower and dignitaries in dedication of U.S. Atomic Energy Commission's headquarters building, Germantown, MD on November 8, 1957

Description: Background on the history and acquisition of ceremonial trowel; Object ID no. 2014.0124.01; On May 2, 2014, Joseph Ball donated to the National Museum of American History (NMAH) the ceremonial trowel in its box, together with a descriptive plaque, all mounted on a felt-covered, wooden platform enclosed in a clear plastic display case. The text inscribed on the plaque is as follows:; "This trowel is one of three fabricated for use by President Dwight D. Eisenhower in dedication of the U.S. Atomic Energy Commission's headquarters building, Germantown, Maryland on November 8, 1957."; "The blade of the trowel is uranium from CP-1, the world's first nuclear reactor. The ferrule and stem are zirconium from the initial critical assembly for the USS Nautilus, the first nuclear-powered submarine. The handle is wood from the west stands of Stagg Field at The University of Chicago beneath which CP-1 was brought to criticality on December 2, 1942, by Enrico Fermi and his colleagues."; "The historic trowel was presented to Eisenhower College by Argonne National Laboratory through the courtesy of the U.S. Atomic Energy Commission."; [Note: Due to radiation safety concerns of the Secret Service, the uranium trowels were dropped from the AEC building dedication ceremony and silver-plated trowels were used instead.]; For a history of the establishment of the AEC headquarters site in Germantown, MD, see; http://science.energy.gov/bes/about/organizational-history/germantown-natural-history/germantown-site-history/; Mr. Ball, an alumnus of Eisenhower College (established in 1968 in Seneca Falls, NY in honor of President Eisenhower), obtained the trowel in 2012 at a silent auction during the 40th alumni reunion of the charter class of 1972 of the now defunct college. (It closed in 1982 owing to lack of students and funding.) The College had many Eisenhower memorabilia, which had been put into storage when the school closed.; A number of the items from the Eisenhower memorabilia inventory were offered at the silent auction, along with the trowel. However, the trowel was not listed in the inventory. The College historian and others Mr. Ball asked knew nothing about the object or how it came to the College. He subsequently got in touch with Thomas Wellock, Historian of the Nuclear Regulatory Commission (NRC), who was able to uncover the curious early history of the trowel. Mr. Ball agreed to loan it to the NRC, which displayed it in their headquarters lobby in Rockville, MD from 2012 to 2014.; Mr. Ball then donated the trowel to the Modern Physics Collection of the NMAH, where it is now in storage.; For a brief and fascinating historical account of the trowel, below are links to the text of two consecutive U.S. NRC Blogs on the subject by Mr. Wellock:; The Mystery of the Atomic Energy Commission Trowel – Part 1; Posted on U.S. NRC Blog on November 26, 2012; http://public-blog.nrc-gateway.gov/2012/11/26/the-mystery-of-the-atomic-energy-commission-trowel-part-i/; The Mystery of the Trowel – Solved; Posted on U.S. NRC Blog on November 28, 2012; http://public-blog.nrc-gateway.gov/2012/11/28/the-mystery-of-the-trowel-solved/; The other ceremonial trowels; their respective locations and descriptive plaques/inscriptions; It has been determined that three uranium-blade trowels were made, and that none of these was used in the cornerstone laying ceremony. Instead, three silver-plated plated trowels were made for use during the ceremony.; 1) ANL. As noted above, one of the two other uranium trowels is at Argonne National Laboratory (ANL), where it appears as part of an historical exhibit on nuclear energy. An image of the ANL display is in Nuclear News, April 2009, p.58. This display can be viewed at:; http://web.anl.gov/eesa/pdfs/2009NuclearExhibitinNuclearNews.pdf; With this trowel came a crude typewritten label reading as follows:; "TROWEL; The Blade is made of Uranium from CP-1.; The Shank and Ferrule is made from Zirconium from; The [First Pile_] Nautilus. [“First Pile” crossed out]; The Handle is made from Benches in the West; Stands close to where the pile was."; In the bottom left corner is a torn, unclear handwritten note: “]l for _________ at Germantown.” The name after “for” may be “Comerston,” “Elmer Loyd,” “Gomer Stoyd,” or something similar.; 2) DOE Headquarters. DOE Historian Terry Fehner confirms that the third uranium trowel is in a display case, along with one of the silver-plated trowels and related ceremonial artifacts, in the lobby of the auditorium at the Department of Energy (DOE) administration building in Germantown, MD.; The uranium trowel has a plaque that reads:; "Symbolic Trowel; Blade - uranium from nuclear reactor; Stagg Field, Chicago (Dec. 2 1942); Handle - portion of squash court door; Ferrule - zirconium from submarine Nautilus prototype reactor"; The silver-plated trowel has a plaque that reads:; "Trowel used in cornerstone laying ceremony November 8, 1957"; Inscription engraved on silver-plated blade:; "Atomic Energy Building; Cornerstone laid by; President Eisenhower; November 8, 1957"; 3) Eisenhower Library. NRC Historian Tom Wellock confirms that a second silver-plated trowel is located at the Eisenhower Presidential Library in Abilene, Kansas. An image from the Library shows that this trowel has an inscription different from that on the DOE silver-plated trowel.; Inscription etched on silver plated blade:; “This trowel was used; by the President of the; United States at the laying of the; cornerstone of the U.S. Atomic Energy; Commission Headquarters Building,; Germantown, Maryland; November 8, 1957"; Presented to Dwight D. Eisenhower; President of the United States; by; Lewis L. Strauss, Chairman; U.S. Atomic Energy Commission”; Reference is made to two memoranda from the DOE archives: the first (Oct. 4 1957, from Acting Manager, AEC Chicago Operations Office to Director, AEC Division of Reactor Development, Washington) describes materials in uranium trowels made by ANL; the second (Oct. 21, 1957, Memorandum from AEC Secretary to AEC Director, Division of Construction & Supply) suggests the inscriptions for the three silver-plated trowels that were to be used at the cornerstone laying on November 8, 1957.; Tentative conclusions, comments, and remaining questions; Based on examination of available images of located trowels and their associated plaques, and the text of the cited AEC memoranda, we can reach the following tentative conclusions, assuming the language in the memoranda to be definitive:; Uranium Trowels; 1) Three uranium trowels were fabricated at ANL but never used for the cornerstone laying ceremony. They are now located, respectively, at: the National Museum of American History, Washington; Argonne National Laboratory, Chicago; and the Department of Energy, Germantown, MD. The trowel on display at DOE apparently is missing its zirconium ferrule (reason unknown), although the accompanying plaque includes mention of ferrule.; 2) The stems and ferrules of the uranium trowels were made from zirconium used in the first naval nuclear reactor critical assembly, Zero Power Reactor-1 (ZPR-1), which was essentially a prototype for design and testing at ANL. The lack of radioactivity in the metal shows that it cannot be zirconium removed from a reactor assembly that was installed and operated on the USS Nautilus. (Zirconium obtained from the actual Nautilus reactor would have attained prohibitively high levels of radioactivity.); 3) The handles of the uranium trowels were made of wood from a portion of the door to the converted squash court in which CP-1 was located under the west viewing stands of Stagg Field, and not from wood benches in the Field’s west stands.; 4) Who authorized the donation of one of the uranium trowels to Eisenhower College, and when? We do not know; all we can say for now is that the label plaque for that trowel was prepared after 1965, when the College was founded, and before 1975, when the name “Atomic Energy Commission” went out of use.; Silver-plated trowels; 1) Apparently three silver-plated trowels were intended to be used during the cornerstone laying ceremony by, respectively, President Eisenhower, AEC Chairman Strauss, and Congressional Joint Committee on Atomic Energy Chairman Durham. Displays for two of these trowels are now located at, respectively, The Eisenhower Presidential Library & Museum, and DOE Germantown, MD.; 2) A comparison of images of these two displays shows that the two trowels have differently shaped blades and different types of wood handles. Further, the inscription on the Eisenhower Library trowel is identical to that suggested by the AEC Secretary for the President’s trowel, whereas the relatively brief inscription on the DOE trowel differs significantly and does not indicate for whom it was intended.; 3) Thus, there is uncertainty concerning the DOE silver-plated trowel. Why is it of a slightly different shape and handle type? Was it actually used in the cornerstone laying ceremony by one of the three dignitaries, and if so, by which one – e.g., AEC Chairman Strauss?; 4) What became of the silver-plated trowels used by AEC Chairman Strauss and Joint Committee Chairman Durham? Can their existence and current location be determined? Our investigations have so far yielded no further information.; Update on Uranium Trowels; Roger Tilbrook, Curator of the Nuclear Energy Exhibit, Nuclear Engineering Division, ANL, has investigated the inconsistencies regarding the uranium trowels. He makes the following points regarding the Argonne trowel:; An Argonne old-timer, A.B. Krisciunas, confirms that the handle is from wood in a squash court door under the stands of Stagg Field at the University of Chicago. The lack of activity from the stem and ferrule indicates that the source of the zirconium was the Zero Power Reactor-1 (ZPR-1) at ANL, rather than a fuel assembly used in the Submarine Test Reactor (STR), or in the USS Nautilus itself.; The uranium blade could have been made from a CP-1 fuel artifact or from CP-2 fuel (which came from CP-1). After comparison of activity measurements, the conclusion is that the blade is from CP-2 uranium.
Location: Currently not on view

maker: Argonne National Laboratory

ID Number: 2014.0124.01
accession number: 2014.0124
catalog number: 2014.0124.01

Data Source: National Museum of American History

Charpak multiwire proportional chamber

Description: This object consists of an aluminum housing with two planes of stainless steel wires, rotated by 90 degrees, in a single window with four preamp units attached, one on each side. The wires are stretched between two planes of stainless steel mesh. See G. Charpak, et. al., Nucl. Instr. Meth. 62, 262 (1968) for details.; Basic Principles and History; A multiwire proportional chamber (MWPC) is constructed with alternating planes of high voltage wires (cathode) and sense wires (anode), which are at ground. All the wires are placed in a special gas environment. Spacing between planes is usually on the order of millimeters and voltage differences are typically in the kilovolt range. When a charged particle passes through the gas in the chamber, it will ionize gas molecules. The freed electrons are accelerated towards the sense wire (anode) by the electric field, ionizing more of the gas. In this way a cascade of charge develops and is deposited on the sense wires. The smaller the diameter of the sense wires, the higher the field gradient near the wire becomes. This in turn causes a larger cascade, increasing the efficiency of the chamber.; Georges Charpak built the first MWPC in 1968. Unlike earlier particle detectors, such as the bubble chamber and the first generation of spark chambers, which can record the tracks left by particles at the rate of only one or two per second, the multiwire chamber records up to one million tracks per second and sends the data directly to a computer for analysis. The price was that each wire, accumulating ions in its immediate neighborhood, must have its own electronic amplifier to record the signal; this was only practical due to the development during the previous decade of compact and inexpensive solid-state amplifiers.; In 1992 Charpak received the Nobel Prize for Physics in acknowledgment of his invention of the MWPC, an electronic particle detector that revolutionized high-energy physics experiments and has had applications in medical physics.; With the invention of the MWPC, high-energy physics entered a new era. The speed and precision of the MWPC and its subsequent generations of detectors – the drift chamber (see Charpak drift chamber, object ID no. 1977.0708.01) and the time-projection chamber – revolutionized the field of experimental particle physics. The MPWC allowed experiments to collect data at much higher collision rates and to test theories predicting the production of rare events and new massive particles. Notable examples include the discoveries of the charm quark at SLAC and Brookhaven in 1974 (Nobel Prize awarded in 1976), the W and Z bosons at CERN in 1983 (Nobel Prize awarded in 1984), and the top quark at Fermilab in 1995. For additional technical information see:; http://www.nobelprize.org/nobel_prizes/physics/laureates/1992/charpak-lecture.pdf and,; http://cds.cern.ch/record/117989/files/CERN-77-09.pdf?bcsi_scan_2687365ababd2c82=b3SiuvtOAg0NfXwMHl9pO/npSm4KAAAArlNvLw==&bcsi_scan_filename=CERN-77-09.pdf; The Modern Physics Collection also contains one of the MPWCs used in the discovery of the charm quark at Brookhaven; see Multiwire proportional chamber from J-particle experiment of S.C.C. Ting at BNL; object ID no. 1989.0050.01.1.
Location: Currently not on view

Date made: 1968

maker: Charpak, G.

ID Number: 1977.0708.02
catalog number: 1977.0708.02
accession number: 1977.0708

Data Source: National Museum of American History

Argonne superconducting solenoid

Description: This object consists of a set of two or three nested solenoids housed within stainless steel cylindrical frames The solenoids are wound from niobium-zirconium (25%) copper coated cable. The frames have holes and slots for circulation of liquid helium within. The solenoid was designed to be used as a high-field magnet for the Argonne 10-inch liquid helium bubble chamber.; Disjoint part 1978.0469.01.2 is a retaining ring (or flange) with notches and bolt holes that was originally mounted with 2 studs inside the outer rim of one face of the cylindrical housing of the solenoid magnet (disjoint part 1978.0469.01.1). Originally, three curved strips, each covering one third of the ring circle, were attached over the ring. These strips, the screws, that presumably held them, and the two studs are not now with the ring. The three arc strips comprise disjoint part 1978.0469.01.3.; When acquired, the Argonne superconducting solenoid consisted of its 3 disjoint parts joined together as the original single object in the acquisition. For display in the "Atom Smashers" exhibit at the National Museum of American History, the ring .01.2 and its 3 associated strips .01.3 were removed to expose the coils of the solenoid assembly .01.1.; In addition, three among the set of nine spacers (irregularly shaped, thin, flat non-metallic pieces) that were mounted with an adhesive on the annular face of the solenoid frame have become separated. The three separated spacers (not numbered) have been retained in storage with the disjoint parts.; Basic Principles and History; A magnetic field is an essential feature in a bubble chamber in order to distinguish the sign of charged particles and to measure their momenta from the curvature of their bubble tracks. Charged particles moving through a magnet field are deflected in a circular path in a direction that is perpendicular to both the magnetic field lines and their direction of motion. In a chamber of a given size, higher momentum particles require correspondingly stronger magnetic fields in order to produce particle tracks of sufficiently small radius of curvature for measurement purposes.; To analyze the tracks from high-energy collisions, it is necessary to maintain the entire chamber in a strong uniform magnetic field (in excess of 20 kilogauss). Conventional (copper-coil) electromagnets that carry the high currents necessary to produce these magnetic fields can be prohibitively massive and can have attendant high cooling requirements. The discovery of superconductivity over a century ago raised the prospect of producing extremely intense electric currents – and thereby, the ability to generate correspondingly high magnetic fields using coils carrying those currents. Niobium was used in the various superconducting materials from which these coils were fabricated. Such niobium-based alloys must be cooled to cryogenic temperatures with liquid helium to become superconductive. In 1955 coils made with drawn niobium wire produced 5.3 kilogauss at a temperature of 1.2 degrees Kelvin. By the 1960’s, coils made of a compound of niobium and tin reached 40 kilogauss at 4 deg. K. The further development and application of these coils was subsequently carried out almost entirely at high-energy accelerator laboratories.; In 1963, a group at Argonne National Laboratory (ANL), together with physicists from Carnegie-Mellon University, began fabricating the first “large” superconducting solenoid magnet. Although built for use with a 10-inch diameter liquid helium bubble chamber, the Argonne superconducting solenoid was intended to test materials and fabrication techniques for building much larger superconducting magnets. The solenoid was originally composed of three concentric nested coils; in that form it produced 67 kilogauss. When used with the 10-inch bubble chamber, the innermost coil was removed. The coils are wound with several types of cable, with multiple strands in case any individual one should prove faulty. Holes and slots in the stainless steel casing, and stainless steel mesh between layers of winding, allow liquid helium to circulate through the magnet.; Success with this first large solenoid led the ANL group to use superconducting coils to provide the magnetic field for a 12-foot diameter liquid hydrogen bubble chamber. Completed in 1969, they were larger by an order of magnitude than any previous superconducting coils. Thereafter, superconducting magnets were use in other bubble chambers of the same size around the world. Among other attributes, superconducting magnets had the benefit of reducing total consumption of electrical power by more than 97%.
Location: Currently not on view

Date made: 1964

designer: Fields, T.H.
manufacturer: Argonne National Laboratory; AVCO Corporation

ID Number: 1978.0469.01.1
accession number: 1978.0469
catalog number: 1978.0469.01

Data Source: National Museum of American History

McMillan synchrotron assembly

Description: Object N-09261.01 consists of an assembly of numerous major subparts or components, most of which were separated during dismantling after the NMAH Atom Smashers exhibition closed.; The major subparts include: coils carrying current to produce magnetic field; laminated steel yoke to provide path for the lines of magnetic field; aluminum clamps and steel tie-bars for clamping magnetic yoke together horizontally; "strong back" for clamping magnet together vertically; toroid-shaped vacuum chamber ("donut") in which the electrons circulate and are accelerated; high vacuum oil diffusion pump for evacuating air from vacuum chamber; assembly for remote positioning of high voltage injector (electron gun); source and transmission line for voltage pulse to injector (electron gun); high voltage transformer (110 kV) of pulse to injector (electron gun); radiation warning light; lead shielding wall to prevent stray radiation from interfering with experiments; magnet to sweep out stray electrons, etc., contaminating the x-ray beam; x-ray beam line; tapered lead plugs for making x-ray beam parallel; electrometer connected to ionization chamber in path of beam (measures beam intensity); crash button; "patch panel" for electronic connections between experiment area and "counting room"; peripheral and/or connecting elements, such as conduit containing cables carrying electric current to upper coil, current-carrying coil for producing magnetic field guide, air blower to cool magnet coils, oscillator to generate 47MHz electric field for accelerating electrons, oil diffusion pump to evacuate acceleration (vacuum) chamber, vacuum-insulated storage vessel ("Dewar") for liquid nitrogen, liquid nitrogen receptacle ("cold trap") to improve vacuum in acceleration chamber by freezing out vapors, target, evacuation port, injector (electron gun), evacuation port, synchrotron light port, RF power input.; Along with the McMillan synchrotron assembly proper N-09261.01, there are 25 related objects in this accession with catalog numbers .02-.26. Mimsy XG catalog records have been created for 13 of the objects in this accession. Additional items: a cross-section of the vacuum chamber and magnet pole pieces are in a separate accession (1978.2302.06) under catalog ID N-10012. There is also a related non-accessioned item N-10022, "Synchrotron Counting Room" sign.; Basic Principles and History; The methods of particle acceleration used before WWII were approaching their limits. The size and cost of cyclotrons and betatrons with ever increasing particle output energy had grown substantially. (See “basic principle of the cyclotron” in Background on Dunning Cyclotron; Object id no. 1978.1074.01 in Modern Physics Collection). For accelerating particles to the highest energies in circular machines, the “synchrotron” was developed in the mid-1940s. In contrast to a cyclotron, particles in a synchrotron are constrained to move in a circle of constant radius by the use of a ring of electromagnets, open in the middle and so much less massive than an equivalent cyclotron magnet. The magnetic field is varied in such a way that the radius of curvature remains constant as the particles gain energy through successive accelerations by a synchronized alternating electric field.; Towards the end of WWII Vladimir Veksler in the USSR and Edwin M. McMillan in the USA independently advanced the following “principle of phase stability”; 1) charged particles forced into a circular path by a magnetic field and accelerated by an oscillating electric field will “bunch” if they lie in the proper phase or “side” of the electric wave; and 2) these particle bunches, if confined in buckets, can be carried to higher energies by gradually increasing the magnetic guide field (as in the electron synchrotron), or by decreasing the oscillation frequency of the electric accelerating field (as in the synchro-cyclotron), or increasing both magnetic field and the electric oscillation frequency (as in the proton synchrotron).; After considerable difficulties and some changes in design, McMillan’s synchrotron began operating in the winter of 1948-49 at its intended energy of about 300 million volts – thought to sufficient to produce subatomic particles called mesons, with a mass between that of the electron and the proton. (In later years mesons would be defined as “hadronic” particles composed of one quark and one antiquark bound together by the strong interaction.) Note: The synchrotron electrons never were brought out of the machine, but were brought into collision with an internal target to produce photons with the bremsstrahlung spectrum; these emerging photon beams (x-rays) would then be used to produce the mesons.; Among the first and most significant experiments performed with this accelerator was production of a new subatomic particle, the “pi-zero” meson. Theoretical physicists had previously predicted the existence of an electrically neutral variety of such particles observed in cosmic rays. In this experiment, J. Steinberger, W.K.H. Panofsky, and J. Steller provided convincing evidence that such charge-neutral mesons were produced by the 330 MeV x-rays emerging from the synchrotron and striking an external target. The experimenters looked for the pair of simultaneous photons into which the unstable meson was expected to decay. They found that the energies of these two photons, and the angle between them, were just what would result from the decay in flight of a particle mass about 150 times that of an electron, moving with a velocity expected for such particles were they created by 300 MeV x-rays. A reproduction of the apparatus for this experiment, made for the NMAH Atom Smashers exhibition, is in the Modern Physics Collection (Object ID no. 1989.3014.01).; Virtually all circular high-energy particle accelerators built since WWII have been based on the principle of phase stability. Although particle energies attainable by pre-War accelerator concepts were sufficient for atom smashing (splitting the nucleus in a target atom), they were not high enough to create the sub-atomic particles that had been discovered in cosmic rays in the 1930’s. With the principle of phase stability, and the ability to build particle accelerators based upon it, the field of “high-energy” or “elementary particle physics” came into existence.

maker: McMillan, Edwin M.

ID Number: EM.N-09261.01
catalog number: N-09261.01
accession number: 269226

Data Source: National Museum of American History

Core memory plane for Telegdi wire spark chamber spectrometer

Description: A rectangular circuit board bearing on each side a grid of fine wires with solder joints and pin connections. From one end extend 32 black insulated wires formed into two tied bundles of 16 each, 90 inches long. The bundles are wrapped at intervals with black tape and with masking tape near the ends. The ends of the wires in each bundle emerge from their black sheaths, pass through short translucent plastic tubes, and enter a socket connector fitting. The fine wires running parallel to the length of the board have yellow insulation; the wires perpendicular to these are in eight sets on each side of the board. One set on each side has brown insulation; another, red insulation, and the remaining twelve appear as bare copper.; The wires of all 16 sets terminate in connector strips along one edge of the board. On the opposite edge is a green plastic pin socket fitting . At two corners are wide copper strips folded around on each side of the board; these are soldered to strips of different metal.; A complete spark chamber spectrometer system consists of a homogeneous magnet containing wire spark chambers with magnetic core readout. Within a spectrometer assembly, each wire chamber is connected to its corresponding core memory plane. The core planes must be located outside the spectrometer magnet. For technical details see B. A. Sherwood, Phys. Rev. 156, 1475 (1967).; For background on the Telegdi spark chamber spectrometer assembly, see description for object ID no. 1977.0532.01.1
Location: Currently not on view

date made: 1963-1964

maker: Telegdi, V. L.; Sherwood, B. A.; Fryberger, D.

ID Number: 1977.0532.01.2
catalog number: 1977.0532.01.2
accession number: 1977.0532

Data Source: National Museum of American History

Separate display vacuum chamber for McMillan synchrotron

Description: Object N-09261.02 is a separate circular vacuum chamber with its associated accessories that were mounted on a wall in the "Atom Smashers" exhibition. This object itself is essentially identical to the vacuum chamber that is an integral subpart of the McMillan synchrotron assembly proper N-09261.01.; Object N-09261.02 consists of an assembly of the following major subparts, most of which were separated during dismantling after the Atom Smashers exhibition closed:; 8 separate circular sectors;; 2 "milk bottles" for evacuation ports ;; electron gun assembly;; target assembly with adjusting mechanism;; synchrotron light port assembly;; RF coaxial power input assembly.; (See curator's notes for details.); For background on the McMillan Synchrotron, see descrption for object ID no. N-09621.01
Location: Currently not on view

maker: McMillan, E. M.

ID Number: EM.N-09261.02
catalog number: N-09261.02
accession number: 269226

Data Source: National Museum of American History

Radon-beryllium neutron source used by E. Fermi & associates, 1933-34

Description: Object EM*N-08430 consists of radon gas and a beryllium rod, enclosed in a glass tube, all enclosed in an exterior brass cylinder. This apparatus was used in 1934-35 by Enrico Fermi and coworkers in producing slow neutrons in investigations on induced radioactivity.; The brass rod pulls apart; inside is a glass tube sealed at both ends. Inside one end of the glass tube is a small sealed glass pod, prevented from sliding by wads of cotton. Inside the pod is a mass of black granules; the tube glass is discolored purple in this pod region. The outer brass rod/tube has internal pads at each end.; History; In their attempts to excite and transform atomic nuclei, physicists were limited throughout the 1920’s to bombarding atoms with particles, chiefly alpha particles, spontaneously emitted by sources consisting of naturally radioactive substances, for example radium. (Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus.) Disadvantages of using alpha particles included the limited supply and great expense of radium and similar substances, as well as the limited energy and uncontrollability of these spontaneous radiations. The situation was overcome by the use of neutrons, first discovered by James Chadwick in 1932. (See Chadwick ionization chamber replica; object ID no. - - - -) Chadwick recognized evidence of the particle in I. and F. Joliot Curie’s description of phenomena resulting from the bombardment of beryllium by alpha particles. Although the husband and wife team missed the neutron discovery, their continuing investigations of the bombardment of light elements by alpha particles led them in 1934 to recognize that in this process radioactivity was being induced artificially in the target nuclei. (See Joliot-Curie apparatus replica; object ID no. EM*N-09624.2); Based on the above discoveries, Enrico Fermi at the University of Rome immediately inferred that if alpha particles could induce artificial radioactivity, neutrons should do so - - and far more readily. He quickly gathered his group of young coworkers to help him exploit the field thus opened.; Basic principles of Fermi’s neutron source; When a radioactive element that emits alpha particles is mixed with a light element such as beryllium, neutrons are emitted because many of the alpha particles are absorbed by the nuclei of the light element. The radon-beryllium mixture in the tube of object no. EM*N-08430 was used as a source of neutrons by Fermi and his associates at the University of Rome in 1934-35 for their investigations of neutron-induced radioactivity, which showed that nuclear reactions could be produced in almost all elements by bombarding them with neutrons.; In Fermi’s neutron source, radon gas (Rn 222) was bled from a solution of radium (Ra 226) and collected on and around the beryllium metal at one end of the tube. The radon decays with a half-life of 3.8 days to lead (Pb 210) by way of two short lived alpha-emitting isotopes. The three alpha particles resulting from the decay of the isotopes interact with the beryllium (Be 9) to produce neutrons.
Location: Currently not on view

Date made: 1934-1935

maker: Fermi; coworkers

ID Number: EM.N-08430
catalog number: N-08430
accession number: 247572

Data Source: National Museum of American History

Sample of Plutonium-239

Description: The discovery of nuclear fission in uranium, announced in 1939, allowed physicists to advance with confidence in the project of creating "trans-uranic" elements - artificial ones that would lie in the periodic table beyond uranium, the last and heaviest nucleus known in nature. The technique was simply to bombard uranium with neutrons. Some of the uranium nuclei would undergo fission, newly understood phenomenon, and split violently into two pieces. In other cases, however, a uranium-238 nucleus (atomic number 92) would quietly absorb a neutron, becoming a nucleus of uranium-239, which in turn would soon give off a beta-particle and become what is now called neptunium-239 (atomic number 93). After another beta decay it would become Element 94 (now plutonium-239); By the end of 1940, theoretical physicists had predicted that this last substance, like uranium, would undergo fission, and therefore might be used to make a nuclear reactor or bomb. Enrico Fermi asked Emilio Segre to use the powerful new 60-inch cyclotron at the University of California at Berkeley to bombard uranium with slow neutrons and create enough plutonium-239 to test it for fission. Segre teamed up with Glenn T. Seaborg, Joseph W. Kennedy, and Arthur C. Wahl in January 1941 and set to work.; They carried out the initial bombardment on March 3-6, then, using careful chemical techniques, isolated the tiny amount (half a microgram) of plutonium generated. They put it on a platinum disc, called "Sample A," and on March 28 bombarded it with slow neutrons to test for fission. As expected, it proved to be fissionable - even more than U-235. To allow for more accurate measurements, they purified Sample A and deposited it on another platinum disc, forming the "Sample B" here preserved. Measurements taken with it were reported in a paper submitted to the Physical Review on May 29, 1941, but kept secret until 1946. (The card in the lid of the box bears notes from a couple of months later.); After the summer of 1941, this particular sample was put away and almost forgotten, but the research that began with it took off in a big way. Crash programs for the production and purification of plutonium began at Berkeley and Chicago, reactors to make plutonium were built at Hanford, Washington, and by 1945 the Manhattan Project had designed and built a plutonium atomic bomb. The first one was tested on July 16, 1945 in the world's first nuclear explosion, and the next was used in earnest over Nagasaki. (The Hiroshima bomb used U-235.); Why is our plutonium sample in a cigar box? G.N. Lewis, a Berkeley chemist, was a great cigar smoker, and Seaborg, his assistant, made it a habit to grab his boxes as they became empty, to use for storing things. In this case, it was no doubt important to keep the plutonium undisturbed and uncontaminated, on the one hand, but also, on the other hand, to make it possible for its weak radiations to pass directly into instruments - not through the wall of some closed container. Such considerations, combined probably with an awareness of the historic importance of the sample, brought about the storage arrangement we see.
Location: Currently not on view

Date made: 1941-05-21
Associated Date: 1941-05-29

referenced: Segre, Emilio; Seaborg, Glenn T.; Kennedy, Joseph W.; Wahl, Arthur C.; Lewis, G. N.; University of California, Berkeley
maker: Segre, Emilio; Seaborg, Glenn

ID Number: EM.N-09384
catalog number: N-09384
accession number: 272669

Data Source: National Museum of American History

Bose-Einstein Condensation Apparatus

Description: The apparatus that was used to produce the first Bose-Einstein Condensate (BEC) observed in a gas of atoms; In 1995, a group of physicists led by Eric A. Cornell and Carl E. Wieman produced the first BEC in a gas of 2000 rubidium atoms at the NIST–JILA laboratory at the University of Colorado at Boulder. Just about four months later, a group led by Wolfgang Ketterle independently produced a BEC with about 200,000 sodium atoms. Cornell, Wieman and Ketterle were awarded the 2001 Nobel Prize in Physics for their accomplishments.; The Cornell and Wieman BEC apparatus consisted of an atomic trap that cooled atoms by means of two different mechanisms. First, six laser beams cooled the atoms, initially at room temperature, while confining them near the center of an evacuated glass box. Next, the laser beams were turned off, and magnetic coils were energized. Current flowing in through the coils generated a magnetic field that further confined most of the atoms while allowing the more energetic ones to escape. Thus, the average energy of the remaining atoms decreases, making the sample colder and even more closely confined to the center of then trap. Ultimately, many of the atoms attain the lowest possible energy state allowed by quantum mechanics, and become a single entity – a BEC. Other research groups are now using BEC principles for investigations in the field of atom quantum optics, including quantum information processing and development of the atomic analogue of the laser.; The core components of the Cornell-Wieman BEC apparatus are in the Modern Physics Collection at the Smithsonian Institution’s National Museum of American History, in accession no. 1998.0213.; Background on the Bose-Einstein Condensate (BEC) phenomenon; [Adapted from “The Bose-Einstein Condensate,” E.A. Cornell and C.E. Wieman in Scientific American, March, 1998, pp 40-45; and from “Very Cold Indeed: The Nanokelvin Physics of Bose-Einstein Condensation,” Journal of Research of the National Institute of Standards and Technology, V. 101, Jul.–Aug. 1996, p. 419]; In June 1995, a team of scientists succeeded in cooling a gas of 2,000 rubidium atoms to a temperature less than 100 billionths of a degree above absolute zero, causing the atoms to lose for a full ten seconds their individual identities and behave as though they were a single “superatom.” That is, the atoms’ physical properties, such as their motions, became identical to one another. This Bose-Einstein Condensate (BEC), the first observed in a gas, can be thought of as the matter counterpart of the laser – except that in the BEC it is atoms, rather than photons of light, that behave in perfect unison (all going in the same direction with the same energy).; The BEC offers a macroscopic window into the strange world of quantum mechanics, the theory of matter based on the observation that elementary particles, such as electrons, have wave properties. Quantum mechanics uses these wavelike properties to describe the structure and interactions of matter. In ordinary macroscopic matter, the incoherent contributions of the large number of constituent atoms obscure the wave nature of quantum mechanics. But as atoms get colder, they start to behave more like waves and less like particles. Cool a cloud of identical atoms so cold that the wave of each atom starts to overlap with the wave of its neighbor atom, and all of a sudden one creates a BEC. In a BEC, the wave nature of each atom is precisely in phase with that of every other. Quantum mechanical waves extend across the collection of atoms, an image of which can be observed with the naked eye.; Some five decades earlier, physicists had realized that the BEC concept could explain superfluidity in liquid helium, which occurs at much higher temperatures than gaseous Bose-Einstein condensation. (Superfluidity is a state of matter in which the matter behaves like a fluid without viscosity and with extremely high thermal conductivity.) When it passes below a critical temperature, liquid helium makes the transition from an ordinary liquid to a superfluid and starts to behave like a quantum fluid. But the helium atoms in the liquid state interact quite strongly, and the system is difficult to understand on an elementary level. Thus, physicists had been pushing for many years to observe Bose-Einstein condensation in a system closer to the gaseous state.; Brief description of fermions and bosons, and Bose-Einstein statistics; All elementary particles, and even composite particles such as atoms, can be divided into bosons and fermions. [The spin of an elementary particle is a truly intrinsic physical property, akin to the particle's electric charge and rest mass, and is expressed as a spin quantum number.] Bosons are particles that have integer spin; 0, 1, 2, 3, and so on (in units of reduced Plank constant, h/(2π)). Fermions are particles that have half-integer spin: 1/2, 3/2, 5/2, and so on, in the same units. Examples of bosons are particles that transmit interactions (i.e., force carriers), such as photons (electromagnetic force), and a large portion of the atoms of individual chemical elements. Examples of fermions are particles that are the elementary building blocks of matter: electrons, protons, neutrons, and the quarks inside protons and neutrons. All atoms are composed of fermions, but if the atom consists of an even number of fermions, it will be a composite particle with integer spin, which is a boson. The new statistics (see below) was first studied in 1924 by Satyendra Nath Bose, so physicists call particles for which only symmetrical states occur in nature bosons. [According to the Oxford English Dictionary, the term “boson” was introduced by physicist Paul Dirac in 1947; P.A.M. Dirac Princ. Quantum Mech, (ed. 3) ix. 210.]; Fermions, the particles with half-integer spin obey Fermi-Dirac statistics. Accordingly, they occupy anti-symmetric quantum states; this property forbids fermions from sharing quantum states – a restriction known as the Pauli Exclusion Principle. Bosons, the particles with integer spin, on the other hand, obey Bose-Einstein statistics (see below). Accordingly, they occupy symmetric quantum states; this property allows bosons to share quantum states. Thus, the latter property allows a collection of identical atoms that are bosons to be cooled to the same quantum state, which is termed a BEC.; Satyendra Nath Bose (1 January 1894 - 4 February 1974) was an Indian mathematician and physicist, best known for his work on quantum mechanics in the early 1920s, which provided the foundation for Bose–Einstein statistics and the theory of the BEC. Specifically, Bose developed a statistical model, based on a counting method that assumed that light could be understood as a gas of indistinguishable quanta or particles. Bose is honored as the namesake of such a particle, a boson; Albert Einstein (14 March 1879 - 18 April 1955) was a renowned, German-born theoretical physicist who developed the theories of special and general relativity, effecting a revolution in physics. In 1924, Einstein received a paper from Bose describing his statistical model. Einstein noted that Bose's statistics also applied to some types of atoms, as well as to the proposed indistinguishable light particles, and submitted his translation of Bose's paper for publication in the Zeitschrift für Physik. Einstein also published his own articles describing the Bose statistical model and its implications, among them the condensate phenomenon that derives from the fact that the number of quantum states available for a collection of bosons at very low energy becomes exceedingly small. With less and less room for all of the particles when the temperature is decreased, they accumulate (condense) in the lowest possible (ground) energy state, as a BEC. [According to the Oxford English Dictionary, the term “Bose-Einstein Condensation” was first used in a 1938 scientific publication; Physical Review, 54 947.] Bose-Einstein statistics are now used to describe the behaviors of any assembly of bosons.
Location: Currently not on view

ID Number: 1998.0213.01.01
catalog number: 1998.0213.01.01
accession number: 1998.0213

Data Source: National Museum of American History

Penning cold-cathode ion source for neon, both parts

Description: Brass Rectangular base to which is screwed cylindrical sopper discharge chamber shell with copper water cooling tubing cemented around the outside and a tantalum insert around the exit slot. Water cooled copper rod with insulated high voltage coaxial power lead fits into slot in shell with tantlum button cathode at top and bogtom of discharge chamber.; Specimen consists of used shell sandblasted clean with new tantalum cathodes and slot insert. Top cathode button the most common, so called "alternate" non water cooled arrangement. Word "neon" printed in capitals indicates shell used with neon gas. Tantalum replaceable lids lacking.; Demonstrates cold cathode heavy ion source.; ED Hudson, ML Mallory and SW Mosko, "High Performance Heavy Ion Source For Cyclotrons," "ORNL-TM-3391" (May 1971); Used with Oak Ridge 63-in. cyclotron (see object ID no. 1977.0359.41).
Location: Currently not on view

Date made: 1971

manufacturer: Oak Ridge National Laboratory

ID Number: 1977.0359.16
catalog number: 1977.0359.16
accession number: 1977.0359
collector/donor number: 76S6 type #6

Data Source: National Museum of American History

Sections of Magnets for Superconducting Super Collider

Description: The principal objects in accession no. 2012.0186 in the NMAH Modern Physics Collection are representations for public display of key magnet components of the Superconducting Super Collider (SSC), a large U.S. Department of Energy particle accelerator facility that was under construction from 1990 to 1993 in Ellis County, Texas, approx. 25 miles south of Dallas. The SSC was designed to produce collisions of opposing beams of protons at energies of 20 trillion electron-Volts (TeV) for experiments to advance the fundamental understanding of matter and energy. The main accelerator ring was to be located in an underground concrete tunnel with a 54-mile oval path that would encircle the City of Waxahachie. The SSC project was terminated by the U.S. Congress in October 1993, largely due to budgetary issues. The object shown in the image is a display model of a short section of a parallel pair of superconducting dipole magnets in their vacuum vessels, cut-through to show in cross-section the cold mass sub assembly (beam pipe, magnet coils, collar, yoke) and the cryogenic system conduits and insulation.; Background on SSC magnet technology; The SSC main ring design contains the two parallel proton beam pipes, each under high vacuum and encased in powerful electromagnets, in order to confine the protons to travel in their respective, opposing, paths around the ring. The two proton beams are accelerated in opposite directions over many million transits around the ring using precisely-timed energy bursts from radiofrequency cavities. When the beams achieve the desired energy, they can be brought into collision in several experimental halls located around the ring, where highly sensitive detectors capture data on the resulting showers of subatomic particles.; A sequence of electromagnets produces the necessary magnetic fields to both guide and focus the proton beams. Dipole magnets produce the field configurations that bend the beams of electrically-charged particles (protons) on their track in the beam pipe around the oval ring, and quadrupole magnets produce the field configurations that narrowly focus the beams along the central axis of the beam pipes. As designed, the SSC main ring was to use 4,326 15.8 meter long dipole magnets and 1,012 5.9 meter quadrupole magnets.; High electrical currents are required in the electromagnet coils in order to produce the strong magnetic fields that are, in turn, required to guide the proton beams in their transits at such high energies. The SSC employs superconducting technology to enable essentially unhindered current flow in the magnet coils. The coils are wound with cables that contain superconducting wire. A strand of the wire contains filaments of niobium-titanium alloy embedded in a copper matrix. For superconductivity to occur in nobium-titanium, the coils must be cooled to extremely low temperatures. Thus, a cryogenic cooling system with liquid helium and liquid nitrogen blankets the coils and iron cores of the magnets.; A similar accelerator technology is used at the Large Hadron Collider (LHC) now operating at CERN, the European Laboratory for High Energy Physics, in Geneva, Switzerland.
Location: Currently not on view

ID Number: 2012.0186.01
accession number: 2012.0186
catalog number: 2012.0186.01

Data Source: National Museum of American History

Brookhaven superconducting dipole magnet

Description: The Inner part of object 1988.0706.01 consists of a cylindrical metal bore tube surrounded on outer surface by insulation, covered by coil windings of braided niobium-titanium conducting wires held in place by white fiberglass-epoxy bands. This structure is surrounded by a yoke of octagonal cross-section, made of an upper and lower half consisting of vertical iron laminations. Surface coating (blueing?) of laminations is black and blue.; About half of the length of the upper half of the yoke is removed to show the coil windings and bands. On both sides of the full-yoke segment are 18 nuts and Allen bolts for joining upper and lower yolk halves, and on both sides of half-yoke segment are 19 more holes without bolts along the cut-away portion.; This object is the fourth in a series of eight one-meter long superconducting model dipoles constructed at Brookhaven National Laboratory (BNL). The coil aperture is 8 cm. Most of the design features incorporated in the full-scale 4.5 meter long dipoles for BNL's proposed ISABELLE proton-proton colliding beam facility were worked out on these shorter model magnets, including the superconducting coils. The conductor in the coil is in the form of a wide braid containing 93 twisted multi-filamentary niobium-titanium (NbTi) superconducting wires; each wire is 0.3 mm in diameter and contains 379 ten-micron NbTi filaments. The braid is filled with InPb for additional electrical stability and mechanical rigidity. The two coil halves are held on the bore tube by fiberglass-epoxy bands. The laminated shield, in addition to enhancing the magnetic field in the bore, maintains the coil structure under a predetermined compression at operating temperature. Mounted on the bore tube, immediately under the surrounding main coil windings, are barely discernable sextapole and decapole auxiliary windings in the form of 7-strand cables made from the same 0.3 mm composite wire; these coils primarily compensate for perturbations in the shape of the magnetic field due to iron saturation at high fields.; For a detailed overview of the development of superconducting magnets for particle accelerators at BNL and Fermilab during the 1970's, see William D. Metz, SCIENCE, Vol. 200, 14 April 1978, pp 188-191. In particular, the BNL magnets have a significantly larger diameter relative to those at Fermilab. This is due to the fact that unlike the Fermilab magnets, whose surrounding steel yoke remains at room temperature, BNL chose to cool the entire magnet including the yoke to liquid helium temperature and have the central beam tube at room temperature ("warm bore, cold iron"), whereas the Fermilab beam tube is at cryogenic temperature ("cold bore, warm iron").; For more on superconducting magnets in the Modern Physics Collection, see object ID no. 2012.0186.01, short section of parallel pair of Superconducting Super Collider (SSC) dipole magnets in their vacuum vessels (display model) [Web title "Sections of Magnets for Superconducting Super Collider"].
Location: Currently not on view

Date made: 1974

manufacturer: Brookhaven National Laboratory

ID Number: 1988.0706.01
accession number: 1988.0706
catalog number: 1988.0706.01

Data Source: National Museum of American History

Charpak drift chamber connected to electronics box

Description: This object consists of two drift chamber assemblies attached to an electronic box. The two drift chamber assemblies have green plastic walls and transparent plastic windows, in metallic frames with parallel wires running horizontally in the first window and vertically in the second. They are attached to a single perforated metallic covered preamp. The latter assembly is attached on one side to rectangular, metal-enclosed, box for electronics. Wires connect the drift chamber assembly to one side of electronics box. Two high voltage cable receptacles protrude on opposite side of electronics box near top edge.; Basic Principles and History; A wire chamber is a chamber with many parallel wires, arranged as a grid and put on high voltage, with the metal casing being on ground potential. As in the Geiger counter, a particle leaves a trace of ions and electrons, which drift toward the case or the nearest wire, respectively. By marking off the wires which had a pulse of current, one can see the particle's path. If one also precisely measures the timing of the current pulses of the wires and takes into account that the ions need some time to drift to the nearest wire, one can infer the distance at which the particle passed the wire. This greatly increases the accuracy of the path reconstruction and is known as a drift chamber.; While testing their newly developed multiwire proportional chamber (see Object ID no. 1977.0708.02), Charpak and his collaborators found that the difference in arrival times of electrons at adjacent wires, they could quickly estimate just where between the two wires an ionizing particle had passed. They showed that this principle of location - - measuring the time for electrons to drift from the point where produced to a sensing wire - - could be extended from one or two millimeters to many centimeters. The essential refinement was the addition of “field shaping” wires which, by producing a uniform electric field, ensured a constant drift velocity of the electrons. In practice, the drift chamber must be preceded or followed by a counter to mark the starting time of the drifting electrons.; In 1992 Charpak received the Nobel Prize for Physics in acknowledgment of his invention of the MWPC, an electronic particle detector that revolutionized high-energy physics experiments and has had applications in medical physics.; For additional technical information, see:; http://www.nobelprize.org/nobel_prizes/physics/laureates/1992/charpak-lecture.pdf and,; http://cds.cern.ch/record/117989/files/CERN-77-09.pdf?bcsi_scan_2687365ababd2c82=b3SiuvtOAg0NfXwMHl9pO/npSm4KAAAArlNvLw==&bcsi_scan_filename=CERN-77-09.pdf
Location: Currently not on view

Date made: 1969

maker: Charpak, G.

ID Number: 1977.0708.01
catalog number: 1977.0708.01
accession number: 1977.0708

Data Source: National Museum of American History

First betatron of Donald Kerst, 1940

Description: Object N-08216 is the assembly of the first Kerst Betatron as it appeared in the Atom Smashers exhibition at the NMAH. mounted horizontally, a toroidal vacuum chamber made of white ceramic with two cylindrical ports, each joined to fused-on glass extensions; circular magnet coils mounted above and below plane of vacuum chamber; rectangular laminated iron yoke surrounding the coils on top, bottom and two sides; enclosing the yoke, a rectangular metal frame of four horizontal angle strips joined by four welded vertical straps, two on each side, and by four bolts, two on each end. Between the yoke laminations and each coil is a thin sheet of slightly flexible, warped, black material, like plastic or impregnated cardboard; each is in two pieces to fit around the central axis. Two circular gray plates are positioned at the top and bottom of the vacuum chamber, separating it from the upper and lower coils, respectively.; It is presumed that the left-hand cylindrical port contains the electron source, and the right-hand port contains the beam of x-rays from the internal target. Wires protrude from both cylindrical ports.; History and basic principles; Among the many investigators who attempted to accelerate electrons by magnetic induction, none were successful until Donald Kerst produced 2.3-MeV electrons in a betatron at the University of Illinois in 1940. He later constructed a number of betatrons of successively higher energies, culminating in the 300-MeV betatron at the University of Illinois. Kerst’s success was due to a very careful theoretical analysis of the orbit dynamics in accelerators (including a study of the requirements for injection); to a preliminary analysis of all conceivable effects relevant to the operation of a betatron; and to a careful and detailed design of the magnet structure, vacuum system, and power supply. This was the first new accelerator to be constructed on the basis of a careful scientific analysis and a completely engineered design. Its success represented a turning point in the technology of particle accelerators from cut and try methods to scientifically engineered designs. All later accelerators, including the newest high energy synchrotrons, have been influenced by this early work of Kerst. It is only in the light of these later developments that we see the importance of the betatron not merely as a valuable instrument in itself but as a milestone in the development of particle accelerators generally. For example, the radial and vertical oscillations of the beam in all particle accelerators are now universally called betatron oscillations after the pioneering work of Kerst and Robert Serber, who together in 1941 published the first theoretical analysis of such oscillations as they occur in the betatron.; The betatron was quickly put to use in industry, medicine, and nuclear physics research. It was the first accelerator to provide gamma rays for photo-nuclear studies. In the late 1940s and early 1950s the betatron was used for much of the experimental research on photo disintegration of the deuteron, on photo-nuclear reactions (including the discovery of the giant dipole resonances), and important early work on nuclear structure from electron scattering. Of great importance was the pioneering use of megavolt electron beams for the production of energetic X rays for the therapeutic treatment of cancer. His fascinating depiction of this treatment included a description of the first use of phantoms and the intense activity precipitated by a student afflicted with brain tumor, heroic efforts that achieved much, but were unable to save the student. Kerst took a one-year leave of absence from the University of Illinois (1940-41), designed a 20-MeV betatron and a 100-MeV betatron working with the engineering staff at General Electric. He oversaw the construction and operation of the 20-MeV betatron, which he brought back to Urbana. During World War II days, Kerst built a 4-MeV portable betatron for inspecting bomb duds in situ and, most importantly, built a 20-MeV betatron at Los Alamos for study of bomb assembly implosions. His work was described in the official history of Los Alamos as: “The technical achievements are amongst the most impressive at Los Alamos.” After World War II Kerst built a 300-MeV betatron at the University of Illinois that was brought into operation in 1950 and provided a facility for studying high energy physics until it was superseded by synchrotrons and then by electron linacs.; (Above text excerpted from Donald William Kerst, 1911—1993, a Biographical Memoir by Andrew M. Sessler and Keith R. Symon, Copyright 1997, National Academies Press, Washington DC.); It is no accident that the magnetic induction accelerator was so late to be realized. The concept had been advanced repeatedly in the preceding twenty years, but the problems of establishing and maintaining a particle beam were far greater than those encountered with several other accelerator types that were reduced to practice in the 1930’s.; Electrons, due to their relatively small mass, are much more “skittish” than the much more massive protons, and in the betatron must make a thousand times more circuits to reach the same energy as protons accelerated in a cyclotron. Where the cyclotron runs continuously, allowing the protons to find their own orbit, the betatron is pulsed: electrons must be injected at the right velocity to be captured into stable orbits, and held in them by a balance between the magnetic fields responsible for their acceleration and their orbit guidance, respectively. Kerst’s success depended decisively upon close mathematical analysis of these orbits, especially those immediately after injection into the vacuum chamber. This analysis was performed in collaboration with theoretical physicist, Robert Serber.; The principle of operation of the betatron is similar to that of a high voltage transformer. Alternating currents in the upper coils produce an increasing magnetic field, thus inducing an electromotive force around the electron’s circular orbit. This force, which Kerst calculated to be only 17 volts maximum acts on the electrons during each of their 200,000 circuits of the vacuum chamber, imparting a total energy of over two million electron volts (MeV).; The electrons are introduced into the vacuum chamber by an injector; they are not brought out of the vacuum chamber, but strike an internal target, converting their energy into x-rays which emerge through a second port.; Kerst, like E.O. Lawrence at the University of California, Berkeley, saw no intrinsic limits to his device. From the moment Kerst’s first device operated successfully in July 1940, he and his University looked forward to one more powerful (300 MeV) even than the cyclotrons being developed at Berkeley. Begun in 1945, immediately after World War II, with a special appropriation from the Illinois State Legislature, it was soon to be outmoded by newer methods of particle acceleration (e.g., the synchrotron).
Location: Currently not on view

date made: early 1940's

maker: Kerst, Donald

ID Number: EM.N-08216
accession number: 233629

Data Source: National Museum of American History

Multiwire proportional chamber from J-particle experiment of S. Ting at Brookhaven

Description: This object consists of a rectangular frame (steel, copper) holding signal wires (gold plated wires) separated by planes of high voltage wires (Cu-Be wire). Three planes of signal wires oriented at 60 degree increments; at +80, +20 and at -40. In operation, the entire chamber was filled with gas: 80% argon to provide an ionization medium for creating a detectable electrical signal; and 20% methylal, both as a spark extinguishing and as a cleaning agent (to prevent ageing of the wires due to carbon deposits). This chamber is one of four from left arm of the spectrometer setup at the Brookhaven Alternating Gradient Synchrotron (AGS), which measured electrons and positrons resulting from decay of a hypothesized massive "J" particle.; Basic Principles and History; A multiwire proportional chamber (MWPC) is constructed with alternating planes of high voltage wires (cathode) and sense wires (anode), which are at ground. All the wires are placed in a special gas environment. Spacing between planes is usually on the order of millimeters and voltage differences are typically in the kilovolt range. When a charged particle passes through the gas in the chamber, it will ionize gas molecules. The freed electrons are accelerated towards the sense wire (anode) by the electric field, ionizing more of the gas. In this way a cascade of charge develops and is deposited on the sense wires. The smaller the diameter of the sense wires, the higher the field gradient near the wire becomes. This in turn causes a larger cascade, increasing the efficiency of the chamber.; Georges Charpak built the first MWPC in 1968. Unlike earlier particle detectors, such as the bubble chamber and the first generation of spark chambers, which can record the tracks left by particles at the rate of only one or two per second, the multiwire chamber records up to one million tracks per second and sends the data directly to a computer for analysis. In 1992 Charpak received the Nobel Prize for Physics in acknowledgment of his invention of the MWPC, an electronic particle detector that revolutionized high-energy physics experiments and has had applications in medical physics.; The MWPC in the J-particle experiment of S.C.C. Ting at Brookhaven; The 1976 Nobel Prize in physics was shared by a Massachusetts Institute of Technology physicist who used Brookhaven's Alternating Gradient Synchrotron (AGS) to discover a new particle and confirm the existence of the charmed quark. Samuel C.C. Ting was credited for finding what he called the "J" particle, the same particle as the "psi" found at nearly the same time at the Stanford Linear Accelerator Center by a group led by Burton Richter. The particle is now known as the J/psi.; Ting's experiment took advantage of the AGS's high-intensity, 30 GeV proton beams, which bombarded a stationary beryllium target to produce showers of particles. The decay modes of these particles were identified using a two-arm spectrometer detection system. J particles decay into various combinations of lighter particles; one of these combinations is an electron and a positron. A small fraction of these enter the detection system, one particle in each arm of the spectrometer. Then dipole magnets deflect them out of the plane of the intense beam and measure their momentum; Cerenkov counters measure their velocity; multi-wire proportional chambers their position; scintillator hodoscopes their moment of passage; lead-glass and lead-lucite shower counters their total energy.; In each spectrometer arm there are 4 MWPCs (Ao, A, B, C) with 2 mm wire spacing and a total of 4,000 wires on each arm. There are eleven planes of proportional wires (2 in Ao, 3 each in A, B, & C), and in A, B, & C the planes are rotated 20 degrees with respect to each other to reduce multitrack ambiguities. To ensure the chambers have 100% uniform efficiency at low voltage and a long live time in the highly radioactive environment, a special argon-methylal gas mixture at 2 deg. C was used.; The identification of the J-particle and its significance; A strong peak in electron and positron production at an energy of 3.1 billion electron volts (GeV) led Ting to suspect the presence of a new particle, the same one found by Richter. Their discoveries not only won the Nobel Prize; they also helped confirm the existence of the charmed quark -- the J/psi is composed of a charmed quark bound to its antiquark.; The J/ψ (or J/psi) is a very special particle. Its discovery was announced in 1974 independently by two groups: one lead by Samuel Ting at Brookhaven National Laboratory (BNL) in New York and the second lead by Burton Richter at Stanford Linear Accelerator Center (SLAC) in California. J/ψ is special because it established the quark model as a credible description of nature. Having been invented by Gell-Man and Zweig as a bookkeeping tool, it was not until Glashow, Iliopoulos and Maiani (GIM) that the concept of quarks as real particles was taken seriously. GIM predicted that if quarks were real, then they should come in pairs, like the up and down quarks. Candidates for the up, down, and strange were identified, but there was no partner for the strange quark. J/ψ was the key.; Like the proton or an atom, the J/ψ is a composite particle. This means that J/ψ is made of smaller, more elementary particles. Specifically, it is a bound state of one charm quark and one anti-charm quark. Since it is made of quarks, it is a “hadron“. But since it is made of exactly one quark and one antiquark, it is specifically a “meson.”; For further details, see; http://hitoshi.berkeley.edu/129A/Cahn-Goldhaber/chapter9.pdf; http://www.nobelprize.org/nobel_prizes/physics/laureates/1976/ting-lecture.pdf
Location: Currently not on view

Date made: 1972-1973

designer: Becker, Ulrich

ID Number: 1989.0050.01.1
accession number: 1989.0050
catalog number: 1989.0050.01.1

Data Source: National Museum of American History

Penning cold-cathode ion source head for carbon

Description: Copper shell with attached water cooling tubing.; Specimen heavily used, not sandblasted, shows extensive corrosion around exit slot. Word "CARBON" in capitals inscribed on outside of shell indicates its use for carbon ion beams; Demonstrates cold cathode wear.; ED Hudson, ML Mallory and SW Mosko, "High Performance Heavy Ion Source For Cyclotrons," "ORNL-TM-3391" (May 1971); Used with Oak Ridge 63-in. cyclotron (see object ID no. 1977.0359.41).
Location: Currently not on view

Date made: 1971

manufacturer: Oak Ridge National Laboratory

ID Number: 1977.0359.17
accession number: 1977.0359
catalog number: 1977.0359.17
collector/donor number: 76S6 type #7

Data Source: National Museum of American History

Alvarez proton linear accelerator

Description: Object 1978.1073.01.1 is the first seven feet of the 40-ft. long Alvarez proton linear accelerator (linac), with two of the total of 9 oscillators. The Alvarez linac became operational in 1947-48.; The accelerator assembly .01.1 consists of the following major components: horizontal cylindrical vacuum tank enclosing a cylindrical copper cavity and central beam tube, (.01.1.01), connected externally to two vertical cylindrical oscillators (.01.1.02 and 01.1.09) and their associated power systems. The vacuum chamber is open at one end to show the internal cavity and linear array of drift tubes at the center. From its open end, five feet (approx.) of top half of the vacuum chamber has been cutaway to show the outer surface of the copper cavity. As displayed in Atom Smashers exhibition, a flange-type support attached under the vacuum tank is mounted on two pyramidal-shaped, vertical supports, which rest on a low platform surface. With the exception of oscillator .01.1.09, the other components numbered from .01.1.03 to .01.1.17 are minor (e.g., bolts, pipe, cables, electrical fittings, etc. - see curator's notes for details).; History and basic principles; The linear resonance accelerator, developed by E.O. Lawrence and colleagues during the 1930’s, was one of the earliest designs for attaining high particle energy without the requirement of correspondingly high voltage. Numerous attempts to realize it were made before World War II, but all proved disappointing, largely due to the limitations of technology for generating high-frequency electric fields.; As the name implies, linear resonance accelerators are straight machines in which, as in circular cyclotrons, the accelerated motion of charged particles is synchronized with an oscillating electric field. They were first made practical by the radar technology developed during World War II. Pulsed radio transmitters of extremely high peak power at ultra-high frequency made it possible to think about adding a million volts to the energy of protons and electrons for each linear foot of the accelerator. The opportunity was recognized by many physicists developing radar in Britain and the U.S. The boldest in exploiting it was Luis W. Alvarez, one of the scientists in Lawrence’s cyclotron group at University of California, Berkeley. In the Alvarez accelerator, an intense 200 MHz electric field is produced within the copper cavity by powerful oscillators - - originally surplus radar transmitters - - for 400 microseconds, 15 times per second. Protons injected into the end of the cavity from a Van de Graaff (electrostatic) accelerator with an energy of 4 MeV are accelerated further by the oscillating electric field when crossing the gaps between the drift tubes, but are shielded by the tubes when the electric field is in the opposite, retarding, phase. Along the length of the cavity, the individual drift tubes (see object ID no. 1978.1073.01.4-.5) lengthen in proportion to the increasing particle velocity, so that the protons always take the same time to travel from gap to gap, thus remaining in step with the oscillating electric field. The proton bunches are longitudinally stable as in a synchrotron, and are stabilized transversely by the action of converging fields produced by focusing grids (see object ID no. 1978.1073.01.3.01-.03). In 1947, the linac’s 40-ft. long cavity accelerated protons to 31.5 MeV, which, until that time was the highest energy to which protons had ever been accelerated. (Berkeley’s synchrocyclotron leap-frogged the energy to 350 MeV the next year.); By 1947 the synchrotron emerged as the most practical concept for a high-energy particle accelerator, and the linac was subsequently used as the proton injector into the synchrotron. A smaller version of the Alvarez linac was used to inject 10 MeV protons into Berkeley’s “Bevatron”, a billion electron volt (BeV) synchrotron. Present injector linacs are hundreds of feet in length and produce particle beams of hundreds of MeV. For basic principles and history of synchrotrons, see McMillian synchrotron, Object ID no. N-09621.01 in the Modern Physics Collection.; Principle of strong focusing; Until 1952 designers of circular accelerators - - cyclotrons, betatrons, synchrotrons - - relied on the relatively “weak” focusing action of the magnetic field guiding ion or electron beams to hold these charged particles in stable circular orbits during acceleration. In 1952 the principle of alternating, or “strong”, focusing of particle beams was discovered at Brookhaven National Laboratory, and immediately found wide application in all types of accelerators.; Focusing forces on a particle deviating vertically are stronger the more the lines of magnetic force bulged outward, and focusing forces on a particle deviating from the orbit circle are much stronger if the magnet gap narrowed, so that the lines of magnetic force bulged inward. These two conditions, incompatible simultaneously, do not completely cancel their effects if applied successively. Thus, a sequence of magnets whose radial field gradients are directed alternatively outward and inward can have a powerful net focusing action on the particles passing through them. This approach is known as alternating-gradient focusing. The same principle applies to the action of electric fields on charged particles. After learning of the possibility and value of applying alternating-gradient focusing to proton linear accelerators, Alvarez’s group demonstrated strong radial focusing of the proton beam with electrostatic quadrupole lenses. In autumn of 1952, they immediately removed the original focusing grids and installed one such electrostatic quadrupole lens inside each drift tube (see object ID no. 1978.1073.01.5.2). The intensity of the proton beam doubled, and would have quadrupled had the insulation of the electrical leads held the required voltage. Thus the first proton linac was also the first strong-focusing accelerator. (The first accelerator to use magnetic alternating-gradient focusing was the 1 GeV synchrotron at Cornell University in 1953.) Before the prototype 32-MeV linac was shipped from Berkeley to its final location for operations at the University of Southern California, all of its drift tubes had been fitted with electrostatic strong-focusing electrodes.
Location: Currently not on view

date made: 1945-48

ID Number: 1978.1073.01.1
catalog number: 1978.1073.01.1
accession number: 1978.1073

Data Source: National Museum of American History

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Energy & Power

Nier Mass Spectrograph

Telegdi digital wire spark chamber spectrometer

Preampliier for multiwire proportional chamber from J-particle experiment of S. Ting at Brookhaven

Ceremonial trowel - one of three fabricated for use by President Eisenhower and dignitaries in dedication of U.S. Atomic Energy Commission's headquarters building, Germantown, MD on November 8, 1957

Charpak multiwire proportional chamber

Argonne superconducting solenoid

McMillan synchrotron assembly

Core memory plane for Telegdi wire spark chamber spectrometer

Separate display vacuum chamber for McMillan synchrotron

Radon-beryllium neutron source used by E. Fermi & associates, 1933-34

Sample of Plutonium-239

Bose-Einstein Condensation Apparatus

Penning cold-cathode ion source for neon, both parts

Sections of Magnets for Superconducting Super Collider

Brookhaven superconducting dipole magnet

Charpak drift chamber connected to electronics box

First betatron of Donald Kerst, 1940

Multiwire proportional chamber from J-particle experiment of S. Ting at Brookhaven

Penning cold-cathode ion source head for carbon

Alvarez proton linear accelerator

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