Energy & Power

• 

  Maser Focusing Assembly

  Description

  This object, the focusing assembly from the second maser, was made at Columbia University in 1954 by a team led by physicist Charles H. Townes. Maser stands for Microwave Amplification by Stimulated Emission of Radiation. Masers operate on the same principals as lasers, but they amplify microwaves instead of light. In fact, masers came first. Microwaves have lower energy levels than light and so were easier to produce, although the maser was not a simple invention.

  After working on microwave radar and other devices during the Second World War, Townes undertook investigations of microwave spectroscopy at Columbia University. Working with James Gordon and Herbert Zeigler, he successfully demonstrated an ammonia-beam maser in April 1954. The unit was quite large so Townes developed a smaller unit later that year, several pieces of which were donated to the Smithsonian in 1965.

  date made

  1954

  associated date

  1953

  maker

  Townes, Charles H.

  ID Number

  EM.323893

  catalog number

  323893

  accession number

  260038

  Data Source

  National Museum of American History

• 

  Assay Flask

  Description

  The term "assay" implies an analysis for only a certain constituent (or constituents) of a mixture. A good example is the assay of an ore for gold. That sort of assay would be done using a dry method, i.e. heating the ore in a crucible.

  An assay can also be performed using a wet method. A good example is the extraction of an alkaloid from dried plant material. The plant sample is placed in a vessel into which a solvent is introduced. The active constituent is separated from the sample and extracted by chemical means.

  The flask featured here, with its sloping sides and narrow mouth, is used for the wet assay method. The sample and solvent would be combined in this vessel. Additional apparatus would be used for the separation and extraction of the active constituent.

  Location

  Currently not on view

  ID Number

  1985.0311.064

  catalog number

  1985.0311.064

  accession number

  1985.0311

  Data Source

  National Museum of American History

• 

  Home-made Laser

  Description

  The term “home-made laser” almost seems a contradiction but that is not the case. This gas laser was built by high school student Stephen M. Fry in 1964, only four years after Ali Javan made the first gas laser at Bell Labs. Fry followed plans published in Scientific American's "The Amateur Scientist" column in September 1964, (page 227).

  The glass tube is filled with helium and neon and, as the magazine reported, "seems to consist merely of a gas-discharge tube that looks much like the letter 'I' in a neon sign; at the ends of the tube are flat windows that face a pair of small mirrors. Yet when power is applied, the device emits as many as six separate beams of intense light."

  The discharge tube is the only piece of this particular laser that remains. The flat windows (called "Brewster windows") are square instead of round, and the electrodes are parallel to the gas tube instead of perpendicular. Otherwise it resembles the drawings in the magazine. Fry later earned a Ph.D. in physics with a dissertation on lasers.

  Location

  Currently not on view

  Date made

  1964

  date ordered, given, or borrowed

  1985-03-15

  maker

  Fry, Stephen M.

  ID Number

  1985.0269.01

  accession number

  1985.0269

  catalog number

  1985.0269.01

  Data Source

  National Museum of American History

• 

  Experimental Laser Crystal

  Description

  A major breakthrough marks only the beginning of a scientist's work. In November 1960 Peter Sorokin and Mirek Stevenson, at IBM's Watson Research Center, successfully demonstrated a second type of laser. They energized a crystal of calcium-fluorine treated with a variety of uranium (written in chemical symbols as CaF2:U3+) to generate a pulse of laser light.

  Sorokin and other colleagues experimented with many elements as they learned more about both pulsed and continuous-wave lasers. This crystal, from mid-1962, was the first one made of strontium, fluorine and samarium (SrF2:Sm2+) to successfully operate. Laser research was a very competitive field. Despite their efforts at IBM, Sorokin told museum staff that a team from Bell Labs, "made the first CW [continuous wave] solid-state laser using an ordinary crystal of CaF2:U3+. After that achievement we abandoned our CW efforts and went on to other topics." Those other topics included significant early work on generating laser beams using liquid dyes.

  Location

  Currently not on view

  date made

  1962

  ID Number

  1985.0268.06

  catalog number

  1985.0268.06

  accession number

  1985.0268

  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%.

  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

• 

  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

• 

  Atomic Energy Commission Uranium Enrichment Chart

  Description

  This small metal rectangle has nomographic charts engraved on both sides that relate to the process of enriching uranium for use in an atomic reactor. The chart on one side is labeled: NORMAL URANIUM FEED REQUIREMENT. It allows one to find the normal uranium feed required (assuming an assay of uranium that is .711% weight U-235) per kilogram of enriched uranium product, assuming different concentrations of uranium in the tails assay. This side of the chart also has the logo of the Atomic Energy Commission of the United States of America.

  The chart on the other side is labeled: SEPARATIVE WORK REQUIREMENT. It allows one to find the amount of separative work required per kilogram of enriched uranium product, given the percentage by weight of uranium in the product and the tails.

  A card with the object describes its use. This card and the object fit into a white plastic case.

  On the mathematics of nomographic charts, see Lipka.

  Reference:

  Joseph Lipka, Graphical and Mechanical Computation. Part I. Alignment Charts New York: John Wiley & Sons, 1921, pp. 65–67.

  Location

  Currently not on view

  date made

  ca 1960

  maker

  U.S. Atomic Energy Commission

  ID Number

  1985.0636.01

  accession number

  1985.0636

  catalog number

  1985.0636.01

  Data Source

  National Museum of American History

• 

  Section of rectangular vacuum chamber of SPEAR (Stanford Positron Electron Accelerating Ring) at SLAC

  Description

  Section of rectangular vacuum chamber with integral sputter ion vacuum pump. Since the complete vacuum chamber makes up a closed circular apparatus (SPEAR), object 1980.0177.03 has an arc-shaped length. Section cut away to reveal titanium sputter in vacuum pump.

  SPEAR (Stanford Positron Electron Accelerating Ring) at SLAC was completed in 1972. SPEAR consists of a single ring some 80 meters in diameter, in which counter-rotating beams of electrons and positrons were circulated at energies up to 4 GeV. SPEAR was the first storage ring/colliding beam facility (collider) to provide important new discoveries in elementary particle physics, e.g., the J/psi meson that is made up of a combination of a quark and an antiquark of an entirely new kind (charm quark) and a third lepton in addition to the electron and the muon (tau lepton). Subsequently, the SPEAR facility has served as an intense x-ray source for research in physics, chemistry and biology. For detailed information, see:

  http://www-ssrl.slac.stanford.edu/content/spear3/spear-history

  https://www6.slac.stanford.edu/news/2011-06-02-shedding-light.aspx

  Date made

  1970-1972

  maker

  Stanford Linear Accelerator Center

  ID Number

  1980.0177.03

  accession number

  1980.0177

  catalog number

  1980.0177.03

  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.

  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

• 

  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

• 

  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

• 

  Oak Ridge 60 Inch Vertical Heavy-ion Cyclotron Dees

  Description

  This object is the dee assembly from the Oak Ridge 63-inch cyclotron, as adapted for the Atom Smashers exhibition at the National Museum of American History.

  The object consists of copper hollow D-shaped electrodes (dees) mounted on heavy stems placed through a steel plate. The dee assembly is positioned vertically, rather than the common practice of being positioned horizontally as in most cyclotrons. The assembly is mounted on a flat painted rectangular base, constructed with unspecified construction board material. After the assembly was received at NMAH, the metal casing enclosing the dee stems was removed and discarded, and prior to being exhibited in the Atom Smashers exhibition, the stems were truncated in length by approximately two feet.

  History and basic principles of the Oak Ridge 63-inch cyclotron

  In 1951 the Oak Ridge National Laboratory was authorized by the Atomic Energy Commission to construct a heavy-particle cyclotron. An accelerator, designated the OREL 63-Inch Heavy-Particle Cyclotron, was then designed and built by the Electronuclear Research Division of the Laboratory. The first beam was obtained on May 20, 1952 and a productive research program was initiated shortly afterwards. The past usefulness of this cyclotron is indicated by the amount of nuclear data derived from its operation.

  This cyclotron was the first built expressly to accelerate ions heavier than hydrogen and helium. Designed by Alexander Zucker, this cyclotron helped open a very active field of atomic and nuclear research, which is now pursued with much larger and costlier accelerators. It constructed was constructed to determine whether the explosion of a very powerful thermonuclear bomb might trigger a chain reaction of nitrogen nuclei, igniting the earth’s atmosphere; experiments with this cyclotron, colliding nitrogen ions with nitrogen ions, established that this fear was unwarranted.

  The basic design of the 63-inch is that of a conventional, fixed-frequency cyclotron. In operation, triply charged nitrogen ions were produced by the ion source and were accelerated in a magnetic field of 15,500 gauss. The ions were then electrostatically deflected at the radius of 25.6 inches yielding an external beam of nitrogen ions with a mean energy of about 28 MeV. The accelerating system operated at a frequency of 5.1 MHz/sec and employed dee-to-earth voltages between 35 and 50 kV.

  The vertical position of the dees is characteristic of cyclotrons designed at Oak Ridge. This departure from common practice at the time originally arose from parasitical use of the Calutrons, the large, ganged electromagnetic mass separators built during the Second World War to produce uranium-235 for the first atomic bombs. This and earlier Oak Ridge cyclotrons were “plugged into” Calutron magnets, in place of one of the scores of uranium isotope separation units.

  Basic principles of the cyclotron

  The cyclotron is the simplest of circular particle accelerators. (Go to https://www.physics.rutgers.edu/cyclotron/theory_of_oper.shtml to see a diagram of a typical cyclotron.) At its center is a vacuum chamber which is placed between the pole pieces of a large electromagnet. Within the chamber is a pair “dees” - two flat D-shaped hollow metallic shells - positioned back-to-back forming a cylindrical space, with a uniform gap between the straight sides of the two dees. The plane of the dees is parallel to the faces of the magnet pole pieces. An alternating voltage is applied across the gap between the dees, creating an associated time-varying electric field in that space.

  Electrically charged particles, such as protons, alpha particles or heavier ions, are introduced into the chamber from an ion source at the center. The charged particles are constrained to travel in a circular path inside the dees in a plane perpendicular to the direction of the static uniform magnetic field produced by the electromagnet. The electric field accelerates the particles across the gap between the dees. The electric field is made to alternate with the “cyclotron period” of the particle (determined by magnetic field strength and the particle’s mass and charge). Thus, when the particles complete a semi-circle and arrive at the gap again, the electric field has reversed, so that the particles are again accelerated across the gap. Due to their increased speed in the constant magnetic field, the particles now move in a larger circle.

  The increasing speed of the particles causes them to move in a larger radius with each half-rotation, resulting in a spiral path outward from the center to the outer rim of the dees. When they reach the rim the particles are pulled out by a deflecting electrode, and hit a target located at the exit point at the rim of the chamber, or leave the cyclotron through an evacuated beam tube to hit a remote target. Nuclear reactions due to the collisions of the particle beam and the target atoms will create secondary particles which may be guided outside of the cyclotron and into instruments for analysis.

  Location

  Currently not on view

  Date made

  May 20, 1952

  maker

  Oak Ridge National Laboratory

  ID Number

  1977.0359.41.1

  accession number

  1977.0359

  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

• 

  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

• 

  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

• 

  Prototype Excimer Laser

  Description

  Ralph Burnham and Nick Djeu made this prototype excimer laser in mid-1975 while at the Naval Research Laboratory. A modified carbon-dioxide laser known as a TEA laser (Transversely Excited, Atmospheric pressure), this laser used a mixture of xenon and fluoride gasses to produce a pulse of ultraviolet laser light. Ultraviolet light has a shorter wavelength than visible light and thus a higher energy level.

  The term "excimer" refers to a molecule of two identical atoms that remains stable when in an excited state. The first laser to use such molecules was made in Moscow in 1970 and used molecules consisting of two xenon atoms. Lasers using molecules of differing atoms (technically called an exciplex-laser) were made by several teams of researchers in the US early in 1975. Burnham and Djeu's breakthrough lay in using a commercially available TEA laser to generate the excimer laser pulse. Their apparatus was much smaller and used less energy than prior excimer lasers that were energized by electron-beams.

  Location

  Currently not on view

  Date made

  ca 1976

  maker

  Naval Research Laboratory

  ID Number

  1996.0343.01

  accession number

  1996.0343

  catalog number

  1996.0343.01

  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

• 

  Energy Ontario DriveSave Fuel Economy Calculator Slide Rule

  Description

  In 1982 the government of the Canadian province of Ontario prepared this silver and orange paper linear slide rule for motorists. The front cover is marked: Energy (/) Ontario. It is also marked: fuel (/) economy (/) calculator. It is also marked: DriveSave (/) Improving the Fuel Economy (/) of Automobiles in Ontario. Inside are instructions for tracking distances driven and fuel purchases on a provided "fuel economy log" and for calculating miles per gallon or liters per 100 kilometers with the provided slide rule.

  The back cover contains driving and maintenance tips for improving fuel economy. It is marked: Ontario. It is also marked: Ministry of (/) Transportation and (/) Communications (/) Hon. James W. Snow (/) Minister. It is also marked: Ministry (/) of (/) Energy (/) Hon. Robert Welch (/) Minister. DriveSave was located in the Ministry of Transportation offices in Downsview, Ontario. Snow served from 1975 to 1984, and Welch served from 1979 to 1983.

  Location

  Currently not on view

  date made

  1982

  maker

  Province of Ontario

  ID Number

  1988.3078.04

  nonaccession number

  1988.3078

  catalog number

  1988.3078.04

  Data Source

  National Museum of American History

• 

  Laser Amplifier Section

  Description

  This is one section of a laser amplifier tube from the Shiva experimental fusion apparatus, operated at Lawrence Livermore National Laboratory from 1978 through 1981. Scientists used the Shiva device to test theories about how lasers might be used to trigger a nuclear fusion reaction. The research program was part of the continuing quest to harness nuclear fusion as a source of energy.

  Lasers are useful in this type of research since they emit a narrow beam of intense radiation. Shiva focused the energy of twenty laser beams on a tiny target of nuclear fuel to determine how the fuel would react. This amplifier tube is a short section of one of the twenty beam paths and contains panels made of neodymium glass that focus the light beam.

  Location

  Currently not on view

  date made

  1977

  maker

  Lawrence Livermore National Laboratory

  ID Number

  1985.0236.11

  accession number

  1985.0236

  catalog number

  1985.0236.11

  Data Source

  National Museum of American History

• 

  Target for Military Laser

  Description

  Potential military uses for lasers have attracted both government funding and popular interest. While laser ”ray guns” remain in the realm of science fiction, significant research has been conducted toward that goal. In the 1980s, tests of a deuterium-fluoride (or DF) chemical laser were conducted at the U.S. Army's Redstone Arsenal. A chemical reaction created the energy necessary to generate a laser beam. As this object shows, that beam can be quite powerful.

  In 1985, the Army transferred this test target to the Smithsonian. The target consists of six steel plates, each about 2 mm thick, bolted together. A hole of decreasing diameter is burned through the target from front to back. Information provided with the target reported that a 130 kilowatt laser illuminated the target from a distance of 60 meters for 5 seconds.

  Location

  Currently not on view

  date made

  1984

  ID Number

  1985.0321.01

  accession number

  1985.0321

  catalog number

  1985.0321.01

  Data Source

  National Museum of American History

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