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
Object Name
Bose-Einstein condensation apparatus (main apparatus)
Physical Description
aluminum (overall material)
titanium (sublimation pump material)
copper (overall material)
stainless steel (overall material)
glass (overall material)
metal (overall material)
paper (overall material)
adhesive tape (overall material)
Measurements
overall: 37 in x 26 in x 23 in; 93.98 cm x 66.04 cm x 58.42 cm
ID Number
1998.0213.01.01
catalog number
1998.0213.01.01
accession number
1998.0213
subject
Science & Mathematics
Measuring & Mapping
Energy & Power
Science & Scientific Instruments
Modern Physics
See more items in
Medicine and Science: Modern Physics
Modern Physics
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
U.S. National Institute of Standards and Technology, Joint Institute for Laboratory Astrophysics
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