__FORCETOC__ The Antihydrogen Trap (ATRAP) collaboration at the

Antiproton Decelerator The Antiproton Decelerator (AD) is a storage ring at the CERN laboratory near Geneva. It was built from the Antiproton Collector (AC) to be a successor to the Low Energy Antiproton Ring (LEAR) and started operation in the year 2000. Antiprotons ...

facility at

CERN The European Organization for Nuclear Research, known as CERN (; ; ), is an intergovernmental organization that operates the largest particle physics laboratory in the world. Established in 1954, it is based in a northwestern suburb of Gene ...

, Geneva, is responsible for the AD-2 experiment. It is a continuation of the

TRAP A trap is a mechanical device used to capture or restrain an animal for purposes such as hunting, pest control, or ecological research. Trap or TRAP may also refer to: Art and entertainment Films and television * ''Trap'' (2015 film), Fil ...

collaboration, which started taking data for the PS196 experiment in 1985. The TRAP experiment (PS196) pioneered cold

antiproton The antiproton, , (pronounced ''p-bar'') is the antiparticle of the proton. Antiprotons are stable, but they are typically short-lived, since any collision with a proton will cause both particles to be annihilated in a burst of energy. The exist ...

s, cold

positron The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. It has an electric charge of +1 '' e'', a spin of 1/2 (the same as the electron), and the same mass as an electron. When a positron collides ...

s, and first made the ingredients of cold

antihydrogen Antihydrogen () is the antimatter counterpart of hydrogen. Whereas the common hydrogen atom is composed of an electron and proton, the antihydrogen atom is made up of a positron and antiproton. Scientists hope that studying antihydrogen may shed l ...

to interact. Later ATRAP members pioneered accurate

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...

spectroscopy Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter wa ...

and observed the first hot antihydrogen atoms.

Experimental setup

ATRAP is a collaboration between physicists around the world with the goal of creating and experimenting with antihydrogen. ATRAP accumulates positrons emitted from a radioactive ²²Na source. There are two effective ways to slow down the fast positrons by inelastic processes. The ATRAP collaboration initially chose a different method to ATHENA (AD-1).

Slowing down and trapping positron

The positrons which were emitted by the ²²Na were first slowed down with a 10 µm thick titanium foil and then passed through a 2 µm thick tungsten crystal. Within the crystal there is a possibility that a positively charged positron and a negatively charged electron form a Rydberg

Positronium Positronium (Ps) is a system consisting of an electron and its antimatter, anti-particle, a positron, bound together into an exotic atom, specifically an onium. Unlike hydrogen, the system has no protons. The system is unstable: the two parti ...

atom. In this process, the positrons lose much of their energy so that it is no longer necessary (as in ATHENA) to decelerate further with collisions in gas. When the loosely bound Rydberg positronium atom reaches the Penning trap at the end of the apparatus, it is

ionized Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule ...

and the positron is caught in the trap. Atrap2

Since this method of positron accumulation was not particularly efficient, ATRAP switched to a Surko-type buffer gas accumulator as is now standard in experiments requiring large numbers of positrons. This has led to the storage of the largest ever number of positrons in an Ioffe trap. Unlike ATHENA, ATRAP has not yet been terminated and can be continuously improved and expanded. ATRAP now has an Ioffe trap, which can store the electrically neutral antihydrogen using a

magnetic quadrupole A quadrupole or quadrapole is one of a sequence of configurations of things like electric charge or current, or gravitational mass that can exist in ideal form, but it is usually just part of a multipole expansion of a more complex structure refl ...

field. This is possible because the magnetic moment of antihydrogen is non-zero. It is intended that

laser spectroscopy Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter wa ...

will be performed on antihydrogen stored in the Ioffe trap.

ATRAP collaboration

The ATRAP collaboration comprises the following institutions:

References

{{Reflist

External Links

Record fo
ATRAP
experiment on INSPRE-HEP Particle experiments CERN experiments pt:ATRAP