ATRAP experiment

Experimental setup

ATRAP was 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 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 and the positron is caught in the trap.

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.

ATRAP has been terminated. ATRAP had an Ioffe trap, which attempted to store the electrically neutral antihydrogen using a magnetic quadrupole field. This was potentially possible because the magnetic moment of antihydrogen is non-zero. Laser spectroscopy was intended to be performed on antihydrogen stored in the Ioffe trap, however no publication was ever made.

ATRAP collaboration

The ATRAP collaboration comprised the following institutions:

• Harvard University, US
• York University, Canada
• University of Mainz, Germany
• Forschungszentrum Jülich, Germany

References

References

1. (September 1990). "Thousandfold improvement in the measured antiproton mass". Physical Review Letters.
2. "Greybook: PS196".
3. "UC San Diego: Department of Physics – Surko Plasma Research Group".
4. (2016). "Electron-cooled accumulation of {{val". [[Journal of Physics B]].
5. "Experiments {{!}} CERN".