• Improves the Q/M comparison of antiproton and proton by nearly a million
• Develops the techniques to get cold antiprotons that will be used at the AD

During 1986 - 1999, our TRAP Collaboration (which has since grown into ATRAP) developed and demonstrated the techniques to slow, trap, and electron-cool antiprotons.  Before TRAP made it possible to accumulate extremely cold antiprotons, only high speed antiprotons, traveling at nearly the speed of light, had been available for study.  The TRAP techniques will be used by ATRAP (and its competitors) to make cold antihydrogen.  Antiprotons are slowed, cooled and eventually stored in thermal equilibrium at 4.2 K, an average energy more than ten billion (10,000,000,000) times lower than the energy of previously available antiprotons.

Months-long confinement of a single antiproton, a background pressure less than 5  x 10^-17 Torr, and nondestructive detection of the radio signal from a single trapped antiproton, made it possible to show that the charge-to-mass ratios of the antiproton and proton differ in magnitude by less than 9 parts in 100 billion (100,000,000,000). This 90 ppt (parts per trillion) comparison is nearly a million times more accurate than previous comparisons, and is the most stringent test of CPT invariance with a baryon system by a similar amount.

The techniques for slowing, cooling and storing cold antiprotons make it possible for ATRAP and its competitors to pursue the production of antihydrogen that is cold enough to trap for precise laser spectroscopy.  TRAP got extremely close to cold antihydrogen with our simultaneous confinement of 4.2 K antiprotons and positrons reported in 1999.

All the initial cold antiproton experiments were carried out at the CERN Laboratory with antiprotons coming from its Low Energy Antiproton Ring (LEAR), a unique facility that then closed.  Antihydrogen experiments in 2000 and beyond will be pursued at the new Antiproton Decelerator ring of CERN which was constructed for this purpose. Using the techniques developed by TRAP, antiprotons will be accumulated within traps rather than in storage rings, thereby reducing the operating expenses to CERN.

1981 - 1985      Proposals 1986      Slow antiprotons in matter      21 MeV --> less than 3 keV  1986      First trapping of antiprotons          < 300           < 3 keV            10 minutes 1989      Hold 105 antiprotons for 2 months           Lifetime > 3.4 months 1989      First electron cooling in a trap           3 keV --> -0.3 meV                            (4.2 K temperature) 1990      First antiproton stacking in a trap

1990      Q/M for antiproton and proton      have same magnitude          to 4 parts in 108 1992      First observation of      one trapped antiproton 1995      Q/M for antiproton and proton      have the same magnitude          to 1 part in 109 1999      Q/M for antiproton and proton      have the same magnitude          to 9 parts in 1011           Most stringent test of CPT           with baryons           Used one antiproton and one H- ion            trapped together in a Penning trap