Extremely cold antiprotons, for mass measurements and antihydrogen

Over the last five years, a series of experiments by our TRAP Collaboration has made it possible to slow, cool and store antiprotons at energies 1010 lower than was previously possible. Despite the extremely low energy, the storage time exceeds 3.4 months. The first example of measurements which become possible with extremely cold antiprotons is a comparison of the antiproton and proton inertial masses which shows they are the same to a fractional accuracy of 4×10−8. This is 1000 times more accurate than previous comparisons and large additional increases in accuracy are anticipated soon. The availability of low energy antiprotons opens other experimental possibilities as well, such as the production and study of trapped antihydrogen atoms. To increase the number of trapped antiprotons we have demonstrated that we can accumulate antiprotons from successive pulsed injections of antiprotons into the trap.