Fermilab

Hi Mark, At the moment, we can store about 10**12 antiprotons in our accumulator ring. It is limited by an interesting instability whereby a few positively charged ions floating around are attracted by the negative charge of the antiprotons, and become trapped in the electrostatic field of the anti- proton beam. Thes positive ions bounce around in unison and eventually cause enough disturbance that they cause the antiprotons to jostle out of their fairly precarious confinement. The losses equal our ability to accumulate antiprotons at about the 10**12 level. Attempts were made to remove these ions by placing electrodes around the machine, but the best we can do is to remove 99% of the trapped ions this way. The remaining 1% is what limits the attainable antiproton intensity. It is not useful to reduce the antiproton velocity because this causes the interparticle electrostatic force to play a larger role, causing heating and loss of the stored antiprotons. -- Probably the best way to get more antiprotons is to simply make them faster, and this is the object of a current major upgrade of our accumulator.

Regards,

Pat Colestock
Fermilab

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