The use of the Fermilab antiproton accumulator in medium energy physics experiments

The Fermilab antiproton Accumulator has been modified for use in a medium energy experiment. The experiment is conducted with circulating antiprotein beam of momentum between 6.7 GeV/c and 3.7 GeV/c colliding with protons from an internal gas jet. Antiproteins are accumulated at the normal momentum of 8.9 GeV/c and then decelerated to the appropriate energy. It is necessary to cool the beam continually during the time it is colliding with the gas jet. The experiment requires new provisions for the control of magnet power supplies and low level rf system and modifications of the cooling system and high level rf systems to permit variable energy operation. Transition must be crossed to decelerate the beam below 5 GeV/c; because the deceleration is very slow, transition can not be crossed in a conventional manner. This paper will describe the required changes to the Accumulator and operating experience with protons