Isolated Bucket RF Systems in the Fermilab Antiproton Facility

Abstract

In the Fermilab p/sup -/p colliding beam facility antiprotons are to be collected in an accumulator ring where the injection/extraction orbit length and rotation period are the same as those of the Booster Ring at T = 8 GeV, namely 474.19 m. and 1.59 X 10/sup -6/ sec. Prior to injection into the Accumulator ring the momentum spread of the antiprotons is reduced by mismatched bunch rotation in a slightly larger Debuncher ring with circumference 505.28 m and rotation period (8 GeV) 1.695 X 10/sup -6/ sec. Several of the beam manipulations in these rings are facilitated by rf systems capable of applying a longitudinal accelerating field for only part of each rotation period. The accelerating field is ''suppressed'' for the remainder of the rotation period. The concept of ''suppressed bucket'' is not new, but the use to which they are put in this project is unique. T /SUB o/ is the synchronous particle rotation period and the voltage is a single complete sinusoid of period T /SUB rf/ . The period T /SUB rf/ can be related to the rotation period by the expression T /SUB o/ = hT /SUB rf/ , where h > 1 but h needmore » not be an integer. The repetition period of the isolated wave can be precisely T /SUB o/ (stationary) or it may differ slightly from T /SUB o/ (moving). Furthermore, the wave need not be sinusoidal as shown or even symmetric about some center point. It must only span some region T /SUB rf/ and it cannot have a dc component. Practical considerations indicate that the wave should be reasonably smooth so that the Fourier spectrum is not excessively broad.« less