Some Suggested Techniques for Achieving Required Main Ring Low Level RF Performance for the Tevatron I Program

Abstract

These techniques are derived from experience with the existing low level rf system and from the results of accelerator experiments directed at the Tev I requirements which were performed using a specially modified low level rf system. The techniques suggested here are not necessarily unique and other techniques may be acceptable. It is important to realize that certain performance requirements on the Booster and Main Ring are substantially different in the Tev I program from those which have been acceptable in the fixed target program. For example, the longitudinal emittance of the bunches has been routinely and intentionally blown up by the 'bunch spreader' during acceleration to improve the smoothness of the spill. In the Tev I case, the 'bunch narrowing' procedure preceding {bar p} production and in bunch coalescing is facilitated by maintaining the smallest possible longitudinal emittance (i.e. the largest possible longitudinal phase space density). Also, during fixed target physics the Main Ring is essentially full (i.e. approx. 1090 of 1113 buckets occupied) so transient beam loading of the rf system is negligible except during injection, whereas for {bar p} production a single high intensity Booster batch (approx. 83 bunches) is to be accelerated causing substantial transient beammore » induced phase shift of the rf voltage during each passage. The low level phase and position error signals are normally derived from an essentially full ring during fixed target operation whereas in the Tev I program the systems must perform adequately with as few as ten adjacent buckets occupied. Because of the differences in emphasis between fixed target operation and Tevatron I operation is seems sensible to use separate low level rf systems for these two modes of operation. If a single low level system were to be used for both modes of operation some compromises may be necessary which might cause performance in either mode to be less than adequate. Because of the severe demands made on accelerator performance in the Tev I program it would seem reasonable to develop a unique system which can be optimized to the requirements.« less