RHIC Ramps: a proposal

Abstract

The non-cyclic nature of a collider such as RHIC is most evident in the way that tuning procedures such as acceleration, re-bucketing, and the low beta squeeze are asynchronously handled. Each procedure - or ramp - is begun when an "event" is transmitted around RHIC to the equipment houses. Various widely distributed pieces of equipment are requested to respond by ramping through a state transition (loosely speaking) from one state to another in a way that is consistent with hardware constraints and that avoids adverse effects on the beam. In all cases of interest here, a piece of equipment is expected to follow a waveform that it is provided by a general purpose VME card called a Wave Form Generator (WFG). Each WFG receives data from the Real Time Data Link (RTDL) line and events from the event line, and responds with a digital output. While the output of a WFG usually goes to a piece of equipment as a setting, such as the current required from a power supply, the output may also be used to generate a variable that is reinserted onto the RTDL line. Appropriate use of this level of indirection (in which a dependent RTDL variable is a function of other RTDL values) leads to conceptual and physical simplifications in the generation of equipment waveforms. A high level description of the proposed way to implement RHIC ramps is presented in this note as the basis for further discussions and work. It is undoubtedly incomplete and is not fully optimized. For example, the requirements of the RF system and the interests of the RHIC RF section have yet to be understood and incorporated.