REVISITINGTHE DEAD RECKONING OF THE AGS ORBIT MEASURING SYSTEM [report]

L. Ahrens
1996 unpublished
This note is an update to an AGS tech note (#183) written in 1982. The subject is the offset between the "raw" beam position reported by the AGS equilibrium orbit measuring system and the true position of the beam. The components contributing to this offset are described. The stepsthe proceduresboth to measure these components and to apply the results to the raw numbers for AGS operations are then given. Over the 15 years since the above report appeared several significant changes have been
more » ... anges have been made to the orbit acquisition or "pick-up" electrode (PUE) system including a mechanical rework of the PUE plates themselves. The resulting system is inherently simpler and somewhat cleaner from a high frequency point of view. An even more significant change, the upgrade of the electronics, is coming soon. The system remains relevant to AGS operations. Until the electronics upgrade, the dynamic range with which the system can cope is significantly less than the range over which the AGS can operate for the physics programs. Nevertheless, at least over a range of from 1 to 5 ~1 0 '~ protons accelerating in AGS, the system gives good orbit information. The "relative" infoi-mationdifference orbitsfrom the system is not the primary subject of this note, but the fact that such data can be taken, and absolute gain calibrations extracted from with-beam experiments allows a basis for moving to absolute measurements for which the offsets of t h s note are essential. Absolute orbits, the pue's best estimate of where the beam center lies in the machine aperture, combined with information from the loss monitor system and the surviving beam intensity measurements give Operations a description of how well the theoretical aperture is being utilizedfor high intensity proton acceleration and, with the future electronics upgrade, for heavy ion acceleration. One rather basic motivation for this note is to provide definitions for the jargon used in implementing the offsets. Despite the existence of a mechanism for generating and applying the offset tables, over the intei-val from 1992 to 1995 this mechanism was either not used or misused resulting in some misinformation being extracted from the absolute positions given by the orbit systemwhich reduced confidence in the system. This note, including the appendices, will contain and explain prescriptions for generating the offset numbers, and suggest checks to see if the numbers being used are appropriate. In particular in each offset type has an associated appendix which describes the last round of data handling. Back in the 1980s the number organizing task was done in the AGS PDP10, and the transfer of the offsets to the AGS orbit application code was internal to the structure. Those days are long gone. For this round, the (rather tedious, trivial, and easily done wrong) analysis is done within "Lotus 123", and the transfer to the application code is "by hand". Surely the next round will move to yet another mechanism, but the pieces will be about the same. Future modifications may allow or require an additional electronics correction to be applied to the
doi:10.2172/1151359 fatcat:faxra3dxajhddp5fpbwjmazzte