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ATF tbt BPMs

ATF tbt BPMs. Y.T. Yan. It is not a good idea to relocate some of the existing TBT BPMs from the two arcs to the two Straights. We need to replace some (about every other one, the same as Mark did in the arcs) regular BPMs with TBT BPMs in the Straights and in the no-TBT-BPM ARC locations.

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ATF tbt BPMs

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  1. ATF tbt BPMs Y.T. Yan It is not a good idea to relocate some of the existing TBT BPMs from the two arcs to the two Straights. We need to replace some (about every other one, the same as Mark did in the arcs) regular BPMs with TBT BPMs in the Straights and in the no-TBT-BPM ARC locations

  2. General BPM Rules – One BPM per 90 degree phase advance(better: one BPM per 60-degree phase advance) • The Current 20 TBT BPMS were chosen in the two arcs (about every other one was chosen). There are still locations in the arcs that have no tbt BPMs. • Current 20 TBT BPMs are located in the right place. • The phase advance between two current TBT BPMs has already been about 128 degree. Slightly larger, but fine.

  3. Mathematical BPM Rules for optics modeling • Each TBT BPM provides 8 geometric orbit data of which 4 will be consumed for determining the BPM gains and BPM cross couplings, leaving only 4 data that can accommodate 4 variables (normal quads, for example) at maximum • Maximum of 8 fitting variables (excluding BPM gains and BPM cross couplings) between two BPMs can be Ok at limited locations • At 2nd stage, We will have dispersion data added as fitting constraints without increasing variables

  4. ATF damping ring BPM count • Total phase advances: (60, 35)*90deg == (90, 52)*60 deg • There are a total of 96 BPMs – about right. • It is the best to have all BPMs to be double-view and turn-by-turn (TBT). • We could have about half (48) of the 96 BPMs to be TBT to begin with. This could allow us to have a maximum of magnet variables of 192 = 48*4.

  5. Summary • It may not be a good idea to move any of the current TBT BPMs to another location. • The best is to have all 96 BPMs to be TBT BPMs. • Half (48) of the BPMs to be TBT BPMs should work in terms of counting variables vs. constraints. We have currently 96 normal quad variables in MIA (including Sextupole Feed-downs). We need additionally about 65 skew variables. (96+65=161 < 192=48*4)

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