‘BBA’ Goals Understand BPM performance –validate use for precision optics tests –justify & specify hardware/software upgrades Beam – Based ‘Alignment’ tests –only 15% quads have indep. PS Align IR trajectories - esp. LER –missing BPM bench calibration –mechanical heating / motion associated with high I –BPM problems with HOM (thought to be fixed) –BPM problems with ? (step changes, calibration…) –dipole kicks –alignment constraints; inclusion of alignment info in DB NLC: T. Smith J. Nelson M. Woodley M. Ross PEP2 / Accelerator Department: J. Yocky PEP2 / Controls: R. Johnson S. Smith

LER BBA has been done before: problems… –BPM & Quads not adjacent –LER model not as well understood as HER –strong sextupoles –found some large offsets using ‘MIA’ techniques  QFCX1_L1: x-plane +1.4mm +/- 0.65mm QFCX1_L2: x-plane +0.26mm +/- 0.4mm y-plane -0.32mm +/- 0.02mm QFCX1_R1: x-plane +1.68mm +/- 0.2mm y-plane -5.3mm +/- 0.2mm* QFCX1_R2: x-plane +2.1mm +/- 0.3mm y-plane -1.4mm +/- 0.15mm * later validated by survey

PEP-II MAC J. Yocky (NLC) 3 Plan: test the BBA process using HER –using orbit fitting, bump & Q scan focus on BPM issues: –Absolute accuracy and stability resolution ~2um for 1000 turn average accuracy should be ~ 50um ‘Step’ changes: –Radiation – caused processor or memory ‘upsets’ shielding added in high rad areas (80% of upsets) not believed to be a large part of the ‘step’ changes –Offset determination using traditional ‘Q shunt’ BBA tests also underway (Sept 29) –Software improvements to calibration procedure auto-cal out of range error handling

PEP-II MAC J. Yocky (NLC) 4 Difference orbit wrt initial Q at this bump setting; fit for a kick at the quad BPM rms ~ 800nm (avg 10) 300 um ‘step’ to be tracked down in coming week

PEP-II MAC J. Yocky (NLC) 5 BBA results for repeated measurements on one quad (mm): Swapping cables & intensity dependence QF17LPR  leads swapped.157at front end ½ I When leads swapped... electronic offset does not change, mechanical offset changes sign. Not consistent with ‘all’ of the offset generated in the electronics Mechanical Database offset: 100um Measured survey offset: – 480um Electronic offset: 810um Software does not use survey offset Consistent with most of the ‘offset’ in the mechanical system No significant current dependence 72um rms

PEP-II MAC J. Yocky (NLC) 6 Comparison of 2 successive data sets using a given quad Final plot in the process: offset derived from fitted kicks vs nearby BPM reading – middle of the quad is x intercept -

PEP-II MAC J. Yocky (NLC) 7 successive offset measurements (mm): QDS2SR03 Y offset to BPMS PR = QDS2SR03 Y offset to BPMS PR = QDS2SR03 Y offset to BPMS PR = QDS2SR03 Y offset to BPMS PR = QDS2SR03 Y offset to BPMS PR = QDS2SR03 Y offset to BPMS PR = rms = 80um