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Beam Position Monitors LCLS Lehman Review October 25, 2006

Beam Position Monitors LCLS Lehman Review October 25, 2006. BPM Pickup Types Striplines Resonant Cavities (in undulator) Requirements / Specifications System overview Status Schedule. Major Steps. Decide on a Digitizer Echotek glitches, lockups, lack of progress Plan B  Plan A:

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Beam Position Monitors LCLS Lehman Review October 25, 2006

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  1. Beam Position MonitorsLCLS Lehman ReviewOctober 25, 2006 • BPM Pickup Types • Striplines • Resonant Cavities (in undulator) • Requirements / Specifications • System overview • Status • Schedule

  2. Major Steps • Decide on a Digitizer • Echotek glitches, lockups, lack of progress • Plan B  Plan A: • Select 4 channel PAD digitizer • 16-bit, 130 Msample/sec digitizer developed for LLRF • Packaging • Schedule • Still schedule trouble • Plan barely finishes on time • No schedule contingency

  3. PRD 1.1-314 Full document:

  4. Beam Position Monitor System Analog Frontend Version Three

  5. BPM Chassis • Analog Frontend • Digitizer • Embedded IOC • 1u chassis

  6. Beam Test • 100 machine pulses • Effective beam charge 0.35 nC • sy = 2.5 microns

  7. 30 400 Resolution vs. Charge • Measured with beam in machine • Tightest machine requirement: 5 micron resolution @ 200 pC • Achieve 4 micron resolution @ 200 pC • Resolution scales like 1/Q for the three measured bunch charges, as expected 5mm @ 200pC

  8. Linearity • Measured IP3 of BPM signal path • found IP3 within a few dB of calculation • Bench test of apparent position vs. amplitude looks good • Test consists of 15 kHz AM of 140 MHz signal • Results impeccable. • But beam test shows big amplitude  position modulation • Discovered prototype not built to schematic • Gain distribution wrong  Fixed • Took further steps: • Raise amp idle current 90 mA  140 mA • Reduce bandwidth of first filter, raise that of second filter • Narrowband filter before 2nd gain stage

  9. Status • Prototype meets resolution requirement • Stability not well established • Long test looks great • Thermal cycle tests not yet done • Proceeding with first article production • Production boards arrived • First-article loading/testing begun

  10. Calibration • Calibrate through BPM • Via stripline-stripline coupling • Performance not yet verified

  11. Schedule

  12. SLC - Aware EPICS PVs VME IOC EVR Archive FIFO Timing Calib. X,Y,TMIT Waveform->U,V,S DedicatedEthernet Timing +Cal Data PAD IOC ADCAcq. diagnosticEPICS PVs AFE CTL AFE Software & Interface

  13. BPM Controls Description • User Interface Layer (EPICS, SLC-aware) • VME IOC • Converts raw waveforms into X,Y,TMIT and feeds them (timestamped) to SLC. • Conversion parameters are Pvs • Controls calibration • PAD IOC • Sends raw data upstream (dedicated ethernet) • Diagnostic EPICS PVs

  14. Software Functionality (Day 1) • From SLC-aware IOC • averaged BPM readings • buffered acquisition • EPICS • raw waveforms • conversion params. (raw position -> x,y) • attenuator settings • diagnostics

  15. Functionality (Near Future) • Calibration [some features may be present at day one; untested]. • More sophisticated history buffers [other than SLC 'buffered acq'] • Filtering of beam codes in EPICS • Adjusting to beam charge in 'real-time'

  16. Conclusions • Good performance demonstrated • Calibration not yet demonstrated • “Integrated” operation not yet demonstrated • Schedule critical

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