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Beam Position Monitor System Review & Schedule Overview

This document review covers the Beam Position Monitor (BPM) system at LCLS, including BPM Pickup Types, System Specifications, and Status. It details troubleshooting, calibration, software functionality, and conclusions on performance.

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Beam Position Monitor System Review & Schedule Overview

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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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