Beam Position Monitors LCLS Lehman Review October 25
Beam Position Monitors LCLS Lehman Review October 25, 2006 BPM Pickup Types Striplines Resonant Cavities (in undulator) Requirements / Specifications System overview Status Schedule October 25, 2006 Beam Position Monitor Status 1 Steve Smith ssmith@slac. stanford. edu
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 October 25, 2006 Beam Position Monitor Status 2 Steve Smith ssmith@slac. stanford. edu
PRD 1. 1 -314 Full document: October 25, 2006 Beam Position Monitor Status 3 Steve Smith ssmith@slac. stanford. edu
Beam Position Monitor System Analog Frontend Version Three October 25, 2006 Beam Position Monitor Status 4 Steve Smith ssmith@slac. stanford. edu
BPM Chassis Analog Frontend Digitizer Embedded IOC 1 u chassis October 25, 2006 Beam Position Monitor Status 5 Steve Smith ssmith@slac. stanford. edu
Beam Test 100 machine pulses Effective beam charge 0. 35 n. C sy = 2. 5 microns October 25, 2006 Beam Position Monitor Status 6 Steve Smith ssmith@slac. stanford. edu
Resolution vs. Charge Measured with beam in machine Tightest machine requirement: 5 micron resolution @ 200 p. C Achieve 4 micron resolution @ 200 p. C Resolution scales like 1/Q for the three measured bunch charges, as expected October 25, 2006 Beam Position Monitor Status 7 5 mm @ 200 p. C 30 400 Steve Smith ssmith@slac. stanford. edu
Linearity Measured IP 3 of BPM signal path found IP 3 within a few d. B of calculation Bench test of apparent position vs. amplitude looks good Test consists of 15 k. Hz 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 m. A 140 m. A Reduce bandwidth of first filter, raise that of second filter Narrowband filter before 2 nd gain stage October 25, 2006 Beam Position Monitor Status 8 Steve Smith ssmith@slac. stanford. edu
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 October 25, 2006 Beam Position Monitor Status 9 Steve Smith ssmith@slac. stanford. edu
Calibration Calibrate through BPM Via stripline-stripline coupling Performance not yet verified October 25, 2006 Beam Position Monitor Status 10 Steve Smith ssmith@slac. stanford. edu
Schedule October 25, 2006 Beam Position Monitor Status 11 Steve Smith ssmith@slac. stanford. edu
Software & Interface VME IOC EPICS PVs SLC - Aware EVR Archive FIFO Timing X, Y, TMIT Calib. Waveform->U, V, S Dedicated Ethernet PAD IOC AFE CTL Timing + Cal Data ADC Acq. diagnostic EPICS PVs AFE October 25, 2006 Beam Position Monitor Status Steve Smith ssmith@slac. stanford. edu
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 October 25, 2006 Beam Position Monitor Status Steve Smith ssmith@slac. stanford. edu
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 October 25, 2006 Beam Position Monitor Status Steve Smith ssmith@slac. stanford. edu
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' October 25, 2006 Beam Position Monitor Status Steve Smith ssmith@slac. stanford. edu
Conclusions Good performance demonstrated Calibration not yet demonstrated “Integrated” operation not yet demonstrated Schedule critical October 25, 2006 Beam Position Monitor Status 16 Steve Smith ssmith@slac. stanford. edu
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