Beam Position & Charge Monitors LCLS Lehman Review July 11, 2007 BPM Pickup Types Striplines Resonant Cavities (in undulator) Requirements / Specifications System overview Status

Requirements Full document:

Had just decided on a digitizer Commercial VME module did not perform Last Review Had just decided on a digitizer Commercial VME module did not perform Switched to 4 channel, 16-bit, 130 Msample/sec digitizer developed for LCLS LLRF Packaging Throw in a box with BPM analog front end Schedule concerns:

Injector BPMs 19 in injector 1 in gun spectrometer 23 Stripline BPMs 19 in injector 1 in gun spectrometer 3 in 135 MeV spectrometer Installed and commissioned in early April just ahead of beam Used to establish 1st beam through injector

BPM Processor

BPM and Timing Racks

BPM Performance Take data synchronized pulse-by-pulse Use linear prediction of each BPM from adjacent BPMS Example: Compare bunch charge pulse-pulse 300 pulses 17 BPMs Average rms/mean 0.0007 May include pulse-pulse variation in losses

Performance Effective beam charge 0.35 nC sx = 2.5 microns Predict BPM position reading from linear fit to adjacent BPMs (Model-independent) 300 machine pulses Effective beam charge 0.35 nC sx = 2.5 microns sy = 1.7 microns

BPM Performance Q~ 200 pC Resolution requirement is 10 microns for the small aperture BPMs Meets resolution requirements

Cavity Position Monitors

LTU and Undulator BPM System Specification Parameter Specification Limit Condition Resolution < 1m 0.2 – 1.0 nC +/- 1 mm range Offset Stability < +/- 1m 1 hour 20.0 +/- 0.56 Celsius < +/- 3m 24 hours +/- 1 mm range Gain Error < +/- 10 % Dynamic Range, Position +/- 1 mm 10 mm diameter vacuum chamber Dynamic Range, Intensity > 14 dB PC Gun

X-Band Cavity BPM Development Five X-Band Cavity BPM built and tested Two qualified vendors for machined parts Brazing procedure optimized to preserve tune Tuning and testing procedures generated

BPM Simulations Cavity BPMs simulated in Microwave Studio, HFSS and Mafia Test data indicates good agreement between simulated model and measured BPMs Port 1 Port 4 Port 2 Port 3 X-Port Y-Port Vertical dipole mode Monopole mode

Cavity BPM Development R&D phase of near completion Testing phase II expected completed by end of July Entering production phase

Undulator System Layout Beam X-band receiver LRU

Receiver Development X-Band down-converter developed from existing Miteq product Modified to meet LCLS requirements 3 channel receiver with common LO 4 first article packaged receivers delivered and presently being tested

X-Band Receiver System Features Input RF Power Surge Limiters Input DC power regulation High/Low gain feature (28/0dB) to extend dynamic range Integrated self-test Multi-mode operation with phase locked LO to control system or free-run mode

BPM Testing Non-Vacuum Single BPM cold test unit complete 04/06 (Phase I) test in APS Injector Test Stand complete 09/06 (Phase II) 3-BPM test in APS LEUTL Complete test matrix to prove compliance to specification Testing phase II expected completed by end of July

LEUTL 3-BPM Test PC gun installed and LEUTL tunnel commissioned PC gun beam 325 MeV (400 pC) to dump 33 Hor. and 23 Vert. micron normalized emittance Compressed beam 1 ps bunch length

In-Tunnel Progress 2-axis translation stage installed and tested provide sub-micron controllable horizontal and vertical motion Multiple experiments presently conducted to verify operation Testing ongoing

Had trouble getting acquisition synchronous Took 2 calibration scans 3 BPM Test June 20 data Had trouble getting acquisition synchronous Took 2 calibration scans One in X, one in Y Move BPMs in 100 micron steps Use to establish phase amplitude scale offset of BPM signal Then mover ran away ending run (Very) Preliminary results look good

X Scan Mover X-scan Steps of 100 microns Predict BPM 2 X from BPMS 1 & 3 Resolution ~8 microns

Y Scan Mover Y-scan Steps of 100 microns Predict BPM 2 Y from BPMS 1 & 3 Resolution ~12 microns

Summary X-Band Cavity BPM Development Nearly Complete 4 Cavity BPM built and tested Machining and braze critical tasks identified BPM phase ll testing expected complete July 07 Production procurement ongoing Receiver Prototype Development Nearly Complete First 4 prototypes assembled and tested with good results 3-BPM testing prototypes incorporate receiver, local oscillator and filter first article packaging Test Qualification Collaborating with SLAC to test and qualify Qualifying system with the same ADC (PAD) as SLAC LINAC BPM upgrade Testing is ongoing at this time with promising results Entering Production phase

Charge Monitors

Charge Monitors t1 t2 t5 t6 t4 t3 Toroids 5-8 Toroids 1-4 IOC ADC EVR LNA + - Baseline Int#1 S1 S3 S4 Beam Pulse Int#2 S/H S5 to Fast Acquisition Board for waveform capture S2 EVR t1 t2 t5 t6 t4 t3 Signal amplitude Dark Current Beam Pulse 4 Chan Fast Digitizer Toroids 5-8 Toroids 1-4 Toroid/Cal Cables Channel Access trig Analog Charge Values IOC ADC EVR MPS Signals Acromag IP330 16 channel, 16-bit 8uS conv. time Raw Data LMR-400 x 8

Charge Monitoring Injector: 6 toroids, 2 Faraday cups All installed Toroid IM01 output shorted by vacuum bolt Replace when we can break vacuum at gun Faraday cup FC01 disabled when first inserted

Toroid amplifier input bandwidth too high Commisioning Toroid amplifier input bandwidth too high Decrease bandwidth seen by first amp Present bandwidth not useful Early indication is that a simple RC filter reduces jitter Presently don’t trust online calibration Use fixed, bench calibration numbers Use online cal for status of health of electronics

Toroid System Next Phase Complete Injector installation/commissioning REmianing in LCLS: 7 more toroids in BC2 LTU Undulator Dump All toroids built Baked Electrically tested On shelf BC2 / BTH west installation design in progress

Backup Slides

Beam Position Monitor System Analog Frontend Version Three

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

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