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

2. Requirements
Full document:

3. 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:

4. 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

5. BPM Processor

6. BPM and Timing Racks

7. 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
May include pulse-pulse variation in losses

8. 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

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

10. Cavity Position Monitors

11. 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 +/ 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

12. 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

13. 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

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

15. Undulator System Layout
Beam
X-band receiver LRU

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

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

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

24. 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

25. Charge Monitors

26. 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

27. 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

28. 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

29. 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

30. Backup Slides

31. Beam Position Monitor System
Analog Frontend Version Three

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

33. 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