1. PEP II Transverse Feedback System
Ron Akre
William Colocho
Anatoly Krasnykh
Vojtech Pacak
Dmitry Teytelman
Uli Wienands
Andrew Young
MAC October 26, 2006
October 26, 2006
PEP TFB R.Akre

2. PEP II Transverse Feedback System
The PEP TFB system takes the vector sum of 2 BPMs, delays the signal by the remainder of 1 turn and delivers a kick to the beam the next time around. Two stripline kickers, one for X and one for Y, are used.
October 26, 2006
PEP TFB R.Akre

3. PEP II TFB Highlights for Run 5b
Fine tuning of receiver chassis to reduce phase transient
New 2 channel GaGe card collects data on Sum Signal
New LBNL Digital Delay lines installed in HER X and Y and LER Y
Lost only 1 power amp this run!
LBNL assistance with transfer function measurements
Fire
October 26, 2006
PEP TFB R.Akre

4. PEP II Transverse Feedback System Run 5 Hardware Problems
Run 5B – 4 Hardware Problems
LER X Digital delay blown fuze
GaGe board computer hard drive storage used up
GaGe board failed
LER X - Kicker Cables, Filter cable, Power Amp
Run 5A - 18 Log Entries associated with hardware problems
16 Power Amp Problems
14 transistors
5 regulator boards
1 High Power Filter Blown: LER Y-
1 Failed BPM Attenuators: LER 2C
October 26, 2006
PEP TFB R.Akre

5. PEP II TFB Receiver PHASE TRANSIENT
Use These Phase Shifters to Remove Phase Transient
PHASE TRANSIENT
October 26, 2006
PEP TFB R.Akre

6. PEP II TFB Digital Delays
Lawrence Berkeley Laboratory
Principal Investigators: Walter Barry and John Byrd
Alex Chin, Larry Doolittle, Alex Ratti, Jonah Weber
Phase 1: bit ADC to clock data into FPGA at 238MHz
Two tap filter with 1 turn delay plus variable delay
238MHz DAC with differential output
Programmable through COM port.
Completed – Installed in LER Y August 2005
Installed in HER X and Y December 2005
Phase 2: Record 16MS, 70mS, of data to external memory
Three trigger modes
Grow/ Damp Measurements
Fault File Data
Software trigger to capture data during running
System Operational but noise levels prevent PEP deployment
– MoA with LBNL in process to get assistance in looking at noise levels
Power Amplifier Overhead and Reliability has Greatly Improved!!!
October 26, 2006
PEP TFB R.Akre

7. PEP II TFB Power Amplifiers and Filters
We only lost one power amplifier during run 5B – likely during by 4 bunch pattern operation with possible bad filter cable. No power transistors failed!
During run 5A we lost 14 output power transistors.
Before two tap delays, orbit offsets and phase transients cause the amplifiers to run close to saturation. The new digital delay two tap filters eliminate orbit offsets and greatly reduce power requirements in the amplifers.
Filters
No filter failures during run 5B. Mechanical cable connector failure to filter load.
October 26, 2006
PEP TFB R.Akre

8. PEP II TFB Data Acquisition System
Added New 2 channel GaGe card
Files are stored in central NFS space
Compiled MatLab routines for analysis of data sets are run from a GUI
October 26, 2006
PEP TFB R.Akre

9. PEP II TFB Data Acquisition System Analysis Software
Compiled MatLab Software Run from GUI Now includes X and Y Sum Channels
Display All Data
Display Selected Data
Plot RMS FFT
Plot Modes
Plot Mode Phase
Plot Mode Growth Fit
High Resolution FFT
High Resolution FFT 2
Plot Spectrogram
W. Colocho, V. Pacak
October 26, 2006
PEP TFB R.Akre

10. 12-08-05 21:17 ~2200mA LER X Y X Y LER CURRENT October 26, 2006
PEP TFB R.Akre

11. HER Y Grow/Damp Measurements
Her Y 1496mA Grow/Damp
October 26, 2006
PEP TFB R.Akre

12. Loss of Directivity: HOM Simulations (single bunch)
Beam Direction
October 26, 2006
PEP TFB R.Akre

13. PEP II TFB Comments and Concerns for Higher Current Running
Feedback Gain and Output Power
Further grow / damp measurements in both HER and LER.
LBNL two tap filters have shown large increases in system gain and amplifier reliability
Systems seem to be well damped – even during arcing conditions
Filters are currently working well – Need to check cables
Kickers
LER X Kicker has problem with electrode support. May not make it through next run in existing condition.
Even with cable fire 7/16DIN Feed-through connectors did not fail.
As the bunch length shortens higher frequencies of beam induced power will need to be directed to proper loads.
Measurements of beam induced power from kicker to amplifiers need to be done.
BPMs
Need to look closely at X- and possibly Y- offset.
October 26, 2006
PEP TFB R.Akre

14. PEP II TFB Near Term Run 6 Tasks
Set up MoA with LBNL to assist with noise, grow/damp, and transfer function measurements
Measure power reflected to amplifier from kicker
Especially LER X- and Y- compared to X+ and Y+
Resolve LER X 11mm offset discrepancy
Grow / damp measurements both planes of both rings
Transfer function measurements in both rings
Install 2 tap filter in LER X
Replace LER X Kicker Cables with all 7/8 inch Heliax
October 26, 2006
PEP TFB R.Akre

15. End of Talk
October 26, 2006
PEP TFB R.Akre

16. LER 3051 and 3031 BPM-to-Receiver cables with 6dB attenuators
Electrical length of all four 3051 BPM channels is the same.
Electrical length of 3031 BPM is the same with ~50 psec tolerance
Amplitudes of A (red), B (yellow), and C (green) 3051 BPM signals are practically the same. Amplitude of D (blue) signal is ~5% less.
Amplitudes of all four 3031 BPM channels is practically the same.
Anatoly Krasnykh
October 26, 2006
PEP TFB R.Akre

17. Result of LER Receiver Cold Testsx2 x1 y1 y2
Receiver #1
Receiver #2
Amplitudes of output receiver signals in X and Y channels are nearly zero if all four inputs have the equal amplitudes.
Amplitudes of error signals are shown when receivers are activated by one channel.
Both LER receivers are fine.
Anatoly Krasnykh
October 26, 2006
PEP TFB R.Akre

18. PEP II TFB Kickers LER X Kicker Before Installation
Uli Wienands, Anatoly Krasnykh, Artem Kulikov, Jay Langton, David Kharakh Many Others
New kickers with moly electrodes, redesigned coax to stripline transition, and 7/16 DIN connectors have been installed in LER.
LER X Kicker Before Installation
LER X Kicker After Run 5B
October 26, 2006
PEP TFB R.Akre

19. Transfer Function Measurements
Attached are the amplitudes the of transfer functions recorded from the photos for the first hundred sidebands. First is vertical, second is horizontal. Lots of caveats in interpreting the data: very uneven bunch patterns, etc. However, the signal strength is very good and we should be able to measure the broadband open loop response of the entire TFB at low current. This will tell us if the system is operating as it should (in the linear mode). As we raise the current, I hope we can identify any impedances which will modify the transfer function. The combination of this data should allow us to predict the linear performance of the system at high current. The final phase would be to monitor the closed loop response to see what we can find out.
John Byrd, Stefano De Santis LBNL
October 26, 2006
PEP TFB R.Akre