Transcript R. Akre

PEP II Transverse Feedback System
Ron Akre
Anatoly Krasnykh
Vojtech Pacak
Uli Wienands
MAC December 13, 2004
December 13, 2004
PEP TFB R.Akre
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.
December 13, 2004
PEP TFB R.Akre
PEP II Transverse Feedback System
Run 4 Problems Logged
• 23 Log Entries associated with problems
(Some Entries have Multiple Problems)
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–
–
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–
12 Power Amp Problems
8 Receiver Setup / Timing
3 Filters - 2 Blown and 1 Broke
2 Problems with Digital Delays
2 Problems with BPM Attenuators
December 13, 2004
PEP TFB R.Akre
PEP II TFB Receiver
Phase shifters were added to phase dX and dY channels in HER. This will allow better
adjustment of phase and reduce sensitivities to drift in reference system.
Orbit offset correction is now done by changing beam orbit to minimize dX and dY
December 13, 2004
PEP TFB R.Akre
PEP II TFB Digital Delays
• Lawrence Berkeley Laboratory
Principal Investigators: John Byrd and Walter Barry
Phase 1: February 2004
2 - 12 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 JTAG port.
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
On board EPICS control with Ethernet for programming
December 13, 2004
PEP TFB R.Akre
PEP II TFB Digital Delays
Xilinx ML300 Power I/O Board
Power
Connector
I/O Connectors
Compact Flash
Card
SLAC TFB CPU Board
System
ACE
JTAG Configuration Port
2 NIM Inputs
2 TTL Inputs
Local
Network
Ethernet
ADC0
FPGA
DDR
SDRAM
Monitor
Signal
Control
Signal
Hybrid
Splitter
DAC
ADC1
Clock Input
119 MHz Sine
Attenuator
PECL
Gate
Frequency
Doubler
Tranformer
Coupling
Power
Splitter
Red = 119 MHz Clock
Tuning Cables
Blue = 238 MHz Clock
New Digital Delays – 2 tap filter and diagnostics are being developed by LBNL
December 13, 2004
PEP TFB R.Akre
Jonah Weber LBNL
PEP II TFB Digital Delays
SLAC Transverse Feedback Digital Delay Module Chassis
(Front)
SLAC TRANSVERSE FEEDBACK DIGITAL DELAY MODULE
+20V
OPB Bus Error
SystemACE Error
FPGA Init
PLB Bus Error
SystemACE Status
FPGA Done
119 MHZ OK
SystemACE Reset
FPGA Program
CPU Reset
SystemACE Mode
JTAG
System Temp
Serial
Port 1
+12V
+5.0V
+3.3V
+2.5V
+1.5V
-12V
(Back)
December 13, 2004
NIM0
INPUT
TTL0
INPUT
119 MHZ
INPUT
DAC+
OUTPUT
NIM1
INPUT
TTL1
INPUT
ADC
INPUT
DACOUTPUT
PEP TFB R.Akre
Power
Serial
Port 2
Ethernet
Jonah Weber LBNL
PEP II TFB Digital Delays
LBNL PEP TFB Digital Delay Board – J. Weber, L. Doolittle, M. Chin, M. Balagot…
December 13, 2004
PEP TFB R.Akre
PEP II TFB Power Amplifiers and Filters
Power Amplifiers
The single largest reliability concern this run. Each of the 8 amplifiers has 8
power transistors summed for the output. During this run we have lost about
30 output power transistors, almost half. There was also loss of some of the
supply current limiting resistors for the output transistors.
During the past down time all the amplifiers have been tested and repaired.
The failure is thought to be due to overdriving the amplifiers. More attention
will be given during this run to power levels into the amplifiers output.
Filters
Previous failures have been due to faulty connectors. New 7/16 DIN
connectors have been installed in LER Y- and there has been no failures.
The by-2 pattern helps greatly in reducing the beam power reaching the
amplifier. During next run we need to measure power coming back to the
amplifiers.
Power spectrum of beam
power from the kicker going
back to the amplifier. New
kicker design should lower
these levels.
December 13, 2004
PEP TFB R.Akre
PEP II TFB Kickers
Uli Wienands, Anatoly Krasnykh, Artem Kulikov, Jay Langton, Many Others
New kickers with moly electrodes, redesigned coax to stripline transition, and
7/16 DIN connectors have been installed in LER.
December 13, 2004
PEP TFB R.Akre
PEP II TFB Kickers
Studies of new kicker designs to improve match and
reduce beam induced power to amplifier continue
A. Krasnykh
December 13, 2004
PEP TFB R.Akre
PEP II TFB Kickers
New stripline kicker designs to improve match at higher frequencies and
reduce propagation delay in beam induced RF pulse.
A. Krasnykh
December 13, 2004
PEP TFB R.Akre
PEP II TFB Data Acquisition System
GAGE 82G PCI 8bit 2GHz 2 Channel Digitizer 16Mb Memory
External clock option
2 Cards 4 Channels – HER X and Y and LER X and Y
Cards are used in a PC running X windows
GAGE card is clocked at
238MHz bunch frequency.
Inputs are from vector
sum out of Analog Signal
Processor for X and Y
Programmable triggers
from HER fault, LER Fault,
and 2 External Sources
can be routed to HER,
LER, or both GAGE cards.
December 13, 2004
PEP TFB TRIGGER CHASSIS
PEP TFB R.Akre
PEP II TFB Data Acquisition System
System for LER installed July 31 - last day of run.
Two data sets on faults collected during high current running – not normal operation.
Only last 700 turns of data before trip are shown. Longitudinal Oscillation is present
in only a portion of the pulse train. It grows to a level where the beam in dumped
due to beam loss, dI/dt abort.
V. Pacak
December 13, 2004
PEP TFB R.Akre
Software Processing of Acquired Transverse Data (LER)
I)
3-D picture of sampled X-transverse signal
• Data arranged into a matrix form:
dim = [4760 x 1746]
• 8-bit resolution, (-127 : +128)
• Sampling freq. fs = 238 MHz
1746 acquired data,
(every second bucket),
sampling fs = 238MHz
~4760 revolutions
apparent sampling
frequency frev = 136.31kHz
Shyam Prabhakar’s PhD thesis under John Fox was a very helpful resource in this work.
V. Pacak
December 13, 2004
PEP TFB R.Akre
Software Processing of Acquired Transverse Data (LER) - 2
II)
2-D time domain display of X/Y transverse motion
Any bunch or any single revolution can be selected
Turn-to-turn transverse position
of the bunch #450
Bunch-to-bunch transverse position
along single revolution #4750
Time of 1 rev. = 1746 x (1/238e6) ~ 7.3 s
Total time = (4760rev) x (1/136.3e3) ~ 35 ms
V. Pacak
December 13, 2004
PEP TFB R.Akre
Software Processing of Acquired Transverse Data (LER) - 3
III)
•
•
FFT of rms value of selected group of bunches and range of revolutions
Apparent sampling freq. frev = 136.31 kHz
Selected bunches #200–600 (by-2 buckets 400-1200)
First 3000 revolutions,
stable beam,
(note the magnitude scale).
Last ~1200 revolutions,
synchrotron instability.
Synchrotron oscillation and harmonic, ~3.8 kHz (LER)
Weak (aliased) X-plane betatron oscillation, ~66 kHz = frev-fb-x,
fb-x ~ 70 kHz (LER)
V. Pacak
December 13, 2004
PEP TFB R.Akre
Software Processing of Acquired Transverse Data (LER) - 4
IV) Mode Evolution, X-transverse
•
•
•
Shown for the last ~1700 revolutions.
Sampling freq. fs = 238 MHz.
(Magnitude of FFT)
Freq. spectrum is calculated for selected
(complete) bunch trains. Single revolution at time.
FFT
Magnitude of freq. spectra plotted
against bunch (mode) number, for each
selected revolution number (time)
Only every 50th mode plotted to avoid
busy picture
h-harmonic number = 3492
(folded at ½ of sampling freq.)
December 13, 2004
V. Pacak
PEP TFB R.Akre
V)
Software Processing of Acquired Transverse Data (LER) - 5
High Resolution FFT, Data filtering tells apart synchrotron and betatron
oscillations.
Unfiltered data
•
•
•
Sampling freq. fs = 238 MHz
Max freq. FNyq = 119 MHz
Plotted FFT done over last 765
revolutions (~ 1.33e6 data points)
•
Freq. resolution increases with
the number of data. (here 178 Hz)
Low-Pass Filter before FFT
805frev
806frev
High-Pass Filter before FFT
fsyn=3.8kHz
3frev
~fb-y=83kHz
December 13, 2004
PEP TFB R.Akre
4frev
V. Pacak
PEP II TFB Concerns for Higher Current Running
Feedback Gain and Output Power – We do not have a factor of 2 margin.
LER ran for several weeks with only 1 power amplifier in vertical. LER was
often lost when HER beam was lost.
Plan to do growth rate measurements in both rings with new acquisition
system
LBNL two tap filter will greatly improve overhead in amplifiers
If larger power amplifiers are required, more rack space is required
Filters are currently working well – no failures with new connector
Only 1 filter, LER Y-, has 7/16DIN connector – the rest use N connectors
Kickers
New Moly electrodes will handle much higher temperatures
7/16DIN Feed-through connectors will replace SC, and eliminate SC to N
adapters.
As the bunch length shortens higher frequencies of beam induced power will
need to be directed to proper loads.
December 13, 2004
PEP TFB R.Akre
PEP II TFB Highlights for Run 5
New Kicker Electrodes and larger, 7/16 DIN, connectors will allow higher
current running in LER – Measurement of both HER and LER kickers will
be done to verify the effects of change in the coax to stripline transition.
The knowledge gained of the system components last run will allow
faster and better setup of the TFB with fewer problems.
Correct orbit offset with beam
Correctly tune up receiver chassis
Added phase shifters to HER receivers
Replace HER BPM Attenuators at BPMs
The new data acquisition system and analysis software will allow a better
understanding of how the system is operating and to what levels the
beam can be stabilized.
New 2 Tap Filter / Delay will lower the forward power levels in amplifiers
December 13, 2004
PEP TFB R.Akre