Design and Performance of the Upgraded SPS Damper after LS1 G. Kotzian for the Damper Team BE-RF-FB,...
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Transcript of Design and Performance of the Upgraded SPS Damper after LS1 G. Kotzian for the Damper Team BE-RF-FB,...
SPS Damper - Gerd Kotzian 1
Design and Performanceof the Upgraded
SPS Damper after LS1
G. Kotzian for the Damper Team
BE-RF-FB, 13. February 2015 MSWG
https://indico.cern.ch/event/367094/
13. Feb 2015
Acknowledgements: BE-RF-FB, BE-RF-CS, BE-RF-PM,BE-BI,BE-OP, BE-ABP,TN-EL
Transverse Damper in General
The transverse damper is a feedback system: it measures the bunch-by-bunch oscillations and damps them by fast electrostatic kickers.
Key elements: Beam position monitor(s)
Signal processing system
Power amplifiers
Electrostatic kickers
Key parameters: Feedback loop gain, phase,
and total loop delay
Kick strength
System bandwidth
2
BPM
BPM Signal Processing
andCorrection calculation
Kicker
Power Amplifier
Ideal equilibrium orbitBeam trajectory
BPM Beam position monitor
Tbeam
Tsignal
D.
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13. Feb 2015 SPS Damper - Gerd Kotzian
SPS Damper - Gerd Kotzian 3
Outline
Objective:
Have a look at the upgraded SPS Damper and its internal structure,to gain insight in what/how the damper can be used e.g. for MDs.
Structure:
o Design of the upgraded SPS Damper
o 2014 Performance
o Outlook for 2015
13. Feb 2015
Damper, not Dumper
SPS Damper - Gerd Kotzian 4
Former SPS Transverse Feedback System
o Last upgrade 1997-2000 in preparation of the SPS as LHC injector
o damping of injection errors and cure of resistive wall impedance driven coupled bunch instability (threshold ~5x1012 protons total intensity)
o operates since 2001 between lowest betatron frequency and 20 MHz (V & H plane) to damp all possible coupled bunch modes at 25 ns bunch spacing
o handles large injection errors of the order of several mm
o Tetrode amplifiers with two tubes drives kicker plates in push-pull configuration installed in tunnel under kicker, 200 W drive power per tetrode, 3 kHz to 20 MHz
o Technology of electronics of system used in SPS until 2012 dates from late 1990’s
13. Feb 2015
SPS Damper - Gerd Kotzian 5
Scope and Motivation for SPS damper upgrade under LIU
Why LS1?
• sharing pick-ups with Orbit System (MOPOS) from Beam Instrumentation Group incompatible with MOPOS upgrade
• requirements for single bunch damping for protons used for LHC p-ion Physics (closer spaced proton bunches, 100 ns)
• ions injection damping with fixed frequency scheme, closer spaced batches
• individual bunch damping for crab cavity studies not possible with previous system (sampling was not synchronous with bunch in previous system)
• LHC doublet scrubbing beam incompatible with previous system
• controls with G64 chassis and MIL-1553 (a.k.a. MMI) became obsolete new controls for power system and LLRF, new RF function generators
13. Feb 2015
SPS Damper - Gerd Kotzian 613. Feb 2015
PU1BEAM
BPMProc.
PU2
BPMProc.
BPMProc.
BPMProc.
KICKER1
PLC1 PLC2200 WDriver
200 WDriver
FinalStage
FinalStage
Electrostatic PU processing
BW ~100MHz
Stripline pickupprocessing
pLHC,ScrubIons
pFT
Damper Signal
Selector
Damper Power System
KICKER2
BeamPos1
BeamPos2
DSPU1
DSPU2
ADC1
ADC2
DAC1
DAC2
BeamPos1
BeamPos2
DSPU1
DSPU2
ADC1
ADC2
DAC1
DAC2
BeamPos1
BeamPos2
DSPU1
DSPU2
ADC1
ADC2
DAC1
DAC2
BeamPos1
BeamPos2
DSPU1
DSPU2
ADC1
ADC2
DAC1
DAC2
SPS Damper LoopspLHC
SPS Damper LoopspFT
SPS Damper LoopsIons
SPS Damper LoopsScrub
from BBQ
from VNA from
VNABaseband Frontend(40 MHz)
RF Frontend200 MHz FSK
Baseband Frontend
RF Frontend200 MHz
Switch M1
Switch M2pLHC
pLHC
pFT
pFT
Ions
Ions
Scrub
Scrub
SURFACE BA2TUNNEL LSS2
cfv-
ba2-
alltr
dam
p[hv
]1cf
v-ba
2-al
ltrda
mp[
hv]2
SPS Damper - Gerd Kotzian 713. Feb 2015
PU1BEAM
BPMProc.
PU2
BPMProc.
BPMProc.
BPMProc.
Electrostatic PU processing
BW ~100MHz
Stripline pickupprocessing
Damper Signal
Selector
BeamPos1
BeamPos2
DSPU1
DSPU2
ADC1Baseband Frontend(40 MHz) ADC2
DAC1
DAC2
BeamPos1
BeamPos2
DSPU1
DSPU2
ADC1RF Frontend
200 MHz FSKADC2
DAC1
DAC2
BeamPos1
BeamPos2
DSPU1
DSPU2
ADC1Baseband Frontend
ADC2
DAC1
DAC2
BeamPos1
BeamPos2
DSPU1
DSPU2
ADC1RF Frontend
200 MHzADC2
DAC1
DAC2
from BBQ
Switch M1
Switch M2pLHC
pLHC
pFT
pFT
Ions
Ions
Scrub
Scrub
from VNA from
VNA
SURFACE BA2TUNNEL LSS2
pLHC,ScrubIons
pFT
KICKER1
PLC1 PLC2200 WDriver
200 WDriver
FinalStage
FinalStage
Damper Power System
KICKER2
SPS Damper LoopspLHC
SPS Damper LoopspFT
SPS Damper LoopsIons
SPS Damper LoopsScrub
cfv-
ba2-
alltr
dam
p[hv
]1cf
v-ba
2-al
ltrda
mp[
hv]2
SPS Damper - Gerd Kotzian 8
Power System Consolidated
13. Feb 2015
Tetrode amplifier in SPS LSS2EM field simulation of kicker
new process control based on PLC in BA2
FESA remotely accessible
SPS Damper - Gerd Kotzian 9
6x Beam Position Monitors installed in LS1
13. Feb 2015
BPCR.221• all BPMs re-cabled with 7/8-inch smooth wall
coaxial cables during LS1; [length ~250..700m]• BPH/BPV: electronics and amplifiers in the
tunnel tested and verified; "hot-spares" readily checked and kept in the tunnel
• BDH / BDV kickers unchanged
RF Faraday cage
SPS Transverse FB
• 2 BPCR (H/V) for LHC type beams (couplers maximum ZT @ 200 MHz)• 2 BPH electrostatic PU (pFT)• 2 BPV electrostatic PU (pFT)
Device Delay
BPH.202 2.48 μs
BPH.204 2.24 μs
BPV.205 2.12 μs
BPV.207 1.88 μs
Device Delay
BPCR.214 0.97 μs
BPCR.221 0.82 μs
H1/H2/V1 1.57 μs
V2 1.31 μs
Approximate transport delays:
SPS Damper - Gerd Kotzian 10
Analog Frontend Control / External Controlo External control (only LHC type beams):
• disable 50 Ohm input termination
• disable attenuation
• enable amplifier
o Two analog frontend types: • RF frontend, used for pLHC and Ions,
LO = 200 MHz, I/Q components
• Baseband frontend (BB), used for pFT and Scrub, only I-component
o Input gain control:• RF: switching attenuators + amp, delay matched
dynamic range: -29 dB to + 10 dB.
• BB: variable gain amplifier (VGA)dynamic range: -27.4 dB to + 26 dB.
o Frontend protection circuitry• input overdrive protection: fast
• enables all attenuators, disables all amplifiers
• no recovery cycle is lost!
• reports as ALARM in LASER; action required!
o ADC overflows (8x)• report as WARNINGS in LASER
13. Feb 2015
I
Q
LO 400.8MHz
IN 2Delta
Constant delay step attenuator
Plus pre amplifier
8
I
QConstant delay step attenuator
Plus pre amplifier
8
Gaussian type low pass, fc~20-40MHz
Gaussian type low pass, fc~20-40MHz
ADC
CLK 40MHz (1)
17
ADC17
IN 1Sum
ADC
CLK 40MHz (2)
17
ADC17
LO 200 MHz
120 MHz
120 MHz
RF frontend schematicFEBbGainFERfGAINFESelect
in LSA
SPS Damper - Gerd Kotzian 11
Beam Position Block (BeamPos)
o 2 BeamPos Blocks per damper loops module = one per pick-up input
o I/Q inputs of SUM and DELTA signals• in ADC sampling clock domain,
hence subject to delay adjustment
o CoRe – Conditioning and Resampling• I/Q phase rotation
• Down sampling: 120 MSPS 40 MSPS (25ns bunch sync)
o Clock domain crossing• from 2x ADC input clocks (delayed per pick-up)
to synchronous reference clock (undelayed)
o Normalization• position calculation (in-phase)
• “quadrature position” indicating head-tail activity
• bypass mode in case of DELTA processing (pFT)
o Overflows (Sum, Delta, Norm)• report as WARNINGS in LASER
13. Feb 2015
I
Q
S
IS
QS
D
ID
QD
Phase rotation to align the S and D vectors
I
Q
S
I’S
Q’S
AD
C s
atur
atio
n
D
I’DQ’D
fDS
DSSS
DSDS
SD
fcosnorm.pos22 QI
QQII
BeamPos1PpmCtrlBeamPos2PpmCtrlSwitchControl
in LSA
Sensitivity of LHC ADT to intra-bunch motion 12
0 1 2 3 4 5-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
Frequency / GHz
De
tect
ed
Am
plit
ud
e [N
orm
aliz
ed
]/ m
m
xN R (f
x)
xbar(fx)
Sensitivity of Frontend to intrabunch motion (LHC ADT)
22. Jan 2014
alternate processing scheme to detect and indicate anti-sym. oscillations:
indication of odd-mode oscillations!
re-evaluate for SPS case
0 0.5 1 1.5 2 2.5 3-0.2
0
0.2
0.4
0.6
0.8
1
1.2
Frequency / GHz
De
tect
ed
Am
plit
ud
e [N
orm
aliz
ed
]/ m
m
xN(f
x)
xbar(fx)
movement of centre-of-charges
normalized position as implemented in the BeamPos Block
Symmetric (even mode) Excitation Anti-symmetric (odd mode) Excitation
NB: although higher even modes visible the damper is acting only in baseband up to 20 MHz – for damping of higher frequencies wideband transverse feedback
13. Feb 2015 SPS Damper - Gerd Kotzian
SPS Damper - Gerd Kotzian 13
Visualization of Bunch Motion
13. Feb 2015
Rapid identification of• quiet bunches• bunches with transverse center of mass motion• bunches with head tail motion• bunches with combination of center of mass and headtail motion with correlation
800 1000 1200 1400 1600 1800 2000 2200-1000
-800
-600
-400
-200
0BPOS-Q7-H-B2
Delta
Example:LHC run 2012
IDELTA
QD
ELT
A
SPS Damper - Gerd Kotzian 14
DSPU – Digital Signal Processing Unit
o 2 DSPUs per damper; one per module; two inputs
o Signal processing• Notch filter
• Hilbert phase shifter / PU vector sum
• Bunch masking
• phase equalizer FIR (up to 64 taps), linearize phase of power system≈ low pass 1st order, cutoff freq. (-3dB) @ 4.5 MHzoperated at 40 MSPS better resolution at lower frequencies
• gain equalizer (up to 64 taps), digital low pass shaping output signaloperated at 120 MSPS
o Clock domain crossing• upsampling: 40 MSPS 120 MSPS
(Interpolated by gain equalizer = LP FIR)
• from synchronous reference clock (undelayed) to 2x DAC output clocks (delayed) implements actual 1-turn delay
o Switches• NotchEnable, PhaseShiftEna, Ch1/Ch2 enable,
Loop/Aux enable, Digital Loop Enable
o Overflows• report as WARNINGS in LASER
13. Feb 2015
phase equalizer FIR, comp. 1st order 4.5 MHz
digital low pass,fc ≈ 16 MHz
DSPU[1,2]EqControlDSPU[1,2]MaskDSPU[1,2]SwitchCtrl
in LSA:
SPS Damper - Gerd Kotzian 15
DSPU – Digital Signal Processing Unit
13. Feb 2015
Functions (from RFFG)- in LSA:
Control signals (FESA) – in LSA:
Excitation input (DDS)
DSPU[1,2]EqControlDSPU[1,2]MaskDSPU[1,2]SwitchCtrl
FGCPpmControl
LoopsControlUse Digital Loop Switches preferred way to disable damper
SPS Damper - Gerd Kotzian 16
Default Timings
o RT task (PPM READ/WRITE)
o 120 MHz resync (200 ms before INJ)
o fRev resync (flywheels in 5 clock domains)
o start function generation (RFFG)
o close damper loops H1/H2 resp. V1/V2 before injection
o scope trigger,
o VNA trigger,
o observation trigger + MEM readout task
o open damper loops
Loop Control:
o Use Digital Loop Switches (preferred way to disable damper)
o Loop ON & OFF timings are required to ensure proper behaviour do not disable
13. Feb 2015
LoopsControlin LSA:
SPS Damper - Gerd Kotzian 17
Clock Distribution: fRF and fREV
o new fiber optic links between Faraday cage in BA3 and Damper racks in BA2• new fibers installed during LS1
• VME FO modules (RX/TX)
• status + diagnostics available (FESA)
o local clock distribution in BA2• active splitting (NIM modules)
o local clock generation• 120 MHz out of 200 MHz fRF
• beam synchronous, for sampling ADCs and DACs
• resync once per cycle to fREV before injection
o fREV resynchronization• 5 clock domains (SynClk, ADC1, ADC2, DAC1, DAC2)
• one flywheel per clock domain,
• resync once per cycle to fREV before injection
o Monitoring possibilities no Alarms (ion cycle does not transmit fRF all the time)
13. Feb 2015
expect over year20 degreesdrift @200MHz
1.9 km fiber links
long-term measurementWinter Summer
CLOCKControlCLOCKPpmControl
in LSA:
SPS Damper - Gerd Kotzian 18
Closed loop delay compensation
o Thanks to Flywheels (generating fREV for each delayed clock) only fixed delay swing of 1 clock period () required (delay chip can do 10.24 ns)• modulo operator “wrapping” the delay around, i.e.
• ADC/DAC/Synclk tagging coarse delay, initial index for flywheels, stay in sync with fRF during ramp
o fixed delay and variable delay• fixed delay PPM, i.e. cycle dependent delays per beam type PU cable delays
− BPH/BPV for pFT beams− BPCRs for pLHC/Scrub/Ion beams
• fixed delay NON-MUXED, i.e. cycle independent delays− BDH/BDV delay same power system for all beam types− Fiber optic delay BA3-BA2
• variable delay PPM, varies throughout the cycle− ADC sampling delay (adjust during setting-up at flat bottom)− DAC fine delay (adjust with closed loop measurements)
o Delay compensation for momentum change, i.e. function(fREV)
o Including stable phase program
NB: to be automated in LSA using make rules.
13. Feb 2015
-5 0 5 10 15 20 253
4
5
6
7
8
9
10
11
12
Cycle Time / ms
Fin
e D
elay
/ n
s
DELAY PU1
DELAY PU2DELAY OUT1
DELAY OUT2
SPS Damper - Gerd Kotzian 19
Functions Distribution
o 3 RFFGs: Horizontal / Vertical / eXperimental• 32bit Serial Control Link, 16bit payload (32bit optional)
• 1ms update rate (up to 16 kHz)
o 16 functions (PPM): gain, phase, PU mixing coeffs, delay• daisy-chained through all 4 damper modules via the backplane:
RFFG pFT pLHC Scrub Ions RFFG
• only 1 module active (ACK) at a time,
• frames return as NACK if no module is active
• tricky if 2 or more modules active at the same time (must be avoided)
• static value output vs. functions (LSA selectable)
o Frontpanel serial links (16bit)• 4x setpoint values to Power Converters
• send as hexadecimal numbers: 0x4300 == 4.3 kV
• voltages out of range will trip the power system EXPERT SETTING
• care must be taken when power cycling these crates: cfv-ba2-alltrdamph1, cfv-ba2-alltrdampv1,if in doubt set power system first to LEVEL1
13. Feb 2015
FGCPpmControlin LSA:
ALLRfFuncGen/ FPSLStaticValues
in LSA:
ALLRfFuncGen/ Functions
in LSA:
SPS Damper - Gerd Kotzian 20
Damper Signal Selector (DSS)
o 2 DSS (H/V), with 2 fully independent channels, to select between inputs Module1 and Module2
o 4 + 1 + 1 + 1 loop inputs per output• 4 damper modules (pLHC, pFT, Ions, Scrub)
• 1 eXperimental module for developments and MDs (Xper)
• 1 transverse excitation input (BBQ Marek Gasior)
• 1 external VNA input
o selectable VNA output• allows for open loop TF measurements
• allows for closed loop TF measurements
• measure one plane, i.e. both modules and pick-ups with one VNA setup + remote controllable switching
13. Feb 2015
ALLDampSigSel/ SwitchPPMControl
in LSA:
Logbook: SPS [Thursday 09-Oct-2014 Night] 00:27
Damper commissioning and setting-up for LHC beam on MD1: parameters for all 4 dampers H1/H2/V1/V2 adjusted. Fine-delay for pick-ups 214 and 221 in H/V determined using the beam transfer function measurement. Input dynamic range adjusted based on +/-5mm bumps and nominal per bunch intensity (1.15e11 ppb, 48 bunches).
Today, for the very first time, the system was set-up completely remotely from the CCC.
SPS Damper - Gerd Kotzian 21
Acquisition and Observation
o provide means to expert users/piquets for diagnostics• triggered by timing freezes acquisition buffers in all channels
• 7 Channels, (16 buffers)− 1 OBS channel (4 buffers, selectable sources)− 6 channels per clock domain (2 buffers each, dedicated)
o OBS data sources available• I/Q data for sum/delta inputs (per pick-up)
• position data (+head-tail component)
• probe various DSPU internal signals
• 40 MSPS, 4 buffers, each 2MSamples, or ~ 2000 turns
o Dedicated channels: 120 MSPS• 2 buffers per channel, each 4095 samples
• 1-turn data (2772 slices) per ADC and DAC channel
• adjustment of sampling delay
• clock tagging (bunch 0)
NB: constant data stream available (in the future) ObsBox! (LMC March 13th 2015)
13. Feb 2015
𝑓 𝑅𝐸𝑉=200 MHz
4620=
120 MHz2772
=40 MHz
924
BufferSettingBufferSelectOBSBufferAcquisition
in FESA3:
INJECTION DAMPING(damper, chromaticity)
approx. 1 ms
SPS Damper - Gerd Kotzian 22
2014 Performance - pFT
13. Feb 2015
SUM
DELTA
[18.9.2014]
• Injection of fixed target proton beam
• Intensity about 10-20% of nominal
• more charges towards the end of the batch
• oscillating in HORIZONTAL
SPS Damper - Gerd Kotzian 23
2014 Performance - pFT
13. Feb 2015
LEGEND:YELLOW delta signal pickup 202; BLUE kick voltage module 1; GREEN kick voltage module 2
Logbook: [Monday 27-Oct-2014, 23:15]
HORIZONTAL
VERTICAL
VNA HORIZONTAL 3MHZ
VNA VERTICAL 3MHZ
approx. 0.7 ms
1 ms
1 ms
RECOHERENCE
• open loop BTF measurement• sweep of two betatron lines• adjustments using phase setting and loop delay• synchrotron sidebands seen
SPS Damper - Gerd Kotzian 24
LHC25ns beam as seen by pFT
13. Feb 2015
[18.9.2014]
• Injected batch of 12 LHC bunches,
• spaced by 25ns,
• intensity about 1.1x1011 ppb. Saturation phenomena develops 10 turns after the injection.
[19.9.2014]The effect comes from an electron cloud and the amplifiers handle it with no problems. It runs like this since 2008.
SUM
DELTA
SPS Damper - Gerd Kotzian 25
2014 Performance - pLHC
13. Feb 2015
Logbook: SPS [Thursday 09-Oct-2014 Night] 00:27
HORIZONTAL
VERTICAL
DAMPER OFF
DAMPER OFF
DAMPER ON
DAMPER ON
SPS Damper - Gerd Kotzian 26
LHC Pilot Setting Up: Open Loop BPCR.214.V
13. Feb 2015
o OL-Ver 100 kHZ o OL-Ver 1 MHZ o OL-Ver 2 MHZ
o OL-Ver 4 MHZ o OL-Ver 6 MHZ o OL-Ver 10 MHZ
[07.12.2014] 18:49 19:35 5-10 min/measurement OPTIMIZE … ?
SPS Damper - Gerd Kotzian 27
pLHC.MD3 - Observations
13. Feb 2015
• Data during MD3 cycle (25ns, no splitting)• Recorded: 4th injection (@ 10800 ms)
SPS Damper - Gerd Kotzian 2813. Feb 2015
~70 turns
1 turn
1st batch 2st batch 3rd batch 4th batch
activity in the last injected batch(+1st order roll-off of damper gain)
SPS Damper - Gerd Kotzian 29
Status End 2014
o Completely new system built and taken into operation (March – Dec)
o Commissioning challenges:• Issue with pFT isolation transformers of all
PU inputs had polarity swapped
• FESA3 class on-the-fly bug-fixing
• at the time no high-level software … all setting-up done in FESA
• All sorts of troubles with the internal observation system …
“… driving your car with windows painted black – you have to get off to see if your lights are on!”
• Setting up of feedback parameters requires stable beam conditions (here I’m not referring to “stable beam”); [tune, chromaticity, injection timing, bucket selection, … ]
• Damper switched OFF by CCC while we were setting up things in BA2 …?!! … communication issue
13. Feb 2015
SPS Damper - Gerd Kotzian 30
Outlook for 2015 – SCRUBBING
o Evaluate scrubbing module Investigate on “phase behaviour”
• compare Scrub vs. pLHC
• sharing same PU and same power system, expect same behaviour …
o Move to full I/Q signal processing
• currently the scrubbing module is too sensitive to sampling delay
• implement in analog, requires modification of HW
• DDC - digital down conversion, modification of FW
o run Scrub + pLHC damper in parallel
• Scrub active during splitting process (40 MHz present)
• pLHC kicks in once splitting is complete (200 MHz restored)
13. Feb 2015
“PU signal”
single bunch doublet
200 MHz BP filtered
40 MHz BP filtered(120 MHz sampled)
Analog signals before digitization:25 ns spaced doublets (during LAB testing)
SPS Damper - Gerd Kotzian 31
Outlook for 2015 – USER INTERFACE
o refactoring damper loops FESA class V2.0• firmware: excess functionality removed (mainly housekeeping, no change in signal
processing!)
• testing using the Xperimental crate, no impact on operations (yet)
o make LSA consistent with new FESA class• adding value generators, for cycle generation definition of “safe settings”
• value generation for timing knobs
• declare make rules for functions, in particular delay/gain
o GUI in JAVA• talks to LSA (set parameters) and FESA (read back)
• loads settings to LSA for 1 active damper (sets others to “safe settings”)
• configure ACQ and fetch OBS data from FESA
• display status and monitoring (frequencies, voltages, and power levels)
• trimming of feedback parameters (in LSA, with history)
• store/recall reference settings
• import/export damper settings to file (consistent snapshot, e.g. for/during MDs)
13. Feb 2015
“RESTORE TO DEFAULT SETTINGS”Kick-off meeting: 18.Feb 2015, 1430 in the CCC
SPS Damper - Gerd Kotzian 32
Outlook for 2015 - AOBs
o OASIS signals• route essential signals to remote samplers
o Logging• Have damper parameters also stored in the MDB + LDB
• Facilitate data retrieval, plotting of e.g. switch statuses
o Prepare for ObsBox ( see LMC on March 13th 2015)• SFP cages per damper module
• install local PCs in BA2
• requires software for the number crunching
o Loop gain tracking• from 14 GeV/c @ INJ to 450 GeV/c @ FT
• need to increase loop gain by factor 32.14, or 30 dB, through the ramp
• analog vs. digital gain (noise issue? limit drive signal?)
13. Feb 2015
SPS Damper - Gerd Kotzian 33
Outlook for 2015 - MDs
MD requests aim on• evaluating concepts for improvements of the damping performance
− different implementations for phase shift filters− adaptive feedback control− test a novel damping algorithm− bunch extrapolation (single bunches, ions), beam gap interpolation (in
between batches)
• develop methods to facilitate loop diagnostics− loop information indispensable during commissioning and for setting-up− easy-to-use repeatable measurements: allows re-qualification of
settings/parameters handy e.g. for cycle generation− review potential for per-bunch head/tail activity monitoring
(test with wideband feedback)
• exploitation of new features− real bunch-by-bunch damper (in view of crab cavity tests)− adding a DDS allows for built-in-network analysis− controlled emittance blow-up, beam cleaning, and bunch shaping using
transverse excitation signals
13. Feb 2015
13. Feb 2015
SPS Damper - Gerd Kotzian 34
Questions?
THANK YOU!
SPS Damper - Gerd Kotzian 35
MD8 – Semi-automated feedback parameter extraction
Objective: extract loop parameters by means of automated measurements
o basis is the classical method with VNA(s)
o automate repeated measurements by means of scripting• adding remote control for VNA(s)
• automatic data collection
• requires interfacing with damper loops, i.e. signal switching
o extract parameters from multiple measurements• closed loop feedback parameters: phase (Hilbert phase shifter, PU mixing coefficients) and delay
(coarse and fine delay)
• but also parameters such as phase and gain equalization, betatron tune, (synchrotron tune)
o Once implemented and proven to work:• this method shall speed up a great deal the setting up
• allows re-qualification of settings/parameters
• scripting could be used compare parameters with LSA settings, and possibly feed back new values
o Measurements done with calibrated VNA(s) serve as reference for other methods/input required for further MDs
13. Feb 2015
SPS Damper - Gerd Kotzian 36
MD9 – Feedback performance evaluation with different phase shift filters
Objective: study different implementations of phase shift filters
o original idea for LHC
o further developed for Q20 optics, in view of wide band feedback
o goal: make feedback phase insensitive to tune variations
13. Feb 2015
-0.5 0 0.5 10
0.2
0.4
0.6
0.8
1
-3
-2-1
0.18+1
+2+3
Root Locus
Real Axis
Imag
inar
y A
xis
Q20
20 turns
-0.5 0 0.5 10
0.2
0.4
0.6
0.8
1
-3
-2-1
0.18+1
+2+3
Root Locus
Real Axis
Imag
inar
y A
xis
Q20
20 turns
Phase compensation for sidebands
Notch, 1T delay, phase rotation
SPS Damper - Gerd Kotzian 37
MD10 – Injection damping using adaptive feedback control
Objective: extract knowledge of per-bunch oscillation amplitude, and boost gain for individual bunches
13. Feb 2015
MD11 – Test a novel damping algorithm
Objective: extract knowledge of per-bunch oscillation phase, and modulate kick for individual bunches
SPS Damper - Gerd Kotzian 38
MD12 – Real bunch-by-bunch damper based on feedback gain equalization
Objective: shaping the time-domain response to generate individual kicks per-bunch, requires feedback gain equalization/gain levelling
o LHC case see W. Hofle, “PERFORMANCE OF THE LHC TRANSVERSE DAMPER WITH BUNCH TRAINS,” WEPME043 - IPAC’13.
o Useful for crab cavity tests
o Individual bunch blow-up (in coast)
o Fully linearized system
13. Feb 2015
LHC ADT
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MD13 – Feedback operation powered by built-in VNA
Objective: achieve same results as MD8 with all-built-in mechanisms (VNA)
o analyze 2 or more pick-up signals at once• 50% of the time (2 pick-ups in the SPS)
• ¼ of the time in case of LHC (ultimately 4 pick-ups)
o Same interface to data and parameters as for the damper loops• no external instrument required (SW maintenance, Windows PC)
• valid for operational use
• with gain equalization, i.e. fully linearized system BTF
13. Feb 2015
MD14 – Controlled emittance blowup, beam cleaning, and bunch shaping using transverse excitation signals
Objective: use results from MD13, i.e. the DDS, and noise generators to inject transverse excitation signals for beam manipulations
o aim: have transverse excitations available for MDs
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MD15 – Frontend noise evaluation
Objective: Evaluate the frontend performance and its sensitivity to low-amplitude transverse beam signals
o Key word: dithering intentionally apply signal to randomize quantization error
13. Feb 2015
MD16 – On the analysis of feedback stability by increasing the frontend gain after injection damping and during acceleration
Objective: Evaluate the loop stability after increasing the frontend gain and once large oscillation amplitudes have been damped.
SPS Damper - Gerd Kotzian 41
MD17 – Performance evaluation using bunch extrapolation/beam gap interpolation
Objective: enhance kick strength for single bunches (iones) and possibly at the tails of batches/trains
o issue: full kick strength only available for frequencies up to < 5 MHz
o Proposed solution: peak hold
13. Feb 2015
MD19 – A different means to determine correct delay adjustment
Objective: Application of different excitation patterns and subsequent correlation to extract delay information.
o Pulse excitation + damping (less destructive)o Modulated sinusoidal (for higher frequencies)o Wavelets + correlation
Dense spacing 100 ns Truly isolated bunches 250 ns
scheme for largespacing