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Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
Breakout Session: Controls
Physics Requirements
and Technology Choices for
LCLS Instrumentation & Controls
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
Outline
Beam position monitorsIssues for the undulator cavity BPMsIssues for signal processing
Power supplies and controllersPulsed operation of DL1 for diagnosticsLow level RF
Source and synchronization issuesFeedback and x-band regulation
Bunch length monitors
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
Cavity Beam Position Monitors
Frequency choiceCavity Iris should be masked from SRVacuum chamber dimensions for the undulator are now chosen12 mm aperture
is close to X-band cutoffEvaluating two frequency choices (Z. Li)
IssuesBPM location with respect to quadrupolesResolution in combination with beam-based alignment with EM quadsSignal processing
5 mm 10 mm
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
Undulator Cavity BPM locations with respect to quadrupoles
Quadrupole and BPM mounted adjacent on the undulator support cradle to ensure 1 um beam based alignment resolution
Also need to keep the distance between the electron beam and the undulator segment axis to less than 70 microns rms
Considering beam position measurement options at downstream end as well
Train-linked undulator sections – see H.-D. Nuhn presentation
Quad BPMassemblies Optional wire monitors,
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
Cavity BPM Signal Processing
X and Y cavity at each undulator plus ~1 phase reference cavity per girder
High-frequency x-band signal is attenuated in a short distance
Incorporate a local mixer to IF at the cavityOnly a simple passive device in the tunnel
Temperature stable
Relatively low radiation loss environment
Distribution of reference x-band oscillator signal in the tunnel
Choose intermediate frequency to match into the RF front end used for stripline
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
Digital BPM Signal Processing
Use same RF front end for stripline BPMs and output from first mixer for cavity BPMs
Initial desire to use a commercially produced BPM processing module (Libera)
We obtained a try out Libera module
Integration into the control system not proceeding fast enough, e.g. could not access raw data in the module.
Present design solutionCommercial VME 8 channel digitizer
RF front end from discrete, commercial components
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
Power supplies and controllers
Requirements Stability of 1E-5 for bunch compressors fast response for feedback correctorsIntegrate with epics controlsreliability
Design solution digital controller/regulator
developed at PSI and further developed at Diamond
commercially supplied power modules
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
Power supplies and controllers
Status Test power supply delivered from PSI
controlled from an epics IOC
long term current stability tests into resistive load are underway
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
Pulsed operation of DL1 for diagnostics•Propose to allow option of pulsing DL1 bends •allow pulse stealing at ~1 Hz into the spectrometer line •monitor beam profile and energy spread•Potentially combine with pulsing of the transverse cavity
•Propose to allow option of pulsing DL1 bends •allow pulse stealing at ~1 Hz into the spectrometer line •monitor beam profile and energy spread•Potentially combine with pulsing of the transverse cavity
•Laminated magnet•Experience at SLAC with damping ring DRIP magnets•Keep two dipoles in series•Need to maintain 1E-4 stability
•Laminated magnet•Experience at SLAC with damping ring DRIP magnets•Keep two dipoles in series•Need to maintain 1E-4 stability
•Laminate magnets now•Develop pulsed supply later
•Laminate magnets now•Develop pulsed supply later
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
Pulsed operation of DL1 for diagnostics
•1 Hz pulsed into the spectrometer line
•1 Hz pulsed into the spectrometer line
•monitor beam profile•monitor beam profile
•monitor energy spread•monitor energy spread•Investigate further if transverse cavity can be optimized for slice measurements in the spectrometer line
•Investigate further if transverse cavity can be optimized for slice measurements in the spectrometer line
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
Low Level RF
Feedback and x-band regulationQuestion that arose last time was how to distinguish drift in the X-band system from errors in the S-band systemSolution is to keep X-band regulation fixed, and compensate errors with the S-band system only
See next slide
Source and synchronization issues noise and stability issues in oscillator and distribution
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
Demonstration of L1 S-band adjustment Demonstration of L1 S-band adjustment to compensate Lx errors – to compensate Lx errors – courteseycourtesey Juhao WuJuhao Wu
Demonstration of L1 S-band adjustment Demonstration of L1 S-band adjustment to compensate Lx errors – to compensate Lx errors – courteseycourtesey Juhao WuJuhao Wu
X-band phase error of + 5o, fixed with L1 S-band
adjustment: phase +2.1°, voltage - 2.1 %
X-band phase error of + 5o, fixed with L1 S-band
adjustment: phase +2.1°, voltage - 2.1 %
X-band amplitude error of 5%, fixed with L1 S-band
adjustment: phase +0.61°, voltage 0.18 %
X-band amplitude error of 5%, fixed with L1 S-band
adjustment: phase +0.61°, voltage 0.18 %
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
Low Level RF Source and synchronization
Present design concept:Microwave crystal oscillator phase locked to SLAC MDL – low noise in the low frequency band
Gun laser oscillator mode locked to crystal oscillator – low noise in the high frequency band
Under evaluationDerive the LLRF 2856 MHz from crystal oscillator or from laser optical output
Distribute LLRF over copper
or optional optical fiber
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
RF/Laser distribution proposed by Ilday et al, MIT at the SLAC Timing workshop
Master laser oscillator
Low noise crystal microwave oscillator
Upgrade path:Fiber distribution
system
RF-optical synchronization module
LLRF to klystron
Optical-laser synchronization module
Baseline Cu Coax distribution
Linac MDL
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
Derivation of LLRF from laser – F. Omer Ilday, MIT
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
Synchronizing Gun and User Lasers – F. Omer Ilday, MIT
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
Non-intercepting detector for off-axis synchrotron radiation
Reflected through a port to: Spectral Power detector
Single shot Autocorrelator
BC1, BC2 Single-shot Bunch Length Detectors
THz autocorrelator
THz power
detector
B4 Bend
Bunch Compressor Chicane
CSR
Vacuum port with reflecting foil
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
The CSR we now understand is dominated by Coherent Edge Radiation
Same spectral and angular distribution characteristics as transition radiation
Need to account for interference effects from adjacent magnets
Experimental investigation at SPPS plannedCan also learn from UCLA expt at BNL-ATF
Bunch Length Monitor Issues
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
Need practical experience in evaluating window materials
Detectors (pyrometers, Golay cells, bolometers)
Autocorrelator designs (mirrors, splitters, detectors)
New development of single-shot autocorrelators
Bunch Length Monitor Issues
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
Power supply controller system layout
IOC
EPICS
Power SupplyDSP Controller
ADCCard
PWMAC Converter
load
DCCT
8 chVME card
ACline
5MHzOptical fiber
PWMsignal
Monitorsignals
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
PSI Digital Power Supplies
ADC/DACCard
DSPController
DCCT
0..6Slaves
Magnet
PWMSignal
Fast Optical Link(5 MHz)
DIO
U1..4
I
PowerConverter
Master
Optical Trigger
Courtesy A. Luedeke, PSI
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
Stripline versus Cavity BPM SignalsP
f700 MHz
500 MHzBP filter
ADCx4
119 MHzClock
24th harmonic
DigitalprocessingRF in
Controlsystem
/4
Stripline
Mixer
LO sync’ed to RF
IF
• noise (resolution) minimized by removing analog devices in front of ADC that cause attenuation• drift minimized by removing active devices in front of ADC
• noise (resolution) minimized by removing analog devices in front of ADC that cause attenuation• drift minimized by removing active devices in front of ADC
C-bandcavity
Dipole mode
coupler
~5 GHz
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
SPPS Laser Phase Noise Measurements – R. Akre 476 MHz
M.O.
x62856 MHz
to linac
MDL3 km
fiber~1 km
VCO
Ti:Salaser osc
diode
EO
scope
Phase detector
2856 MHz
Patrick Krejcik
LCLS FAC [email protected]
April 7-8, 2005
Beam based feedback will stabilize RF AAgainst drift and jitter up to ~10 Hz
But no diagnostic to distinguish drift of X-bandLinearization, higher-harmonic RF has the tightest tolerance
No unique beam measurement
Energy and Bunch Length Feedback Loops
L0 L1
DL1
DL1Spectr. BC1 BC2
L2 L3
BSY 50B1
DL2
Vrf(L0)
Φrf(L2)Vrf(L1) Φrf(L3)E E E
Φrf(L2) zΦrf(L1) zE
