linac coherent light source (lcls) accelerator system jitter model longitudinal feedback model
DESCRIPTION
LCLS Longitudinal Feedback with CSR as Diagnostic Tool Juhao Wu Stanford Linear Accelerator Center LCLS FAC Meeting, SLAC Oct. 12, 2004. Linac Coherent Light Source (LCLS) accelerator system Jitter model Longitudinal feedback model Coherent Synchrotron Radiation (CSR) as diagnostic tool - PowerPoint PPT PresentationTRANSCRIPT
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
LCLS Longitudinal Feedback with CSR as
Diagnostic Tool
Juhao WuJuhao WuStanford Linear Accelerator CenterStanford Linear Accelerator Center
LCLS FAC Meeting, SLACOct. 12, 2004
Linac Coherent Light Source (LCLS) accelerator system Jitter modelLongitudinal feedback model
Coherent Synchrotron Radiation (CSR) as diagnostic toolBunch length: Gaussian, step, and double-horn structureDetector
Discussion
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
LCLS Accelerator SystemLCLS Accelerator SystemLCLS Accelerator SystemLCLS Accelerator System
Electron beam at birth: peak current ~ 100 ampereXFEL calls for very high peak current ~ several kilo ampereCompress the bunch, and accelerate the bunch
Electron beam at birth: peak current ~ 100 ampereXFEL calls for very high peak current ~ several kilo ampereCompress the bunch, and accelerate the bunch
Bunch Compressor; Linac AcceleratorBunch Compressor; Linac Accelerator
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
klystron phase rms klystron phase rms 0.07 0.07°°(20 sec)(20 sec)
klystron ampl. rms klystron ampl. rms 0.06 0.06%%(60 sec)(60 sec)
measured RF performancemeasured RF performance
X-bandX-band XX--
Jitter budget (< 1 minute time-scale)Jitter budget (< 1 minute time-scale)Jitter budget (< 1 minute time-scale)Jitter budget (< 1 minute time-scale)
Do we need a feedback system?
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
LCLS Accelerator SystemLCLS Accelerator SystemLCLS Accelerator SystemLCLS Accelerator System
LCLS accelerator system model (P. Emma): a 5-stage linac-bend segments
LCLS accelerator system model (P. Emma): a 5-stage linac-bend segments
L0
RFgun
L3L2X
i i = 1= 1 i i = 2= 2 i i = 3= 3 i i = 4= 4 i i = 5= 5
bends of zero strength at bends of zero strength at ii = 2 = 2
DL1DL1 BC1BC1 BC2BC2 DL2DL2L1
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
LCLS Accelerator SystemLCLS Accelerator SystemLCLS Accelerator SystemLCLS Accelerator System
Linac
RF
Wakefield (structure wake) (K. Bane)
Chicane and Dog-leg (2rd order map)
Linac
RF
Wakefield (structure wake) (K. Bane)
Chicane and Dog-leg (2rd order map)
]cos[ kzeVEE
0/2
0)( szea
cZzw
56656 TRzz
SLACSLAC S-Band: S-Band:ss00 1.32 mm 1.32 mm
aa 11.6 mm 11.6 mmzz < ~6 mm < ~6 mm
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
SPPS Accelerator System Jitter MeasurementSPPS Accelerator System Jitter MeasurementSPPS Accelerator System Jitter MeasurementSPPS Accelerator System Jitter Measurement
Courtesy of P. Emma
Peaks around (f1 =0.08) and (f2 =1.7) Hz
Data rate 10 Hz, not 120 Hz
Peaks around (f1 =0.08) and (f2 =1.7) Hz
Data rate 10 Hz, not 120 Hz
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
H randn step
step
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jj tt
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LCLS Accelerator System Jitter ModelLCLS Accelerator System Jitter ModelLCLS Accelerator System Jitter ModelLCLS Accelerator System Jitter Model
We model the jitter as the follows:We model the jitter as the follows:
time run total and rand
Hz Hz with
stepstep :)(
;60/1;1.0
;1;7.1;08.0
334422
551121
Nt
BABABA
BABAff
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
LCLS Performance (No Feedback )LCLS Performance (No Feedback )LCLS Performance (No Feedback )LCLS Performance (No Feedback )
‘free’ machine‘free’ machine %50.0/
%;26.0/
std
EE
EE %50.0/
%;26.0/
std
EE
EE
%7.1564/
%;4.247/
std
II
II %7.1564/
%;4.247/
std
II
II
ps
ps
std 4.1
;5.0
t
t ps
ps
std 4.1
;5.0
t
tAt undulator entranceAt undulator entrance
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
LCLS Feedback System SchematicLCLS Feedback System SchematicLCLS Feedback System SchematicLCLS Feedback System Schematic
Observables: Energy: E0 (at DL1), E1 (at BC1), E2 (at BC2), E3 (at DL2) CSR power bunch length: z,1 (at BC1), z,2 (at BC2)
Controllables: Voltage: V0 (in L0), V1 (in L1), V2 (effectively, in L2)
Phase: 1 (in L1), 2 (in L2 ), 3 (in L3)
Observables: Energy: E0 (at DL1), E1 (at BC1), E2 (at BC2), E3 (at DL2) CSR power bunch length: z,1 (at BC1), z,2 (at BC2)
Controllables: Voltage: V0 (in L0), V1 (in L1), V2 (effectively, in L2)
Phase: 1 (in L1), 2 (in L2 ), 3 (in L3)
Courtesy of P. KrejcikCourtesy of P. Krejcik
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
MC
d
d
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dV
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dV
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LCLS Feedback AlgorithmLCLS Feedback AlgorithmLCLS Feedback AlgorithmLCLS Feedback Algorithm
MCO OGMCC 1 beforeafter
We are linearlinear
We are linearlinear
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
LCLS Feedback SystemLCLS Feedback SystemLCLS Feedback SystemLCLS Feedback System
LCLS feedback model
Include Proportional gain, Integral gain, and Derivative gain (PID): Integral gain helps at the low frequency regime
Cascade scheme: we need to keep the off-diagonal elements in the M-matrix
Pulse rep rate: 120 Hz
LCLS feedback model
Include Proportional gain, Integral gain, and Derivative gain (PID): Integral gain helps at the low frequency regime
Cascade scheme: we need to keep the off-diagonal elements in the M-matrix
Pulse rep rate: 120 Hz
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
Bode Plot (Bode Plot (E/E)E/E)Bode Plot (Bode Plot (E/E)E/E)
off
on
EE
EE
/
/log20 10
off
on
EE
EE
/
/log20 10
P:0.2; I:0.5P:0.2; I:0.5P:0.2P:0.2
0.0
/
/arg
off
on
EE
EE
Integral Gain helps!Integral Gain helps!
I:0.5I:0.5
Similar Bode PlotBode Plot for (I / II / I) Similar Bode PlotBode Plot for (I / II / I)
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
LCLS Feedback Performance (Use CSR LCLS Feedback Performance (Use CSR P / P)P / P)LCLS Feedback Performance (Use CSR LCLS Feedback Performance (Use CSR P / P)P / P)
feedback offfeedback off feedback on (Integral gain:0.5Integral gain:0.5)feedback on (Integral gain:0.5Integral gain:0.5) %50.0/
%;26.0/
std
EE
EE %50.0/
%;26.0/
std
EE
EE
%09.0/
%;0007.0/
std
EE
EE %09.0/
%;0007.0/
std
EE
EE
%5.10/
%;12.0/
std
II
II %5.10/
%;12.0/
std
II
II
%7.1564/
%;4.247/
std
II
II %7.1564/
%;4.247/
std
II
II
ps
ps
std 16.0
;003.0
t
t ps
ps
std 16.0
;003.0
t
t
ps
ps
std 4.1
;5.0
t
t ps
ps
std 4.1
;5.0
t
t
At undulator entranceAt undulator entrance
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
dd
IdFN
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Idee
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02
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Coherent Synchrotron RadiationCoherent Synchrotron RadiationCoherent Synchrotron RadiationCoherent Synchrotron Radiation
CSR as nondestructive diagnostic tool For a group of Ne electrons
CSR spectrum
CSR as nondestructive diagnostic tool For a group of Ne electrons
CSR spectrum
Form factor Form factor
2
2ˆ2
),,(
),,(
dxdydzezyxn
dxdydzeezyxnF
ikz
Rnikikz
with
1),,( dxdydzzyxn
Single electronSingle electron
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
Wake-induced Cubic termWake-induced Cubic termWake-induced Cubic termWake-induced Cubic term
Longitudinal phase-space before BC2 Longitudinal phase-space before BC2
Blue: only L2
Black: L2 + L1 (with BC1)
Red: L2 + L1+ wake (with parabolic dist.)
Wake with parabolic dist. leads to the double-horn
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
Wake for parabolic distributionWake for parabolic distributionWake for parabolic distributionWake for parabolic distribution
For a parabolic distribution, the induced wake is For a parabolic distribution, the induced wake is
032
300
0
22/3
510
3
633252
12120615158)(
s
z
a
csNeLZH
se
eHzV
z
z
and [V]
with
[V]
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
Wake-induced Cubic termWake-induced Cubic termWake-induced Cubic termWake-induced Cubic term
Longitudinal phase-space change due to BC2 Longitudinal phase-space change due to BC2
Blue: after BC2
Red: before BC2
Wake with parabolic dist. leads to the double-horn
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
Current profile after BC2Current profile after BC2Current profile after BC2Current profile after BC2 Wake-induced double-horn
structure Wake-induced double-horn
structure
With Laser-Heater
( )
Laser-Heater smears out the double-horn, however …
keV 47Em 21zm 21z
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
Bunch spectrum after BC2Bunch spectrum after BC2Bunch spectrum after BC2Bunch spectrum after BC2
Sharp-edge induces high freq. component Sharp-edge induces high freq. component Red: with Laser-Heater
( )
Black: Gaussian with same
Blue: Step [J. Galayda] with same
keV 47E
m 21z
m 21z
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
Integrated CSR PowerIntegrated CSR PowerIntegrated CSR PowerIntegrated CSR Power
Detector matters Detector mattersRed solid curve: Gaussian with same z
Black dashed curve: Step with same z
Red dots: Real with Laser-Heater
o
z m
8.41,8.40,8.39
11,21,32
2
2,
THz )6,54.0(f
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
Integrated CSR PowerIntegrated CSR PowerIntegrated CSR PowerIntegrated CSR Power Stay in the low frequency regime Stay in the low frequency regime
Red solid curve: Gaussian with same z
Black dashed curve: Step with same z
Red dots: Real with Laser-Heater
o
z m
8.41,8.40,8.39
11,21,32
2
2,
THz )4.0,24.0(f
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
Integrated CSR PowerIntegrated CSR PowerIntegrated CSR PowerIntegrated CSR Power
Stay in the low frequency regime Pyroelectric Detector? Detector with fixed , the integrated power
Stay in the low frequency regime Pyroelectric Detector? Detector with fixed , the integrated power
2
22
3/4
3/110
det
2
4
,3
2,
3
21063.3),(
z
z rad
WINP
with
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
DiscussionDiscussionDiscussionDiscussion
Given the jitter budget and the SLAC linac jitter, our calculation shows that a longitudinal phase space Feedback system is mandatory!!!
Studied the energy and bunch length feedbackLow frequency jitter is not hard to correctNeed understanding on a more realistic jitter modelNeed measurement from A-line?
CSR: a good candidate for the bunch length measurement; easy to be implemented into the feedback
Given the jitter budget and the SLAC linac jitter, our calculation shows that a longitudinal phase space Feedback system is mandatory!!!
Studied the energy and bunch length feedbackLow frequency jitter is not hard to correctNeed understanding on a more realistic jitter modelNeed measurement from A-line?
CSR: a good candidate for the bunch length measurement; easy to be implemented into the feedback
Juhao Wu
Feedback & CSR [email protected]
Oct. 12 – 13, 2004
Acknowledgement Acknowledgement Acknowledgement Acknowledgement
Collaboration with P. Emma
Help and discussion with L. Hendrickson, M. Hogan, Z. Huang, P. Krejcik, M. Ross, et al.
Thank committee for the invitation
Collaboration with P. Emma
Help and discussion with L. Hendrickson, M. Hogan, Z. Huang, P. Krejcik, M. Ross, et al.
Thank committee for the invitation