Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004 Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004 Juhao Wu, SLAC Juhao Wu, SLAC Feedback and CSR Feedback and CSR 1 [email protected][email protected]LCLS Feedback Study and CSR as Diagnostic Tool Juhao Wu Juhao Wu Stanford Linear Accelerator Center Stanford Linear Accelerator Center ICFA Miniworkshop on XFEL Short Bunch Measurement and Timing, SLAC July 29, 2004 Linac Coherent Light Source (LCLS) accelerator system Linac Coherent Light Source (LCLS) accelerator system Jitter model Jitter model Feedback model Feedback model Coherent Synchrotron Radiation (CSR) as diagnostic tool Coherent Synchrotron Radiation (CSR) as diagnostic tool Bunch length: Gaussian and double-horn structure Bunch length: Gaussian and double-horn structure Microbunching Microbunching Discussion Discussion
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Linac Coherent Light Source (LCLS) accelerator system Jitter model Feedback model
LCLS Feedback Study and CSR as Diagnostic Tool Juhao Wu Stanford Linear Accelerator Center ICFA Miniworkshop on XFEL Short Bunch Measurement and Timing, SLAC July 29, 2004. Linac Coherent Light Source (LCLS) accelerator system Jitter model Feedback model - PowerPoint PPT Presentation
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Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao WuJuhao WuStanford Linear Accelerator CenterStanford Linear Accelerator Center
ICFA Miniworkshop on XFEL Short Bunch Measurement and Timing, SLACJuly 29, 2004
LCLS Feedback Study and CSR as Diagnostic Tool
Juhao WuJuhao WuStanford Linear Accelerator CenterStanford Linear Accelerator Center
ICFA Miniworkshop on XFEL Short Bunch Measurement and Timing, SLACJuly 29, 2004
Linac Coherent Light Source (LCLS) accelerator system Linac Coherent Light Source (LCLS) accelerator system Jitter modelJitter model Feedback modelFeedback model
Coherent Synchrotron Radiation (CSR) as diagnostic toolCoherent Synchrotron Radiation (CSR) as diagnostic tool Bunch length: Gaussian and double-horn structureBunch length: Gaussian and double-horn structure MicrobunchingMicrobunching
DiscussionDiscussion
Linac Coherent Light Source (LCLS) accelerator system Linac Coherent Light Source (LCLS) accelerator system Jitter modelJitter model Feedback modelFeedback model
Coherent Synchrotron Radiation (CSR) as diagnostic toolCoherent Synchrotron Radiation (CSR) as diagnostic tool Bunch length: Gaussian and double-horn structureBunch length: Gaussian and double-horn structure MicrobunchingMicrobunching
DiscussionDiscussion
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 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
LCLS Accelerator System Jitter MeasurementLCLS Accelerator System Jitter MeasurementLCLS Accelerator System Jitter MeasurementLCLS Accelerator System Jitter Measurement
Courtesy of P. Emma
Courtesy of P. Emma
Peaks around 0.08 and 1.7 Hz
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Coherent Synchrotron RadiationCoherent Synchrotron RadiationCoherent Synchrotron RadiationCoherent Synchrotron Radiation CSR as nondestructive diagnostic tool For a group of Ne electrons
CSR spectrum
dd
IdFN
dd
Idee
dd
Id
e
N
j
c
Rnitie
j
j
02
22
02
2
1
ˆ2
Form factor
2
2ˆ2
),,(
),,(
dxdydzezyxn
dxdydzeezyxnF
ikz
Rnikikz
with
1),,( dxdydzzyxn
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Current profile after BC2Current profile after BC2Current profile after BC2Current profile after BC2 Wake-induced double-horn structure Wake-induced double-horn structure
Black: with Laser-Heater
( )
Red: without Laser-Heater
( )
Laser-Heater smears out the double-horn, however … Laser-Heater smears out the double-horn, however …
keV 47E
keV 3E
m 21zm 21z
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 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 Black: with
Laser-Heater
( )
Red: without Laser-Heater
( )
Blue: Gaussian with same ( )
Green: Step with same ( )
keV 47E
keV 3E
m 21z
m 21z
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Initial density modulation due to drive uv laser ripple energy modulation through long. impedance Z(k), Energy modulation density modulation by a chicane Growth of slice energy spread / emittance!
Initial density modulation due to drive uv laser ripple energy modulation through long. impedance Z(k), Energy modulation density modulation by a chicane Growth of slice energy spread / emittance!
t
Current modulation
1% 10%Gain=10
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Microbunching after BC2Microbunching after BC2Microbunching after BC2Microbunching after BC2 Current profile with microbunching at 100/40 m Current profile with microbunching at 100/40 m
Black: with microbunching(20% at 100/40 m)
Red: without microbunching
m 21zm 21z
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Bunch spectrum after BC2Bunch spectrum after BC2Bunch spectrum after BC2Bunch spectrum after BC2 Microbunching inf. in the bunch spectrum Microbunching inf. in the bunch spectrum
Black: with microbunching (20% at 100/40 m)
Red: without microbunching
Blue: Gaussian with same ( )
Green: Step with same ( )
m 21z
m 21z
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Bunch spectrum after BC2Bunch spectrum after BC2Bunch spectrum after BC2Bunch spectrum after BC2 Microbunching inf. in the bunch spectrum Microbunching inf. in the bunch spectrum
Black: with microbunching (20% at 500/40 m)
Red: without microbunching
Blue: Gaussian with same ( )
Green: Step with same ( )
m 21z
m 21z
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Bunch spectrum after BC1Bunch spectrum after BC1Bunch spectrum after BC1Bunch spectrum after BC1 Smooth parabolic distribution Smooth parabolic distribution
Black: with microbunching (5% at 500/4 m)
Red: without microbunching
Blue: Gaussian with same ( )
m 190z
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Given the jitter budge and the experiment measurement, a Feedback system is mandatory!!!So far, studied the energy and bunch length feedback
Low frequency jitter is not hard to correctHowever, the white noise is hard to deal with; need sort out what is the real white noise content
P. Emma’s ``too’’ new discovery about the timing jitter 1-to-1 transfer necessaries one more timing feedback CSR: a good candidate for the bunch length measurement; needed for the feedback; however
The double-horn structure complicates situationMicorbunching easier to be detected at BC1, because
The double-horn structure complicates situation
Given the jitter budge and the experiment measurement, a Feedback system is mandatory!!!So far, studied the energy and bunch length feedback
Low frequency jitter is not hard to correctHowever, the white noise is hard to deal with; need sort out what is the real white noise content
P. Emma’s ``too’’ new discovery about the timing jitter 1-to-1 transfer necessaries one more timing feedback CSR: a good candidate for the bunch length measurement; needed for the feedback; however
The double-horn structure complicates situationMicorbunching easier to be detected at BC1, because
The double-horn structure complicates situation
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004