Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
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
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
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
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
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
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)
We need a feedback systemWe need a feedback system Courtesy of P. Emma
Courtesy of P. Emma
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
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
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
LCLS Accelerator SystemLCLS Accelerator SystemLCLS Accelerator SystemLCLS Accelerator System
Linac
RF
Wakefield (structure wake)
Bend (2rd order map)
Linac
RF
Wakefield (structure wake)
Bend (2rd order map)
]cos[ kzeVEE
0/2
0)( szea
cZzw
56656 TRzz
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
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) Bunch length Peak current: I1 (at BC1), I2 (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) Bunch length Peak current: I1 (at BC1), I2 (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
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
LCLS Feedback AlgorithmLCLS Feedback AlgorithmLCLS Feedback AlgorithmLCLS Feedback Algorithm
MC
d
d
V
dV
d
V
dV
V
dV
d
d
V
dV
d
V
dV
V
dV
d
EdE
d
EdE
VdV
EdE
d
EdE
VdV
EdE
VdV
EdE
d
IdI
VdVI
dI
d
IdI
VdVI
dI
VdVI
dI
d
EdE
VdVE
dE
d
EdE
VdVE
dE
VdVE
dE
d
IdI
VdVI
dI
VdVI
dI
d
EdE
VdVE
dE
VdVE
dEVdV
EdE
E
dE
I
dI
E
dE
I
dI
E
dE
E
dE
M
3
2
2
1
1
0
3
2
2
1
1
0
3
3
2
3
2
3
1
3
1
3
0
3
2
2
2
2
1
2
1
2
0
2
2
2
2
2
1
2
1
2
0
2
1
1
1
1
0
1
1
1
1
1
0
1
0
0
3
2
2
1
1
0
0
0
000
000
00000
MCO MCO OGMCC 1 beforeafterOGMCC 1 beforeafter
We are linearlinear
We are linearlinear
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
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
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
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 0.0
/
/arg
off
on
EE
EE
Integral Gain helps!Integral Gain helps!
I:0.5I:0.5
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
Bode Plot (Bode Plot (I/I)I/I)Bode Plot (Bode Plot (I/I)I/I)
off
on
II
II
/
/log20 10
off
on
II
II
/
/log20 10
P:0.2; I:0.5P:0.2; I:0.5P:0.2P:0.2
0.0
/
/arg
off
on
II
II 0.0
/
/arg
off
on
II
II
Integral Gain helps!Integral Gain helps!
I:0.5I:0.5
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
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
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
[%])(
)1(1.060
)27.1sin(1.0)208.0sin(
1, H
randn
step
step
N
jj tt
ttt
V
dV
][)(
)1(1.060
)27.1sin(1.0)208.0sin(
1,
H
randn
step
step
N
jjtt
tttd
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 with stepstep :)( Nt
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
LCLS Feedback PerformanceLCLS Feedback PerformanceLCLS Feedback PerformanceLCLS Feedback Performancefeedback offfeedback off feedback on (Integral gain:0.5Integral gain:0.5)feedback on (Integral gain:0.5Integral gain:0.5)
%60.0/
%;21.0/
std
EE
EE %60.0/
%;21.0/
std
EE
EE
%09.0/
%;0007.0/
std
EE
EE %09.0/
%;0007.0/
std
EE
EE
%5.8/
%;10.0/
std
II
II %5.8/
%;10.0/
std
II
II %4.608/
%;0.169/
std
II
II %4.608/
%;0.169/
std
II
II
ps
ps
std 15.0
;003.0
t
t ps
ps
std 15.0
;003.0
t
t
ps
ps
std 6.1
;5.0
t
t ps
ps
std 6.1
;5.0
t
t
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
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
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
Linac Wake/ImpedanceLinac Wake/ImpedanceLinac Wake/ImpedanceLinac Wake/Impedance
(capacitive)
VV(( ss
)/M
V/n
C/m
)/M
V/n
C/m
ss//ssFWFW
1 mm1 mm
500 500 mm
250 250 mm
100 100 mm 50 50 mm 25 25 mm
s
Linac wake Green function (K. Bane)
SLACSLAC S-Band: S-Band:ss0 0 1.32 mm 1.32 mmaa 11.6 mm 11.6 mmss < ~6 mm < ~6 mm
To first order in 1/k
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
Wake for parabolic distributionWake for parabolic distributionWake for parabolic distributionWake for parabolic distribution
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]
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
Wake-induced Cubic termWake-induced Cubic termWake-induced Cubic termWake-induced Cubic term 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 Wake with parabolic dist. leads to the double-horn
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
Wake-induced Cubic termWake-induced Cubic termWake-induced Cubic termWake-induced Cubic term Longitudinal phase-space change due to BC2
Blue: after BC2
Red: before BC2
Wake with parabolic dist. leads to the double-horn Wake with parabolic dist. leads to the double-horn
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
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
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
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
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
CSR spectrum after BC2CSR spectrum after BC2CSR spectrum after BC2CSR spectrum after BC2
ISR power spectrum from a bending magnetfor an azimuthal milliradian of the electron orbit () and integrated over all the vertical angles
ISR power spectrum from a bending magnetfor an azimuthal milliradian of the electron orbit () and integrated over all the vertical angles
];[3
4
][][][1042.8)(
3
3/73/18
o
c A
IθP
for
mmAmpm /mm][W/mradisr
).()(2 isrcsr /mm][W/mrad Hence, PFNθP e
(m)(m) z z (mm)(mm) (mm)(mm) f (THz)f (THz) IIpeak peak (A)(A) PPcsrcsr(kW)(kW)
BC1BC1 2.42.4 0.190.19 0.190.19 1.61.6 400400 0.260.26
BC2BC2 14.514.5 0.0210.021 0.0210.021 14.314.3 34003400 75.275.2
Assuming |F|2=1%, /=1%, for 1 nC charge bunch Assuming |F|2=1%, /=1%, for 1 nC charge
bunch
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
Black: with Laser-Heater
( )
Red: without Laser-Heater
( )
Blue: Gaussian with same ( )
Green: Step with same ( )
keV 47E
keV 3E
m 21z
m 21z
CSR spectrum after BC2CSR spectrum after BC2CSR spectrum after BC2CSR spectrum after BC2 Fix detector Fix detector
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
CSR spectrum after BC2CSR spectrum after BC2CSR spectrum after BC2CSR spectrum after BC2 Fix detector Fix detector 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
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
Instability mechanismInstability mechanism
t
Energybi bf >> bi or G= bf/ bi >> 1k
R
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
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
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
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
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
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
Black: with microbunching (20% at 100/40 m)
Red: without microbunching
Blue: Gaussian with same ( )
Green: Step with same ( )
CSR spectrum after BC2CSR spectrum after BC2CSR spectrum after BC2CSR spectrum after BC2 Fix detector Fix detector
m 21z
m 21z
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
Black: with microbunching (20% at 100/40 m)
Red: without microbunching
Blue: Gaussian with same ( )
Green: Step with same ( )
CSR spectrum after BC2CSR spectrum after BC2CSR spectrum after BC2CSR spectrum after BC2 Fix detector Fix detector
m 21z
m 21z
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
Microbunching after BC2Microbunching after BC2Microbunching after BC2Microbunching after BC2
Current profile with microbunching at 500/40 m Current profile with microbunching at 500/40 m
Black: with microbunching(20% at 500/40 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
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
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
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
Black: with microbunching (20% at 500/40 m)
Red: without microbunching
Blue: Gaussian with same ( )
Green: Step with same ( )
CSR spectrum after BC2CSR spectrum after BC2CSR spectrum after BC2CSR spectrum after BC2 Fix detector Fix detector
m 21z
m 21z
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
Black: with microbunching (20% at 500/40 m)
Red: without microbunching
Blue: Gaussian with same ( )
Green: Step with same ( )
CSR spectrum after BC2CSR spectrum after BC2CSR spectrum after BC2CSR spectrum after BC2 Fix detector Fix detector
m 21z
m 21z
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
Microbunching after BC1Microbunching after BC1Microbunching after BC1Microbunching after BC1
Current profile with microbunching at 500/4 m Current profile with microbunching at 500/4 m
Black: with microbunching(5% at 500/4 m)
Red: without microbunching
m 190zm 190z
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
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
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
Black: with microbunching (5% at 500/4 m)
Red: without microbunching
Blue: Gaussian with same ( )
CSR spectrum after BC1CSR spectrum after BC1CSR spectrum after BC1CSR spectrum after BC1 Fix detector Fix detector
m 190z
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
Black: with microbunching (5% at 500/4 m)
Red: without microbunching
Blue: Gaussian with same ( )
CSR spectrum after BC1CSR spectrum after BC1CSR spectrum after BC1CSR spectrum after BC1 Fix detector Fix detector
m 190z
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
DiscussionDiscussionDiscussionDiscussion
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
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
To-do listTo-do listTo-do listTo-do list
Implement the CSR-based bunch length diagnostic into the feedback simulation code
Implement the timing feedback
Sort out the real white noise component
Create a more realistic jitter model
Need to weight gain differently for different loop
Implement the CSR-based bunch length diagnostic into the feedback simulation code
Implement the timing feedback
Sort out the real white noise component
Create a more realistic jitter model
Need to weight gain differently for different loop
Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004Miniworkshop on XFEL Short Bunch, SLAC, July 26 – 30, 2004
Juhao Wu, SLACJuhao Wu, SLAC
Feedback and CSRFeedback and CSR
[email protected]@SLAC.Stanford.EDU
Acknowledgement Acknowledgement Acknowledgement Acknowledgement
Collaboration with P. Emma, L. Hendrickson, Z. Huang, P. Krejcik, et al.
Thank committee for the workshop and invitation
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