CSR micro-bunching in compressorsCSR micro-bunching in compressors Superconducting wiggler can reduce effectSuperconducting wiggler can reduce effect FEL gain evaluation after system trackingFEL gain evaluation after system tracking
CSR micro-bunching in compressorsCSR micro-bunching in compressors Superconducting wiggler can reduce effectSuperconducting wiggler can reduce effect FEL gain evaluation after system trackingFEL gain evaluation after system tracking
Paul EmmaPaul EmmaJanuary 17, 2002January 17, 2002
LCLSLCLS Tracking Studies Tracking Studies
LLNLLLNLLLNLLLNL
UCLUCLAA
UCLUCLAA
CSR WorkshopCSR Workshop
LCLS Accelerator and Compressor SchematicLCLS Accelerator and Compressor SchematicLCLS Accelerator and Compressor SchematicLCLS Accelerator and Compressor Schematic
(12/01/01)(12/01/01)
SLAC linac tunnelSLAC linac tunnel undulator hallundulator hall
Linac-0Linac-0L L =6 m=6 m
Linac-1Linac-1L L =9 m=9 m
rf rf = = 38°38°
Linac-2Linac-2L L =330 m=330 mrf rf = = 43°43°
Linac-3Linac-3L L =550 m=550 mrf rf = = 10°10°
BC-1BC-1L L =6 m=6 m
RR5656= = 36 mm36 mm
BC-2BC-2L L =22 m=22 m
RR5656= = 22 mm22 mm DL-2DL-2L L =66 m=66 mRR56 56 = 0 = 0
DL-1DL-1L L =12 m=12 mRR56 56 0 0
undulatorundulatorL L =120 m=120 m
7 MeV7 MeVz z 0.83 mm 0.83 mm 0.2 %0.2 %
150 MeV150 MeVz z 0.83 mm 0.83 mm 0.10 %0.10 %
250 MeV250 MeVz z 0.19 mm 0.19 mm 1.8 %1.8 %
4.54 GeV4.54 GeVz z 0.022 mm 0.022 mm 0.76 %0.76 %
14.35 GeV14.35 GeVz z 0.022 mm 0.022 mm 0.02 %0.02 %
...existing linac...existing linac
newnew
rfrfgungun
25-1a25-1a30-8c30-8c
21-1b21-1b21-1d21-1d XX
Linac-Linac-XXL L =0.6 m=0.6 mrfrf==
21-3b21-3b24-6d24-6d
BC2BC25.4 GeV5.4 GeV
BC1BC10.25 GeV0.25 GeV
undulatorundulator14.3 GeV14.3 GeV
LCLS Linac LayoutLCLS Linac Layout
before BC1before BC1= 250 MeV= 250 MeVzz 830 830 mm
before BC2before BC2= 4.5 GeV= 4.5 GeVzz 190 190 mm
after BC1after BC1= 250 MeV= 250 MeVzz 190 190 mm
after BC2after BC2= 4.5 GeV= 4.5 GeVzz 22 22 mm
under-compression of head under-compression of head & tail from 3& tail from 3rdrd-order term-order term
L2 wakes induce L2 wakes induce newnew 33rdrd-order correlation-order correlation
over-compression over-compression of head and tailof head and tail
* written by M. Borland, * written by M. Borland, ANL/APSANL/APS
Compression Evolution using Compression Evolution using Elegant*Elegant*
HEADHEAD
33rdrd-order energy-time correlation from injector-order energy-time correlation from injector
11stst, and 2, and 2ndnd-order correctable -order correctable with S-band and X-band RF…with S-band and X-band RF…
33rdrd-order term generated with space charge and -order term generated with space charge and ((ss) in gun-to-linac drift () in gun-to-linac drift (C. LimborgC. Limborg))
EE00 = 150 MeV = 150 MeV
33rdrd-order term remains…-order term remains…
22ndnd-order fit-order fit
energy ‘chirp’energy ‘chirp’
Smoothed Parmela dist. input to LCLSSmoothed Parmela dist. input to LCLS
NN = 2 = 2101066
plus temporal plus temporal smoothingsmoothing
at 150 MeV, before any bendsat 150 MeV, before any bends
CSR CSR ONON in in upstream bends upstream bends
(BC1, etc)(BC1, etc)
CSR CSR OFFOFF in in upstream bends upstream bends (BC1, etc)(BC1, etc)
LCLS bunch tracked to start of BC2LCLS bunch tracked to start of BC2
CSR in BC1 CSR in BC1 causes causes microbunching at microbunching at entrance to BC2entrance to BC2
……otherwise have otherwise have smooth dist. at smooth dist. at BC2 entranceBC2 entrance
cubic correlation cubic correlation term generates term generates head/tail spikes head/tail spikes at end of chicaneat end of chicane
SC wigglerSC wiggler
Add Super-Conducting Add Super-Conducting wiggler prior to BC2 to wiggler prior to BC2 to increase incoherent increase incoherent energy spread (×10)energy spread (×10)
wiggler field limited by wiggler field limited by -function-function
4 T4 T
10 cm10 cm
20 cm20 cm5 cm5 cm
20 cm20 cm
90 cm90 cm
EE00 = 4.54 GeV = 4.54 GeV
EE//EE00 3×10 3×1055
xx//xx00 7% 7%
At BC2:At BC2:
EE11 = 14.3 GeV = 14.3 GeV
zz0 0 195 195 mm
zz1 1 22 22 mm
zz00zz11EE//EE11 8.4×10 8.4×1055
At Undulator:At Undulator:
Superconducting Wiggler in Superconducting Wiggler in LCLSLCLS……
BC2 chicaneBC2 chicane
Using Stupakov Using Stupakov CSR model (based CSR model (based on Saldin et. al.) on Saldin et. al.) and and ElegantElegant trackingtracking
Superconducting wiggler Superconducting wiggler OFFOFF
CSR may still be CSR may still be over-estimated in over-estimated in present trackingpresent tracking
SC-wiggler SC-wiggler OFFOFF
SC-wiggler SC-wiggler ONON
LCLS Distribution After BC2 ChicaneLCLS Distribution After BC2 Chicane
ss = 24.8 = 24.8 mm
EE//EE00 = 0.726 % = 0.726 %
bunch headbunch head
EE00 = 4.54 GeV = 4.54 GeV
(SC-wiggler (SC-wiggler ONON, CSR , CSR ONON in upstream bends) in upstream bends)
wiggler wiggler 3 3101055 incoherent energy incoherent energy spreadspread
LCLS Distribution After BC2 ChicaneLCLS Distribution After BC2 Chicane
ss = 24.8 = 24.8 mm
EE//EE00 = 0.736 % = 0.736 %
bunch headbunch head
33101066 incoherent incoherent energy spreadenergy spread
EE00 = 4.54 GeV = 4.54 GeV
(SC-wiggler (SC-wiggler OFFOFF, CSR , CSR ONON in upstream bends) in upstream bends)
LCLS Distribution After BC2 ChicaneLCLS Distribution After BC2 Chicane
ss = 24.8 = 24.8 mm
EE//EE00 = 0.716 % = 0.716 %
bunch headbunch head
wiggler wiggler 3 3101055 incoherent energy incoherent energy spreadspread
EE00 = 4.54 GeV = 4.54 GeV
(SC-wiggler (SC-wiggler ONON and CSR and CSR OFFOFF in upstream bends) in upstream bends)
no CSR in no CSR in upstream bendsupstream bends
LCLS Distribution After BC2 ChicaneLCLS Distribution After BC2 Chicane
ss = 24.8 = 24.8 mm
EE//EE00 = 0.736 % = 0.736 %
bunch headbunch head
33101066 incoherent incoherent energy spreadenergy spread
EE00 = 4.54 GeV = 4.54 GeV
no CSR in no CSR in upstream bendsupstream bends
(SC-wiggler (SC-wiggler OFFOFF, CSR , CSR OFFOFF in upstream bends) in upstream bends)
Final Final xx--xx Phase Space ( Phase Space (LCLSLCLS input) input)
//00 2.5 2.5
Slice Mismatch and Oscillation (LCLS Input)Slice Mismatch and Oscillation (LCLS Input)
Slice Emittance (LCLS)Slice Emittance (LCLS)
LCLS BC2 CSR-integrated-wake (tracked dist.)LCLS BC2 CSR-integrated-wake (tracked dist.)
Transverse RF Transverse RF deflector used to deflector used to diagnose ‘slice’ diagnose ‘slice’ emittance after BC2emittance after BC2
screen at 6.2 MeV after BC2 screen at 6.2 MeV after BC2 with transverse-RF with transverse-RF OFFOFF
Transverse RF Transverse RF ONON ( (VV = 20 MV) = 20 MV)
Sliced Beam After Injector and Linac TrackingSliced Beam After Injector and Linac Tracking
osc-amp/osc-amp/ mismatchmismatch
xx
yy
( )0 0 02 /2z bg aa gbº - +
( )1/222
4x x
x x
x x xR
a b
b e
ì üï ï¢+ +ï ïï ïº í ýï ïï ïï ïî þ xx yy
LLGG < 4 m < 4 m
Ming-Xie Ming-Xie methodmethod
New awareness of CSR micro-bunching and new New awareness of CSR micro-bunching and new design optimizationdesign optimization
Projected emittance doubles over linac, but slice Projected emittance doubles over linac, but slice parameters allow parameters allow LLGG < 4 m < 4 m
Projected emittance growth presents a diagnostics Projected emittance growth presents a diagnostics and tuning challenge (use transverse RF)and tuning challenge (use transverse RF)
Stability studies and Stability studies and GenesisGenesis results results (see M. Borland talk…)(see M. Borland talk…)
SummarySummary
