Sensitivity Studies for the LCLS Photoinjector beamline

1
Sensitivity Studies for the LCLS Photoinjector
beamline C. Limborg, P.Bolton, D.H. Dowell,
S.Gierman, J. Schmerge SLAC, MS 69 , 2275 Sand
Hill Road, Menlo Park CA 94025 USA

• Project Performance Goal
• ?projected lt 1.2 mm.mrad
• ?slice lt 1.0 mm.mrad for 80 slices out of 100
• ?slice (80) projected emittance for the core
  80 slices
• for 1nC, 10ps pulse at 150 MeV,in the presence of
  jitter errors at 120Hz repetition rate

Nominal Tuning Thermal emittance of 0.72
mm.mrad Finite rise time of 0.7ps (from 10-90
level)
PARMELA Simulations Varying Single Parameter
Alignment
Alignment Effects of Transverse Wakefields in
Linac Sections
Effects of

Effects of
Wakefields


m

m
Position
150
m maximum
Position
150
m maximum

m
Position
150
m maximum
Angular 0.12
mrad
Angular 0.12
mrad
Angular 0.12
mrad
m
m
With alignment steering those requirements
are easily met (B
With alignment steering those requirements
are easily met (B
PM resolution 20
PM resolution 20
m )
m )
m
With alignment steering those requirements
are easily met (B
PM resolution 20
m )
Alignment Laser Position Steering
Alignment Laser Position Steering
Alignment Laser Position Steering
Creates offset and angle of bunch
Creates offset and angle of bunch
Creates offset and angle of bunch
Creates head
-
tail
centroids
offsets and angles
Creates head
-
tail
centroids
offsets and angles
Creates head
-
tail
centroids
offsets and angles
Creates slice
Creates slice
emittance
emittance
growth
growth
Creates slice
emittance
growth
Criteria
Criteria
Criteria
ge
ge
(80) at entrance
Linac
not increase by more than 5
(80) at entrance
Linac
not increase by more than 5
ge
(80) at entrance
Linac
not increase by more than 5
slice
slice
slice
m
m
Head
-
tail
centroid
offset less than 100
m
Head
-
tail
centroid
offset less than 100
m
m
Head
-
tail
centroid
offset less than 100
m
m
m
Result 100
m
Result 100
m
m
Result 100
m
Laser Performances
Longitudinal Space Charge Instability
A modulation on top of the flat part of the laser
temporal profile can generate some
micro-structures in the longitudinal phase space
which can then be amplified by the longitudinal
space charge force. The mechanism of this
instability is based on the amplification of
plasma oscillation.