Transcript Performance Analysis using Ginger

GINGER Results for the
NEW LCLS Undulator Configuration
William M. Fawley
Lawrence Berkeley National Laboratory
Presented to LCLS Undulator Parameter Workshop
24 October 2003
Outline of GINGER Study
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First determine best K for peak gain for monochromatic
cases at l=1.5, 0.15, and 0.1 nm
Examine taper performance for SASE runs at 0.15-nm,
11.47 GeV base case
SASE performance at 0.1 nm with E=14.04 GeV
Study of taper sensitivity for 1.5 nm case
No wake effects examined --- need ELEGANT timedependent beam parameters
Some additional S2E SASE results for ICFA03 study –
envelope reconstruction looks surprisingly good
Study Parameters/Bottom-Line Results
l
E
FEL r
Lgain
Zsat
Psat
Pmax
0.1 14.04 GeV 4.27E-4
8.4
116
3.5 GW
7 GW
0.15
11.46
5.23E-4
6.2
92
6.0 GW
48 GW
1.5
3.63
1.6E-3
1.86
30
12 GW
84 GW
SASE results; best taper for 0.15, 1.5 nm
Effects of Linear K Taper on LCLS
SASE Output Power at l=0.15nm
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GINGER SASE runs
New drift space/undulator
configuration
Quadrupole strengths &
Twiss parameters from
H.-D. Nuhn
Taper begins at z=75 m;
simple linear decrease with
z (including drift spaces)
Max power obtained around
0.3 to 0.4% taper;
excessively large tapers
appear to lead to rapid
debunching with z and thus
reduced gain
Bunching and Inverse Bandwidth vs Z:
0.15-nm LCLS
GINGER SASE runs for new LCLS drift
space/undulator configuration
SASE Results at 0.1-nm Wavelength
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No taper
“1st” saturation at ~110 m
Output power ~6 GW
No obvious anomalies --but little margin for any
beam degradation
1.5-nm Taper Results
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1.5 nm option is a “cake-walk” for LCLS parameters
“1st” saturation at ~30 m; simple linear tapering begins at z=25 m
Tapering increases power over 6-fold to > 80 GW
60 m of undulator gives most of output power
More “intelligent” tapers probably could increase power to >100 GW
New GINGER Results for ICFA03
“2nd-Order” Simulation Study
• Extension of results for
ICFA03-Zeuthen S2E study
for LCLS
• Full SASE simulation
extended over full beam
head region
- results low-pass filtered
in time (original resolution = 12 attoseconds)
• In regions where 5D
distribution is “simple”,
full SASE and envelope
reconstruction agree
surprisingly well
• Similar runs underway for
wake case
(CSR but no wake fields)
Output P for SASE;
peak P(z) for no slippage cases
Where might we go from here?
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Need ELEGANT runs with/without CSR effects to produce
time-dependent 5D distributions at undulator entrance
Examine temporal sensitivity of P(z) to taper
Examine “
“ to wakes
One optimization criterion is maximizing product of power
times the inverse bandwidth (at least for experiments in
which monochromatization will be done)
See if results with taper are more sensitive to undulator
errors, beam offset/pointing errors
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Perhaps greater sensitivity to phase jitter but does deeper
ponderomotive well help?
Develop taper algorithm for undulator with drift spaces &
consider effects of “spiky” SASE P(t)