Transcript S2E (start-to-end) Simulations at DESY T. Limberg

S2E (start-to-end) Simulations
at DESY
T. Limberg
TESLA Collaboration Meeting in Frascati, May 2003
Introduction and earlier results
Tools
Status S2E at DESY
Workshop at Zeuthen
Introduction
In SASE-FEL’s there are no ‘amnesia
devices’ like damping rings; the beam in
the undulator still remembers the gun
Changes in the beam distribution add up
in a complicated manner because of CSR
fields and wake fields
Exact phase space distribution must be
fed into an FEL code to predict machine
performance
Integrated Modeling of the TESLA X-ray FEL
T. Limberg and Ph. Piot, DESY, Hamburg, Germany
Proceedings of the 2001 Particle Accelerator Conference, Chicago
M. Borland et al,
P. Emma for LCLS,....
TTF-II Compression System
Two stage compression to avoid space charge emittance dilution on one
hand and reduce non-linear effects from the RF system on the other.
BC2
BC2
BC3
BC3
Longitudinal Phase Space Evolution
Transverse emittance, peak current, mean energy of
longitudinal slices and energy spread along the bunch
at the undulator entrance (ca. 60% of the bunch
saturates @ l=6nm)
(s > 0 corresponds to the bunch tail)
Simulation Tools
Tracking Codes with simple 1D CSR Model:
elegant,...
Tracking Codes with Space Charge:
– 2D: ASTRA, PARMELA
– 3D: GPT, (ASTRA)
CSR 3D (includes space charge, but limited to a
few thousand sub-bunches):
– TraFiC4
– M. Dohlus tracking code
FEL codes (GENESIS...)
M. Dohlus’ Self consistent Tracking Code
Fsc  READPRN( field_sc( j) )
Fn  READPRN( field_ns cj
( ))
Xs c  READPRN( phas _s cj
( ))
Xn  READPRN( phas _ns (cj) )
i  i1
1 10
5
2000
0
Fsci 0
Fni 0
1000
Fsci 1
1 10
5
2 10
5
3 10
0
Fni 1
1000
5
1 10
4
5 10
0
5 10
Xsci 2  Xni 2
5
5
1 10
2000
4
1 10
4
5 10
5
0
5 10
Xsci 2  Xni 2
1 10
5
4
i  i
0.01
Xsci 3X0i 3
Xni 3X0i 3
Xsci 0
0
4 10
4
2 10
4
Xni 0
0
0.01
4
1 10
2 10
5
0
5 10
5
Xsci 2  Xni 2
1 10
2 10
4
2 10
4
0
Xsci 1
Xni 1
5 10
2 10
4
4 10
4
2 10 1 10
4
4
4
4
0 1 10 2 10
Xsci 0  Xni 0
1 10
4
5 10
0
5 10
Xsci 2  Xni 2
5
5
1 10
4
0
Xsci 1
Xni 1
4
2 10
4
4 10
4
1 10
4
5 10
0
5 10
Xsci 2  Xni 2
5
5
1 10
4
4
TraFiC4 Self consistent Tracking
Divergence Problem understood
Test Scenario:
Simulation Parameters:
q=1nC, Imax=500A,
Sub Bunch Length: 2.5e-6m
Beam Line: 1m long dipole with 2.77degree
deflection angle and a subsequent drift of 3m.
Comparison of longitudinal Phase Space
M. Dohlus’ self-consistent
tracking code
TraFiC4 with new selfconsistent Algorithm
(F. Stulle, A.Kabel)
TraFiC4 with old leapfrog Algorithm
Increasing the Transverse Size
of the Sub-Bunches
Sub-BunchRadius: 2.5 um
Sub-BunchRadius: 5 um
Sub-BunchRadius: 25 um
S2E Simulation Schemes
elegant (1D CSR, no spac e c harge )
T4
elegant T4 elegant
T4
ASTRA
T4
ASTRA
T4
GPT
T4
GPT
T4 means Tra FiC4
TTF-II Starting Scenario (l=30nm)
ACC 4 on, ACC 5 off,
ACC 6 not yet installed
BC2
BC2
BC3
Transverse emittance, current, energy spread along the
bunch and longitudinal phase space at exit of BC-3
(including CSR effects in 1-d model) (E. Schneidmiller)
Transverse emittance, current, energy spread along the
bunch and longitudinal phase space at entry of undulator
(including space charge effects in upstream drift)
Status
S2E with ASTRA, TraFiC4 and elegant done for
– X-FEL (old integrated scheme)
– TTF2 design case with 3rd harmonic RF
S2E for realistic start up phase ofn TTF2:
–
–
–
–
Elegant input decks done (Nina)
S2E with ASTRA and elegant under way (J.P. Carneiro)
GPT set up for TTF2 tracking (F. Stulle)
TraFiC4 problem with self consistent tracking of very short subbunches seems fixed (necessary for modelling of extremely spiked
longitudinal beam profiles)
– M. Dohlus code will be further developed as test bed for new
algorithms
– Phase space manipulating codes to hand the beam back and
forth between the codes have to be revived (and improved)
– Need to explore parameter space (only 1 nC case up to now)
S2E Workshop
August 18-22, 2003 at DESY-Zeuthen
Chair: J. Galeyda, J. Rossbach
(Berlin, GERMANY)
Contact: Christel Oevermann (DESY, Hamburg)
www.desy.de/s2e
Program Monday
08:30Physics of PARMELA (0.5 h)
Physics of ASTRA (0,5 h) (K. Floettmann)
New Developments in GPT
10:00 Coffee
Calculations of LCLS injector with ASTRA and comparison with SLAC
calculation
Calculation of XFEL injector with PARMELA and comparison with DESY
calculation
Calculation of one of the two above with HOMDYN or TREDI?
11:30 - 15:30 Lunch break
Injector parameter measurements and simulations so far Physics not yet
(properly?) included in calculations
Expected jitter and temporal structures in bunch profiles; gain vs.
modulation wavelength for the Injector (i.e. if the laser is modulated, what is
the intensity modulation of the electron bunch out of the injector?)
19:00
Dinner
Program Tuesday
CSR calculations 8:30 Chicane modeling 1-D vs. 3-D
(M. Dohlus) latest results
10:00 Coffee
Modulation amplification gains and possible 'seeding'
sources
Gain curve for complete TTF-2 (F. Stulle)
Influence of shielding on gain
11:30-15:30 Lunch break
CSR measurements and simulation so far
Physics not yet (properly?) included in calculations
Expected jitter due to CSR effects
19:00 Dinner
Program Wednesday
Morning: FEL simulation codes and
calculations
11:30-15:30: Lunch break
Afternoon: Excursion
Program Thursday
S2E calculations:
8:30 LCLS X-FEL
10:00 Coffee
TTF-II
Italian machines?
11:30-15:30: Lunch break
Comparison of S2E calculations and performance of
existing machines
Physics not yet (properly?) included in calculations
19:00 Dinner
Program Friday
Morning:
Simulations of Stability Issues and Tuning
strategies
11:30-15:30: Lunch break
Afternoon:
Contingency, Discussion of further work,
Closing remarks