S2E (start-to-end) Simulations at DESY

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S2E (start-to-end) Simulations at DESY

• T. Limberg
• TESLA Collaboration Meeting in Frascati, May 2003

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• Introduction and earlier results
• Tools
• Status S2E at DESY
• Workshop at Zeuthen

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Introduction

• In SASE-FELs 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

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Integrated Modeling of the TESLA X-ray FELT.
Limberg and Ph. Piot, DESY, Hamburg,
GermanyProceedings of the 2001 Particle
Accelerator Conference, Chicago
M. Borland et al, P. Emma for LCLS,....
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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
BC3
BC2
BC3
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Longitudinal Phase Space Evolution
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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 _at_ l6nm)(s gt 0 corresponds
to the bunch tail)
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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...)

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M. Dohlus Self consistent Tracking Code
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TraFiC4 Self consistent Tracking Divergence
Problem understood

• Test Scenario
• Simulation Parameters
• q1nC, Imax500A,
• Sub Bunch Length 2.5e-6m
• Beam Line 1m long dipole with 2.77degree
  deflection angle and a subsequent drift of 3m.

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Comparison of longitudinal Phase Space
M. Dohlus self-consistent tracking code
TraFiC4 with new self-consistent Algorithm(F.
Stulle, A.Kabel)
TraFiC4 with old leap-frog Algorithm
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Increasing the Transverse Size of the Sub-Bunches
Sub-Bunch-Radius 2.5 um
Sub-Bunch-Radius 5 um
Sub-Bunch-Radius 25 um
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S2E Simulation Schemes
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TTF-II Starting Scenario (l30nm)
BC2
BC2
BC3
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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)
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Transverse emittance, current, energy spread
along the bunch and longitudinal phase space at
entry of undulator (including space charge
effects in upstream drift)
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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 sub-bunches 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)

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S2E Workshop

• August 18-22, 2003 at DESY-Zeuthen
• Chair J. Galeyda, J. Rossbach
• (Berlin, GERMANY)

www.desy.de/s2e
Contact Christel Oevermann (DESY, Hamburg)
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Program Monday

• 0830Physics of PARMELA (0.5 h) 
• Physics of ASTRA (0,5 h) (K. Floettmann) 
• New Developments in GPT  
• 1000   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?  
• 1130 - 1530 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?)
• 1900         Dinner 

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Program Tuesday

• CSR calculations 830  Chicane modeling    1-D
  vs. 3-D (M. Dohlus) latest results   
• 1000 Coffee          
• Modulation amplification gains and possible
  'seeding' sources
• Gain curve for complete TTF-2 (F. Stulle)
• Influence of shielding on gain 
• 1130-1530 Lunch break 
• CSR measurements and simulation so far
• Physics not yet (properly?) included in
  calculations   
• Expected jitter due to CSR effects  
• 1900 Dinner   

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Program Wednesday

• Morning FEL simulation codes and calculations
• 1130-1530 Lunch break 
• Afternoon Excursion

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Program Thursday

• S2E calculations
• 830 LCLS  X-FEL
• 1000 Coffee
• TTF-II 
• Italian machines?
• 1130-1530 Lunch break 
• Comparison of S2E calculations and performance of
  existing machines
• Physics not yet (properly?) included in
  calculations
• 1900 Dinner

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Program Friday

• Morning
• Simulations of Stability Issues and Tuning
  strategies
• 1130-1530 Lunch break
• Afternoon
• Contingency, Discussion of further work, Closing
  remarks