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. BC2BC3 BC2BC3

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 =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

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 self- consistent Algorithm (F. Stulle, A.Kabel) TraFiC4 with old leap- frog Algorithm

Increasing the Transverse Size of the Sub-Bunches Sub-Bunch- Radius: 2.5 um Sub-Bunch- Radius: 5 um Sub-Bunch- Radius: 25 um

S2E Simulation Schemes

TTF-II Starting Scenario ( TTF-II Starting Scenario ( =30nm) 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 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)

S2E Workshop August 18-22, 2003 at DESY-Zeuthen Chair: J. Galeyda, J. Rossbach (Berlin, GERMANY) Contact: Christel Oevermann (DESY, Hamburg)Christel Oevermann

Program Monday 08:30Physics of PARMELA (0.5 h) 08:30Physics of PARMELA (0.5 h) Physics of ASTRA (0,5 h) (K. Floettmann) Physics of ASTRA (0,5 h) (K. Floettmann) New Developments in GPT New Developments in GPT 10:00 Coffee 10:00 Coffee Calculations of LCLS injector with ASTRA and comparison with SLAC calculation Calculations of LCLS injector with ASTRA and comparison with SLAC calculation Calculation of XFEL injector with PARMELA and comparison with DESY calculation Calculation of XFEL injector with PARMELA and comparison with DESY calculation Calculation of one of the two above with HOMDYN or TREDI? Calculation of one of the two above with HOMDYN or TREDI? 11: :30 Lunch break Injector parameter measurements and simulations so far Physics not yet (properly?) included in calculations 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 19:00 Dinner

Program Tuesday CSR calculations 8:30 Chicane modeling 1-D vs. 3-D (M. Dohlus) latest results CSR calculations 8:30 Chicane modeling 1-D vs. 3-D (M. Dohlus) latest results 10:00 Coffee 10:00 Coffee Modulation amplification gains and possible 'seeding' sources Gain curve for complete TTF-2 (F. Stulle) Influence of shielding on gain Influence of shielding on gain 11:30-15:30 Lunch break 11:30-15:30 Lunch break CSR measurements and simulation so far Physics not yet (properly?) included in calculations Physics not yet (properly?) included in calculations Expected jitter due to CSR effects Expected jitter due to CSR effects 19:00 Dinner 19:00 Dinner

Program Wednesday Morning: FEL simulation codes and calculations 11:30-15:30: Lunch break 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 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