S2E (Start-to-End) Simulations for PAL-FEL Aug. 25 2008 Kyungpook Nat l Univ. Eun-San Kim 1
Contents I Lattice and layout for a 10 GeV linac II Beam parameters and distributions III Pulse-to-pulse stability studies for RF tolerance budgets IV Low-charge case of 0.2 nc VI Summary 2
I. Lattice and layout for a 10 GeV linac 3
Lattice for 10 GeV Linac BC1 BC2 BTL 4
Layout Injector f rf =21.2 o f rf =21 o f rf=20 o Undu. M1 L1 X BC1 M2 L2 BC2 M3 L3 M4 BTL q=1 nc q=1 nc q=1 nc q=1 nc s z =2.9 ps s z =0.94 ps s z =0.078 ps s z =0.078 ps e x =0.93 mm e x =1.05 mm e x =1.10 mm e x =1.10 mm e y =0.93 mm e y =1.11 mm e y =1.14 mm e y =1.06 mm s d =0.2 % s d =0.93 % s d =0.53 % s d =0.037 % E=0.135 GeV E=0.42 GeV E=2.84 GeV E=10.0 GeV M : Matching section X : X-band Linac ( 31.6 MV/m) L : S-band Linac (27 MV/m) 5
Bunch length (fs rms) X-band RF A X-band rf in decelerating phase is used to linearize energy-time correlation prior to BC1. 90 87 5.7 % variation in bunch length at f rf =1 deg. 84 Frequency : 11.424 GHz Cavity length : 0.6 m Energy loss : 15.2 MeV Phase angle : -208 deg. from crest 81 78 75 72-1.5-1.0-0.5 0.0 0.5 1.0 1.5 f rf 6
Emittance (mm) X-band RF 1.16 1.14 Horizontal Vertical 1.12 1.10 1.08 1.06 1.04-1.5-1.0-0.5 0.0 0.5 1.0 1.5 f rf 7
Peak current (A) Peak current (A) Bunch compressor I Bending angle : 0.098 rad R 56 : -64.4 mm 600 Compression factor : 3 600 400 400 200 200 0-2.0x10-3 -1.0x10-3 0.0 1.0x10-3 2.0x10-3 0-6.0x10-4 -3.0x10-4 0.0 3.0x10-4 6.0x10-4 8
Peak current (A) Peak current (A) Bunch compressor II Bending angle : 0.0396 rad R 56 : -49.5 mm 600 Compression factor: 12 13600 400 10200 200 6800 3400 0-6.0x10-4 -3.0x10-4 0.0 3.0x10-4 6.0x10-4 0-4.0x10-5 -2.0x10-5 0.0 2.0x10-5 4.0x10-5 9
Beam Transport Line - Horizontal bending angle of 1 deg. - Almost isochronous and thus no variation in bunch length - To analyze beam energy, energy spread, and final tuning in the entrance of undulator 10
Unit RF system Two rf columns for each klystron 20cm 50 cm 50 cm 20cm QF Correctors 4 RF columns BPM QD (CH, CV) 11
List of components M1 L1 BC1 M2 L2 BC2 M3 L3 M4 BTL Tot Quad 4 0 6 4 18 5 4 24 4 18 88 Bend 4 4 4 12 X-band Column S-band column 1 1 4 28 96 128 64 BPMs and 64 H/V correctors 12
II. Beam parameters and distributions 13
Longitudinal distributions 135.6 0.427 after BC1 MeV GeV 134.6-1.5mm after injector 0 1.5 mm 0.411-0.6mm 0 0.6mm 2.88 after BC2 10.02 In the entrance of undulator GeV GeV 2.82-30um 30um 9.98-30um 0 0 14 30um
Y-emittance (um) Energe spread (%) Peak current (A) X-emittance (um) Slice beam distributions in entrance of undulator 1.6 13600 10200 6800 3400 1.4 1.2 1.0 0.8 0.6 0.4 0-4.0x10-5 -2.0x10-5 0.0 2.0x10-5 4.0x10-5 1.6 0.2-4.0x10-5 -2.0x10-5 0.0 2.0x10-5 4.0x10-5 1.4 1.2 0.010 1.0 Core part 0.8 0.005 0.6 0.4 0.2-4.0x10-5 -2.0x10-5 0.0 2.0x10-5 4.0x10-5 0.000-3.0x10-5 -2.0x10-5 -1.0x10-5 0.0 1.0x10-5 15
Beam performance S2E simulation Design goal Wavelength (nm) 0.1 0.1 Peak power (GW) 6 / 4.6 (w/o, w undulator wake) 4.5 (w/o undulator wake) Energy (GeV) 10 10 Bunch charge (nc) 1 1 Slice emittance (mm) (x/y) 0.85 / 0.83 1.1 / 1.1 Peak current (ka) 3.9 3.4 Bunch length (fs) 78 100 Core slice energy spread (%) < 0.005 0.015 16
Radiation power in undulator (OLD) S2E simulation Design goal No undulator wake Undulator length 17
III Pulse-to-pulse stability studies for RF tolerance budgets - Successive 30 bunches are tested. 18
X-emittance (um) Y-emittance (um) Slice emittances under rf jitters (0.5 ps rms timing + 0.1 deg rms phase + 0.05% rms voltage) 1.4 with jitters without jitters 1.4 with jitters without jitters 1.2 1.2 1.0 1.0 0.8 0.8 0.6 0.6-6.0x10-5 -4.0x10-5 -2.0x10-5 0.0 2.0x10-5 4.0x10-5 -6.0x10-5 -4.0x10-5 -2.0x10-5 0.0 2.0x10-5 4.0x10-5 No jitter : ave. : 0.85 um With jitter: ave.: 0.86 um No jitter : ave.: 0.83 um With jitter : ave. : 0.83 um 19
Energy spread (%) Slice energy spread and peak current under rf jitters Peak current (A) (0.5 ps rms timing + 0.1 deg rms phase + 0.05% rms voltage) 0.005 0.004 0.003 with jitters without jitters 6800 with jitters without jitters 0.002 3400 0.001 0.000-4.0x10-5 -3.0x10-5 -2.0x10-5 -1.0x10-5 0.0 1.0x10-5 0-6.0x10-5 -4.0x10-5 -2.0x10-5 0.0 2.0x10-5 4.0x10-5 20
Bunch length (ps rms) Bunch length under rf jitters (0.5 ps rms timing + 0.1 deg rms phase + 0.05% rms voltage) 0.12 0.11 0.10 0.09 1st bunch without jitters 0.08 0.07 0.06 0.05 0.04 0 5 10 15 20 25 30 Bunch ID 21
III Low-charge case of 0.2 nc 22
Layout Injector f rf =21.3 o f rf =15 o f rf =13 o Undu. M1 L1 X BC1 M2 L2 BC2 M3 L3 M4 BTL q=0.2 nc q=0.2 nc q=0.2 nc q=0.2 nc s z =1.67 ps s z =0.2 ps s z =0.07 ps s z =0.07 ps e x =0.45 mm e x =0.52 mm e x =0.51 mm e x =0.50 mm e y =0.45 mm e y =0.48 mm e y =0.46 mm e y =0.45 mm s d =0.048 % s d =0.72 % s d =0.16 % s d =0.012 % E=0.135 GeV E=0.41 GeV E=2.92 GeV E=10.0 GeV M : Matching section X : X-band Linac ( 31.6 MV/m) L : S-band Linac (27 MV/m) 23
Energy spread (%) Emittance (um) Peak current (A) 0.8 0.6 Slice beam distributions in entrance of undulator Horizontal Vertical 5000 4000 0.4 0.2 3000 2000 1000 0.0-8.0x10-5 -6.0x10-5 -4.0x10-5 -2.0x10-5 0.0 2.0x10-5 4.0x10-5 0-8.0x10-5 -6.0x10-5 -4.0x10-5 -2.0x10-5 0.0 2.0x10-5 4.0x10-5 0.010 0.008 0.006 0.004 0.002 0.000-8.0x10-5 -6.0x10-5 -4.0x10-5 -2.0x10-5 0.0 2.0x10-5 4.0x10-5 24
Longitudinal distributions 135.7 0.424 MeV GeV 135.4 after injector 0.411 after BC1-0.6mm 0.6mm -0.12mm 0.12mm 2.93 10.02 In the entrance of undulator GeV GeV after BC2 2.912-30um -30um 9.98-30um 30um 25
Beam performance S2E simulation Wavelength (nm) 0.1 Peak power (GW) ~ 1 Energy (GeV) 10 Bunch charge (nc) 0.2 Avg. slice emittance (mm) (x/y) 0.38 / 0.38 Avg. peak current (ka) 0.65 Bunch length (fs) 70 Slice energy spread (%) < 0.01 26
Summary Lattice is designed to be very flexible to control emittance growth with matching sections. We performed S2E simulations in a designed 10 GeV linac that satisfy required slice beam parameters in the entrance of undulator. Results on S2E simulations show saturation power of ~5 GW in 0.1 nm at the undulator and are well within our FEL performance goals. Jitter budgets on RF systems are also studied. Their effects on the beam properties are estimated to be acceptable values technically. Intense R&D on low charge options will be continuously perform. 27