Dong Wang Shanghai Inst. of Applied Physics (SINAP) Mini-workshop on Present and Future FEL Schemes December 11-12, 2008, Shanghai

Transcription

1 Plans for FEL experiments at SDUV Dong Wang Shanghai Inst. of Applied Physics (SINAP) Mini-workshop on Present and Future FEL Schemes December 11-12, 2008, Shanghai

2 About SDUV: Shanghai Deep UV FEL Facility 1 hour drive SDUV is at old campus of SINAP. New campus hosts 3.5 GeV SSRF Soft X-ray FEL Hard X-ray FEL?

3 SDUV-FEL Experiment Hall Jiading campus, SINAP, Shanghai, China

4 SDUV: a brief history Initially, 100 MeV linac prototype for the injector of 3.5 GeV Light Source , Plans for DUV FEL test facility, 300 MeV, 88nm SASE Changed goal: 160 MeV, HGHG Repositioned: FEL facility for 1) users in many fields (supported by CAS) 2) FEL/laser/e- test bed (supported by SINAP)

5 SDUV: 6 th HG FEL user facility Maybe the only FEL user facility in China in next 5 years. Potential users are surprisingly interested in doing experiments on SDUV SDUV HGHG Shanghai China in

6 SDUV-FEL Facility: a multi-purpose platform Laser-electron FEL physics study Photo-injector Experiment FEL user facility 1st: 262,131 nm 3rd: 87,44nm THz rad.: 0.1-1mm Seed laser: nm HHG:30nm (with SIOM) Pump-probe Optical based fs timing and synchronization ps laser:1047,262nm

7 Main parameters for 2-stage HGHG Electron beam: E = 160 MeV,Ip >= 300 A,ε <= 6.0 mm-mrad, 2~3 ps length Seed laser: λs=786nm τ=100fs Ps=20~50 MW Modulators: stage-1 stage-2 λu (mm) (fixed gap) a u Lm (m) Radiators: stage-1 stage-2 λu (mm) (fixed?) a u Lr(m) β (m) 3 4 λ-fel(nm)

8 SDUV: current status

9 SDUV, Phase-I (2009) and phase-ii (2010) Phase-I: SASE, Single-stage HGHG 262nm R 1047nm M Phase-II: Cascaded two-stage HGHG 131nm R 262nm M 262nm R nm M

10 Newly designed double-modulator section Dispersion section Dispersion R56_max: ~5mm section Laser inj. chicane R56_max: ~40mm Laser injection 1 To radiator 2nd modulator 5cm, gap flexible Laser injection 2 1st modulator Under design Linac exit Key capabilities: Double modulators Double chicanes (with large R56) Double lasers, etc. Possibilities of doing FEL experiments: two-modulator type, laser-modulation type, etc.

11 Laser parameters Type Wavelength Pulse energy Pulse duration Power as IR seed Company Repetition rate_max. Bandwidth Pulse shapes Energy stability Drive laser (since 2006) Nd-YLF 1047 / 262 nm 1.2mJ / 0.2mJ 8-10 ps ~20MW(split) Time-bandwidth 100 Hz ~0.1nm Gaussian <2% Seed laser (2009) Ti:Sa 786 / 262 nm 6mJ / 0.6mJ 2ps/100fs/(30fs) 3~50 GW Coherent 50 Hz ~10nm Gaussian <2%

12 Plans for FEL experiments at SDUV Cascaded HGHG scheme 2-stage, 262 nm to 131 nm, then hopefully the routine operation mode for users. Have to wait for new undulators and optical synchronizations. Seed laser comes earlier. New modulation schemes Two-modulator with pi-shift EHGHG Echo(!) Other important FEL studies harmonic operation mode laser heater ESASE and related, and your input

13 Interesting experiments in near future (before undulators for 2nd-stage HGHG are ready) New bunching schemes for HGHG: Two-modulator type: ----increase bunching efficiency for high harmonics E. Allaria and G. De Ninno, PRL 99, (2007)

14 Proposed as FERMI Alternative More detailed comparative studies: BESSY/Fermi E. Allaria and G. De Ninno, PRL 99, (2007)

15 EHGHG Modulator Dispersive Section Reverse Modulator Qika Jia, Applied Physics Letters 93, (2008), talk in this workshop

16 Beam Echo Effect Dramatic enhancement of bunching at high harmonics compared to single modulator scheme (below) by many order of magnitude. G. Stupakov, LBNL X-ray FEL Workshop, October 23-25, 2008

17 Simulations to understand the scheme Jianhui Chen

18 Typical numbers: 10 th and 24th harmonic E0=160MeV Sig_E=32keV Laser Wavelength=1047nm R56(1)=10mm+R56(2)=1.1mm 10th harmonic (R56(1)=22.15mm+R56(2)=0.94mm 24th harmonic) Parameter studies show that bn is not sensitive to errors in R56 or laser modulations More simulations are underway. SLAC is doing 3-D with Elegant and Genesis.

19 Seems we are able to try all of them In terms of the efficiency, (bunching/modulation), especially at very high harmonics, Echo effect is very interesting. SLAC people are interested in this, obviously. Discussions going on. More collaborations on experiments are planned. Hopefully, these schemes would be tested and compared to the original HGHG scheme. 4 th harmonic, 1047nm => 262nm 10 th harmonic and higher, 30 th : => ~30 nm

20 Beam diagnostics: important Energy spectrometer BPM (including cavity BPM) ICT OTR five in modulator section, discussing with BI group Deflecting cavity just tested alone. But wont be powered in operation. Pop-in screens in six 1.5m radiator undulators Optical spectrometers( nm, nm, 30-10nm, etc.) A lot things to be done.

21 Remarks SDUV is on its way towards a FEL test bed. Newly modified layout is capable of doing some very interesting experiments, e.g., two modulator schemes, in near future, say, One of the outstanding issues is the diagnostics. More discussions / collaborations are needed.

22 Thank you for your attention 谢谢!