Study for an xray laser at MIT Bates Laboratory

1. Study for an xray laser at MIT Bates Laboratory William S. Graves MIT-Bates Presented at ICFA S2E workshop DESY-Zeuthen August, 2003 mitbates.mit.edu/xfel contains text of proposal to NSF

2. Design Team Principal Investigator David E. Moncton

3. Introduction • MIT is proposing a study to NSF to design an x-ray laser user facility. Proposal submitted in April, 2003. • It is based on a free electron laser driven by a high repetition rate superconducting RF linac of about 4 GeV energy reaching wavelengths of 3 angstroms. • FELs have recently demonstrated most of the important technologies. • Superconducting linac at the DESY Tesla Test Facility FEL has saturated output at 90 nm with high repetition rate. • BNL has demonstrated fully coherent seeded FEL and harmonic generation in the IR and UV. • LEUTL FEL at ANL first to demonstrate good agreement with physics models, saturating in the visible and UV, and successful use of long segmented undulators.

4. Study Proposal • 3 year study leading into to construction of a multi-beamline user facility • 5 beamlines already proposed + 4 additional concepts • Study will fund groups to design 10 beamlines. User program committee (A. Bienenstock, chair) met in July to discuss user program and beamline solicitation process. • Scientific workshop planning underway. • Accelerator advisory committee to meet in September to review initial concept. • Develop laser, accelerator, and beamline designs to level of Conceptual Design Report in first half of study, detailed design and prototype R&D in second half. • Significant education and project management initiatives in proposal.

5. User program • Plan 10 (of a possible 30) beamlines in construction project • “Principal users” will lead beamline development • Peer Review process will select Principal Users • Plan to integrate Principal Users in project team • Include initial (10) beamline costs in project budget • Include beamline operations in facility operating budget • Question #1: What is “the deal” for Principal Users? • Question #2: What is the selection process?

6. MIT Commitment • MIT has embraced the x-ray laser concept for the future of Bates Laboratory • The existing 80-acre parcel of land and its existing infrastructure will be made available • MIT will fund a series of early scientific workshops across the relevant fields • MIT will empanel and support distinguished advisory committees to guide the science, and technology, as well as user program development and project management • MIT is committing funds to hire additional project staff in the immediate future in technology areas such as x-ray optics/beamline design • MIT Center for Materials Science and Engineering (Physics Dept) provides administration

7. Facility concept • Laser output from FEL is closely coupled with seed and pump/probe lasers. • Use mature technologies: TESLA SRF linac, long segmented undulators, seeded and SASE operation. • Three undulator halls: UV, nanometer, and x-ray. • Three ebeam energies: 1, 2, and 4 GeV to drive the respective halls. • 3-7 undulator beamlines per hall: total beamlines 10-20. • Accelerator repetition rate 10 – 20 kHz: ~1 kHz per beamline to match conventional lasers. • Low average current (~1 mA) with high average flux. • Preserve future upgrade to 1 angstrom with improvements in accelerator and undulator technology.

8. MIT-Bates Laboratory

9. Facility concept Master oscillator Fiber link synchronization UV Hall X-ray Hall Seed laser Pump laser Seed laser Pump laser Undulators 100 nm Undulators 30 nm 1 nm Injector laser 10 nm 0.3 nm SC Linac 0.3 nm SC Linac 0.1 nm 1 GeV 2 GeV 4 GeV 10 nm Future upgrade to 0.1 nm at 8 GeV 3 nm 1 nm Undulators Seed laser Pump laser Nanometer Hall 500 m Use of multiple injectors and/or low energy linacs is under consideration

10. Superconducting Undulator λ = 14 mm K = 1.3 Better Gun ε = 0.75 μm 2X M$ 3X M$ 4X M$ 5X M$ Superconducting Undulator “Miracle Gun” ε = 0.1 μm Hybrid Undulator Parameters VISA: λ = 18 mm, K=1.4, B=0.8 T 23mm: λ = 23 mm, K=2.4, B=1.1 T LCLS: λ = 30 mm, K=3.9, B=1.4 T 0.1 nm 0.3 nm 1 nm 10 nm 100 nm Electron Bunch Parameters Q = 0.5 nC ΔE/E = 0.02% T = 250 fs ε = 1.5 μm

11. 5 5 5 3 3 4.5 4.5 4.5 4 4 4 2.5 4) 3.5 2.5 - 3.5 3.5 120 3 70 80 60 70 100 40 50 50 80 40 60 110 120 90 110 90 3 100 /E (x1.0e dE/E (.01%) 3 Peak current (kA) Peak current (kA) 2 2.5 2.5 2 2.5 dE 2 2 2 40 50 1.5 50 40 90 1.5 100 1.5 110 90 60 1.5 80 120 100 70 110 1.5 60 70 80 120 1 1 1 0.2 0.4 0.6 0.8 1 1.2 1.4 1 0.2 0.4 0.6 0.8 1 1.2 1.4 1 0.2 0.4 0.6 0.8 1 1.2 1.4 0.2 0.2 0.4 0.4 0.6 0.6 0.8 0.8 1 1 1.2 1.2 1.4 1.4 Norm. emittance (mm) Norm. emittance (um) Electron beam performance Contour lines are SASE saturation lengths at 0.3 nm wavelength. FEL performance estimates using M. Xie’s parameterization. Note sensitivity to emittance regardless of peak current and energy spread.

12. Injector • RF multicell photoinjector with independent phase control for velocity bunching. • Probably copper…alternatives will be studied. Work with J. Corlett group at LBL. Input profile for parmela simulations Desire performance that is insensitive to vagaries of space charge effects.

13. Parmela longitudinal Mean energy Current profile RMS energy spread Energy projection

14. Parmela transverse Note change in slice emittance 0.3 mm thermal emittance See P. Emma method to correct twist in phase space.

15. Linac • TESLA-type SRF linac. • Prefer CW for stability and timing flexibility, but cost is issue. • Two chicanes for bunch compression, limit total R56 and other bends for precise timing control and small CSR effects. • Fast ebeam switches to select beamlines at kHz rate, could be ferrite or RF deflectors.

16. Output at 5w0 seeds 2nd stage Output at 25w0 seeds 3rd stage Final output at 125w0 Input seed w0 3rd stage 1st stage 2nd stage Cascaded HGHG • Number of stages and harmonics to be optimized during study. • Simulations of cascade with GINGER now underway. See FEL 2003. • Seed longer wavelength (100 – 10 nm) beamlines with ~200 nm harmonic from synchronized Ti:Sapp laser. • Seed shorter wavelength (10 – 0.3 nm) beamlines with ~10 nm HHG pulses as well as 200 nm.

17. Bandwidth seeding • 3 x 1011 photons/pulse at 1 kHz = 3 x 1014 ph/sec • Bandwidth seeding: 100 fs = 36meV (l = 0.1nm) 1013 ph/sec at 1 meV resolution • Bandwidth seeding: 1 ps = 3.6 meV 1014 ph/sec at 1 meV Note: in Phase 1, with 0.1nm radiation provided in 3rd harmonic, intensities would be down by a factor of 100.

18. Seeded and SASE comparison Seeded and SASE time profiles and spectra. Different schemes require different undulator length.

19. High Harmonic Generation for seeding HHG is method of generating short EUV pulses by focusing ultrashort conventional laser pulse in gas jet. Output pulse energy of few nJ in ~1 fs at 30 nm. F. Kaertner (MIT) leads our effort. Courtesy of M. Murnane and H. Kapteyn, JILA

20. HHG has produced wavelengths from 50 nm to few angstroms, but power is very low for wavelengths shorter than ~10 nm. • Best power at 30 nm. • Improvements likely to yield 10 nJ at 5 nm. • Rapidly developing technology. HHG spectra for 3 different periodicities of modulated waveguides. Courtesy of M. Murnane and H. Kapteyn, JILA

21. Femtosecond synchronization • Goal is to synchronize multiple lasers and electron beam to level of 10 fs. • MIT has locked multiple independent lasers together with sub-fs accuracy using optical heterodyne detector (balanced cross correlator). • Optical clock signals delivered over several hundred meter fiberoptic have been stabilized at ~10 fs level using active monitoring and control of fiber length.

23. Experimental result: Residual timing-jitter The residual out-of-loop timing-jitter measured from 10mHz to 2.3 MHz is 300 as (a tenth of an optical cycle) Long Term Drift Free

24. Several technologies have reached sufficient maturity to enable design of an x-ray laser user facility. • Superconducting linac with photocathode gun allows high repetition rate beamlines. • Users expected to be integral part of design team. The performance of all the facility’s lasers is critical. • Much of the study activity will be addressed to endstation/beamline design. Experiments will be part of integral to the construction proposal. • Stability in energy and timing is critical to success.