E163: Laser Acceleration at the NLCTA

Transcription

1 E163: Laser Acceleration at the NLCTA C. D. Barnes, E. R. Colby*, B. M. Cowan, R. J. Noble, D. T. Palmer, R. H. Siemann, J. E. Spencer, D. R. Walz Stanford Linear Accelerator Center R. L. Byer, T. Plettner Stanford University * Spokesman. 1

2 Outline Introduction Future requirements for high energy accelerators High efficiency high gradient acceleration Lasers as power sources for acceleration Technical issues The E163 Proposal Context Experimental program Facility requirements, construction, and cost Future Potential 2

3 Requirements for Future High Energy Linear Colliders Near Term: Center-of-mass energy TeV Luminosity >10 34 cm -2 s -1 ILC Long Term: >3 TeV and readily extendable Luminosity >10 35 cm -2 s -1 and increasing with 2 Compactness, power efficiency, and reliability 3

4 Requirements for high efficiency high gradient acceleration Power efficiency improves with decreasing stored energy P ac G 2 E cm E cm Collider s center-of-mass energy G Accelerator Gradient Acceleration field wavelength power source efficiency Resistance to breakdown and surface damage improve with decreasing pulse length: Less opportunity for plasma formation Less energy available to do damage 4

5 Requirements for high efficiency high gradient acceleration High gradient, high efficiency acceleration requires a power source with high fluence and efficiency: E Pac 1 cm 2 G SOURCE FLUENCE 5

6 Outline Introduction Future requirements for high energy accelerators High efficiency high gradient acceleration Lasers as power sources for acceleration Technical issues The E163 Proposal Context Experimental program Facility requirements, construction, and cost Future Potential 6

7 Coherent Sources of Radiation Source Frequency [GHz] Source Fluence [TW/cm 2 ] 7

8 Efficiency of Power Sources Source Efficiency [%] SLAC PPM Klystron =2.624 cm t =3 sec P ave =27 kw =65% TUBES FEMs FELs LASERS (RF Compression, modulator losses not included) Yb:KGd(WO 4 ) 2 =1.037 t =112 fsec P ave =1.3 W =28% Source Frequency [GHz] 8

9 Outline Introduction Future requirements for high energy accelerators High efficiency high gradient acceleration Lasers as power sources for acceleration Technical issues The E163 Proposal Context Experimental program Facility requirements, construction, and cost Future Potential 9

10 Phase-Locking of Lasers Diddams, et al, Direct Link between Microwave and Optical Frequencies with a 300 THz Femtosecond Laser Comb, Phys. Rev. Lett., 84 (22), p.5102, (2000). [Figures below are from this reference] R. Shelton, et al, Phase-Coherent Optical Pulse Synthesis from Separate Femtosecond Lasers, Science, 293, 17 AUG (2001). 10

11 Making Laser-driven Accelerator Structures Conventional waveguide structures scaled to optical wavelengths would: Have impossible machining tolerances (~ /1000) Rapidly ablate if powered with lasers Have very tiny beam holes (~ /10) How can structures be made? By using fundamentally different kinds of structures: Quasioptics By using fundamentally different means of fabrication: Lithography 11

12 Interferometric Acceleration Interaction Length : ~1000 ~0.1 Z R Slit Width ~10 Crossing angle: E 1 E 1z E 1x x Slit Width ~10 z Electron beam E 2z E 2 E 2 x Waist size: w o ~100 Terminating Boundary E 1x + E 2x = 0 E 1z + E 2z > 0 no transverse deflection nonzero electric field in the direction of propagation Terminating Boundary The laser beams are polarized in the XZ plane, and are out of phase by 12

13 electric field E z (V/m) ) m o lts/ E z (V fie l d c c tri e l 6 x Example: =0.8 slit =16 m, w o = 50 m, = 20 mrad longitudinal field V ) e (k n g ai y g n er e 200 energy gain (kev) potential distance (microns distance ( m) Accelerator cell Length: 1000 m distance (microns distance ( m) E T 2 map 16 m slit 13

14 Effect of varying slit width Laser Off Laser On Slit: 5 m Slit: 10 m Slit: 20 m Energy Modulation (kev) 5 psec laser pulse, 2 ps electron beam 14

15 Effect of varying laser pulse duration Laser Off Laser On 5 m slits, 2 ps Electron Beam 15

16 Making Laser-driven Accelerator Structures Photolithography A well-understood process widely used in industry Feature sizes down to 130 nm can be reliably produced A variety of materials and processes can be used Highly complex structures can be made Mass-production is cost-effective, even for complex designs Extensive fabrication facilities are available at Stanford for rapid prototyping 16

17 Large-Market Technologies U.S. Government, projected for 2002[1]: Revenue: $2.1 trillion DOE and NSF: = $7.7 billion Semiconductor industry, domestic, in 1999[2]: Revenue: $168.6 billion R&D: $22 billion Telecommunications industry, worldwide, proj. for 2001[3]: Revenue: $1 trillion (including services) R&D: $25 billion [4] (top 30) Laser machining & welding, $30 billion/year laser diode bars [1] The Budget of the United States Government, FY2002, OMB. [2] Is Basic Research the Government s Responsibility?, Cahners Business Information, (2000). [3] J. Timmer, Telecommunications Services Industry, Hoover s Business Network, (2000). [4] International Science Yearbook 2001, Cahners Business Information,

18 Outline Introduction Future requirements for high energy accelerators High efficiency high gradient acceleration Lasers as power sources for acceleration Technical issues The E163 Proposal Context Experimental program Facility requirements, construction, and cost Future Potential 18

19 The Laser Electron Accelerator Project SLAC: R.H. Siemann J.E. Spencer E. Colby C. Barnes B. Cowan HEPL: T.I. Smith R.L. Swent Ginzton Labs: R.L. Byer T. Plettner LEAP First funded by Stanford patent money, subsequently funded though the DOE-HEP office of Advanced Accelerator Research in 1997, renewed in Objective: To demonstrate laser driven electron acceleration in a dielectric structure in vacuum. 19

20 The LEAP Accelerator Cell crossed laser beams High Reflectance Dielectric coated surfaces Accelerator cell slit electron beam Computed Field Intensity, E t 2 Fused silica prisms and flats ~1 cm 20

21 The LEAP Accelerator Cell 1 cm Electron Beam 21

22 The LEAP Experimental Setup accelerator cell crossed laser beams Camera ~ 1 m Vacuum chamber electron beam ~ 1 cm Electron beam doped YAG screen Diagnostics: spatial monitor streak camera Image intensified camera spectrometer magnet 22

23 The Interaction Chamber Beam Direction ABOVE: The single laser pulse is split into two pulses, delayed and reduced in size in this secondary vacuum chamber. LEFT: The laser acceleration cell is mounted amidst diagnostics in this chamber.laser profile, alignment, and slit width diagnostics are mounted in the foreground. 23

24 Precision Low-Charge Spectrometry Intensity energy time 2 kev (1:10 4 ) resolution spectrometry with sub-picocoulomb beams 24

25 Laser and Electron Beam Timing and Position Overlap Diagnostics intensified gain camera XYBION 1SG350-U-E streak camera HAMAMATSU C-1587 Cerenkov cell tilt stage electron beam pellicle YAG screen holder 25

26 Laser Relative Phase Diagnostic piezo crystal variable delay arm leakage field Incoming laser pulse = 180 o = 0 o accelerator cell diffuser screen CCD camera fixed delay arm 26

27 Technical Roadmap LEAP 1. Demonstrate the physics of laser acceleration in dielectric structures 2. Develop experimental techniques for handling and diagnosing picocoulomb beams on picosecond timescales 3. Develop simple lithographic structures and test with beam Phase I. Phase II. E163 Characterize laser/electron energy exchange in vacuum Demonstrate optical bunching and acceleration Phase III. Test multicell lithographically produced structures Now and Future 1. Demonstrate carrier-phase lock of ultrafast lasers [NIST, Stanford] 2. Continue development of highly efficient DPSS-pumped broadband mode- and carrier-locked lasers [DARPA Proposal, SBIR Solicitation] 3. Devise power-efficient lithographic structures [SBIR Solicitation] 4. Devise stabilization and timing systems for large-scale machine [LIGO] 5. Damage Threshold Improvement 27

28 Outline Introduction Future requirements for high energy accelerators High efficiency high gradient acceleration Lasers as power sources for acceleration Technical issues The E163 Proposal Context Experimental program Facility requirements, construction, and cost Future Potential 28

29 Phase I: Laser Acceleration Scientific Goals: Thoroughly characterize the dependencies of the energy modulation on: Interaction length Crossing angle Slit width Relative laser phase Physical tolerances of the cell crossed laser beams High Reflectance Dielectric coated surfaces electron beam Accelerator cell slit Computed Field Intensity, E t 2 Technical Goals: Commission the experiment at the NLCTA Make progress understanding electric field breakdown issues and the attendant design implications Timing synchronization Fused silica prisms and flats E 29

30 Optical Bunching UNBUNCHED 1 2 ENERGY BUNCHED 3 4 PHASE Simulation: GENESIS (S. Reiche) for 0.8 laser, 60 MeV electron beam 30

31 Phase II: Prebunch and Accelerate Scientific Goals: Demonstrate and quantify optical bunching Demonstrate and quantify acceleration Determine the impact of beam transport on bunching washout Technical Goals: Commission the IFEL prebuncher Understand mechanical stability required to maintain attosecond-scale timing synchronism Implement optical bunching diagnostics E 31

32 STELLA (Staged Electron Laser Acceleration) experiment at the BNL ATF IFEL ACCELERATOR BPM IFEL BUNCHER BPM 0.6 GW, 180 ps CO2 laser beam ELECTRON SPECTROMETER BPM Steering coil Focusing quadrupoles BPM Steering coil Focusing quadrupoles 46 MeV 0.5 nc 2 mm mrad 3.5 ps Optically accelerated beam Source: W. Kimura, I. Ben-Zvi. Optically bunched beam Incoming e - beam 32

33 Phase III: Multicell Structures Scientific Goals: Demonstrate multi-stage acceleration of optically bunched beam Quantify micropulse wakefields Incoming plane waves Lenslet Array Phase Control Lenslet Array Electron beam Technical Goals: Master lithographic production techniques for silica or silicon microstructures Make progress understanding damage threshold issues Fabricate integrated accelerator components Devise and test methods of beam focussing Electron beam Transmission Mode Structure E 33

34 Outline Introduction Future requirements for high energy accelerators High efficiency high gradient acceleration Lasers as power sources for acceleration Technical issues The E163 Proposal Context Experimental program Facility requirements, construction, and cost Future Potential 34

35 Experimental Requirements Parameter Value Comment Electron Beam Properties Bunch Charge 50 pc Beam Energy 60 MeV Transverse Emittance < 2.5 mm-mr Normalized Bunch Length < 5 ps FWHM Energy Spread < 20 kev FWHM Pulse Repetition Rate 10 Hz Laser Beam Properties (for experiment) Pulse Energy 1 mj Pulse Wavelength 800 nm Pulse Length ps FWHM, variable Pulse Repetition Rate 10 Hz Timing jitter w.r.t. electron beam < 1 ps Present Values at HEPL 5 pc 28 MeV 10 mm-mr ~5 ps ~20 kev 10 Hz 1 mj 800 nm ps 10 Hz <3 ps 35

36 Why move the experiment to the NLCTA? LEAP has been hosted at HEPL for the last 4 years and has enjoyed their support. The lack of run time and marginal beam quality will not allow further progress on this experiment at HEPL. Additionally, the future of an accelerator facility on campus is in doubt, as Stanford Campus plans call for the renovation of Hansen and Ginzton Laboratories. The experimental program described here will require more than two years to complete so the move to a facility with good beam quality and a long-term future is pressing. The Advanced Accelerator Research Committee met in summer 1999 to examine facilities on the SLAC site for conducting advanced acceleration experiments and concluded that the NLCTA was the best location for such experiments. 36

37 E163 Layout at the NLCTA (from the Proposal) 37

38 NLCTA Injector Upgrade 38

39 Resource Requirement Summary Total Materials and Services: $0.96M 9.4 FTE-years of SLAC Labor: $1.03M Value of existing equipment that will be transferred to E163: $1.13M 39

40 E163 Labor Estimates 40

41 E163 Budget Estimate E163 Costs SLAC Labor SLAC Labor Cost to SLAC Preexisting Preexisting hours k$ k$ LEAP E163 Weighted Average Hourly Rate for Labor (not burdened) $62.21 ($110,000 for 1768 hours per FTE) E163 Shielding Enclosure Relocate utilities at penetration 1 Core drill extraction line 2.5 Concrete-material cost 31 Structure assembly 14 Electrical Installation 22 Plumbing Installation 5 Cabling, Racks, Cable Trays 22 PPS, MPS, BCS 20 Total Estimated Labor E163 Beamline Components Vacuum system Bending dipoles air-cooled quads 50 6 steering magnets 3 3 Spectrometer magnet 150 Optical bunching wiggler 20 Diagnostics 20 5 Power Supplies for magnets 40* Total Estimated Labor E163 Experimental Apparatus Interaction Vacuum Chamber and Hardware Optical Table 8 Micropositioning systems+movers 4 Mirror positioners and controller CCD Video Cameras 4 2 Xybion Cameras 40 PI*MAX Camera 40 Picosecond Timing System 10 Streak Camera C1587** 200 Total Estimated Labor (ARDB personnel) E163 Data Acquisition Room Nanosecond Timing Electronics, Scopes, etc. 50 Move E-162 Trailer and reconnect electricity 8 Total Labor Estimate (ARDB Personnel) Injector Gun Solenoid Diagnostics Total Labor Estimate Laser Room Construction 100 Optical Transport lines to gun and experiment Total Labor Estimate 80 Laser System Oscillator Amplifier 150 Diagnostics Optical components Optical Tables Total Labor Estimate S-Band RF Power Source Klystron, Pulse transformer, & Solenoid modulator 100 LLRF 25 Waveguide 50 Total Estimated Labor Utilities and Services B&H 50 Access and Penetrations 5 Total Labor Estimate (Included elsewhere in specific catagories) Control System Electronics 50 Total Labor Estimate PPS, MPS, BCS Fast-closing gate valve 18 Electronics and Detectors 50 Total Labor Estimate (From 98 SSRL Estimate) Totals (k$) hours k$ k$ k$ LABOR LABOR M&S LEAP * We expect to scrounge this from SLAC Pre-exist ** We expect to continue our long-term loan of this camera from Prof. S. Harris Pre-existing equipment values (columns 4 and 5 on the E163 Costs spreadsheet) are best-guess replacement costs. Labor estimates are based on original ORION labor estimates, scaled to reflect the reduced scope of the E163 experiment. Labor is valued at $110,000 per FTE per year, for a total of 1768 hours per year. Cost estimates for equipment are best-guess, with the exception of the laser system, gun solenoid, and laser room, which are industry quotes. Labor costs (e.g. for the modulator) assume assembly is from parts, with no large subassemblies available. ARDB physicist labor costs are not included in the total estimated labor costs. 41

42 Summary Schedule for E163 Facility Construction NOW E163 Experimental Program Begins 42

43 Future Potential The proposed E163 installation at ESB will be a versatile acceleration test facility developed at nominal cost using existing beam facilities at the NLCTA. Picosecond electron and photon beams with very high energy densities are available together with diagnostics suitable for a broad range of picosecond time-scale experiments. Modularity and versatility have been preserved to insure the facility is broadly usable. The E163 collaboration plans to make future applications to the EPAC to explore other lithographic accelerator structures. 43

44 Multicell Structure Concepts TIR Fused Silica at 1.06 TIR Silicon at 1.06 TIR Silicon at 2.5 Electron beams 44