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W.S. Graves MIT Presented at High Brightness Electron Beams Workshop San Juan, PR March, 2013

High Brilliance X-rays from Compact Sources. W.S. Graves MIT Presented at High Brightness Electron Beams Workshop San Juan, PR March, 2013. W.S. Graves, MIT, March 2013. People. MIT

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W.S. Graves MIT Presented at High Brightness Electron Beams Workshop San Juan, PR March, 2013

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  1. High Brilliance X-rays from Compact Sources W.S. Graves MIT Presented at High Brightness Electron Beams Workshop San Juan, PR March, 2013 W.S. Graves, MIT, March 2013

  2. People MIT K. Berggren, J. Bessuille, P. Brown, W. Graves, R. Hobbs, K.-H. Hong, W. Huang, E. Ihloff, F. Kaertner, D. Keathley, D. Moncton, E. Nanni, M. Swanwick, L. Vasquez-Garcia, L. Wong, Y. Yang, L. Zapata DESY J. Derksen, A. Fallahi, F. Kaertner Jefferson Lab F. Hannon, J. Mammosser, ... NIU D. Mihalcea, P. Piot, I. Viti SLAC V. Dolgashev, S. Tantawi With funding from DARPA AXis, DOE-BES, and NSF-DMR W.S. Graves, MIT, March 2013

  3. Basic Layout for ICS 3 m Gun Linac Quads ICS X-rays IR laser or THz Cathode laser ebeam dump W.S. Graves, MIT, March 2013

  4. X-band ICS source with 1 kHz rep rate ELECTRON SPECTROMETER ICS X-RAY GENERATOR EMITTANCE EXCHANGE LINE LINAC RF GUN Equipment cost $3M X-rays 0.1 – 12 keV Not shown - klystron and modulator housed in one 19” X 6’ rack - instrumentation & power supplies housed in one 19” X 6’ rack - 10W (10 mJ at 1 kHz) mode locked Ti:Sapp amplifier for photocathode and ICS collision - x-ray optics W.S. Graves, MIT, March 2013

  5. X-band ICS source with 1 kHz rep rate RF GUN ICS X-RAY GEN. ELECTRON SPECTROMETER EMITTANCE EXCHANGE LINE LINAC W.S. Graves, MIT, March 2013

  6. Optimized X-band SW Structure Coupler to two adjacent cells Simulated p-mode with coupling Standing wave accelerator structure with distributed coupling Feed power Structures by S. Tantawi and V. Dolgashev of SLAC • Just 3 MW RF power to accelerate 20 MeV in 1 m • 1 kHz rep rate with 9.3 GHz klystron developed for medical linacs • 1 kHz solid-state modulator with <.01% stability • RF gun is 2.5 cell 9.3 GHz structure needing just 2 MW to produce 200 MV/m on cathode W.S. Graves, MIT, March 2013

  7. RF amplifiers Inverse Compton scattering 30 kW beam dump Superconducting RF photoinjector operating at 400 MHz and 4K Bunch compression chicane X-ray beamline 4 MeV 30 MeV multi kW cryo-cooled Yb:YAG drive laser Electron beam of ~1 mA average current at 10-30 MeV Coherent enhancement cavity with Q=1000 giving multi MW cavity power 8 m RF amp RF amp RF amp High Repetition Rate ICS with SRF Linac W.S. Graves, MIT, March 2013

  8. High Repetition Rate ICS with SRF Linac Emittance exchange beamline NiowaveInc SRF gun ICS x-ray generator Jefferson Lab SRF linac Equipment cost $15M X-rays 0.1 – 12 keV W.S. Graves, MIT, March 2013

  9. Superconducting Accelerator R&D for Coherent Light Sources PI: J. Mammosser, JLab Goal: develop a low cost, high efficiency SRF solution suitable for compact light sources and other uses • Compare spoke and elliptical b=1 cavities • Evaluate cavity materials, including Nb3SN • Evaluate beam dynamics for highest brightness. • Develop digital LLRF system for cavity / module testing • Evaluate options for a low cost versatile cryostat Beam dynamics Single cell CLS concept Nb3Sn RF system Spoke cavity Elliptical cavity

  10. Superradiant X-rays via ICS ICS (or undulator) emission is not a coherent process, scales as N Super-radiant emission is in-phase spontaneous emission, scales as N2 N electrons Steps Emit array of electron beamlets from cathode 2D array of nanotips. Accelerate and manipulate correlations of beamlet array. Perform emittance exchange (EEX) to swap transversebeamlet spacing into longitudinaldimension. Arrange dynamics to give desired period. Modulated electron beam backscatters laser to emit ICS x-rays in phase. FEL gain appears possible. W.S. Graves, MIT, March 2013

  11. Emittance Exchange (EEX) Beamlets from tips y Current x t Acceleration x’ Energy x t EEX x’ Energy x t Bunched beam emits coherent ICS y Current x t W.S. Graves, MIT, March 2013

  12. Layout for Super-radiant ICS Quads RF gun Dipoles Linac RF deflector ICS X-rays Nanocathode Emittance Exchange (EEX) ebeam dump IR laser or THz W.S. Graves, MIT, March 2013

  13. Nanostructured Cathodes W.S. Graves, MIT, March 2013

  14. Au Nanopillar Array Geometry 10 nm 30 nm 80° W.S. Graves, MIT, March 2013

  15. Nano Stripes • Note similarity of stripes to wavefronts. • Emittance exchange demagnifies pattern and transforms periodicity from ‘x’ to time. SEMs of tips fabricated by R. Hobbs, MIT Nano Structures Lab 110 nm wide Au lines at 500 nm pitch 18 nm wide Au lines at 100 nm pitch W.S. Graves, MIT, March 2013

  16. Cathode spot size maps to pulse length Cathode stripes Large laser spot makes long pulse Laser spot Current EEX time Number cathode stripes illuminated sets number of micropulses after EEX Laser spot Current EEX time y Small laser spot makes short pulse x W.S. Graves, MIT, March 2013

  17. Tune resonant wavelength with quadrupole Weak quad images cathode at low demagnification Longer wavelength Current EEX y t x Strong quad images cathode at large demagnification Shorter wavelength EEX y Current t x W.S. Graves, MIT, March 2013

  18. Simulation of 300x40 Tip Array through EEX 5M particles tracked, similar to full bunch charge z-d slope due to imperfect matching (correctable) Bunching at 13.5 nm 10 fs bunch length W.S. Graves, MIT, March 2013

  19. Tests of coherent ICS code Simulations by NIU grad student Ivan Viti using Lienard-Wiechert solver written by Alex Sell of MIT. Work in progress. Examine radiation from many nanobunches Simulations are designed to study coherent radiation opening angle, bandwidth, and electron beam size effects. Emittance is set unrealistically small to remove its effect. Purpose is to explore radiation properties. W.S. Graves, MIT, March 2013

  20. Radiation from many nanobunches Bandwidth tends to 1/(number bunches) for large numbers of bunches Opening angle tends to W.S. Graves, MIT, March 2013

  21. 13.5 nm flux vs transverse ebeam size Bunching factor = 0.2 13.5 nm photons/shot RMS electron beam size (microns) W.S. Graves, MIT, March 2013

  22. 13.5 nm GENESIS Simulations *Undulator period = ½ laser wavelength • .01 micron emittance is consistent with 150 MV/m cathode field and 5 pC • 45 fs bunch length contains 1000 periods at 13.5 nm • Assume uniform bunching factor of 0.2 (not yet a start to end simulation) • FEL rho parameter = .0012 • FEL gain length = 20 microns W.S. Graves, MIT, March 2013

  23. 13.5 nm FEL Simulations 280 kW peak Power growth over 300 periods Bunching factor • 14 nJ or 109 photons/pulsein 0.15% bandwidth • Emittance requirement during exponential gain =50 Very different ratio than cm period undulator W.S. Graves, MIT, March 2013

  24. 13.5 nm Power and Spectrum Simulations Radiation RMS size during interaction Spectrum 0.15% BW Optical guiding allows larger ebeam size 280 kW peak Power vs time 50 fs W.S. Graves, MIT, March 2013

  25. GENESIS Simulated 13.5 nm Performance *Avg values rise 5 orders of magnitude for SRF linac • Simulations use aggressive but achievable parameters • Complete start-to-end simulations in development W.S. Graves, MIT, March 2013

  26. Summary • Nanobunched beam and ICS heading toward tabletop x-ray laser • Develop accelerator technology specifically for this application • SRF at 4K with low heat load and modular construction • kHz rep rate x-band gun & linac using only 6 MW total RF power • Inexpensive to test and develop • Compact highly stable RF power supplies are commercially available • Nanoengineered cathodes likely to have big impact on high brightness beams $3M ~$15M W.S. Graves, MIT, March 2013

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