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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 1 W.S. Graves,

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Presentation on theme: "W.S. Graves MIT Presented at High Brightness Electron Beams Workshop San Juan, PR March, 2013 High Brilliance X-rays from Compact Sources 1 W.S. Graves,"— Presentation transcript:

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

2 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 NIU D. Mihalcea, P. Piot, I. Viti SLAC V. Dolgashev, S. Tantawi Jefferson Lab F. Hannon, J. Mammosser,... W.S. Graves, MIT, March 2013 With funding from DARPA AXis, DOE-BES, and NSF-DMR

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

4 RF GUN LINAC EMITTANCE EXCHANGE LINE ICS X-RAY GENERATOR ELECTRON SPECTROMETER 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 X-band ICS source with 1 kHz rep rate Equipment cost $3M X-rays 0.1 – 12 keV W.S. Graves, MIT, March 2013

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

6 6 Simulated  -mode with coupling Standing wave accelerator structure with distributed coupling Feed power Coupler to two adjacent cells 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 Optimized X-band SW Structure Structures by S. Tantawi and V. Dolgashev of SLAC W.S. Graves, MIT, March 2013

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

8 Niowave Inc SRF gun Jefferson Lab SRF linac Emittance exchange beamline ICS x-ray generator High Repetition Rate ICS with 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  =1 cavities Evaluate cavity materials, including Nb 3 SN Evaluate beam dynamics for highest brightness. Develop digital LLRF system for cavity / module testing Evaluate options for a low cost versatile cryostat RF system Spoke cavity Elliptical cavity Nb 3 Sn CLS concept Single cell Beam dynamics

10 Superradiant X-rays via ICS Steps 1.Emit array of electron beamlets from cathode 2D array of nanotips. 2.Accelerate and manipulate correlations of beamlet array. 3.Perform emittance exchange (EEX) to swap transverse beamlet spacing into longitudinal dimension. Arrange dynamics to give desired period. 4.Modulated electron beam backscatters laser to emit ICS x-rays in phase. FEL gain appears possible. ICS (or undulator) emission is not a coherent process, scales as N Super-radiant emission is in-phase spontaneous emission, scales as N 2 N electrons W.S. Graves, MIT, March 2013

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

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

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

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

15 110 nm wide Au lines at 500 nm pitch18 nm wide Au lines at 100 nm pitch Nano Stripes Note similarity of stripes to wavefronts. Emittance exchange demagnifies pattern and transforms periodicity from ‘x’ to time. 15 SEMs of tips fabricated by R. Hobbs, MIT Nano Structures Lab W.S. Graves, MIT, March 2013

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

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

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

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

22 nm GENESIS Simulations *Undulator period = ½ laser wavelength Laser parametersUnits Pulse energy100mJ Pulse length1ps Waist size w07 micron Pulse shapeflattop A0 at waist0.3 Wavelength1.0micron Undulator period*0.5micron Electron parametersUnits Peak current100A Pulse length45fs Norm. emittance0.01 micron Energy1.7 MeV RMS energy spread0.1 % Bunching factor0.2 Beta function at IP1mm.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 nm FEL Simulations Power growth over 300 periods Bunching factor 280 kW peak 14 nJ or 10 9 photons/pulse in 0.15% bandwidth Emittance requirement during exponential gain =50 Very different ratio than cm period undulator W.S. Graves, MIT, March 2013

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

25 25 GENESIS Simulated 13.5 nm Performance 13.5 nm Output 1 kHz rep rate Units Photons per pulse10 9 Pulse energy14 nJ Average flux*10 12 photons/s Bandwidth (FWHM)0.1% Average brilliance*5 x photons/(s.1% mm 2 mrad 2 ) Peak brilliance3 x photons/(s.1% mm 2 mrad 2 ) Opening angle0.8mrad Source size1.5 mm Pulse length50fs Repetition rate1kHz Avg current5nA *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 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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