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Compact FEL Based on Dielectric Wakefield Acceleration J.B. Rosenzweig UCLA Dept. of Physics and Astronomy Towards a 5 th Generation Light Source Celebration.

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Presentation on theme: "Compact FEL Based on Dielectric Wakefield Acceleration J.B. Rosenzweig UCLA Dept. of Physics and Astronomy Towards a 5 th Generation Light Source Celebration."— Presentation transcript:

1 Compact FEL Based on Dielectric Wakefield Acceleration J.B. Rosenzweig UCLA Dept. of Physics and Astronomy Towards a 5 th Generation Light Source Celebration of Claudio Pellegrini Catalina Island — October 2, 2010 J.B. Rosenzweig UCLA Dept. of Physics and Astronomy Towards a 5 th Generation Light Source Celebration of Claudio Pellegrini Catalina Island — October 2, 2010

2 FELs are Big Science Size=$

3 Creating a compact FEL  High brightness beam  Very low charge (pC)  Attosecond pulse  Few norm. emittance  High field, short undulator  With HBB, large  short L g  Lowers e- energy needed  2 GeV hard X-ray FEL  High brightness beam  Very low charge (pC)  Attosecond pulse  Few norm. emittance  High field, short undulator  With HBB, large  short L g  Lowers e- energy needed  2 GeV hard X-ray FEL Hybrid cryo-undulator: Pr-based, SmCo sheath 9 mm, up to 2.2 T FEL w/1 pC driver at 2.1 GeV J.B. Rosenzweig, et al., Nucl. Instruments Methods A, 593, 39 (2008) F.H. O’Shea et al, PRSTAB 13, (2010)

4 Scaling the accelerator in size  Lasers produce copious power (~J, >TW)  Scale in  by 4 orders of magnitude  challenges in beam dynamics  Reinvent resonant structure using dielectric  GV/m fields possible, breakdown limited…  GV/m allows major reduction in size, cost of FEL, LC  To jump to GV/m, mm-THz may be better:  Beam dynamics, breakdown scaling  Need new power source…  Lasers produce copious power (~J, >TW)  Scale in  by 4 orders of magnitude  challenges in beam dynamics  Reinvent resonant structure using dielectric  GV/m fields possible, breakdown limited…  GV/m allows major reduction in size, cost of FEL, LC  To jump to GV/m, mm-THz may be better:  Beam dynamics, breakdown scaling  Need new power source… Resonant dielectric laser-excited structure (with HFSS simulated fields)

5 New paradigm for high field acceleration: wakefields  Coherent radiation from bunched, v~c, e - beam  Any slow-wave environment  Powers exotic schemes: plasma, dielectrics  Resonant or non-resonant (short pulse) operation  THz regime easily w/in reach  High average power beams can be produced  Tens of MW, beats lasers… good for FEL, LC  Intense beams needed, synergy with many fields  X-ray FEL, ICS X-ray source, intense THz sources  Coherent radiation from bunched, v~c, e - beam  Any slow-wave environment  Powers exotic schemes: plasma, dielectrics  Resonant or non-resonant (short pulse) operation  THz regime easily w/in reach  High average power beams can be produced  Tens of MW, beats lasers… good for FEL, LC  Intense beams needed, synergy with many fields  X-ray FEL, ICS X-ray source, intense THz sources Wakefields in dielectric tube

6 Schematic of wakefield-based collider J. Rosenzweig, et al., Nucl. Instrum. Methods A (1998). (concept borrowed from W. Gai…) Similar to original CLIC scheme Study for plasma wakefield accelerator  due to charge asymmetry in PWFA Not a problem for DWA… FEL can avoid all this complexity, use one module

7 The dielectric wakefield accelerator  High accelerating gradients: GV/m level  Dielectric based, low loss, short pulse  Higher gradients than optical possible  Unlike plasma, no charged particles in beam path…  Use wakefield collider schemes  CLIC style modular system  Afterburner (energy multiplier) possible for existing linacs  Spin-offs  High power CCR THz source  High accelerating gradients: GV/m level  Dielectric based, low loss, short pulse  Higher gradients than optical possible  Unlike plasma, no charged particles in beam path…  Use wakefield collider schemes  CLIC style modular system  Afterburner (energy multiplier) possible for existing linacs  Spin-offs  High power CCR THz source Coherent Cerenkov scaling Cerenkov scaling

8 Dielectric Wakefield Accelerator Heuristic View  Electron bunch (  ≈ 1) drives wake in cylindrical dielectric structure  Dependent on structure properties  Generally multi-mode excitation  Wakefields accelerate trailing bunch  Mode wavelengths (quasi-optical)  Peak decelerating field  Design Parameters Ez on-axis, OOPIC * Extremely good beam needed  Transformer ratio (unshaped beam)

9 T-481: Test-beam exploration of breakdown threshold  1 st ultra-short, high charge beams  Beyond pioneering work at ANL…  Much shorter pulses, small radial size  Higher gradients…  Leverage off E167 PWFA  48 hr FFTB run  Excellent beam 3 nC,  z ≥ 20  m, 28.5 GeV  Goal: breakdown studies  Al-clad fused SiO 2 fibers  ID 100/200  m, OD 325  m, L= 1 cm  Avalanche v. tunneling ionization studies  Prediction: beam can excite E z ≤12GV/m  1 st ultra-short, high charge beams  Beyond pioneering work at ANL…  Much shorter pulses, small radial size  Higher gradients…  Leverage off E167 PWFA  48 hr FFTB run  Excellent beam 3 nC,  z ≥ 20  m, 28.5 GeV  Goal: breakdown studies  Al-clad fused SiO 2 fibers  ID 100/200  m, OD 325  m, L= 1 cm  Avalanche v. tunneling ionization studies  Prediction: beam can excite E z ≤12GV/m T-481 “octopus” chamber

10 Beam Observations, Analysis View end of dielectric tube; frames sorted by increasing peak current View end of dielectric tube; frames sorted by increasing peak current Multi-mode excitation – 100 fs, pulses separated by ps — gives better breakdown dynamics? Breakdown determined by benchmarked OOPIC simulations Breakdown limit: 5.5 GV/m decel. Field (10 GV/m accel.?) ultrashort bunch longer bunch Post mortem images

11 E169 Collaboration H. Badakov , M. Berry , I. Blumenfeld , A. Cook , F.-J. Decker , M. Hogan , R. Ischebeck , R. Iverson , A. Kanareykin , N. Kirby , P. Muggli , J.B. Rosenzweig , R. Siemann , M.C. Thompson , R. Tikhoplav , G. Travish , R. Yoder , D. Walz   Department of Physics and Astronomy, University of California, Los Angeles  Stanford Linear Accelerator Center  University of Southern California  Lawrence Livermore National Laboratory  Manhattanville College  Euclid TechLabs, LLC Collaboration spokespersons H. Badakov , M. Berry , I. Blumenfeld , A. Cook , F.-J. Decker , M. Hogan , R. Ischebeck , R. Iverson , A. Kanareykin , N. Kirby , P. Muggli , J.B. Rosenzweig , R. Siemann , M.C. Thompson , R. Tikhoplav , G. Travish , R. Yoder , D. Walz   Department of Physics and Astronomy, University of California, Los Angeles  Stanford Linear Accelerator Center  University of Southern California  Lawrence Livermore National Laboratory  Manhattanville College  Euclid TechLabs, LLC Collaboration spokespersons UCLA

12 E169 at FACET: overview  Research GV/m acceleration scheme in DWA  Goals  Explore breakdown issues in detail  Determine usable field envelope  Coherent Cerenkov radiation measurements  Varying tube dimensions  Impedance, group velocity dependences  Explore alternate materials  Explore alternate designs and cladding  Slab structure (permits higher Q, low wakes)  Radial and longitudinal periodicity…  Observe acceleration  Awaits FACET construction  Reapproval recently submitted  Add AWA group to collaboration  Research GV/m acceleration scheme in DWA  Goals  Explore breakdown issues in detail  Determine usable field envelope  Coherent Cerenkov radiation measurements  Varying tube dimensions  Impedance, group velocity dependences  Explore alternate materials  Explore alternate designs and cladding  Slab structure (permits higher Q, low wakes)  Radial and longitudinal periodicity…  Observe acceleration  Awaits FACET construction  Reapproval recently submitted  Add AWA group to collaboration Already explored At UCLA, BNL Bragg fiber CVD deposited diamond Slab dielectric structure (like optical)

13 Observation of THz Coherent Cerenkov Neptune  Chicane-compressed (200  m) 0.3 nC beam  Focused with PMQ array to  r ~100  m (a=250  m)  Single mode operation  Two tubes, different b, THz frequencies  Extremely narrow line width in THz  Higher power, lower width than THz FEL  Chicane-compressed (200  m) 0.3 nC beam  Focused with PMQ array to  r ~100  m (a=250  m)  Single mode operation  Two tubes, different b, THz frequencies  Extremely narrow line width in THz  Higher power, lower width than THz FEL

14 Transverse wakes and slab- symmetric structures  Slab symmetric structures: why?  Can accelerate more charge  Mitigate transverse wakes  Slab symmetric structures: why?  Can accelerate more charge  Mitigate transverse wakes  Transverse wakes at FACET  Observable BBU with >10 cm  Transverse wakes at FACET  Observable BBU with >10 cm Simulated FACET, Initial, 10.7 cm distribution (courtesy AWA group) 4 GV/m simulated wakes for FACET experiment

15 E-169 at FACET: Acceleration  Observe acceleration cm tube length longer bunch, acceleration of tail “moderate” gradient, 1-3 GV/m single mode operation  z  m  r < 10  m EbEb 25 GeV Q nC  Phase 3: Accelerated beam quality Momentum distribution after 33 cm (OOPIC) Witness beam Alignment, transverse wakes, BBU Group velocity & EM exposure Positrons. Breakdown is different? FACET beam parameters for E169: acceleration case Longitudinal E-field Witness beam, acceleration and BBU

16 A High Transformer Scenario using Dielectric Wakes  How to reach high energy with DWAs?  Enhanced transformer ratio with ramped beam  Does this work with multi- mode DWA?  Scenario: MeV ramped driver; 5-10 GeV X- ray FEL injector in <10 m  How to reach high energy with DWAs?  Enhanced transformer ratio with ramped beam  Does this work with multi- mode DWA?  Scenario: MeV ramped driver; 5-10 GeV X- ray FEL injector in <10 m Symmetric beam R<2 Ramped beam R>>2

17 A FACET test for light source scenario  Beam parameters: Q=3 nC, ramp L=2.5 mm,U=1 GeV  Structure: a =100  m, b =100  m,  =3.8  Fundamental f=0.74 THz  Performance: E z >GV/m, R=9- 10 (10 GeV beam)  Ramp achieved at UCLA. Possible at ATF, FACET?  Beam parameters: Q=3 nC, ramp L=2.5 mm,U=1 GeV  Structure: a =100  m, b =100  m,  =3.8  Fundamental f=0.74 THz  Performance: E z >GV/m, R=9- 10 (10 GeV beam)  Ramp achieved at UCLA. Possible at ATF, FACET? Longitudinal wakefields Longitudinal phase space after 1.3 m DWA (OOPIC) R. J. England, J. B. Rosenzweig, and G. Travish, PRL 100, (2008) Ramped beam using sextupole-corrected dogleg compression

18 Multipulse operation: control of group velocity  Multiple pulse beam-loaded operation in linear collider  Needs low v g  Low Q,  beams shorter, smaller  Can even replace large Q driver  Use periodic DWA structure in ~  -mode, resonant excitation  Multiple pulse beam-loaded operation in linear collider  Needs low v g  Low Q,  beams shorter, smaller  Can even replace large Q driver  Use periodic DWA structure in ~  -mode, resonant excitation Accelerating beamDriving beam Example: SiO 2 /diamond structure

19 Standing wave wakes in periodic dielectric structures  4 pulse train excitation, 2- separation  Rms pulse length  suppresses HOM  4 pulse train excitation, 2- separation  Rms pulse length  suppresses HOM

20 Initial multi-pulse experiment: uniform SiO 2 DWA at BNL ATF  Exploit Muggli pulse train slicing technique  400  m spacing, micro-Q=25 pC,  z =80  m  DWA dimensions: a =100  m, b =150  m  Exploit Muggli pulse train slicing technique  400  m spacing, micro-Q=25 pC,  z =80  m  DWA dimensions: a =100  m, b =150  m

21 BNL multi-pulse experiments  Array of 1 cm tubes  Si0 2, also diamond   m  Large aperture 490 mm case first  Use PMQs later…  Operation of pulse train with both chirp signs  Sextupole correction used  CTR autocorrelation  Array of 1 cm tubes  Si0 2, also diamond   m  Large aperture 490 mm case first  Use PMQs later…  Operation of pulse train with both chirp signs  Sextupole correction used  CTR autocorrelation 4-drive + witness in spectrometer CTR autocorrelation and FFT

22 Recent results from BNL multi- pulse experiments  Single, multi- bunch wakes observed  Wakes without mask give fundamental resonant  ~490  m, per prediction  Resonant wake excitation, CCR spectrum measured  Excited with 190  m spacing (2 nd harmonic)  Misalignments yield  300  m, 1 st deflecting mode  Single, multi- bunch wakes observed  Wakes without mask give fundamental resonant  ~490  m, per prediction  Resonant wake excitation, CCR spectrum measured  Excited with 190  m spacing (2 nd harmonic)  Misalignments yield  300  m, 1 st deflecting mode 1 st deflecting mode Fundamental level) 2 nd harmonic CCR autocorrelation Frequency spectrum

23 Towards GV/m: multiple pulse DWA experiment at SPARC/X  Uses laser comb technique  Bunch periodicity:  m (0.63 ps)  0.5 of BNL case  Scaled structure  MeV  4 pulses + witness  1 GV/m, energy doubling in <70 cm  Uses laser comb technique  Bunch periodicity:  m (0.63 ps)  0.5 of BNL case  Scaled structure  MeV  4 pulses + witness  1 GV/m, energy doubling in <70 cm >1.1 GV/m wakes in scaled

24 Honey, I shrunk the FEL (not quite yet…CP’s 80 th )  FEL itself gets small with small Q, high brightness beams; innovative undulators  Lower energy needed  Ultimate limit in optical undulators?  Wakefields give very high field  DWA gives a credible path  Booster for hard X-ray FEL in few m  Scaling to low Q synergistic, hard  Expect rapid experimental progress  1 st ATF; then FACET, SPARC/X, etc.  FEL itself gets small with small Q, high brightness beams; innovative undulators  Lower energy needed  Ultimate limit in optical undulators?  Wakefields give very high field  DWA gives a credible path  Booster for hard X-ray FEL in few m  Scaling to low Q synergistic, hard  Expect rapid experimental progress  1 st ATF; then FACET, SPARC/X, etc. TV/m simulated PWFA using LCLS 20 pC beam


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