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Plasma Acceleration Presented by: Mark Hogan On behalf of: The E-164/E-164X Collaboration

Plasma Acceleration Presented by: Mark Hogan On behalf of: The E-164/E-164X Collaboration C. D. Barnes, I. Blumenfeld, F.J. Decker, P. Emma, M.J. Hogan * , R. Ischebeck, R. Iverson, N. Kirby, P. Krejcik, C. L. O'Connell, R.H. Siemann and D. Walz Stanford Linear Accelerator Center

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Plasma Acceleration Presented by: Mark Hogan On behalf of: The E-164/E-164X Collaboration

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  1. Plasma Acceleration Presented by: Mark Hogan On behalf of: The E-164/E-164X Collaboration C. D. Barnes, I. Blumenfeld, F.J. Decker, P. Emma, M.J. Hogan*, R. Ischebeck, R. Iverson, N. Kirby, P. Krejcik, C. L. O'Connell, R.H. Siemann and D. Walz Stanford Linear Accelerator Center C. E. Clayton, C. Huang, D. K. Johnson, C. Joshi*, W. Lu, K. A. Marsh, W. B. Mori and M. Zhou University of California, Los Angeles S. Deng, T. Katsouleas*, P. Muggli and E. Oz University of Southern California Work supported by Department of Energy contracts DE-AC02-76SF00515 (SLAC), DE-FG03-92ER40745, DE-FG03-98DP00211, DE-FG03-92ER40727, DE-AC-0376SF0098, and National Science Foundation grants No. ECS-9632735, DMS-9722121 and PHY-0078715.

  2. Plasma Accelerators Showing Great Promise! Laser Driven Plasma Accelerators: • Accelerating Gradients > 100GeV/m (measured) • Narrow Energy Spread Bunches • Interaction Length limited to mm’s Beam Driven Plasma Accelerators: Large Gradients: • Accelerating Gradients > 30 GeV/m (measured!) • Interaction Length not limited Unique SLAC Facilities: • FFTB • High Beam Energy • Short Bunch Length • High Peak Current • Power Density • e- & e+ Scientific Question: • Can one make & sustain high gradients in plasmas for lengths that give significant energy gain?

  3. Linear PWFA Theory: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + + + + + + + + + + + + + + + - + + + + + + + + + + + + + + + - - - - - - - - - + + + + + + + + + + + + + + + + - - + + + + + - + + + + + - + + + + + + + + + + + + + + + - - - - + + + + + + + + + + + + + + + - - - - - - - - - - - electron beam - - - - - - - - - - - - - - - - - - - - - - - - - Decelerating - - - - - - - - Accelerating - - - - - - - - - - - - - - - - - - - Ez Ez: accelerating field N: # e-/bunch sz: gaussian bunch length kp: plasma wave number np: plasma density nb: beam density  Short bunch! m m Forand or PWFA: Plasma Wakefield Acceleration • Looking at issues associated with applying the large focusing (MT/m) and accelerating (GeV/m) gradients in plasmas to high energy physics and colliders • Built on E-157 & E-162 which observed a wide range of phenomena with both electron and positron drive beams: focusing, acceleration/de-acceleration, X-ray emission, refraction, tests for hose instability… • A single bunch from the linac drives a large amplitude plasma wave which focus and accelerates particles • For a single bunch the plasma works as an energy transformer and transfers energy from the head to the tail

  4. y x z PWFA Experiments @ SLAC Share Common Apparatus Located in the FFTB Energy Spectrum “X-ray” Li Plasma Gas Cell: H2, Xe, NO ne≈0-1018 cm-3 L≈2.5-20 cm  FFTB ∫Cdt X-Ray Diagnostic, e-/e+ Production Plasma light e- N=1.81010 z=20-12µm E=28.5 GeV Coherent Transition Radiation and Interferometer Imaging Spectrometer Cherenkov Radiator Optical Transition Radiators Dump 25m FFTB

  5. Electron Beam Refraction at the Gas–Plasma Boundary Matching e- Wakefield Acceleration e+ qµ1/sinf q≈f o BPM Data – Model Phase Advance  ne1/2L Nature411, 43 (3 May 2001) Beam-Plasma Experimental Results (6 Highlights) Focusing e- X-ray Generation Wakefield Acceleration e- Phase Advance  ne1/2L Phys. Rev. Lett.93, 014802 (2004) Phys. Rev. Lett.88, 154801 (2002) Phys. Rev. Lett.88, 135004 (2002) Phys. Rev. Lett.90, 214801 (2003) Phys. Rev. Lett.93, 014802 (2004)

  6. Damping Ring 50 ps RTL FFTB 9 ps 0.4 ps <100 fs SLAC Linac Add 12-meter chicane compressor in linac at 1/3-point (9 GeV) 1 GeV 20-50 GeV 1.5% Existing bends compress to <100 fsec 30 kA 80 fsec FWHM 28 GeV ~1 Å Short Bunch Generation In The SLAC Linac • Bunch length/current profile is the convolution of an incoming energy spectrum and the magnetic compression • Dial FFTB R56 & linac phase, then measure incoming energy spectrum.

  7. First Measurement of SLAC Ultra-short Bunch Length! • CTR Michelson Interferometer • Fabry-Perot resonance: • l=2d/nm, m=1,2,…, n=index of refraction • Modulation/dips in the interferogram • Smaller measured width: • sAutocorrelation < sbunch ! • Other issues under investigation: • Detector response (pyro vs. Golay) • Alternate materials: • HDPE, TPX, Si, Diamond ($$$) Autocorrelation: z ≈ 9 µm z≈9 µm Gaussian Bunch z≈18 µm or ≈60 fs

  8. Non-Invasive Energy Spectrometer Upstream of Plasma

  9. Phase Space Retrieval via LiTrack* *K. Bane & P. Emma • Extension of previous work on SLC • More compression stages • More free parameters • Shorter bunches • Requires good measurements, good intuition or really good guessing! • Not automated (yet!) • Single shot and non-destructive!

  10. Space charge fields are high enough to field (tunnel) ionize - no laser! • No timing or alignment issues • Plasma recombination not an issue - However, can’t just turn it off! - Ablation of the head Plasma Source Starts with Metal Vapor in a Heat-Pipe Oven Peak Field For A Gaussian Bunch: Ionization Rate for Li:  See D. Bruhwiler et al, Physics of Plasmas 2003

  11. 31.5 30.5 29.5 28.5 Energy [GeV] 27.5 26.5 25.5 24.5 No Plasma np = 2.8 x 1017 e-/cm3 Accelerating Gradient > 27 GeV/m! (Sustained Over 10cm) • Large energy spread after the • plasma is an artifact of doing single • bunch experiments • Electrons have gained > 2.7 GeV • over maximum incoming energy in • 10cm • Confirmation of predicted • dramatic increase in gradient with • move to short bunches • First time a PWFA has gained • more than 1 GeV • Two orders of magnitude larger • than previous beam-driven results • Future experiments will accelerate • a second “witness” bunch M.J. Hogan et al. Phys. Rev. Lett. 95, 054802 (2005)

  12. Summer 2004: • Results Recently Published • Outdated within two weeks! Summer 2005: • Increased beamline apertures • Plasma Length increased from 10 to 30 cm

  13. Summer 2004: • Results Recently Published • Outdated within two weeks! Summer 2005: • Increased beamline apertures • Plasma Length increased from 10 to 30 cm • Energy Gain > 10GeV! …but spectrometer redesign necessary to transport more of the low energy electrons

  14. Test of Notch Collimator - December 2005 Access to time coordinate along bunch x DE/E  t Insert tantalum blade as notch collimator  • Do not compress fully to preserve two bunches separated in time Exploit Position-Time Correlation on e- bunch in FFTB Dog Leg to create separate drive and witness bunch

  15. Test of Notch Collimator - December 2005 Energy Spectrum Before Plasma: High Energy Low Energy Energy Spectrum After Plasma: Shot # (Time) Energy Gain Ta Blade 100-300µm Wide 1.6cm Long (4 X0) Energy Loss • Acceleration correlates with collimator location (Energy) • No signature of temporally narrow witness bunch - yet! • Other interesting phenomena also correlate (see next slide) • Collimated spectra more complicated than anticipated

  16. Always New Things to Look At! (Part 1) Narrow Energy Spread! Energy [GeV]

  17. Trapped Particles Always New Things to Look At! (Part 2) • Two Main Features • 4 times more charge • 104 more light! Dipole

  18. 20cm 30cm • Particles are trapped and accelerated out of the plasma • Trapped particle energy scales with plasma length: 5GeV @ 30cm • Primary beam (28.5GeV) is also radiating after the plasma! 10cm Always New Things to Look At! (Part 2)

  19. Future Experiments - Part 1 (Next 2.5 months) • Create two bunches via notch collimator in FFTB and accelerate witness bunch with narrow energy spread • FFTB will soon be demolished to make way for LCLS What should we do to go out with a bang? Make the Highest Energy Electrons Ever @ SLAC! "Far better is it to dare mighty things, to win glorious triumphs, even though checkered by failure, than to take rank with those poor spirits who neither enjoy much nor suffer much, because they live in the gray twilight that knows not victory or defeat." Theodore Roosevelt, 1899 Use ~ 1 Meter-long Plasma to Double the Energy of Part of the Incoming Beam 28.5 GeV  57GeV

  20. Future Experiments - Part 2 (A Couple Years) 5.7GeV in 39cm SABER (South Arc Beamline Experimental Region): Short Pulse e+ Are the Frontier: Evolution of a positron beam/wakefiled and final energy gain in a self-ionized plasma 

  21. First measurement of the SLAC Ultra-short Bunch Length Demonstration of Field Ionized Plasma Source Measured Accelerating Gradients > 27 GeV/m (over 30cm) in a PWFA 31.5 30.5 29.5 Autocorrelation Amplitude [a.u.] 28.5 Energy [GeV] 27.5 26.5 25.5 Position [mm] 24.5 No Plasma Np = 2.8x1017 e-/cc Plasma Wakefield Accelerator Research Summary Over the past 5 years 20 Peer reviewed publications covering all aspects of beam plasma interactions: Focusing (e- & e+), Transport, Refraction, Radiation Production, Acceleration (e- & e+) E-164X Accomplishments Bright Future: Two bunch experiment, Energy Doubler, and longer term positrons @ SABER

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