1. 1 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. 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

2. U C L A 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? 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? Plasma Accelerators Showing Great Promise!

3. U C L A PWFA: Plasma Wakefield Acceleration E z : accelerating field N: # e - /bunch  z : gaussian bunch length k p : plasma wave number n p : plasma density n b : beam density or m For and + + + + + + + + + + + + ++ ++ + + + + + + + + + + + + + + - -- -- - - - - - - - -- - - - -- - - - - - - - - - - --- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- - -- - - - - - - - - -- - - - - - - - - - - - - - - -- - - - ---- - - - - - - - --- - - - - - - - - - - - - - - - - -- - - - - - - - - - - electron beam +++++++++++ +++++++++++++++ +++++++++++++++ +++++++++++++++ - - - - - - - -- Ez Accelerating Decelerating  Short bunch! m Linear PWFA Theory:  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. U C L A Located in the FFTB FFTB PWFA Experiments @ SLAC Share Common Apparatus e-e- N=1.8  10 10  z =20-12µm E=28.5 GeV Optical Transition Radiators Li Plasma Gas Cell: H 2, Xe, NO n e ≈0-10 18 cm -3 L≈2.5-20 cm Plasma light X-Ray Diagnostic, e-/e + Production Cherenkov Radiator Dump ∫Cdt Imaging Spectrometer x z y Energy Spectrum “X-ray” 25m Coherent Transition Radiation and Interferometer  FFTB

5. Wakefield Acceleration e - Focusing e - Phys. Rev. Lett. 88, 154801 (2002) Beam-Plasma Experimental Results (6 Highlights) X-ray Generation Phys. Rev. Lett. 88, 135004 (2002) Phase Advance   n e 1/2 L Matching e - Phase Advance   n e 1/2 L  1/sin  ≈≈ o BPM Data – Model Electron Beam Refraction at the Gas– Plasma Boundary Nature 411, 43 (3 May 2001) Wakefield Acceleration e + Phys. Rev. Lett. 90, 214801 (2003) Phys. Rev. Lett. 93, 014802 (2004)

6. U C L A 28 GeV Existing bends compress to <100 fsec ~1 Å Add 12-meter chicane compressor in linac at 1/3-point (9 GeV) Damping Ring 9 ps 0.4 ps <100 fs 50 ps SLAC Linac 1 GeV 20-50 GeV FFTB RTL 30 kA 80 fsec FWHM 1.5% 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 R 56 & linac phase, then measure incoming energy spectrum.

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

8. U C L A Non-Invasive Energy Spectrometer Upstream of Plasma

9. U C L A 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! 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. U C L A 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 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 

11. U C L A Accelerating Gradient > 27 GeV/m! (Sustained Over 10cm) No Plasma n p = 2.8 x 10 17 e - /cm 3 Energy [GeV] 31.5 30.5 29.5 28.5 27.5 26.5 25.5 24.5 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 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. 14 Access to time coordinate along bunch Exploit Position-Time Correlation on e - bunch in FFTB Dog Leg to create separate drive and witness bunch x   E/E  t 1.Insert tantalum blade as notch collimator 2Do not compress fully to preserve two bunches separated in time  Test of Notch Collimator - December 2005

15. 15 Low Energy High Energy Energy Spectrum Before Plasma: Energy Spectrum After Plasma: Shot # (Time) Ta Blade 100-300µm Wide 1.6cm Long (4 X 0 ) 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 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 Energy Loss Energy Gain Test of Notch Collimator - December 2005

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

17. Trapped Particles Two Main Features 4 times more charge 10 4 more light! Two Main Features 4 times more charge 10 4 more light! Always New Things to Look At! (Part 2) Dipole

18. 10cm 30cm 20cm 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! 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! Always New Things to Look At! (Part 2)

19. U C L A Create two bunches via notch collimator in FFTB and accelerate witness bunch with narrow energy spread Future Experiments - Part 1 (Next 2.5 months) "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 FFTB will soon be demolished to make way for LCLS Use ~ 1 Meter-long Plasma to Double the Energy of Part of the Incoming Beam 28.5 GeV  57GeV What should we do to go out with a bang? Make the Highest Energy Electrons Ever @ SLAC!

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

21. U C L A 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 Demonstration of Field Ionized Plasma Source Energy [GeV] 31.5 30.5 29.5 28.5 27.5 26.5 25.5 24.5 No Plasma N p = 2.8x10 17 e - /cc Measured Accelerating Gradients > 27 GeV/m (over 30cm) in a PWFA First measurement of the SLAC Ultra-short Bunch Length Position [mm] Autocorrelation Amplitude [a.u.] Plasma Wakefield Accelerator Research Summary Bright Future: Two bunch experiment, Energy Doubler, and longer term positrons @ SABER