Bob Siemann SLAC HEPAP Subpanel on Accelerator Research • Plasma Wakefield Acceleration • Facilities and Opportunities • Concluding Remarks Dec 21, 2005 HEPAP Accel Research Subpanel 1 Plasma Wakefield Acceleration Presented by: Bob Siemann On behalf of: The E157, E162, E-164, E-164X, E167 Collaborations S. Deng,* T. Katsouleas, S. Lee,* R. Maeda, P. Muggli, E. Oz* and W. Quillinan University of Southern California B. Blue,* C. E. Clayton, E. Dodd, R. A. Fonseca, R. Hemker,* C. Huang,* D.K. Johnson,* C. Joshi, W. Lu,* K.A. Marsh, W. B. Mori, C. Ren, F. Tsung, S. Wang* and M. Zhou* University of California, Los Angeles R. Assmann, C. D. Barnes,* I. Blumenfeld,* F.-J. Decker, P. Emma, M.J. Hogan, R. Ischebeck, R.H. Iverson, N.A. Kirby,* P. Krejcik, C. O'Connell,* P. Raimondi, S.Rokni, R.H. Siemann, D. Walz and D. Whittum Stanford Linear Accelerator Center P. Catravas, S. Chattopadhyay, E. Esarey and W. P. Leemans Lawrence Berkeley National Laboratory The authors of at least one of our peer-reviewed papers * = the 14 students in these collaborations 1
Plasma Accelerators Showing Great Promise Scientific Question: Accelerating Gradients > 100 GeV/m have been measured in Scientific Question: Accelerating Gradients > 100 GeV/m have been measured in laser-plasma interactions. Can one make & sustain such high gradients for laser-plasma interactions. Can one make & sustain such high gradients for lengths that give significant energy gain? lengths that give significant energy gain? We are studying the underlying beam/plasma physics and looking at issues associated with applying the large focusing (MT/m) and accelerating (GeV/m) gradients in plasmas to high energy physics and colliders Unique SLAC Facilities The SLAC Linac & FFTB which have • High Beam Energy • Short Bunch Length • High Peak Current • Power Density • e- & e+ Dec 21, 2005 HEPAP Accel Research Subpanel 3 Plasma Wakefield Acceleration - I PWFA Accelerator Concept Ions - - - - - -- - - - - - - -- Plasma e - -- - - - - - - - -- - - - - - - - - - - - - - - - - -- - - - -- - - - - - - - -- - - - - - - - -- - - - -- - -- -- -- - + + + + + + + + + + + + + + + - - - + + - + + + + + + + + + + + + + + + - - - - - + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + - + + + + + + + + + - - ------ - -- - - - - -- - - - - - --- - - - - - -- - e l e c t r o - - - - - n - --- - - - - - - - - - -- - - - - - - - - - b - e a m Ez Ez Decelerating Accelerating E z : accelerating field N : # e - /bunch E z , linear ∝ N σ z : gaussian bunch length � ⇒ Short bunch! k p : plasma wave number σ z 2 n p : plasma density n b : beam density Fully relativistic plasma simulations agree with σ z dependence Dec 21, 2005 HEPAP Accel Research Subpanel 4 2
Plasma Wakefield Acceleration - II Closer to Reality - - - - - -- - - - - - - -- Plasma e - -- - - - - - - - -- - - - - - - - - - - - - - - - - -- - - - -- - - - - - - - -- - - - - - - - -- - - - -- - -- -- -- - + + + + + + + + + + + + + + + - - - + + - - - - + + + + + + + + + + + + + + + - - + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + - + + + + + + + + + - - ------ - -- - - - - -- - - - - - --- - - - - - -- - e l e c t r - - - - - o n - --- - - - - - - - - - -- - - - - - - - - - - b e a m Ez Ez Decelerating Accelerating In most of the experiments a single bunch from the linac drives a large amplitude plasma wave which focus and accelerates particles AND the tail of that bunch is used to measure the accelerating field. ⇒ σ λ π ∝ σ 2 ~ 1 When combined with ⇒ N σ 2 ~ n E z plasma p z z z Dec 21, 2005 HEPAP Accel Research Subpanel 5 Plasma Wakefield Acceleration - III Reality Dec 21, 2005 HEPAP Accel Research Subpanel 6 3
PWFA Experiments Located in the FFTB Beam Switch Yard PEP II (BSY) North Damping End Ring Station A (ESA) Positron Return Line Positron Source e-gun FFTB Linac South Damping Ring 3 km Energy Li Plasma Spectrum Gas Cell: H 2 , Xe, NO � FFTB n e ≈ 0-10 18 cm -3 “X-ray” ∫ Cdt L ≈ 2.5-20 cm X-Ray y x Diagnostic, Plasma light e - e-/e + z Production N =1.8 × 10 10 Coherent σ z =20-12µm Imaging Transition Cherenkov Optical Transition Spectrometer E =28.5 GeV Radiation and Radiators Radiator Dump Interferometer 25m FFTB Dec 21, 2005 HEPAP Accel Research Subpanel 7 Evolution of One Part Of the Apparatus The SLAC linac and FFTB: A stable yet flexible resource and facility • Develop experience & expertise • Explore physics ArF laser (193 nm) to photoionize Li vapor 2x10 10 Be window σ z = 600 μ m Early Experiments Li plasma 1x10 14 cm -3 Li plasma 1x10 14 cm -3 1.4 m water jacket Upstream OTR Downstream OTR 2x10 10 Magnet σ z = 15 μ m Cherenkov cell 3x10 17 Toroid The Present Run .3 m filter wheels OTR, CTR, plasma light (spectrograph & gated camera) long λ auto- Cherenkov correlator & OTR Dec 21, 2005 HEPAP Accel Research Subpanel 8 4
3 Highlights of Early Experimental Results ( σ z = 600 μ m) Electron Beam Refraction at the Gas– 05190cec+m2.txt 8:26:53 PM 6/21/00 Positron Acceleration impulse model BPM data Plasma Boundary θ∝ 1/sin φ 0.3 0.2 0.1 θ (mrad) 0 Matching e - θ ≈ φ -0.1 600 o BPM Data L=1.4 m Plasma OFF σ 0 =14 µm -0.2 Plasma ON 500 Envelope – Model ε N =18 × 10 -5 m-rad -0.3 β 0 =6.1 cm 400 -8 -4 0 4 8 φ (mrad) α 0 =-0.6 σ x (µm) 300 Nature 411 , 43 (3 May 2001) Phys. Rev. Lett. 90 , 214801 (2003) 200 100 BetatronFitShortBetaXPSI.graph 0 0 2 4 6 8 10 12 14 Phase Advance Ψ ∝ n e Ψ 1/2 L Phys. Rev. Lett. 93 , 014802 (2004) Dec 21, 2005 HEPAP Accel Research Subpanel 9 Short Bunches ( ) ∝ N σ 2 E z z Damping Ring Damping Ring 50 ps 50 ps SLAC Linac SLAC Linac FFTB FFTB RTL RTL 1 GeV 1 GeV 20 20- -50 GeV 50 GeV 9 ps 9 ps 0.4 ps 0.4 ps <100 fs <100 fs Add 12- Add 12 -meter chicane compressor meter chicane compressor Add 12-meter chicane compressor in linac at 1/3- in linac at 1/3 -point (9 GeV) point (9 GeV) in linac at 1/3-point (9 GeV) Plasma Production by Tunnel Ionization 〈 E 〉 = 28.493 GeV, N e = 2.133 × 10 10 ppb σ E / 〈 E 〉 =1.51% (FWHM: 4.33%) No ionization Complete ionization 4 4 2 2 Δ E / 〈 E 〉 /% Δ E / 〈 E 〉 /% Energy Spectrum 1.5% 1.5% 0 0 −2 −2 0 0.5 1 1.5 2 0.1 0.2 0.3 z /mm n /10 3 σ z = 28.0 µ m (FWHM: 24.6 µ m, Gauss: 11.0 µ m) 30 kA 30 kA I pk = 30.631 kA 30 25 80 fsec FWHM 20 80 fsec FWHM I /kA 15 10 28 GeV 28 GeV Dec 21, 2005 5 HEPAP Accel Research Subpanel ← Increasing Bunch Length 10 0 0.1 0.2 0.3 z /mm Phys. Rev. Lett. 93 , 014802 (2004) 5
Summer 2004: Accelerating Gradient > 27 GeV/m! (Sustained Over 10cm)* • Electrons have gained > 2.7 • Electrons have gained > 2.7 GeV over maximum incoming GeV over maximum incoming energy in 10cm energy in 10cm • Confirmation of predicted • Confirmation of predicted dramatic increase in gradient dramatic increase in gradient with short bunches with short bunches • First time a PWFA has gained • First time a PWFA has gained No Plasma n p = more than 1 GeV & two orders more than 1 GeV & two orders 2.8x10 17 cm -3 of magnitude larger than of magnitude larger than previous beam-driven results previous beam-driven results * Large energy spread after the plasma is an artifact of doing single bunch experiments Dec 21, 2005 HEPAP Accel Research Subpanel 11 Summer 2005: Next PRL Cover?? • Increased Beamline apertures • Increased Beamline apertures • Increased plasma length to 30 • Increased plasma length to 30 cm cm • Electrons have gained > 10 GeV • Electrons have gained > 10 GeV Large amplitude plasma waves are sustained for at least 30 cm! Dec 21, 2005 HEPAP Accel Research Subpanel 12 6
Always New Things to Look At! Trapped Particles Coherent (at λ ~ 500 nm) Narrow Energy Spread Cherenkov Radiation Next Step = 2-bunches ~ 80 MeV produced by collimation Either > 500 MeV or bunching of the 28.5 GeV beam Dec 21, 2005 HEPAP Accel Research Subpanel 13 Future Plasma Acceleration Research Three different time horizons I. The remainder of the lifetime of the FFTB • two bunch experiment • understanding of the trapped particles from the plasma • the energy doubling experiment 2x10 10 σ z = 15 μ m Incident Energy Li plasma 3x10 17 cm -3 Li plasma 3x10 17 cm -3 1.0 m Dipole Dump Magnet II. The Intermediate term – experiments at the NLC Test Accelerator III. Long term - high energy experiments with short bunch e + at SABER Return to these in a few minutes Dec 21, 2005 HEPAP Accel Research Subpanel 14 7
Facilities and Opportunities Dec 21, 2005 HEPAP Accel Research Subpanel 15 Facilities and Opportunities The plasma acceleration program at the FFTB provides an excellent example of the ingredients of a successful accelerator research program University/national lab collaboration Compelling scientific questions – both benefit state-of-the-art facilities Experienced experimentalists, powerful scientific apparatus and rapid scientific progress follow naturally from these three Dec 21, 2005 HEPAP Accel Research Subpanel 16 8
Recommend
More recommend
