Bob Siemann SLAC HEPAP Subpanel on Accelerator Research •Plasma Wakefield Acceleration •Facilities and Opportunities •Concluding Remarks
Dec 21, 2005
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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
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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+
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Plasma Wakefield Acceleration - I
PWFA Accelerator Concept
Ions
- - - -- --- - --- - --- ---- - - - - - -- - - - ------ -+ + + -- -+---- + + + + ----+------+ + + -+ + ++ + -+ + ++ + + + ++ +--++ ++ ++ +++ + + + - + ++ ++ + + --+ ++ ++ + ++ +---+ + + + ++ ++ ++ ++ + + +- + + + + -+ - + + + + -+ + + + + + + -- -- --- - ---- - -- - -- - - --- - --- ----- - - - ------ ---- Ez Accelerating Decelerating
Plasma e-
electron beam
Ez ,linear ∝
N
σ2 z
⇒ Short bunch!
Fully relativistic plasma simulations agree with σz dependence
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Ez: accelerating field N: # e-/bunch σz: gaussian bunch length kp: plasma wave number np: plasma density nb: beam density
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Plasma Wakefield Acceleration - II
Closer to Reality
- - - --- - ---- - --- - -- -- - -- - - - - - -- - - ------- + + + + -+---- + + + + ----+------+ + + -+ + + + -+ + ++ + + + + ++ - ++ + + ++ + + + ++ +--++ ++ ++ +++ + + + - + ++ ++ + + -- + + + +--- - + + + + ++ + + + +- + + + + -+ - + + + + -+ + + + + -- -- --- - ---- - -- - - -- - - --- - - - ----- - - - ------ ---- Ez Accelerating Decelerating
Plasma e-
electron beam
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 z ~ λ plasma π
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Reality
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⇒
When combined with Ez ~ N σ z2
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n p ∝ 1 σ z2
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Plasma Wakefield Acceleration - III
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PWFA Experiments Located in the FFTB
North Damping Ring Positron Return Line e-gun Linac
Beam Switch Yard (BSY) Positron Source
PEP II
End Station A (ESA)
FFTB
South Damping Ring
3 km
FFTB
Energy Spectrum “X-ray”
Li Plasma Gas Cell: H2, Xe, NO ne≈0-1018 cm-3 L≈2.5-20 cm Plasma light
eN=1.8×1010 σz=20-12µm E=28.5 GeV Coherent Transition Radiation and Interferometer
y x z
∫Cdt
X-Ray Diagnostic, e-/e+ Production
Optical Transition Radiators
Imaging Cherenkov Spectrometer Radiator 25m
Dump
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FFTB
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Evolution of One Part Of the Apparatus
The SLAC linac and FFTB: A stable yet flexible resource and facility • Develop experience & expertise • Explore physics
2x1010 σz = 600 μm ArF laser (193 nm) to photoionize Li vapor
Be window
Li plasma 1x10 1.4 m Upstream OTR
14
cm-3
water jacket
Early Experiments
2x1010 σz = 15 μm
Downstream OTR
Magnet Cherenkov cell Toroid
filter wheels long λ autocorrelator
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3x10
The Present Run
.3 m
OTR, CTR, plasma light (spectrograph & gated camera)
Cherenkov & OTR
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3 Highlights of Early Experimental Results (σz = 600 μm)
05190cec+m2.txt 8:26:53 PM 6/21/00
Electron Beam Refraction modelthe Gas– at BPM data impulse Plasma Boundary
0.3 0.2
Positron Acceleration
θ∝1/sinφ
θ (mrad)
0.1 0 -0.1 -0.2 -0.3 -8 -4 0
θ≈φ
o
Matching e600 500 400
BPM Data – Model
4 8
σ (µm) x
L=1.4 m σ0=14 µm β0=6.1 cm εN=18×10-5 m-rad
Plasma OFF Plasma ON Envelope
φ (mrad)
α0=-0.6
300 200 100 0
Nature 411, 43 (3 May 2001)
Phys. Rev. Lett. 90, 214801 (2003)
BetatronFitShortBetaXPSI.graph
0
2
4
6
8
10
12
14
Ψ Phase Advance Ψ ∝ ne1/2L
Phys. Rev. Lett. 93, 014802 (2004) Dec 21, 2005 HEPAP Accel Research Subpanel 9
Short Bunches ( Ez ∝ N σ z2 )
50 ps
RTL
Damping Ring
SLAC Linac
1 GeV 9 ps 0.4 ps 20-50 GeV 20-
FFTB <100 fs
Add 12-meter chicane compressor Add1212-meter chicane compressor in linac at 1/3-point (9 GeV) in linac at1/31/3-point (9 GeV)
σ /〈E〉=1.51% (FWHM: 4.33%) 4 2 0 −2 0 0.5 1 n/103 1.5 2
E
Plasma Production by Tunnel Ionization
No ionization Complete ionization
〈E〉 = 28.493 GeV, N = 2.133×1010 ppb e 4 2
ΔE/〈E〉 /%
ΔE/〈E〉 /%
Energy Spectrum
1.5%
0 −2 0.1 0.2 z /mm 0.3
30 kA 80 fsec FWHM 28 GeV Dec 21, 2005
σ = 28.0 μm (FWHM: 24.6 μm, Gauss: 11.0 μm)
z
30 25
I /kA
Ipk = 30.631 kA
20 15 10 5 0 0.1
Phys. Rev. Lett. 93, 014802 (2004)
0.2 z /mm
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0.3
Bunch Length
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Summer 2004: Accelerating Gradient > 27 GeV/m! (Sustained Over 10cm)*
• Electrons have gained > 2.7 GeV over maximum incoming energy in 10cm • Confirmation of predicted dramatic increase in gradient with short bunches
No Plasma
np = 2.8x1017 cm-3
• First time a PWFA has gained more than 1 GeV & two orders of magnitude larger than previous beam-driven results
* Large energy spread after the plasma is an artifact of doing single bunch experiments
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Summer 2005: Next PRL Cover??
• Increased Beamline apertures • Increased plasma length to 30 cm • Electrons have gained > 10 GeV
Large amplitude plasma waves are sustained for at least 30 cm!
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Always New Things to Look At! Trapped Particles Narrow Energy Spread
Next Step = 2-bunches produced by collimation Coherent (at λ ~ 500 nm) Cherenkov Radiation
~ 80 MeV
Either > 500 MeV or bunching of the 28.5 GeV beam
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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
2x1010 σz = 15 μm Li plasma 3x1017cm-3 1.0 m
Incident Energy 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
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Facilities and Opportunities
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Facilities and Opportunities
The plasma acceleration program at the FFTB provides an excellent example of the ingredients of a successful accelerator research program Compelling scientific questions University/national lab collaboration – both benefit
state-of-the-art facilities
Experienced experimentalists, powerful scientific apparatus and rapid scientific progress follow naturally from these three
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Scientific Questions & Collaborations
Potential of plasma acceleration (USC/UCLA/SLAC)
Positron Acceleration
The photonics revolution & particle acceleration (Stanford/SLAC)
Limits of high gradient acceleration (ANL/LBNL/Maryland/MIT/NRL/SLAC)
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State-of-the Art Facilities: The NLCTA
The NLCTA is located in End Station B, which is the location of some ILC & LARP R&D, high gradient research, and the laser acceleration experiment (E163)
• Significant investment in the past for the warm ILC – 300 MeV X-band linac • Augmented with an S-band photoinjector for E163 • Additional X-band and L-band RF power is being developed or is available • Ti:Sapphire laser system installed • Space for experiments at 60 MeV and at 300 MeV
NLCTA
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Accelerator Research at the NLCTA
Use of the NLCTA for ILC related R&D continues and this R&D relies on some of the same systems as the non-ILC accelerator research Concentrate on non-ILC accelerator R&D at the NLCTA for this subpanel • High gradient RF studies – Sami Tantawi’s talk • Laser acceleration – Bob Byer’s talk • Plasma acceleration – Experiments at the NLCTA in the intermediate term Laser Room NLCTA 60 MeV beam 300 MeV beam An example Drive-witness configuration with variable delay E163 Hall
Plasma Experiment Location
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State-of-the Art Facilities:
SABER
The FFTB has been a gold mine for science •Plasma acceleration (E157, E162, E164, E164X, E167) •Plasma focusing (E150) •Positron production (E166) Short Bunches •High energy cosmic rays (FLASH (E165)) •Short pulse x-ray physics (SPPS) The LCLS will be constructed in the straight-ahead line presently occupied by the FFTB, and SABER has been proposed as a replacement.
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Science at SABER
The SABER white paper includes science in • Plasma Wakefield Acceleration and Beam-Plasma Physics • Inverse Compton Scattering • An Intense THz Light Source for Surface Chemistry • Magnetism and Solid State Physics • Laboratory Astrophysics Experiments
Energy Charge per pulse Pulse length at IP Spot size at IP Momentum spread Drift space available for experimental apparatus
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Up to 30 GeV nominal 3 nC e or e per pulse with full compression; 5 nC without full compression. 30 μm with 4 % momentum spread; 42 μm with 1.5 % momentum spread. 10 μm nominal (η = η’ = 0) 4 % full width with full compression; < 0.5 % full width without compression. 2 m from last quadrupole to focal point. Approximately 23 m from the focal point to the Arc 3 magnets
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Plasma Experiments at SABER Short Pulse e+ Are the Frontier
Evolution of a positron beam/wakefield and final energy gain in a self-ionized plasma
5.7 GeV in 39cm N = 8.8x109 σr = 11 μm σz = 19.6 μm np = 1.8x1017 cm-3
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Concluding Remarks
Dec 21, 2005
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Accelerator Research at SLAC
Accelerator research at SLAC is relevant to high energy physics with research • Supporting operating accelerators • Designing the International Linear Collider • Exploring the technology and physics for accelerators in the future Past accomplishments have been crucial in defining high energy physics today - storage rings and linear collider The research includes theory, simulation, experiment, and technology development. • The results support accelerators that are centerpieces for other sciences. For example the LCLS. Collaboration and education are vital aspects of our work. • We work hand-in-hand with scientists from other labs and universities • Education of students from collaborating institutions and from Stanford
Sho Wang & Chris Clayton
Chris Barnes
Caolionn O’Connell
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