review of ultra high-gradient acceleration schemes ...epaper.kek.jp/e02/talks/mozgb004.pdf · m....
TRANSCRIPT
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Review of Ultra HighReview of Ultra High--gradient gradient Acceleration Schemes, Results of Acceleration Schemes, Results of
ExperimentsExperimentsR. R. AssmannAssmann, CERN, CERN--SLSL
Reporting also on work done at SLAC, as member of and in collaboration with the Accelerator Research Department B (ARDB) under R. Siemann.
Thanks to my former co-workers and colleaguesM. Hogan (SLAC), C. Joshi (UCLA), T.Katsouleas (USC), W. Leemans (LBNL), J. Rosenzweig (UCLA), R. Siemann (SLAC)F. Amiranoff (Ecole Polytechnique)
for help and advice with this talk.Picture courtesy T. Katsouleas
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1) Why ultra-high gradients?The Livingston plotLimits for new particle acceleratorsBasic requirements for particle physics The promise of ultra-high gradients
2) How to get ultra-high gradients?Overview on schemes being followedPrinciples (plasma and vacuum concepts)
3) Experimental results - HighlightsPlasma wakefield accelerationLaser wakefield accelerationLaser acceleration
4) Moving towards usage in a linear colliderConsiderationsThe plasma booster for the Higgs?
5) Conclusion
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The Livingston plotThe Livingston plot
M. Tigner: �Does Accelerator-Based Particle Physics have a Future?�Physics Today, Jan 2001 Vol 54, Nb 1
The Livingston plot shows a saturation effect!
Practical limit for accelerators at the energy frontier:
Project cost increases as the energy must increase!Cost per GeV C.M. proton has decreased by factor 10 over last 40 years (not corrected for inflation)!
Not enough: Project cost increased by factor 200!
New technology needed�
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Basic requirements Basic requirements beyondbeyond next next generation egeneration e++ee-- linear colliderslinear colliders
Beam energy c.m. > 5 TeV
Luminosity > 1035 cm-2 s-1
Beam power(consequence): ~ 100 MW
Example:
Energy = 2.5 TeVLuminosity = 1035 cm-2 s-1
IP spot size = 10 nmBunch population = 5 109
New technologies for high energy colliders must be compatible with reasonable beam power:
Good efficiencyLow emittance (beam size)High bunch charge
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The promise of ultraThe promise of ultra--high gradientshigh gradients
Final energy = Active acceleration length × Accelerating gradient
1. Accelerators become longer.
2. Without �cheap� technology they become more expensive.
3. They do not fit on the sites of existing laboratories (more difficult
approval, additional infrastructure cost).
Exponential increase in energy without exponential increase in accelerating gradient:
Ultra-high gradients of up to 100 GV/m have been observed (gain of 3 orders of magnitude).
What is the status of this technology? Can we build ultra-short high-energy colliders?
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Feasible gradients in metallic structures:
Collider Gradient
SLC 20 MeV/m SLAC 1988-1997
ILC 70 - 85 MeV/m SLAC, KEKTESLA 25 - 35 MeV/m DESYCLIC 150 MeV/m CERN
What are ultraWhat are ultra--high accelerating gradients?high accelerating gradients?
Ultra-high accelerating gradients: 1 - 100 GeV/m
�obtained with various new technologies!
See talk by W. Wuensch�
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1) Why ultra-high gradients?The Livingston plotLimits for new particle acceleratorsBasic requirements for particle physics The promise of ultra-high gradients
2) How to get ultra-high gradients?Overview on schemes being followedPrinciples (plasma and vacuum concepts)
3) Experimental results - HighlightsPlasma wakefield accelerationLaser wakefield accelerationLaser acceleration
4) Moving towards usage in a linear colliderConsiderationsThe plasma booster for the Higgs?
5) Conclusion
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Advanced accelerator researchAdvanced accelerator research
Two types of advanced accelerators:
1. Wakefield accelerators
Dielectrics and microstructures (RF and two beam)
Plasma
2. Laser accelerators
Vacuum
Plasma
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! Laser Wake Field Accelerator(LWFA)A single short-pulse of photons
! Self Modulated Laser Wake Field Accelerator(SMLWFA)Raman forward scattering Instability
! Plasma Beat Wave Accelerator(PBWA)Two-frequencies, i.e., a train of pulses
! Plasma Wake Field Accelerator(PWFA)A high energy electron bunch
Concepts For PlasmaConcepts For Plasma--Based AcceleratorsBased AcceleratorsPioneered by J.M. Dawson
evolves to
Courtesy T. Katsouleas
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Basic principle and scaling rules 1Basic principle and scaling rules 1
I) Generate homogeneous plasma channel:GasLaserPlasma
II) Send dense electron beam towards plasma:
Beam density nb> Gas density n0
= ion = electron
Beam excited plasma. Also lasers can be used (laser wakefield acceleration).
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III) Excite plasma wakefields:
Electrons are expelled
Ion channelr
z
Basic principle and scaling rules 2Basic principle and scaling rules 2
Space charge force of beam ejects all plasma electrons promptly along radial trajectories
Pure ion channel is left: Ion-focused regime, underdense plasma
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Equilibrium condition: n
r
n0
Drive beam
Ion channel
Quasineutralplasma
an(neutralization radius)
Ion charge neutralizes beam charge:
0nna b
rn ⋅=σ
Beam size
Beam and plasma densities determine mostcharacteristics of plasma wakefields!
SLC:nb/n0 = 10
Basic principle and scaling rules 3Basic principle and scaling rules 3
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driving force: Space charge of drive beam displaces plasma electrons.
restoring force: Plasma ions exert restoring force
Electron motion solved with ...
Space charge oscillations(Harmonic oscillator)
++++++++++++++ ++++++++++++++++
----- --- ----------------
--------------
--------- ----
--- -------------------- - --
---- - -- ---
------ -
- -- ---- - - - - - ------ - -
- - - - --- --
- -- - - - - -
---- - ----
------
electron beam
+ + + + + + + + + + ++ + + + + + + + + + + + + + ++ + + + + + + + + + + + + + ++ + + + + + + + + + + + + + +-
- --
--- --
EzEz
Basic principle and scaling rules 4Basic principle and scaling rules 4
Longitudinal fields can accelerate and decelerate!
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Basic principle and scaling rules 5Basic principle and scaling rules 5
N re e
z
− ⋅→ ≈
σ1 (SLC: 0.2)
W n V mz ≈ ⋅ ⋅100 0 /
Accelerating field
Plasma density n0 1014 to 1015...
~ GV/m
Wavelength:
λ p mmcm
n≈ ⋅
−
11015 3
0
λp ~ mm
∝ N b zσ 2
(roughly)
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Basic principle and scaling rules 6Basic principle and scaling rules 6
W
rn e
T
m
n
cmr = ⋅ ⋅ = ⋅
−2 960
1002 0
14 3π π
Plasma ions move relatively little Constantfocusinggradient
β γϖ
= ⋅2c
p
Plasma �structures� are also super-strong �quadrupoles�!
(many thousand T/m)
... need to handle acceleration and focusing!
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Basic observationsBasic observations
� High accelerating gradients (many GV/m)
� Short wavelengths (< mm)
Short bunches (< 100µm)
� Strong transverse focusing (> kT/m), small β (< cm)
Small matched beam sizeRigid tolerances
Plasma based acceleration:
Availability of short bunches for experiments is limited!
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1) Why ultra-high gradients?The Livingston plotLimits for new particle acceleratorsBasic requirements for particle physics The promise of ultra-high gradients
2) How to get ultra-high gradients?Overview on schemes being followedPrinciples (plasma and vacuum concepts)
3) Experimental results - HighlightsPlasma wakefield accelerationLaser wakefield accelerationLaser acceleration
4) Moving towards usage in a linear colliderConsiderationsThe plasma booster for the Higgs?
5) Conclusion
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10 2
10 3
10 4
100 120 140 160 180 200
3.5 MeV4.1MeV6.5MeV5.0MeV7.3MeV8.6MeV5.2 MeV,
Cloud Chamber
}
Ele
ctro
n S
igna
l (A
U)
Pressure (mTorr)
Calculated trajectory
Acceleratedelectron track
Low energynoise
7.25 cm
3.4 cm
Bext
e-
Ultrahigh-gradient acceleration of injected electrons by laser-excited relativistic electron plasma waves
C.E. Clayton et al., Phys. Rev. Letters 70, 37 (1993)
Cloud chamber photograph Resonance curve
� Conclusive evidence of injected electron acceleration.
� First evidence of resonant acceleration.
UCLA
Courtesy C. Joshi, UCLA
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100
101
102
103
104
105
106
1 10
30% model25% model
Elec
trons
/MeV
Electron energy (MeV)303
InjectionEnergy
TrappingEnergy
Trapped electron acceleration by a laser-driven relativistic plasma wave
M. Everett et al. Nature 368, 527 (1994)
� First observation of energy gain beyond trapping threshold
� Evidence for energy loss as well as energy gain by plasma wave
UCLA
Courtesy C. Joshi, UCLA
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Observation of energy gain:
100 MeV
over
0.6 mm
Observation of electron energies beyond the linear dephasing limit from a laser-excited relativistic plasma wave
D. Gordon et al., Phys. Rev. Letters 80, 2133 (1998)UCLA
=> at least 160 GeV/m acceleration gradient
Courtesy C. Joshi, UCLA
Done at Rutherford Laboratories, UK
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The NEPTUNE Facility for 2nd Generation Advanced Accelerator Experiments
C. Joshi, J. Rosenzweig, C. Pellegrini, K.A. Marsh,S. Tochitsky, and C.E. Clayton
� Acceleration of injected, high-current beam to 100 MeV.� Acceleration of a pre-bunched electron beam.� Beam-physics studies.
Goals:
Laser-oscillatorroom
Experimenthall
Injectorlinac
Plasmaaccelerator
Amplifier hall
Controlroom
UCLA
Courtesy C. Joshi, UCLA
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Table-top Laser-Driven Electron Acceleration(via self-modulated laser wakefield in plasma)
D. Umstadter,S.-Y. Chen,A. Maksimchuk,R. Wagner,
Courtesy T. Katsouleas, USC
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Antonio C. Ting, Chris I. Moore, Rich Fischer, Dmitri Kaganovich, Ted Jones
NRL EXPERIMENTAL PROGRAM
Self-Modulated Laser Wakefield Accelerator:
Production of up to
100 MeV electrons
at >100 GV/m gradient
has been observed (over ~ mm). A. Ting, et al, Phys. Plasmas, 4, 1889 (1997)D. Kaganovich, et al, PRE, 59, R4769 (1999)
6 8 10 20 40 60 80100 200
103
104
105
106Shot 12 (10 kG)Shot 26 (10 kG)Shot 29 (5 kG)
Shot 33 (5 kG)Shot 39 (2.5 kG)Shot 40 (2.5 kG)
Rel
ativ
e #
of e
lect
rons
/MeV
/Ste
radi
anElectron energy (in MeV)
SM-LWFA electron energy spectrum
Courtesy T. Katsouleas, USC
Injection and channel guiding for the GeV range (longer).
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Laboratoire pour l�Utilisation des Lasers Intenses (LULI)CNRS - CEA - Ecole Polytechnique - Université Paris 6
LPNHE - LSI �LPGP - IC - LOA - CPTH100 TW LULI laser facility
35 fs, 600 mJ, 2.1019W/cm2, 10 Hz
≈ 100 MeV in
E >100 GV/m
Few nC > 4 MeVDivergence : few mrad
106
107
108
109
1010
1011
0 10 20 30 40 50 60 70Num
ber o
f ele
ctro
ns [/
MeV
/sr]
Electron energy [MeV]
detection threshold
ne=1.510 20 cm-3 T=2.6 MeV
ne=5.10 19 cm-3 T=8.1 MeV
Self-modulated wakefield experiments - 1 single laser pulse focused in a gas jet
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The potential energy gain is huge
The effective acceleration length is limited by diffraction of the laser beam
What about guiding the laser beam over 1 m ?
l0 = 1 µm , ne = 1017e-/cm3 , g = 100 : ∆W = 20 GeV over L = 1 m
Some laser guiding scheme is necessary to reach high energy gains
L=2ZR
E
Laser beam
Plasma wave
Laser guiding in dielectric capillary tubes
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Production of electron beams with low energy spreads and pulse-to-pulse energy stability in a plasma-based accelerator requires:
� Injection of femtosecond electron bunches
� Injection with femtosecond timing
Laser triggered injection of background plasma electrons into a plasma wake by beating of two colliding pulses
[E. Esarey et al., PRL, 79, 2682 (1997)]
Colliding pulse injector
Reference:E.Esarey et al., PRL '97C.B. Schroeder et al., PRE '99
ψ = plasma wake phase = tzk pp ω−
a2a1
a0
-17.5 -15 -12.5 -10 -7.5 -5 -2.5 0-0-0.75
-0.5
-0-0.25
0
0.5
0.751
0.25
Nor
mal
ized
po
tent
ials
Courtesy W. Leemans LBNL
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E-157 & E-162 & E-164 Collaborations
R. Assmann, F.-J. Decker, P. Emma, M. J. Hogan*, R.H. Iverson, C. O�Connell, P. Krejcik, P. Raimondi, R.H. Siemann, D. Walz
Stanford Linear Accelerator Center
B.E. Blue, C.E. Clayton, C. Huang, C. Joshi*, K.A. Marsh, W.B. Mori, S. Wang
University of California at Los Angeles
T. Katsouleas*, S. Lee, P. Muggli University of Southern California
� Extraordinarily high fields developed in beamplasma interactions
� Many questions related to the applicability ofplasmas to high energy accelerators andcolliders
Address these questions via experiments "
� E-157: First experiment to study Plasma WakefieldAcceleration (PWFA) of electrons over meter scaledistances
� Physics for positron beam drivers qualitativelydifferent (flow-in vs. blow-out) "E-162
� Opportunity for dramatically shorter bunches in theFFTB in 2003 with correspondingly highergradients (> GeV/m) " E-164
Plasma Wakefield Acceleration in Meter-long Plasmas
UCLA
Courtesy M. Hogan, T. Katsouleas
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Located in the FFTB
e- or e+
N=2·1010
σz=0.6 mmE=30 GeV
IonizingLaser Pulse
(193 nm)Li Plasma
ne≈2·1014 cm-3
L≈1.4 m
CerenkovRadiator
Streak Camera(1ps resolution)
BendingMagnet
X-RayDiagnostic
Optical TransitionRadiators Dump
12 m
∫Cdt
Experimental Layout
FFTB
UCLA
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0
100
200
300
400
500
600
0 2 4 6 8 10 12 14
BetatronFitShortBetaXPSI.graph
Plasma OFFPlasma ONEnvelope
σ x (µm
)
Ψ
L=1.4 mσ0=14 µm
εN=18×10-5 m-radβ0=6.1 cmα0=-0.6
� Smaller �matched� beam size at the plasma entrance reduces amplitude of the betatron oscillations measured at the OTR downstream of the plasma� Allows stable propagation through long plasmas (> 1 meter )
0
50
100
150
200
250
300
-2 0 2 4 6 8 10 12
05160cedFIT.graph
σX
DS
OTR
(µm
)
ψ=K*L∝ ne1/2L
σ0 Plasma Entrance=50 µm
εN=12×10-5 (m rad)β0=1.16m
E-157 E-162 Run 2
Beam Propagation Through A Long Plasma
C. E. Clayton et al., PRL 1/2002
Phase Advance Ψ ∝ ne1/2L
Plasma OFF
Phase Advance Ψ ∝ ne1/2L
s x (µ
m)
UCLA
E-157/E-162 collaboration
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UCLA
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
-8 -4 0 4 8
θ (m
rad)
φ (mrad)
θ∝ 1/sinφ
θ≈φo BPM DATA
Impulse Model
rc=α(nb/ne)1/2rb
θφ
Head
Plasma, ne
AsymmetricChannel
Beam Steering
SymmetricChannel
Beam Focusing
e-++++
++++++++
++++++++
++++++++
++++++++
+++++++++ + ++++
- - - - - - - - -
- - - - - - - - - - - - - - - - - - - - - - - - - - -
Core
Electron Beam Steering:Refraction At Plasma�Gas Boundary
P. Muggli et al., Nature 411, 2001
� Vary plasma � e- beam angle φusing UV pellicle
� Beam centroid displacement@ BPM6130, 3.8 m from theplasma center
E-157 collaboration
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Refraction of an Electron Beam:Interplay Between Simulation & Experiment
Laser off Laser on
3-D OSIRIS
PIC Simulation
Experiment(Cherenkov
images)
1 to 1 modeling of meter-scale experiment in 3-D!
P. Muggli et al., Nature 411, 2001
UCLA
E-157 collaboration
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Betatron Radiation of X-rays
l Peak brightness ~ 1019 photons/sec-mm2-mrad2-.1%bw!
Plasma focusing strength of 6000T/m acts as a strong undulator
UCLA
E-157 collaboration
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Average energy gain (slice average): 156 ±40 MeV(≈1.5 ×108 e-/slice)
Average energy loss (slice average): 159 ± 40 MeV
PicosecondGaussian
Slice Analysisof Many Events
-200
-150
-100
-50
0
50
100
150
200
-6 -4 -2 0 2 4 6 8
SliceEnergyGain3curves.graph
ne=1.6×1014 (cm-3)
ne=2.0×1014 (cm-3)
ne=(2.3±0.1)×1014 (cm-3)
Rel
ativ
e En
ergy
(MeV
)
τ (ps)
+σz +2σz +3σz-2σz -σz
E-162: Use Imaging SpectrometerTo Measure Energy Loss & Gain
Preliminary�
UCLA
E-164: > 1 GeV/m (2003) E-162 collaboration
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Other schemesOther schemes
Laser acceleration in vacuum (LEAP):
Two crossed laser scheme: �Only tantalizing of the interaction signature�.Power source: Laser.New proposal�
Inverse free electron laser (STELLA):
Power source: Laser.Successful staging. 90 MeV/m goal.Limit from synchrotron radiation at ~ 200 GeV. Bunches of femto-second length.
Di-electric wakefield accelerator:
Possible gradients: 100 MeV � 1GeVPower source: Drive beam.
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1) Why ultra-high gradients?The Livingston plotLimits for new particle acceleratorsBasic requirements for particle physics The promise of ultra-high gradients
2) How to get ultra-high gradients?Overview on schemes being followedPrinciples (plasma and vacuum concepts)
3) Experimental results - HighlightsPlasma wakefield accelerationLaser wakefield accelerationLaser acceleration
4) Moving towards usage in a linear colliderConsiderationsThe plasma booster for the Higgs?
5) Conclusion
RA EPAC02 36
Efficiency 1Efficiency 1
High beam power requires:
Efficient power generation
Progress in the field of lasers:
High peak power is possible (~ 100 TW )
Wall-plug-to-photon efficiency: 20 � 40 %
Better stability (pointing stability in sub µrad regime)
Efficiency of beam-driven PWFA: ~ 30% LEAP at the ORION Center
Robert L. Byer & Robert H. Siemann
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C. D. Barnes et al, SLAC PROPOSAL E-163
Efficiency 2Efficiency 2
Accelerating Microstructures:Re-use the laser beams for increasing efficiency!
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High quality beam transport 1High quality beam transport 1
Short accelerator, but what about emittance?R. Assmann, K. Yokoya, NIM 1997
Parameter PWFA LWFAAcceleration 1 GeV/m 30 GeV/mWavelength 2 mm 100 µmFocusing field 6,000 T/m 600,000 T/mModule length 6 m 1 mInjection energy 1 GeV 1 GeVFinal energy 1 TeV 1 TeVAcc. length 1 km 33 m
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Matched beam size at injection energy:
0
2
4
6
8
10
12
1e-08 1e-07 1e-06 1e-05
σ 0 [
µm]
γε [m-rad]
SLC
NLC
PWFALWFA
NLC type emittance requires sub-micron spot size!
High quality beam transport 2High quality beam transport 2
4 10-8 m rad
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High quality beam transport 3High quality beam transport 3
Tolerance for alignment beam - plasma wakefield:
� emittance 4 10-8 m rad with 200% emittance growth� Number of plasma cells: 167 or 33 (LWFA)
RMS alignment tolerance: < 300 nm (PWFA) 30 nm (LWFA)
High energy plasma-wakefield accelerator will have difficult alignment problems, but...
New ideas: Hollow plasma channels
No ions on axis, no focusing!Acceleration still works...
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0
100
200
300
400
500
600
700
800
900
0 0.5 1 1.5 2 2.5
channel Radius R wp/c
e+
e-
Positron longitudinal wake amplitude is comparable to e- in a hollow plasma:
Hollow plasma channels with eHollow plasma channels with e++ and eand e--
T. Katsouleas, USC
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The first step: A plasma afterburner?The first step: A plasma afterburner?
A 100 GeV-on-100 GeV e-e+ Collider at SLAC based on Plasma Afterburners
50 GeV e50 GeV e-- 50 GeV e50 GeV e++e-WFA e+WFA
IP
LENSESAfterburners
SLAC facilities
3 km
30 m
E-157 collaboration
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Afterburner vs. E157 ComparisonAfterburner vs. E157 Comparison
� Bunch: � Number: 1 - σz= .65mm
� Plasma� Density: 0 - 5e14 cm-3
� Length: 1.4 m
� Betatron Oscillations:� 0-5
� Bunches:� Number: 2- σz= .065mm, .033 mm� Separation: .019 mm
� Plasma� Density: 2e16 cm-3
� Length: 7 m
� Betatron Oscillations:� 100
E-157 Afterburner
Can we control 7 m of plasma?
Studies are ongoing for this idea�
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1) Why ultra-high gradients?The Livingston plotLimits for new particle acceleratorsBasic requirements for particle physics The promise of ultra-high gradients
2) How to get ultra-high gradients?Overview on schemes being followedPrinciples (plasma and vacuum concepts)
3) Experimental results - HighlightsPlasma wakefield accelerationLaser wakefield accelerationLaser acceleration
4) Moving towards usage in a linear colliderConsiderationsThe plasma booster for the Higgs?
5) Conclusion
RA EPAC02 45
Advanced accelerator concepts have made impressive progress:
High gradient acceleration up to 160 GV/m demonstrated.
Beam-plasma interaction of 30 GeV SLAC beam in 1.4m long plasma.
Experimental results in excellent agreement with predictions.
New applications (fsec science, plasma wiggler, kicker, lens,�).
Many problems still to be addressed for building a high energy collider�� but no fundamental show stopper!?
Accelerator physics moves into the right direction (small emittance, short bunches).
Can a plasma afterburner on a �conventional� accelerator be the first step?
ConclusionConclusion
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Plasma Accelerator Progress and the Livingston Curve
0
1
2
3
4
5
6
7
1930 1940 1950 1960 1970 1980 1990 2000 2010
LivingstonCurrent statusfuture
Log
of E
nerg
y in
MeV
Year
RAL/IC/UCLA/LULI NRL, UM
UCLA
UCLA Port J. LLNL/UCLA
?
SLAC/USC/UCLA/LBL
LEP
E-164/ORIONE-162
T. K
atso
ulea
s, U
SC