e-169: wakefield acceleration in dielectric structures a proposal for experiments at the saber...
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E-169: Wakefield Acceleration in Dielectric
Structures
A proposal for experiments at the SABER facility
E-169: Wakefield Acceleration in Dielectric
Structures
A proposal for experiments at the SABER facility
J.B. RosenzweigUCLA Dept. of Physics and
AstronomySLAC EPAC - December 4, 2006
J.B. RosenzweigUCLA Dept. of Physics and
AstronomySLAC EPAC - December 4, 2006
E169 CollaborationE169 Collaboration
H. Badakov, M. Berry, I. Blumenfeld, A. Cook, F.-J. Decker, M. Hogan, R. Ischebeck, R. Iverson, A. Kanareykin, N. Kirby, P. Muggli, J.B. Rosenzweig, R. Siemann, M.C. Thompson,
R. Tikhoplav, G. Travish, D. Walz
Department of Physics and Astronomy, University of California, Los AngelesStanford Linear Accelerator CenterUniversity of Southern California
Lawrence Livermore National LaboratoryEuclid TechLabs, LLC
Collaboration spokespersons
H. Badakov, M. Berry, I. Blumenfeld, A. Cook, F.-J. Decker, M. Hogan, R. Ischebeck, R. Iverson, A. Kanareykin, N. Kirby, P. Muggli, J.B. Rosenzweig, R. Siemann, M.C. Thompson,
R. Tikhoplav, G. Travish, D. Walz
Department of Physics and Astronomy, University of California, Los AngelesStanford Linear Accelerator CenterUniversity of Southern California
Lawrence Livermore National LaboratoryEuclid TechLabs, LLC
Collaboration spokespersons
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UCLA
Proposal MotivationProposal Motivation
Take advantage of unique experimental opportunity at SLAC SABER: ultra-short intense beams Advanced accelerators for high energy
frontier Promising path: dielectric wakefields
Extend successful T-481 investigations Dielectric wakes >10 GW Complete studies of revolutionary technique
Take advantage of unique experimental opportunity at SLAC SABER: ultra-short intense beams Advanced accelerators for high energy
frontier Promising path: dielectric wakefields
Extend successful T-481 investigations Dielectric wakes >10 GW Complete studies of revolutionary technique
Colliders and the energy frontier
Colliders and the energy frontier
Colliders uniquely explore energy frontier
Exp’l growth in equivalent beam energy w/time Livingston plot: “Moore’s
Law” for accelerators We are now falling off
plot! Challenge in energy, but
not only…luminosity as well
Colliders uniquely explore energy frontier
Exp’l growth in equivalent beam energy w/time Livingston plot: “Moore’s
Law” for accelerators We are now falling off
plot! Challenge in energy, but
not only…luminosity as well
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Meeting the energy challenge
Meeting the energy challenge
Avoid gigantism Cost above all
Higher fields give physics challenges Linacs: accelerating
fields
Enter world of high energy density (HED) physics Impacts luminosity
challenge…
Avoid gigantism Cost above all
Higher fields give physics challenges Linacs: accelerating
fields
Enter world of high energy density (HED) physics Impacts luminosity
challenge…
z
d
Linear accelerator schematic
HED in future colliders: ultra-high fields in
accelerator
HED in future colliders: ultra-high fields in
accelerator High fields in violent accelerating systems
High field implies small Relativistic oscillations… Limit peak power Limit stored energy
Diseases Breakdown, dark current Pulsed heating Where is source < 1 cm?
Approaches High frequency, normal cond. Superconducting Lasers and/or plasma waves
High fields in violent accelerating systems
High field implies small Relativistic oscillations… Limit peak power Limit stored energy
Diseases Breakdown, dark current Pulsed heating Where is source < 1 cm?
Approaches High frequency, normal cond. Superconducting Lasers and/or plasma waves
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€
eE z /mcω ~ 1
Scaling the accelerator in size
Scaling the accelerator in size
Lasers produce copious power (~J, >TW) Scale in size by 4 orders of magnitude < 1 m challenge in beam dynamics Reinvent the structure using dielectric
To jump to GV/m, only need mm-THz Must have new source…
Lasers produce copious power (~J, >TW) Scale in size by 4 orders of magnitude < 1 m challenge in beam dynamics Reinvent the structure using dielectric
To jump to GV/m, only need mm-THz Must have new source…
Resonant dielectric structure schematic
Possible new paradigm for high field accelerators: wakefields
Possible new paradigm for high field accelerators: wakefields
Coherent radiation from bunched, v~c e- beam Any impedance environment
Non-resonant, short pulse operation possible
Also powers more exotic schemes Plasma, dielectrics…
Intense beams needed by other fields X-ray FEL, X-rays from Compton scattering THz sources
Coherent radiation from bunched, v~c e- beam Any impedance environment
Non-resonant, short pulse operation possible
Also powers more exotic schemes Plasma, dielectrics…
Intense beams needed by other fields X-ray FEL, X-rays from Compton scattering THz sources
High gradients, high frequency, EM power from wakefields: CLIC @ CERNHigh gradients, high frequency, EM
power from wakefields: CLIC @ CERNCLIC wakefield-powered resonant scheme
CLIC 30 GHz, 150 MV/m structures
CLIC drive beam extraction structure
Power
The dielectric wakefield accelerator
The dielectric wakefield accelerator
Higher accelerating gradients: GV/m level Dielectric based, low loss, short pulse Higher gradient than optical? Different breakdown
mechanism No charged particles in beam path…
Use wakefield collider schemes Afterburner possibility for existing accelerators CLIC style modular system
Spin-offs THz radiation source
Higher accelerating gradients: GV/m level Dielectric based, low loss, short pulse Higher gradient than optical? Different breakdown
mechanism No charged particles in beam path…
Use wakefield collider schemes Afterburner possibility for existing accelerators CLIC style modular system
Spin-offs THz radiation source
Dielectric Wakefield Accelerator
Overview
Dielectric Wakefield Accelerator
Overview
Electron bunch ( ≈ 1) drives Cerenkov wake in cylindrical dielectric structure
Variations on structure featuresMultimode excitation
Wakefields accelerate trailing bunch
Mode wavelengths
€
n ≈4 b − a( )
nε −1
Peak decelerating field
€
eE z,dec ≈−4Nbremec
2
a8π
ε −1εσ z + a
⎡
⎣ ⎢
⎤
⎦ ⎥
Design Parameters
€
a,b
€
σ z
€
Ez on-axis, OOPIC
*
Extremely good beam needed
€
R =E z,acc
E z,dec
≤ 2
Transformer ratio
Experimental BackgroundArgonne / BNL experiments
Experimental BackgroundArgonne / BNL experiments
Proof-of-principle experiments (W. Gai, et al.)
ANL AATF
Mode superposition (J. Power, et al. and S. Shchelkunov, et al.)
ANL AWA, BNL
Transformer ratio improvement (J. Power, et al.)
Beam shaping Tunable permittivity structures
For external feeding (A. Kanareykin, et al.)
Proof-of-principle experiments (W. Gai, et al.)
ANL AATF
Mode superposition (J. Power, et al. and S. Shchelkunov, et al.)
ANL AWA, BNL
Transformer ratio improvement (J. Power, et al.)
Beam shaping Tunable permittivity structures
For external feeding (A. Kanareykin, et al.)
Tunable permittivity
E vs. witness delay
Gradients limited to <50 MV/m by available beam
T-481: Test-beam exploration of breakdown
threshold
T-481: Test-beam exploration of breakdown
threshold Leverage off E167 Existing optics Beam diagnostics Running protocols
Goal: breakdown studies Al-clad fused silica fibers
ID 100/200 m, OD 325 m, L=1 cm
Avalanche v. tunneling ionization Beam parameters indicate ≤12
GV/m longitudinal wakes 30 GeV, 3 nC, σz ≥ 20 m
48 hr FFTB run, Aug. 2005 Follow-on planned, no time
Leverage off E167 Existing optics Beam diagnostics Running protocols
Goal: breakdown studies Al-clad fused silica fibers
ID 100/200 m, OD 325 m, L=1 cm
Avalanche v. tunneling ionization Beam parameters indicate ≤12
GV/m longitudinal wakes 30 GeV, 3 nC, σz ≥ 20 m
48 hr FFTB run, Aug. 2005 Follow-on planned, no time
T-481 “octopus” chamber
T481: Beam ObservationsT481: Beam Observations
Multiple tube assemblies Alignment to beam path Scanning of bunch lengths for
wake amplitude variation Excellent flexibility: 0.5-12
GV/m Vaporization of Al cladding…
dielectric more robust Observed breakdown threshold
(field from simulations) 4 GV/m surface field 2 GV/m acceleration field!
Correlations to post-mortem inspection
Multiple tube assemblies Alignment to beam path Scanning of bunch lengths for
wake amplitude variation Excellent flexibility: 0.5-12
GV/m Vaporization of Al cladding…
dielectric more robust Observed breakdown threshold
(field from simulations) 4 GV/m surface field 2 GV/m acceleration field!
Correlations to post-mortem inspection
View end of dielectric tube; frames sorted by increasing peak currentView end of dielectric tube; frames sorted by increasing peak current
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1.00 107
1.20 107
1.40 107
1.60 107
1.80 107
2.00 107
2.20 107
2.40 107
0 50 100 150 200
08170cs
Breakdown Camera Pixel Sum
Bunch Length Variable[rms XRAY]
Breakdown Threshold Observation
Breakdown Threshold Observation
OOPIC Simulation StudiesOOPIC Simulation Studies
Parametric scans Heuristic model
benchmarking Determine field levels in
experimentMulti-mode excitation
Single mode excitation
Example scan, comparison to heuristic model Fundamental
0
5 109
1 1010
1.5 1010
40 60 80 100120140160
E_dec,max (OOPIC)E_acc max (OOPIC)E_dec,theory
Ez (V/m)
a ( )m
T-481: Inspection of Structure Damage
T-481: Inspection of Structure Damage
ultrashortbunch
longerbunch
Aluminum vaporized from pulsed heating!
Laser transmission test
Bisected fiber
Damage consistent with beam-induced discharge
Proposal: E169 at SABERProposal: E169 at SABER
Research GV/m acceleration scheme in DWA Push technique for next generation accelerators Goals
Explore breakdown issues in detail Determine usable field envelope Coherent Cerenkov radiation measurements: Explore alternate materials Explore alternate designs and cladding: Varying tube dimensions
Impedance change Breakdown dependence on wake pulse length
Research GV/m acceleration scheme in DWA Push technique for next generation accelerators Goals
Explore breakdown issues in detail Determine usable field envelope Coherent Cerenkov radiation measurements: Explore alternate materials Explore alternate designs and cladding: Varying tube dimensions
Impedance change Breakdown dependence on wake pulse length
Proposal: E-169 at SABERHigh-gradient Acceleration
Goals in 3 Phases
Proposal: E-169 at SABERHigh-gradient Acceleration
Goals in 3 Phases Phase 1: Complete breakdown study
Coherent Cerenkov (CCR) measurement
explore (a, b, σz) parameter space
Alternate cladding
Alternate materials (e.g. diamond)
Explore group velocity effect
σz≥ 20 m
σr< 10 m
U 25 GeV
Q 3 - 5 nC
€
UC ≈eNb E z,decLd
2
€
Un ≈π 2nNb
2remec2σ z
2Ld
2a b − a( )2
8π ε −1( )εσ z + ε −1( )a[ ]exp −
nπσ z
2 b − a( ) ε −1
⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟
2 ⎡
⎣
⎢ ⎢
⎤
⎦
⎥ ⎥
A. Kanareykin
Total energy gives field measure
Harmonics are sensitive σz diagnostic
CVD deposited diamond
€
T = Ld / c − vg( ) ≤ εLd / c ε −1( )
E-169 at SABER: Phase 2 & 3E-169 at SABER: Phase 2 & 3
Phase 2: Observe acceleration
10 cm tube length
longer bunch, σz ~ 150 m
moderate gradient
Single mode
σz150 m
σr< 10 m
energy 25 GeV
Q 3 - 5 nC Phase 3: Scale to 1 m fibers
Ez on-axisBefore & after momentum distributions (OOPIC)
*
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Alignment
Group velocity….
Experimental Issues: THz DetectionExperimental Issues: THz Detection
Conical launching horns
Signal-to-noise ratio
Detectors
Impedance matching to free space
Direct radiation forward
Background of CTR from tube end
SNR ~ 3 - 5 for 1 cm tube
Pyroelectric
Golay cell
Helium-cooled bolometer
Michelson interferometer for autocorrelation
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THz in Wider UseTHz in Wider Use
Screening/remote sensing
Atmosphere spectroscopy
Defect analysis Synergy with LCLS
Many chemical and organic molecules have distinct absorption spectra in THz
Transparency of many materials
Safe for living tissue
UCLA
Detection of chemical and biological hazards
Mittelman, et al.
Experimental Issues: Alternate DWA design, cladding, materials
Experimental Issues: Alternate DWA design, cladding, materials
Aluminum cladding used in T-481
Dielectric cladding
Bragg fiber? Alternate dielectric: CVD
diamond High breakdown threshold Doping gives dow SEC
Vaporized at even moderate wake amplitudes
Low vaporization threshold due to low pressure
and thermal conductivity of environment
Lower refractive index provides internal reflection
Low power loss, damage resistatnBragg fiber
E-169 at SABER: Implementation/DiagnosticsE-169 at SABER: Implementation/Diagnostics
New precision alignment vessel?
Upstream/downstream OTR screens for alignment
X-ray stripe CTR/CCR for bunch length Imaging magnetic
spectrometer Beam position monitors and
beam current monitors Controls…Heavy SLAC involvement
Much shared with E168
E-169 TimelineE-169 Timeline
SABERoperational
January2007
January2008
January2009
3-weekrun
3-weekrun Phase 3 ?
Phase 1: 3 weeks @ SABERPhase 2: 3 weeks @ SABERPhase 2+: + 6 months
Conclusions/directionsConclusions/directions
Unique opportunity to explore GV/m dielectric wakes at SABER Flexible, ultra-intense beams Only possible at SLAC SABER Low gradient experiments at UCLA Neptune
Extremely promising first run Collaboration/approach validated
Much physics, parameter space to explore
Unique opportunity to explore GV/m dielectric wakes at SABER Flexible, ultra-intense beams Only possible at SLAC SABER Low gradient experiments at UCLA Neptune
Extremely promising first run Collaboration/approach validated
Much physics, parameter space to explore
Marx panel recommendation
July 2006
Marx panel recommendation
July 2006“A major challenge for the accelerator science community is to identify and develop new concepts for future energy frontier accelerators that will be able to provide the exploration tools needed for HEP within a feasible cost to society. The future of accelerator-based HEP will be limited unless new ideas and new accelerator directions are developed to address the demands of beam energy and luminosity and consequently the management of beam power, energy recovery, accelerator power, size, and cost.”
“A major challenge for the accelerator science community is to identify and develop new concepts for future energy frontier accelerators that will be able to provide the exploration tools needed for HEP within a feasible cost to society. The future of accelerator-based HEP will be limited unless new ideas and new accelerator directions are developed to address the demands of beam energy and luminosity and consequently the management of beam power, energy recovery, accelerator power, size, and cost.”
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