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.”