An overview of the advanced accelerator research at SLAC. Experiments are being conducted with the goal of exploring high gradient acceleration mechanisms.

An overview of the advanced accelerator research at SLAC. Experiments are being conducted with the goal of exploring high gradient acceleration mechanisms. One line of research is devoted to plasma wakefield acceleration where a plasma wave is excited by a beam. Particles in the head of the beam lose energy to this wave while those in the tail are accelerated by it. These experiments are conducted with 30 GeV electron and positron beams with bunch lengths between 10 and 600 microns. Results include acceleration, focusing and transport, and plasma production through tunneling ionization. The other line of research is devoted to laser-driven accelerators. These linacs shrunk down to the micron scale are concepts based on laser and photonic developments. The concepts and planned experimental work are described. This work is performed by UCLA, USC, Stanford, SLAC collaborations.

Plasma Wakefield And Laser-Driven Accelerators

Bob Siemann, SLAC

1. Introductory Comments2. Vacuum Laser Acceleration3. Plasma Wakefield Acceleration4. Summary

Advanced Accelerator Physics at SLACAdvanced Accelerator Physics at SLAC

T. Katsouleas, S. Deng, S. Lee, P. Muggli, E. OzUniversity of Southern California

B. Blue, C. E. Clayton, V. Decyk, C. Huang, D. Johnson, C. Joshi, J.-N. Leboeuf, K. A. Marsh, W. B. Mori, C. Ren, F. Tsung, S. Wang

University of California, Los Angeles

R. Assmann, C. D. Barnes, F.-J. Decker, P. Emma, M. J. Hogan, R. Iverson, P. Krejcik, C. O’Connell, P. Raimondi, R.H. Siemann, D. R. Walz

Stanford Linear Accelerator Center

Beam-Driven Plasma Acceleration: E-157, E-162, E-164, E-164X

R. L. Byer, T. Plettner, T. I. Smith, R. L. SwentStanford University

E. R. Colby, B. M. Cowan, M. Javanmard, X. E. Lin, R. J. Noble, D. T. Palmer, C. Sears, R. H. Siemann, J. E. Spencer, D. R. Walz, N. Wu

Stanford Linear Accelerator Center

J. RosenzweigUniversity of California, Los Angeles

Vacuum Laser Acceleration: LEAP, E-163

Science Innovation

Particle Physics Discoveries

• 2 ’s• J/• W & Z• top

Accelerator Innovations• Phase focusing• Klystron• Strong focusing• Colliding beams• Superconducting magnets• Superconducting RF

Plasma Wakefield And Laser-Driven Accelerators

1. Introductory Comments

2.Vacuum Laser Acceleration3. Plasma Wakefield Acceleration4. Summary

Vacuum Laser AccelerationLEAP & E163

Motivation For This Research

J. Limpert et al, “Scaling Single-Mode Photonic Crystal Fiber Lasers to Kilowatts”

Pump Power

Output

Pow

er

73%

CW

Output

Pow

er

1 kW

20061992

Carrier Phase-Locked Lasers Diddams et al

“Direct Link between Microwave and Optical Frequencies with a 300 THz Femtosecond Laser Comb”, Phys. Rev. Lett., 84 (22), p.5102, (2000).

z

E1

E2

E1z

E2z

E1x

E2x

xSlit Width ~10

Waist size: wo~100

Crossing angle:

Crossed laser beams

Fused silicaPrisms and flats

High reflectancedielectric coatedsurfaces

~1 cm

e-

e-

Crossed Laser Beam Accelerator• Large size compared to • All of our experimental work to date• Valuable test bed for low charge, psec timing• Low shunt impedance and poor efficiency

Photonic Crystal Fibers

X. Lin, Phys. Rev. ST-AB, 4, 051301 (2001).

e- beam passageradius = 0.678

Fused SilicaVacuum Holes

False color map of Ez

The photonic crystal confines the accelerating mode to the region near

the beam tunnel

Blaze Photonics

Large aperture fiber(not an accelerator)

2-D Photonic Lattice

B. M. Cowan, Phys. Rev. ST-AB, 6, 101301 (2003).

Vacuumsilicon

Extra thickness on sides of beam passage to get vphase = c

Planar structure that could be fabricated lithographically

3-Dimensional Woodpile

B. M. Cowan

S. Y. Lin et. al., Nature 394, 251 (1998)

0

0.1

0.2

0.3

0.4

0.5

Position around Brillouin zone edge

No

rma

lize

d f

req

ue

nc

y a/

2c

Omnidirectional band gap

-4 -2 0 2 4-6

-4

-2

0

2

4

x/a

y/a

Demodulated Ez at z = 0

-1.5

-1

-0.5

0

0.5

1

1.5

-4 -2 0 2 4-6

-4

-2

0

2

4

x/a

y/a

Demodulated Ez at z = a/2

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

-4 -2 0 2 4-6

-4

-2

0

2

4

x/a

y/a

Demodulated Ez at z = 0

-1.5

-1

-0.5

0

0.5

1

1.5

-4 -2 0 2 4-6

-4

-2

0

2

4

x/a

y/a

Demodulated Ez at z = a/2

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

Accelerating Mode ½ Lattice Period Apart

Properties of a Laser Driven Linear Collider

• High efficiency, carrier phase-locked lasers• 104-105/bunch limited by wakefields• Laser energy recirculation• High laser & beam repetition rate• Debunching of the beam after acceleration• Invariant Emittance ~ 10-11 m

Next Slides

PBGFA Efficiency

2 20 19.5C

GZ

P

2

0 20

1130

2 /

HH

H

qcZG

Z Zr

0

4max

max

5 3.

7.4

0.

1 10 '

5. %

38 /

2

q fC e

P kW

G GeV

s

m

0 2 2

1

41gC C H

F Hg

PZ cZ cZG G G G q

dUqG

dz

= 0(no charge)

= max

q/qmax

/max

= 0(no gradient)

Loaded gradient is reduced from

unloaded one by wakefields in the

fundamental mode and radiation

Train of beam pulses separated by the period of the laser cavity

Actively mode locked laser with accelerator structure in the laser cavity

= 0

1%

2%

5%No energy recovery

~ qopt/2: ½ of energy accelerates beam,½ is radiated away

Plasma Wakefield And Laser-Driven Accelerators

1. Introductory Comments2. Vacuum Laser Acceleration

3.Plasma Wakefield Acceleration4. Summary

Plasma Wakefield AccelerationE157, E162, E164 & E164X

6 8 1 0 2 0 4 0 6 0 8 01 0 0 2 0 0

1 03

1 04

1 05

1 06

S h o t 1 2 (1 0 k G ) S h o t 2 6 (1 0 k G ) S h o t 2 9 (5 k G )S h o t 3 3 (5 k G ) S h o t 3 9 (2 .5 k G ) S h o t 4 0 (2 .5 k G )

Re

lativ

e #

of

ele

ctro

ns/

Me

V/S

tera

dia

n

E le c tro n e n e rg y ( in M e V )

SM-LWFA electron energy spectrum

A. Ting et al, NRL

Motivation For These Experiments

Extraordinarily high fields developed in beam plasma interactions but there are many questions related to the applicability for focusing and acceleration

Self modulated laser wakefield acceleration

E > 100 MeV, G > 100 GeV/m

Physical Principles of the PlasmaPhysical Principles of the Plasma Wakefield Accelerator Wakefield Accelerator

• Space charge of drive beam displaces plasma electrons

• Plasma ions exert restoring force => Space charge oscillations

• Wake Phase Velocity = Beam Velocity

• When z/p ~1 ( Np ~1/z2)

++++++++++++++ ++++++++++++++++

----- -------------------

---- -----------

-------- --------------------------- --

-

---- --- ---

-------

- -- ------ - -- ------ - -

- - - - --- --

- -- - - - - -

--------

------

electron beam

+ + + + + + + + + + ++ + + + + + + + + + + + + + ++ + + + + + + + + + + + + + +

+ + + + + + + + + + + + + + +-

- --

--- --

EzEz

2~ bpk

z

NE

Located in the FFTB

e-

N=2·1010

z=0.6 mmE=30 GeV

IonizingLaser Pulse

(193 nm) Li Plasmane≈2·1014 cm-3

L≈1.4 m

CerenkovRadiator

Streak Camera(1ps resolution)

BendingMagnet

X-RayDiagnostic

Optical TransitionRadiators Dump

12 m

∫Cdt

E-162: Experimental LayoutRun 1 Positrons

• Optical Transition Radiation (OTR)

• Cherenkov (aerogel)

- Spatial resolution ≈100 µm - Energy resolution ≈30 MeV

-1:1 imaging, spatial resolution ≈9 µm

y,E

x

U C L A

e-

N=1.81010

z=20-12µmE=28.5 GeV

Optical TransitionRadiators

IP0: Li Plasma Gas Cell: H2, Xe, NO

ne≈0-1018 cm-3

L≈2.5-20 cm

Plasma light

X-RayDiagnostic,

e-/e+

Production

CherenkovRadiator Dump

∫Cdt

ImagingSpectrometer

IP2:

xz

y

EnergySpectrum“X-ray”

25m

CoherentTransition

Radiation andInterferometer

y

x

Upstream

y

x

Downstream

• X-ray Chicane

-Energy resolution ≈60 MeV

• Plasma Light

E

E164 & E164X Apparatus

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

-8 -4 0 4 8

05190cec+m2.txt 8:26:53 PM 6/21/00impulse model

BPM data

(m

rad)

(mrad)

plasma

gasbeam

Blowout region

Ion channel

laser

Electron Beam Refraction at the Gas–Plasma Boundary

e+ Acceleration

Some E-157 & E-162 Highlights

X-Ray Production

e+

Total internal reflectionImpulse Model Data e+ Focusing

Noplasma

1.5x1014 cm-3

0

50

100

150

200

250

300

-2 0 2 4 6 8 10 12

05160cedFit.2.graph

X

DS

OT

R (µ

m)

K*Lne1/2

0 uv Pellicle

=43 µm

N

=910-5 (m rad)

0=1.15m

Transverse Wakefields and Betatron Oscillations

Some E-157 & E-162 Highlights

MismatchedMatched

Beam Image

Tim

e

Horizontal Dimension

Head

Tail

~5

psec

e- Acceleration1.4 m long plasma

1.5x1014

1.9x1014

F = -eEz

electron beam

front portion of

bunch loses

energy to generate the wake

back portion of

bunch is accelerate

d

En

erg

y

Head Tail

No Plasma

With Plasma

BeamDistributi

on

e-ion

column

Recent results address the question of whether large gradients can be generated and sustained over appreciable distances

Key: G ~1/(bunch length)2

High-gradient acceleration of particles possible over a significant distance

Tilt is due to small, uncorrected horiz. dispersion

A single 200 sec long run sorted by a rough measurement of peak current

Density = 2.55×1017/cm-3

7.4 GeV

Plasma Wakefield And Laser-Driven Accelerators

1. Introductory Comments2. Vacuum Laser Acceleration3. Plasma Wakefield Acceleration

4.Summary

SummarySummary

Plasma Wakefield Acceleration• Electron & positron transport and acceleration in a long plasma• Accelerating gradients greater than 15 GeV/m sustained over 10 cm• Many results to come: higher gradients, more energy gain, trapped particles, multiple bunches, …

Laser-driven accelerator structures• Based on rapidly advancing field of photonics• Concepts for accelerator structures• Analyses of wakefields and efficiency• Promise of rapid experimental advances with construction of SLAC experiment E163