The ALPHA-X Project

Mark WigginsTechnical Manager

The Cockcroft Institute

• Introduction to the ALPHA-X project

• Achievements to date in laser-plasma acceleration

• Future plans in current phase and next phase

Contents

ALPHA-X Beam Line – still under construction (nearly ready!)

Numerical simulations

Facility experimentsRutherford Appleton LabFriedrich-Schiller-University Jena, GermanyLund Laser Centre, SwedenL.Berkeley N.L., USA

ALPHA-X Basic Technology Project

Advanced Laser Plasma High-energy Accelerators towards X-rays

• Consortium of 7 U.K. research teams

• >20 national & international collaborating groups

• First phase (extended through Feb 2007)

• Funding secured for next phase (EPSRC, 4 years)

Imperial

College Z. Najmudin

U. Abertay-Dundee

A. MacLeod

U.

St. AndrewsA. Cairns

U.

OxfordS. Hooker

U.

DundeeA. Gillespie

U.

StrathclydeD. Jaroszynski

Rutherford App. Lab.

Daresbury Lab.P. Norreys & M. Poole

• A programme to investigate laser-plasma acceleration of electrons.

• A source of ultra-short, coherent, short-wavelength pulses of radiation.

• Allows high-resolution time-resolved experiments in physics, chemistry

and biology.

Project Goals

Motivated by…

• Very large acceleration gradients in wakefield accelerators (1 GeV/cm).

• Conventional RF accelerators (1 MeV/cm).

• Potential for compact, high-energy electron (and other particle) sources

and short-wavelength radiation sources

& much cheaper!

Revolutionary technique

Beam Line

photoinjecto

r

plasma

channelundulator

Oxford• Plasma Channel

wakefield accelerator100MeV – 1GeV electrons

D.L. ASTeC(Jim Clarke,Ben Shepherd)

• Undulatorcoherent radiation pulses down to ~ 3nm

• RF Photoinjectorelectron bunch production6.3MeV, 100fs, 100pC

Brookhaven N.L.T.U. EindhovenLAL Orsay (Terry Garvey)

e- e-

e-

UV fs laser

RF10MW

20TW fs laser

Laser Wakefield Acceleration

X [m]

(z-vt) (z-vt)

Ln

• 2-D example (A. Reitsma) e.g. PRL 94, 085004 (2005).

• Electrons are accelerated in the wakefield if their initial velocity is sufficiently close to the phase velocity of the wakefield for trapping to occur

vgvz

• Long electron bunch simulations (simple model – de Loos & van der Geer)

Achievements - simulations

GeneralParticleTracercode

Achievements - simulations

-200 0 200 400

GPT t [fs]

0

20

40

60

R [m

icro

n]

-200 0 200 400

GPT t [fs]

0

20

40

60

R [m

icro

n]

Flat cathode Curved cathode

de Loos et al. PRST-AB (accepted for publication)

• Electron distribution at capillary entrance (from photoinjector)

Achievements – external experiments

• Quasi-monoenergetic electron bunches from plasma accelerator

• Mangles et al., Nature 431, 535 (2004).

• RAL ASTRA laser (40fs, 0.5J)

• All-optical injection (electrons

from background plasma)

• Supersonic gas jet

3%

(a) At FSU Jena (Strath.) 47MeV, 3% PRL 96, 105004 (2006).(b) At LLC (Imperial) 150MeV, 3% PRL 96, 215001 (2006).(c) At LBNL (Oxford) 1GeV (capillary), 3% Nature Phys 2, 696 (2006).

(a)

(b)

(c)

Tremendous results!

• charge (10s pC)• peak current (kA)• divergence (few mrad)

Beam quality improvingall the time

Achievements – external experiments

Future plans - immediate

• First operation of Beam Line • laser only with gas jet, capillary

• RF photoinjector

• Undulator• electrons from plasma accelerator

• generation of UV radiation pulses• preliminary studies made at RAL, Jena

2

a1

2

2u

2u

• Fundamental FEL Equation

Electron E [MeV] Radiation [nm]

50 846

100 211

500 8

[u = 15mm, au = 0.8]

Future plans – next phase

• Wakefield Acceleration

External injection of ultra-short electron bunches from RF gun

Two-stage system1st stage: bunch compression2nd stage: acceleration

Structured capillariestaperedsteppedundulated

Plasma undulatoru ~ 10s or 100s of microns (compact!)

Future plans – next phase

• Coherent Radiation SourcesTHz pulses (coherent transition radiation)Backscattering off plasma wakes & ionisation frontsShort bunch injection in undulator

FEL Amplifier

• FEL gain parameter is a function of

energy (-1)

peak current (I1/3)

emittance (-1/3)

• ~ 0.003 for ALPHA-X parameters (500MeV electrons)

• Need / < 2 for reasonable gain i.e. / 0.6%

• Stimulated FEL emission ~106 greater than spontaneous emission

• Great rewards if you can achieve it!

• Peak brilliance »1020 photons / s / 0.1% BW / mrad2 / mm2

for realistic ALPHA-X parameters

Future plans – next phase

High-brightness extreme-UV radiation pulses

Summary

• Ambitious project to investigate laser-plasma acceleration

of electrons

• Combines

short electron bunch generation & propagation (PI)

wakefield acceleration (LWFA)

amplification of short-wavelength radiation (FEL)

•Also

novel ultrafast electron diagnostics

initial applications programme

•Strong theoretical programmeRobin Tucker (CI) Bob Bingham (RAL)Tito Mendonca (IST, Portugal) Pulsar PhysicsGennady Shvets (UT Austin, USA) Alan Cairns (U StA.)

Dino Jaroszynski (Director)

Ken Ledingham, Slava Pavlov, Riju Issac, Paul McKenna,

Enrico Brunetti, Bernhard Ersfeld, Albert Reitsma,

Jordan Gallacher, Andrey Lyachev, Richard Shanks, David Carroll

• ALPHA-X Consortium MembersDaresbury Lab, Rutherford Appleton Lab, Imperial College, Oxford University,

University of St. Andrews, University of Dundee, University of Abertay-Dundee

• ALPHA-X CollaboratorsLAL Orsay, Pulsar Physics, U. Twente, T.U. Eindhoven, IST, LBNL, FSU Jena, CLIO, FOM, IAP,

UTA, LPGP, LLC, UCLA, CAS, NRL, T.U. Crete, JINR, USC, U. Milan, R.-U. Bochum, MPI

• John Dainton Cockcroft Institute

• Robin Tucker Cockcroft Institute & Lancaster University

Acknowledgements

First phase is funded by theResearch Councils UK

Basic Technology Programme

Thank you