The ALPHA-X Project Mark Wiggins Technical Manager The Cockcroft Institute
Mar 28, 2015
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