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AAC June 2012 SCAPA [email protected]
Scottish Universities Physics Alliance
The development of laser-driven plasma accelerators:
progress and outlook
Dino Jaroszynski University of Strathclyde
AAC June 2012 SCAPA [email protected]
• Accelerators and light sources
• Acceleration in plasma
• Narrow energy spread and low emittance beams
• Femtosecond duration bunches
• Improvements of stability and dark current
• FEL, betatron and undulator radiation
• Radiation imaging
• New projects
• Outlook
Outline of talk
AAC June 2012 SCAPA [email protected]
CERN – LHC 27 km circumference
SLAC
50 GeV in 3.3 km
20 MV/m
7 TeV in 27 km
7 MV/m
Large accelerators depend on superconducting RF cavities and magnets
AAC June 2012 SCAPA [email protected]
Synchrotrons light sources and free-electron lasers: tools for scientists
Synchrotrons and FELs – huge size
and cost is determined by accelerator
technology
Diamond
undulator
synchrotron
DESY undulator
AAC June 2012 SCAPA [email protected]
Livingston plot
New ideas
lead to new
technologies
Acceleration
gradient
currently limits
maximum
energy
Laser
wakefield
accelerators?
(from tesla.desy.de)
AAC June 2012 SCAPA [email protected]
Plasma media: capillary, gas jet and plasma cells (Strathclyde)
2 mm
Gas jet
1 J, 40 fs
= 300 MeV
200
consecutive
Images
(Strathclyde)
4 cm
Gas Cell
10 J, 50 fs
= 850 MeV
(at RAL)
4 cm
Plasma capillary
10 J, 50 fs
~ 1 GeV (at RAL)
AAC June 2012 SCAPA [email protected]
Strathclyde Plasma waveguide medium
4 cm long
preformed
plasma
waveguide
n = 1018 cm-3
Originally developed by
Simon Hooker’s group D. Spence & S. M. Hooker. Physical Review
E 63015401 (2001).
Strathclyde laser micromachining method: Jaroszynski et al., Philosophical Transactions of the Royal Society (2006)
Wiggins et al,, Review of Scientific Instruments (2011)
AAC June 2012 SCAPA [email protected]
Particles accelerated by electrostatic fields of plasma waves
[V/cm]E e n
Accelerators:
Surf a 10’s cm long
microwave –
conventional
technology
Surf a 10’s mm long
plasma wave –
laser-plasma
technology 2
max
2
3
ga
0g
p
Tajima and
Dawson
1979 Accelerating gradients up
to 1 TV/m
AAC June 2012 SCAPA [email protected]
Bubble structure – relativistic regime
laser
self-injected
electron bunch
undergoing
betatron
oscillations
ion bubble
First experiments
on controlled
acceleration:
2004
ALPHA-X (UK)
LBNL (US)
LOA (France)
0
2
paR
ion bubble radius
AAC June 2012 SCAPA [email protected]
Theory: Influence of non-ideal laser and plasma parameters on LWFAs
Lasers with higher order modes*
less energy
into
accelerated
electrons
QuickPIC
laser energy
spreads sideways
Non-ideal plasma density profiles*
d
non uniformity
amplitude
density non-
uniformity:
may lower
energy gain
*J. Vieira et al., Plasma Phys. Control. Fusion 54, 055010 (2012).
QuickPIC
AAC June 2012 SCAPA [email protected]
AAC June 2012 SCAPA [email protected]
Energy scaling with density: bubble regime – experimental data
2
0
max
2
3
g a
1E16 1E17 1E18 1E19 1E2010
6
107
108
109
1010
1011
En
erg
y [
eV
]
Density [cm-3]
a0: 2 → 10
0g
p
Progress!
Experimental data from the community since 2006
AAC June 2012 SCAPA [email protected]
ALPHA-X: Advanced Laser Plasma High-energy Accelerators towards X-rays – Template for SCAPA
Compact R&D facility to develop and apply
femtosecond duration particle, synchrotron,
free-electron laser and gamma ray sources
70 75 80 85 90 95 1000
250
500
750
1000
No
. e
lec
tro
ns
/ M
eV
[a
.u.]
Electron energy [MeV]
(b)
(a)
electron beam spectrum
phase contrast
imaging
with 50 keV
photons
beam emittance: <1 p mm mrad
CTR: electron
bunch duration:
1-3 fs 0.7%
Brilliant particle source: 10 MeV → GeV, kA peak current, fs duration
FEL 1J 30 fs
capillary &
0 5 10 15
0.0
0.1
0.2
0.3
Measured TR signal
1 fs
1.5 fs
2 fs
2.5 fs
3 fs
4 fs
TR
(J/m
)
Wavelength (mm)
= 2.8 nm – 1 mm
(<1GeV beam)
ALPHA-X
@ Strathclyde
30 TW
AAC June 2012 SCAPA [email protected]
Narrow energy spread low emittance beams
100 110 120 130 140 150
8000
10000
12000
14000
16000
18000
Ch
arg
e/u
nit e
nerg
y [
a.u
.]
Energy [MeV]
0.75%
63 MeV 170 MeV
Maximum energy obtained in
2 mm = 360 MeV
Absolute energy
spread < 600 keV
Strathclyde
AAC June 2012 SCAPA [email protected]
-0.75 -0.50 -0.25 0.00 0.25 0.50 0.75
-3
-2
-1
0
1
2
3
4
0 5000 10000 15000
x' [m
rad
]
x[mm]
arb. counts
• divergence 1 – 2 mrad for this run
with 125 MeV electrons
• average N = (2.2 0.7)p mm mrad
• best N = (1.0 0.1)p mm mrad
• Elliptical beam: N, X > N, Y
• Upper limit because of resolution
• Second generation mask with hole ~ 25 mm and improved detection system
0 1 2 30
5
10
Count
nx
[p mm mrad]
(a)
0 1 2 30
5
10
Count
ny
[p mm mrad]
(b)
Experimental Results – emittance
See Brunetti et al., PRL (2010) and Wed. WG 5
AAC June 2012 SCAPA [email protected]
-6 -4 -2 0 2 40
5
10
15
20
cou
nts
horizontal position (mrad)
x = 1.4 mrad
(a)
-6 -4 -2 0 2 40
5
10
15
20
cou
nts
vertical position (mrad)
(b)
y = 1.3 mrad
Electron
beam
recorded on
YAG screen
High
resolution
Electron beam pointing deviation is less
than one spot size
Electron Beam- Pointing Stability at Strathclyde
no PMQs PMQs in
AAC June 2012 SCAPA [email protected]
AAC June 2012 SCAPA [email protected]
Recent electron bunch measurements – CTR from foils
1.4 – 1.8 fs CTR measurements at source
Lundh et al., Nature Physics (2011)
32 fs CTR measurements using EO
Cross-correlator
Debus et al., Phys. Rev. Lett. (2010)
Earlier measurements by
Leemans et al., PRL 2003
Tilborg et al., Optics Letter
2008, PRL 2006
Glinec et al. (PRL 2007) &
Lin et al., (PRL 2012)
measured visible CTR
AAC June 2012 SCAPA [email protected]
Improved stability and tunability: Shock-front injection
5 µm transition
ATLAS
28 fs
550 –
800 mJ
8 fs, 70 mJ pulses
MeV
See talk by Laszlo Veisz
AAC June 2012 SCAPA [email protected]
Study of self-injection threshold and simple model to predict self-injection threshold
• Shows how self-focusing and pulse
compression are needed to explain
the threshold density for self-
injection
• Developed a simple model for
predicting threshold density based
on experimental parameters:
• Simple model in good agreement
with Imperial College and other
reported experiments over 3 orders
of magnitude in laser pulse energy
SPD Mangles et al PRSTAB 2012
AAC June 2012 SCAPA [email protected]
Background-free, tunable, self-injected, LWFA electron beams
Reduced energy spread
P= 42 TW
S. Banerjee et al., Phys. Plasmas 19, 056703
(2012).
1.2
0.48
ne (1019
cm-3)
Tunable
(a) P = 34 TW, ne0 = 7.8×1018 cm-3
(b) P = 42 TW, ne0 = 6×1018 cm-3
(c) P = 58 TW, ne0 = 5.3×1018 cm-3 • Kalmykov et al., Plasma Phys.
Control. Fusion 53(1), 014006 (2011) & talk in WG1, Thurs.
• Kalmykov et al., New J. Phys. 14 (2012) 033025 & talk in WG1, Wed.
AAC June 2012 SCAPA [email protected]
Beams generated in 3 regimes up
Relativistic self-focusing in a plasma channel
• Electron beams with energies up to 900 MeV
using 3.2 J, 55 fs pulses from Astra-Gemini
• Electron beams generated on 100% of 22
shots
• Low beam divergence 3.5 ± 1 mrad
• Electrons beams generated in self-guided,
plasma channel, and hybrid guiding regimes
• GRENOUILLE measurements show first
observation of laser pulse compression in
plasma channel
0.4 1 4
data
Emax [1]
Ldeph = Lcap
1000
800
600
400
200
0
plasma channel zone
plasma cannel and rel. focusing zone
self-guiding zone
max. el
ectr
on
en
ergy /
MeV
Raw electron spectra (22 consecutive shots)
plasma density / 1018 cm-3
Laser pulse duration vs. plasma density
AAC June 2012 SCAPA [email protected]
f/40
1.1 T
dipole
magnet
Image plate
for < 0.5 GeV e-
Image plate
for GeV e- Beam
deflector
Beam
dump
e-
Energy (GeV)
2GeV 1GeV
Div
erg
en
ce
(mra
d.)
ne = 3.3 x 1017 cm-3
For details see:
X. Wang, WG1 Tuesday 10:30am talk
N. Fazel, Tuesday pm student poster slide courtesy Mike Downer, U. Texas-Austin
120 - 150 J
150 fs
7 cm
uniform
gas cell
99.99% high
purity He
QTOT = 1.8 nC
laser
polarization energy
calibration
fiducials
• sub-mrad beam
divergence
• negligible < 500
MeV dark current
• Self-injection
down to 1017 cm-3
Electrons accelerated beyond 2 GeV at the Texas Petawatt Laser
See LLNL results @ 1.3 GeV
AAC June 2012 SCAPA [email protected]
Dual screen electron spectrometer allows measurement of beams > 1 GeV with Astra Gemini
1.3
• dual screen spectrometer allows
accurate energy measurement with fully
open magnet, providing large aperture
for betatron x-ray measurements
• 1.3 GeV electrons from 15 mm gas jets
in self-injecting, self-guiding regime
• betatron oscillations produce bright
hard x-rays peaked at ~ 30 keV
1.34 GeV
1.28 GeV
1.16
1.09
AAC June 2012 SCAPA [email protected]
High Energy Electron Spectra
300 400 500 600
0
50
100
150
200
charg
e d
ensity [a.u
.]
Energy [MeV]
300 400 500
-50
0
50
100
150
200
Charg
e d
ensity [a.u
.]
Energy [MeV]
2.8%
600 800 1000-20
0
20
40
60
Charg
e d
ensity [a.u
.]
Energy [MeV]
3.9%
Strathclyde/SUPA/IST/RAL
GEMINI: Measurements
limited by spectrometer
resolution – maximum
energy measured 850
MeV
AAC June 2012 SCAPA [email protected]
Bernhard Hidding1,2J.B.Rosenzweig, Y. Xi, G. Andonian, S. Barber, O. Williams2, F. Kleeschulte, G. Pretzler1, D. Bruhwiler3, K. Lotov4, M. Litos, M. Hogan5 P. Muggli6
Trojan Horse Plasma Photocathode Wakefield Acceleration
Idea: Use laser-plasma-produced electron bunches as plasma wave drivers in low-ionization threshold gases (e.g., alkali metal vapors). Advantages: no dephasing, strongly reduced diffraction (emittance) issues. Electron bunches from laser-plasma-accelerators could be especially well suited to drive plasma waves due to their compactness (see Hidding et al., PRL 104, 195002, 2010) Furthermore, a synchronized low-energy laser a0 0.015 can be used to release electrons of higher-ionization threshold species such as helium at arbitrary position within the blowout. This results in ultrahigh beam quality beams. Such a beam brightness transformer is ideal for light source applications such as FEL, Thomson scattering etc. (see Hidding et al., PRL 108, 035001, 2012, patent 2011, and talks in WG 4 on Tuesday)
Proof of concept experiments w/ laser-plasma-accelerators and at FACET planned: E 210: Trojan Horse Plasma Wakefield Acceleration, 2013 @FACET
Emittance and brightness of generated beams:
AAC June 2012 SCAPA [email protected]
• Wiggler motion – electron deflection angle q ~(px/pz) is much larger than the angular
spread of the radiation j(1/γ)
• Only when k & p point in the same direction do we get a radiation contribution.
• Spectrum rich in harmonics – peaking at
• Radiation rate therefore only emission at dephasing length
1ua
deflection angle – au /
j=1/
33
8
ucrit
ah
2W dL
Synchrotron radiation from an ion channel wiggler: betatron radiation
AAC June 2012 SCAPA [email protected]
Resonant betatron motion
2 /( )Lyy y y F m / ( / )LyF e dA dt y A y
22
0 '2121'~gz
Cipiccia et al.,
Nature
Physics, 2011
AAC June 2012 SCAPA [email protected]
Spectra:
Ec = 50 - 60 keV
Electron energy: 63070 MeV
ne= 2 x1018cm-1 r = 3 mm &
a ≈ 20
Ec = 150 keV
r = 7 mm
a = 50
Ec = 450 keV
r = 20 mm
a = 150
108 photons between .1 and 7 MeV
Brilliance 1023 photons/(s mrad2 mm2 0.1%bandwidth)
Betatron Radiation X-ray Spectra Measurements
Cipiccia et al., Nature
Physics, 2011
AAC June 2012 SCAPA [email protected]
Ar
He magnet gap
10 mrad
I II
III IV
(a)
(b)
(c)
He Ar
50pC 500pC
7 mrad < 1 mrad
He
(a) (b)
(c)
Ar
5 (MeV) 10 15 20
(d)
Betatron radiation enhancement (>2.8keV, 10mrad, 2x10^8 phs, >1021 phs/s/../0.1%BW)
Using Ar clusters an electron beam with
large charge will be accelerated which
enhances the betatron radiation.
Electrons Betatron x-ray
Betatron radiation using 3TW laser + clusters
L.M. Chen et al.
IoP-CAS, Beijing
AAC June 2012 SCAPA [email protected]
Betatron radiation to measure source size and emittance
source size of synchrotron radiation: rsyn = (1.8
0.3) µm
electron bunch radius rbunch = (1.6 0.3) µm
estimated peak brightness: 51021
photons/(smmmrad20.1%bandwidth)
see talk by M.C. Kaluza, WG 1+5 on Thursday
10:30 a.m. M. Schnell et al.: PRL 108, 075001 (2012).
• e- spectrometer - beam energy & divergence
• betatron radiation - beam source size
• combined to obtain emittance on a single shot
• emittance minimised in the matched regime
AAC June 2012 SCAPA [email protected]
AAC June 2012 SCAPA [email protected]
Divergence and source size
r = 7 mm source size
• divergence ≈
14 mrad
Betatron Radiation: phase contrast imaging at Strathclyde
Cipiccia et al.,
Nature Physics, 2011
Also see
Karsch’s talk
AAC June 2012 SCAPA [email protected]
Recent VUV radiation undulator measurements
Strathclyde
undulator
radiation as an
electron energy
spectrometer:
Undulator:
100 period
1.5 cm
wavelength
Matched
transport system
Electron
spectrometer
after undulator:
simple low
resolution dipole
magnet
Also VUV
measurements by
Grüner’s group
AAC June 2012 SCAPA [email protected]
Synchrotron, betatron and FEL radiation peak brilliance
ALPHA-X ideal 1GeV bunch
FEL: Brilliance 5 – 7
orders of magnitude larger
u 1. cm
n = 1 p mm mrad
te = 1-10 fs
Q = 1 – 20 pC
I = 1-25 kA
d < 1%
I(k) ~ I0(k)(N+N(N-1)f(k)) FEL = spontaneous
emission x 107
betatron source
AAC June 2012 SCAPA [email protected]
Outlook
2
0
max
2
3
g a
1E16 1E17 1E18 1E19 1E2010
6
107
108
109
1010
1011
En
erg
y [
eV
]
Density [cm-3]
a0: 2 → 10
0g
p
Need a combination of bubble regime (Need to be above
critical power for relativistic self-focussing) and linear regime
to get to very high energies
AAC June 2012 SCAPA [email protected]
International projects
• FACET – electron beam driven plasma wakefield accelerator:
100 GeV stage
• BELLA – laser driven plasma wakefield accelerator: 10 GeV
stage
• IZEST – Laser-driven plasma wakefield accelerator: 100 GeV
stage on PETAL Laser at LMJ
• EuroNNAC – Proton beam driven plasma wakefield accelerator
at CERN: 1-10 GeV Proof of Concept
• Fermilab – proton driven PWFA
AAC June 2012 SCAPA [email protected]
Laser Plasma Accelerator
using conventional accelerator paradigm
Large-scale plasma-based acceleration
(Wim Leemans)
Laser: Ti:sapphire
40 J, 30 fs, 1 Hz
Parameter
Plasma density np 1017 cm-3
a0 1.4
Plasma wavelength p 108 mm
Pulse duration tL 57 fs
Spot radius rL 90 mm
Laser power P 563 TW
P/Pc 1.8
AAC June 2012 SCAPA [email protected]
Facility for Accelerator Science and Experimental Test Beams – uses first
2km of the SLAC linac
Parameters
Energy 23 GeV
Charge 3 nC
Sigma z 14 mm
Sigma r 10 mm
Peak Current 22 kA
Species e- & e+
Ez = 37GV/m
Gain =15 GeV
DE/E =3%
Drive bunch:
σz = 30 μm
N = 3x1010 e-
Witness bunch:
σz = 10 μm
n =1x1010 e-
σr0 = 3 μm
Δz = 115 μm
(~400 fs)
ne=1017cm-3
Acceleration physics identical for PWFA and LWFA
AAC June 2012 SCAPA [email protected]
AAC June 2012 SCAPA [email protected]
EuroNNAc: PROTON-DRIVEN PWFA @ CERN
Proton beam SPS
Energy E0 450 GeV
Np 10.5 x 1010
DE/E0 0.03 %
z 12 cm
n 3.6 mm-mrad
r 200 mm
5 m
TT61 West ~600m tunnel + experimental area
Plasma
Length Lp 5 -10 m
ne 7x1014 cm-3
p 1.3 mm
fpe 240 GHz
~ GeV gain of externally injected e- over
5 - 10 m of plasma in self-modulated p+
driven PWFA
AAC June 2012 SCAPA [email protected]
IZEST 100GeV @ LMJ Bordeaux Laser-Plasma Accelerator Experiment
Energy > 3 kJ
• Wavelength > 1053 nm
• Pulse duration between 0.5 and 10 ps
• Intensity on target > 1020 W/cm²
• Intensity contrast (short pulse): 10-7 at -7 ps
• Energy contrast (long pulse): 10-3
Design
guideline
1. self-injected
electron beam
from the injector
2. Quasi-linear
wakefield in the
accelerator
Find the optimum plasma density
Drive laser pulse
500 fs, 3.5 kJ max.
Acceleration length < 30 m
Gain
E~100GeV
Charge
Q~100pC
Quality
DE/E~1%
Emittance:
n~ 1p mm-mrad
Stability
100% reproducible
Mourou, Tajima et al.
(International Zetawatt Exawatt Science Technology)
AAC June 2012 SCAPA [email protected]
Scottish Centre for the Application of Plasma Based Accelerators
Strathclyde: 2 Chairs (searching now*),
2 PDRAs, Technicians
Glasgow: 1 Reader
USW: 2 Readers/Lectures
Edinburgh SUPA Fellow
SCAPA: infrastructure + staff + beam
lines
* contact: [email protected]
1200 m2 laboratory space: 200-300 TW
laser and 7+ “beam lines” - particles
and coherent and incoherent radiation
sources for applications: nuclear
physics, health sciences, plasma
physics etc. Also part of Strathclyde
Technology and Innovation Centre (TIC)
Bunker B Bunker C
Bunker A
Control Area
10 m
Shielded area of laboratory