Neely - HZDR

Laser driven ion acceleration developments
David Neely
Central Laser Facility, STFC, Oxfordshire, UK
University of Strathclyde, Glasgow, Scotland
Kansai Photon Science Institute and PMRC, JAEA, Kyoto, Japan
Advanced Accelerator Concepts Workshop 2010
June 13-19th 2010, Annapolis
Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, UK.
Telephone: (44)1235 446150 Fax: (44)1235 445888
e-mail: david.neely@stfc.ac.uk
Central Laser Facility
Astra Gemini Ti:Sapphire 40 fs, 12 J
Vulcan Nd:Glass 700 fs, 240 J
LULI, PMRC, GSI,
IOP, BNL, FZD
LIBRA –
Laser
Induced
Beams of
Radiation for
Applications
£5M, 2007 -2012
Ion application requirements
Proposed applications and requirements
•Radiography (density measurements)
•Deflectometry (field measurements)
•Isochoric heating of matter
•Fusion Energy (Fast Ignition)
•Injection into conventional accelerators
•Cancer therapy
•Production of isotopes for PET
Industrial applications (implantation,
lithography)
Nuclear/particle physics applications
…..
Med-energy (5-25 MeV p+)
Broad band
Med - High efficiency
High-energy (50-250 MeV p+)
Narrow band (∆E/E ~ %)
Divergence control/transport
Ion acceleration regimes
LIBRA experiments:
Radiation
pressure
24
10
Laser intensity [W/cm2]
• TNSA ion scaling with laser
parameters
• Influence of target properties
on TNSA ions
22
10
• Enhanced TNSA with limited
mass targets
20
10
underdense
plasma
Coulomb
explosion
• Enhanced TNSA with
controlled density gradients
18
•Enhanced TNSA with foam
layers
10
TNSA
16
• Acceleration from liquid drops
and spray
Target Normal Sheath Acceleration
10
• RPA with ultrathin targets
• Acceleration from gas jets
19
10
20
10
21
10
22
10
23
10
24
10
Plasma electron density ne [cm−3]
Courtesy of T. Esirkepov (adapted)
Target normal sheath acceleration
Hot electron propagation
MeV energy,mC- µC charge
M Borghesi et al.,
MeV/u ions
I>1019Wcm2
a0>3
Plasma
Target
Relatvistic electron production
Space charge field:
E~Thot/λDebye~MeV/µm=1012V/m
Properties:
 Maximum energy: protons ~65 MeV; ions ~10 MeV/u;
 High brightness: >1012 protons in ps pulse
 Source size ~100 µm; (virtual source ~10 µm);
 Emittance εN ~0.005π mm.mrad
 Energy conversion efficiency up to 10%
Excellent probe for
fields in plasmas
TNSA ion max energy scales with ~I1/2
Maximum proton energy (MeV)
70
60
50
Fuchs et al Nat Phys 2006
isothermal model
10 micron (1 ps)
25 microns (1ps)
25 micron (various)
isothermal model
2-phases model
2-phases with 3-D effects
40
30
20
10
0
1019
1020
2
Laser intensity (W/cm )
1021
•Mora PRL 90, 185002 (2003): isothermal expansion
• Fuchs et al Nat. Phys. 2, 48 (2006):
• Scaling study up to ~5×1019 W/cm2;
Model revised to include dual temperature phase;
Mora, PRE 72, 056401 (2005)
Robson et al, Nat. Phys. 3, 58 (2007)
Schreiber et al., PRL (2006)
500fs scaling: 200 MeV protons
requires >4 1021Wcm-2 (>1kJ)
Schreiber Scaling: 200 MeV @ 100J 40fs
TNSA polarisation dependence at 1018 Wcm-2
At 1018 Wcm-2 the hot electron and proton energies are more
related to the P component of the electric field than the
ponderomotive potential.
Figures from Cottei et al,
Phys. Rev. Lett. 99, 18, 18502 (2007)
TNSA ion energy scaling at 1020 Wcm-2
4
120
10
°
C; 35
C; 0
100
°
Al; 35
°
Al; 0
80
CHO; 35°
Schreiber
Andreev PRL
60
40
20
a0 = 18.0 normal
(b)
Number of heavy ions (arb. units)
Maximum C6+ energy (MeV)
°
a0= 18.0 oblique (35°)
3
10
2
10
1
10
0
10
0
1
10
2
3
10
10
Target thickness (nm)
0
4
10
• Maximum ion energy increases with decreasing target thickness
(saturation achieved for TNSA from ultrathin targets)
• Higher maximum ion energy and flux with 0° compared to 35°
incidence – new energy absorption mechanism?
10
30
20
Energy (MeV)
40
50
DC Carroll et al.
New Journal of Phys 2010,
Enhancing TNSA - Limited mass targets
X-ray pinhole
imaging
200 µm
16
J Fuchs, M Borghesi T Cowan et al.,
Au 2 μm Feb08
thick
Feb09
target
14
12
10
8
6
L.Romagnani et al,
PRL, 95,195001
(2005)
Target
foil
4 mm
McKenna et al, Phys Rev Lett (2007)
4
1000
4
10
5
10
6
10
7
10
Surface (µm²)
Size of standard targets
Increase in both the maximum ion
energy and conversion efficiency
Enhancing TNSA – Targets with foam layers
Proton energy [MeV]
Optimize energy conversion into electrons using foam layers
(increases the surface area)
6
5
4
3
2
1
0
Protons
PM Bypass
Protons
PM Gold
Protons
Mean
Protons
0
Foam
Laser
P Gallegos et al.,
10
20
Density [mg/c.c.]
30
The maximum proton energy is sensitive
to the density of the foam layer
Enhancing TNSA controlled pre-plasma
→ Proton measurements show that controlled pre-plasma
expansion leads to enhanced energy coupling to fast electrons
7
35
Iabl
∆t
30
25
20
Energy conversion efficiency (%)
Maximum proton energy (MeV)
40
15
200
100
0
Scale length, LO (µm)
P. McKenna et al, LPB 26 591-596 (2008)
D.C. Carroll et al, CRP 10 188-196 (2009)
V Malka this conference
6
Iabl
∆t
5
4
3
2
1
0
Laser
200
100
0
Scale length, LO (µm)
Preplasma
Target Normal Sheath Acceleration- tuning
Axial Spectra
Best
-100um
-200um
-300um
focus
Beam energy tuneable shot to shot
Al 50nm, 35fs 1019 Wcm-2@ 1010 contrast
-ve moves target
towards parabola
-400um
-500um
Ion acceleration from droplet and spray targets
S Ter-Avetisyan et al.,
Laser forward direction
O+
O5+
H+
90
degree direction
O1
MeV
First observation of MeV negative ions
O
+
Ion acceleration from gas jet targets
P. Shkolnikov, I Pogorelsky,
Z Najmudin, UCLA
this conference
 ATF Laser:
 CO2 λ=10.6μm
 Contrast ratio 10-3
 Pulse energy ~ 3J
 Pulse length ~ 6ps
 I ~ 5x1015W/cm2
 Target:
 Hydrogen Gas Jet,
1mm nozzle.
Ion acceleration regimes
Radiation
pressure
24
10
Laser intensity [W/cm2]
• TNSA ion scaling with laser
parameters
• Influence of target properties
on TNSA ions
22
10
• Enhanced TNSA with limited
mass targets
20
10
Coulomb
explosion
underdense
plasma
18
•Enhanced TNSA with foam
layers
10
TNSA
16
• Enhanced TNSA with
controlled density gradients
• Acceleration from liquid drops
and spray
Target Normal Sheath Acceleration
10
• RPA with ultrathin targets
19
10
20
10
21
10
22
10
23
10
24
10
Plasma electron density ne [cm−3]
Courtesy of T. Esirkepov (adapted)
Radiation pressure acceleration of ions
Laser field sweep away all electrons,
forming an electrostatic field
Stage 1
To produce 1 GeV protons in τ = 1 laser period we need I ~1.2×1023 W/cm2.
Ions pulled by the charge separation field move together with electrons.
Stage 2
Plasma forms a mirror accelerated
by the laser field radiation pressure.
The difference between the incident and reflected wave
energy is taken by the mirror:
Because me<<mi almost all energy transfers to ions:
T. Esirkepov et al., PRL 92, 175003 (2004)
B. Qiao et al, PRL, 102, 145002 (2009)
Courtesy of T. Esirkepov
∆E ≈ EL − EL ≈ (1 − 1 4γ 2 ) EL
∆Eion ≈ (1 − 1 4γ 2 ) EL .
Two Modes of RPA
Hole-Boring Mode (HB)
Light-Sail Mode (LS)
In both modes it has been found that
circular polarization (at normal
incidence) results in an interaction
which is much more clearly radiation
pressure dominated than linear
polarization at all intensities.
dp 2 I  1 − v / c 
= 

dt
c 1+ v / c 
RPA has potential to reach
high energies and
conversion
efficiencies.
Does Elementary RPA work? – 1D Numerical
Validation
•1D3P Electromagnetic PIC simulations.
•Used 100fs sin4t circularly polarized pulse.
•Peak intensity of 2x1021Wcm-2. λ = 1μm.
•80ncrit, 150nm thick foil composed of protons.
•Run simulations up to 400fs.
Circular Polarization
Linear Polarization
Phase Space
RPA with circular polarised laser pulses
Issues :
• Electron heating (competition
with TNSA)
• Stability of acceleration
(Rayleigh-Taylor- like instabilities)
For I=1021 Wcm2
Circular polarisation suppresses hot
electron generation
- no TNSA, few γ-rays
RPA dominates
2
10
40
y[µm]
Movie by C.Bellei
101
20
0
0
5
x[µm]
10
100
Robinson et al., New
J.Phys,
10, 013021 (2008)
500
1
400
0.8
300
0.6
200
0.4
100
0.2
00
100
200
300
400
Conversion Efficiency
Foil thickness:100nm
150nm
250nm
350nm
Proton energy [MeV]
RPA: a promising ion source
400
Time (fs)
200 MeV predicted in quasi-monoenergetic
beam at ~ 1021 Wcm-2
Efficiency into 200 MeV peak >60%
Divergence angle: 4°
Feasible with current generation of lasers
assuming supergaussian spot.
(~50J in 50 fs - Astra Gemini Parameters)
Changing Z of target ions, but keeping mass
density and target thickness constant did not
change results.
Changing wavelength of radiation did not change
results (provided target was still opaque).
Astra GEMINI laser facility
Petawatt upgrade to existing Astra Ti:Sapphire Laser
Two synchronised CPA beams, independently configurable
COMPRESSOR
OUT: 15 J, 30fs
26
30 J PUMP
LASER
26
30 J PUMP
LASER
35 J PUMP LASER
25 J Ti:S
Ti:Sa
AMPLIFIER
0.5 PW CMPRESSOR
Pulse duration ~ 50 fs
CHAMBER
25 J Ti:S
Ti:Sa
AMPLIFIER
Repetition rate ~1 shot/minute
0.5 PW COMPRESSOR
INTERACTION
EXISTING ASTRA
Status for ion acceleration:
26
30 J PUMP
LASER
Energy on target up to 10 J (~200 TW)
Intensity up to 0.5-1x1021 W/cm2
Contrast ~ 107, 1010 with plasma mirrors (50%)
COMPRESSOR
15 J, 30fs
fsOUT
OUT
OUT: 15 J, 30fs
26
30 J PUMP
LASER
35 J PUMP LASER
New Laser Area
21
Gemini experiment arrangement
Focusing
parabola
Plasma
mirrors
Collimating
parabola
Double plasma
mirror system
Off-axis f/2
parabola
target
Proton beam spatial
profile monitor
H+
C6+
C
H
Thomson
parabola
spectrometers
6+
+
MCP
magnetic
deflection
gap in
spectra
EMCCD
electric
deflection
Laser Conditions:
•Linear polarisation @ 35˚
•Linear polarisation @ 0˚
•Circular polarisation @0˚
•Intensity ~7×1020 Wcm-2
•Contrast ~1010
Experimental results
First clear evidence of quasi-monoenergetic RPA acceleration
Experimental Data: Protons
Experimental Data: Carbon
Experimental
Parameters:
6J, 40fs, 5 1020 Wcm-2,
circular polarisation, 10
nm C
PIC Simulations: Protons
PIC Simulations: Carbon
Simulations: 2D PIC,
On axis data shown
Evidence of Rayleigh-Taylor instabilities in RPA?
Z Najmudin et al.
Rayleigh-Taylor-like structures observed in proton beam acceleration
from ultrathin foil targets driven by the Vulcan PW laser
Proton beam profiles:
50 nm
Pegoraro et al, PRL 99 (2007)
E. Ott et al, PRL 29 (1972)
5 nm
 ‘R-T Instability occurs when a light fluid is
accelerated into a heavy fluid’
 Light “fluid” = photons of laser beam.
 Heavy fluid = plasma of ionised target.
RPA with 10 PW pulses should generate
relativistic protons
2D OSIRIS PIC simulations
performed by C. Bellei, Imperial
College and A.P.L. Robinson, RAL
Cyrogenic H target, density = 40 ncr
IL = 1.25x1023 Wcm-2, tL=25 fs
→ Relativistic ion energies obtained
(p up to 2.5 GeV, C6+ up to 1 GeV/u)
Conclusion
• Target Normal Sheath Acceleration
• Robust, High efficiencies 9%
• Delivering many (20) scientific application suitable beams
• Improved absorption and coupling understanding
• Radiation Pressure
•High Efficiency
•First indications of RPA dominance observed
• Future experiments needed to measure new scaling
• Future directions
• 40 fs 700 TW (2010) @109 contrast, 10PW (2013), ELI,
• Targetry
• Multi-pulse options
Co-workers
O Tresca,1 R Prasad,2 L Romagnani,2 P S Foster,3,2 P Gallegos,1,3
S Ter-Avetisyan,2 J S Green,3 S Karr, M J V Streeter,3,4 N Dover,4 C
A J Palmer,4 C M Brenner,1,3 F H Cameron,3 K E Quinn,2 R Evans, 4
J Schreiber,4 A P L Robinson,3 T Baeva,3 M N Quinn,1 X H Yuan,1 Z
Najmudin,4 M Zepf,2 M Borghesi,2 P McKenna,1 P Shkolnikov,5 I
Pogorelsky,6 C-G Wahlström,7 Y T Li, 8 M H Xu, 8
1 SUPA Department of Physics, University of Strathclyde
2 School of Mathematics and Physics,
Queen’s University Belfast
3 Central Laser Facility, STFC
Rutherford Appleton Laboratory
4 The Blackett Laboratory, Imperial College London
5 Stony Brook University, USA
6 BNL, USA
7Lund Laser Centre, Sweden
8 Beijing National Laboratory