Transcript Laser ion acceleration – principle and applications - Heinrich

Time-resolved proton probing of laserinduced front and rear side plasma
expansion phenomena
M. Amin1, M. Borghesi2, C. A. Cecchetti2, J. Fuchs3, M. Kalashnikov4, P. V. Nickles4,
A. Pipahl1, G. Priebe5, E. Risse4, W. Sandner4,6, M. Schnürer4, T. Sokollik4, S. TerAvetisyan4, T. Toncian1, P. A. Wilson2, and O. Willi1
1Institut
für Laser- und Plasmaphysik, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
2School of Mathematics and Physics, The Queen’s University Belfast BT7 1NN, UK
3Laboratoire pour l’Utilisation des Lasers Intenses, UMR 7605 CNRS-CEA-École Polytechnique-Université Paris
VI, 91128 Palaiseau, France
4Max-Born-Institut, Max-Born-Str. 2a, 12489 Berlin, Germany
5CCLRC Daresbury Laboratory, Warrington, Cheshire, WA4 4AD, UK
6Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany
Introduction (1)
● Short pulse (~1 ps) high power (~1018 W/cm2) laser
● Thin (~10 µm) metal target
 Plasma expansion on the target surface
Munib Amin – ILPP Düsseldorf
2
Introduction (2) – Example
● 50 µm Ta wire, ~ 10 J, 0.4 ps
100 µm
0 ps / 3.0 ps
5.9 ps
10.1 ps
● Plasma expansion
 covers
an area of a few square millimeters
 is accompanied by strong electric fields
 spreads along the surface on the picosecond timescale
Munib Amin – ILPP Düsseldorf
Experiment performed at the LULI 100TW facility
3
Introduction (3) – Benefits
● Electric fields in an expanding plasma can be used to control charged
particle beams. Example: The laser proton lens*
Laser pulse
Focusing, energy
selection
Proton beam
(polyenergetic,
divergent)
Metal foil cylinder
● A better understanding of the field evolution could allow to design new
targets for beam focusing, collimation or displacement.
Munib Amin – ILPP Düsseldorf
*T. Toncian, et al., Science 312, 410-413 (2006).
4
How to accelerate protons
● To accelerate protons using a laser you need
Thin
foil target (~10 µm)
A laser
• with short pulse duration (about 1 ps or less)
• with a high intensity (about 1019 W/cm2 or more)
• that will not perturb or even burn the target before the main pulse
arrives (high contrast)
● You get
Proton
•
•
•
•
emission from the rear side of the target
Up to 1013 protons
Proton energies of up to about 60 MeV
A divergent proton beam of high longitudinal and transversal
laminarity
Small virtual source size (less than 10 µm)
Munib Amin – ILPP Düsseldorf
A. Maksimchuk, et al., Phys. Rev. Lett., 84, 4108-4111 (2000).
R. A. Snavely, et al., Phys. Rev. Lett., 85, 2945-2948 (2000).
S. P. Hatchett, et al., Phys. Plasmas 7, 2076-2082 (2000).
5
Laminarity
● Longitudinal laminarity: a class of a certain energy cannot overtake
another one
● Transversal laminarity: Trajectories do not cross
Proton
generation foil
Slow protons
Fast protons
Virtual source
Munib Amin – ILPP Düsseldorf
M. Borghesi, et al., Phys. Rev. Lett., 92, 055003 (2004).
T. E. Cowan, et al., Phys. Rev. Lett., 92, 204801 (2004).
6
Probing – principle
Object moving downwards
● An object varying in time can be probed by a laser generated proton
beam (point projection).
Munib Amin – ILPP Düsseldorf
M. Borghesi, et al.,Plasma Phys. Control. Fusion 43, A267–A276 (2001).
7
Probing – electric field
Higher density
Displacement
++
+
● Each proton is displaced by the electric field
depending on its direction of emission and its
initial kinetic energy.
● The density distribution of a class of protons
having the same energy is influenced in a
specific way.
● Thus the temporal evolution of the electric
field can be mapped.
Munib Amin – ILPP Düsseldorf
Lower density
Higher density
Proton
trajectories
8
Probing – deflectometry (1)
● In proton deflectometry a mesh is projected to the detector plane.
● The green arrow identifies a certain grid node.
Munib Amin – ILPP Düsseldorf
9
Probing – deflectometry (2)
● The electric fields in the plasma deflect the protons and the projection of the
mesh appears distorted.
● The grid nodes can still be identified. Their displacement can be measured.
Munib Amin – ILPP Düsseldorf
10
2D proton imaging – with MCP
● TiSa:
40 fs,
~ 1019 W/cm2
● Nd:glass
1.5 ps
~1018 W/cm2
Graphics by Th. Sokollik
● magnification: ~10
● observed area: ~3 mm
● proton energy: 1.4 - 2 MeV
● exposure time: ≤ 400 ps
Munib Amin – ILPP Düsseldorf
Experiment performed at the Max-Born-Institut Berlin 11
Results
Region of
widened mesh
Image editing by Th. Sokollik
Direction of the
incoming laser
Cross section
seen by the
spectrometer
Shadow of the target
Displaced
target edge
No interaction laser
Munib Amin – ILPP Düsseldorf
Increase of proton density
along horizontal line
5J shot to the target
12
Proton Streak Camera
A slit cuts out a one dimensional cross
section of the obtained proton density
distribution. This cross section is
dispersed into a second dimension
concerning the kinetic energy of the
protons.
Graphics by Th. Sokollik
Munib Amin – ILPP Düsseldorf
Experiment performed at the Max-Born-Institut Berlin 13
Image obtained using the spectrometer
Glass laser shot: 0.3 J in focus, 6 x 1017 W/cm2, 1.5 ps
Proton energy
Slow decrease
Region of high field strength
No widening
Protons hitting the front
Munib Amin – ILPP Düsseldorf
Region of
increased intensity
and mesh line
density
14
Temporal and spatial field evolution on the target surface
Laser pulse 2
RCF stack
(detector)
Laser pulse 1
Proton beam
Metal foil cylinder
Proton generation
foil
● A proton beam is used to probe the electric field on the surface of a laser
irradiated metal foil cylinder.
● The density distribution of the electron beam is recorded by a stack of
radiochromic films.
Munib Amin – ILPP Düsseldorf
Experiment performed at the Vulcan Laser of the 15
Rutherford Appleton Laboratory
Images obtained using the radiochromic film stack
Glass laser shot:
20 J, 1.7 x 1019 W/cm2, 1.2 ps
7.32 MeV
6.48
5.55
4.48
3.14
1.06
120
300
38 ps
49
63
84
ps
Munib Amin – ILPP Düsseldorf
--160
12
38
2.3
18
11ps
ps
ps
-6.8
75 ps
72
67
61
48
ps
RCF calibration by Toma Toncian 16
Reconstruction of the electric field – an iterative method
Experiment 1: Streaking
Experiment 2: Imaging
Modelling
Imaging
Streaking
Experimental
result
Experimental
result
Parameter fit
Simulation
Munib Amin – ILPP Düsseldorf
Parameter
transfer
Parameter fit
Simulation
17
Comparison – simulation and experiment (1)
Time of flight/ns
Energy/MeV
Energy/MeV
Deflection on MCP/mm
Time of flight/ns
● Target charge up: 10-4 C/m2
● Decay time: 600 ps
Munib Amin – ILPP Düsseldorf
● Velocity of front propagation: 1.4 x 106 m/s
● Maximum field strength: 3.75 x 108 V/m
● Decay time: 3 ps
[decay ~ (1 + t / τ)-1]
Image editing by Th. Sokollik 18
Comparison – simulation and experiment (2)
● Maximum field strength: 1.1 x
V/m
● Propagation velocity over target surface: 0.3 x speed of light
1010
Munib Amin – ILPP Düsseldorf
7.32 MeV
6.48
5.55
4.48
3.14
1.06
19
Outlook
● Future work will concentrate on
conceiving a model that bases
on simulations reconstructing
the plasma processes of this
special phenomenon.
● Such a model might also apply
to the plasma expansion inside
a hollow target that is used to
manipulate charged particle
beams.
Munib Amin – ILPP Düsseldorf
20
Thank you.
Munib Amin – ILPP Düsseldorf
Projects were funded by DFG TR18, GRK 1203 and 21
Laserlab Europe
Modelling
● Setting up a one dimensional field configuration from simulations or
previously published models or experimental results
● Setting reasonable starting parameters for the analysis of the
experimental results
● Generalizing to three dimensions according to the experimental
geometry
Munib Amin – ILPP Düsseldorf
22
The electric field configuration
● The fraction of laser energy absorbed by hot electrons and the
hot electron temperature are estimated depending on laser
intensity and wave length according to Fuchs[2006].
● The electric field is supposed to build up in a plasma expanding into
vacuum as described by Mora[2003].
● Spatial dependence in one dimension and temporal evolution
are given by PIC and MHD-simulations conducted by
Romagnani[2005].
Munib Amin – ILPP Düsseldorf
J. Fuchs, et al., Nature Physics 2, 48-54 (2006).
P. Mora, Phys. Rev. Lett. 90, 185002 (2003).
L. Romagnani, et al., Phys. Rev. Lett. 95, 195001 (2005).
23
Electric field strength/(V/m)
Electric field evolution – Mora field
8
3.5x10
6
0 ps
8
3.0x10
8
5 ps
8
10 ps
2.5x10
2.0x10
8
1.5x10
8
1.0x10
7
5.0x10
0.0
0.0
0.2
0.4
0.6
0.8
1.0
1.2
4.0x10
6
3.5x10
6
3.0x10
6
2.5x10
6
2.0x10
6
1.5x10
6
1.0x10
5
5.0x10
0.0
0.0
250 ps
500 ps
750 ps
0.2
0.4
0.6
0.8
1.0
1.2
Distance from target surface/mm
Munib Amin – ILPP Düsseldorf
24
Electric field strength/(V/m)
Electric field evolution – charge up
250 ps
6
8x10
6
7x10
6
6x10
6
5x10
6
4x10
6
3x10
6
2x10
6
1x10
0
0.0
500 ps
750 ps
0.2
0.4
0.6
0.8
1.0
1.2
Distance from target surface/mm
Munib Amin – ILPP Düsseldorf
25
Electric field strength/(V/m)
Total electric field
8
7
3.5x10
1.2x10
0 ps
8
3.0x10
250 ps
7
1.0x10
5 ps
8
2.5x10
8.0x10
10 ps
8
2.0x10
500 ps
6
750 ps
6
8
6.0x10
8
4.0x10
7
2.0x10
1.5x10
6
1.0x10
6
5.0x10
0.0
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0.0
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Distance from target surface/mm
Munib Amin – ILPP Düsseldorf
26
One dimensional electric field
Field strength /
(V/m)
Position / m
Time / s
The field distribution according to Mora[2003] and Romagnani[2006] is
modelled in one dimension.
Munib Amin – ILPP Düsseldorf
27
Generalizing to more dimensions
Front
E
E
x
x
y
Weaker and retarded
The field distribution can be generalized to two or three dimensions by
assuming the expansion to start later and the electron density to be lower at
larger distances from the centre of the interaction.
Munib Amin – ILPP Düsseldorf
28
The target geometry
The one dimensional field distribution
is applied along the dashed lines
x
t3
t2
t1
y
Plain target
Munib Amin – ILPP Düsseldorf
Curved or cylindrical target
29
Overview
● Quasi monoenergetic particles can be generated by
A special
treatment of the foil target (thin layer or dots containing the
particles to be accelerated on the rear surface)
A second target that selects one velocity class of protons: a laser
irradiated hollow metal foil cylinder
● The proton beam can be focused by using
A hemispherical
proton generation foil
A second target that focuses the divergent proton beam: a laser
irradiated hollow metal foil cylinder
Munib Amin – ILPP Düsseldorf
B. M. Hegelich, et al., Nature, 439, 441-444 (2006).
H. Schwoerer, et al., Nature, 439, 445-448 (2006).
P. K. Patel, et al., Phys. Rev. Lett. 91, 125004 (2003).
T. Toncian, et al., Science 312, 410-413 (2006).
30
Overview – applications
● Medical applications
Maybe one day
Tumour
therapy
Production of radioisotopes
●
●
●
●
Fast ignition
Ion source for conventional particle accelerators
Isochoric heating: creation of warm dense matter
Diagnostics for dense plasmas: proton probing
Munib Amin – ILPP Düsseldorf
Routine
F. Pegoraro, et al., Laser and Particle Beams, 22, 19–24 (2004).
M Roth, et al., Plasma Phys. Control. Fusion, 47, B841–B850 (2005).31
P. K. Patel, et al., Phys. Rev. Lett. 91, 125004 (2003).
K. W. D. Ledingham, et al., Science 300, 1107 (2003).
How to accelerate protons – hot electrons
+ + ++
+ ++
+ +
+ + ++
+ ++
+ +
Munib Amin – ILPP Düsseldorf
Hatchett, et al., Phys. Plasmas 7, 2076 (2000).
A. Pukhov, Phys. Rev. Lett., 86, 3562-3565 (2001).
32
How to accelerate protons – TNSA (Target Normal Sheath
Acceleration)
Munib Amin – ILPP Düsseldorf
33
Detection – radiochromic film stack
RCF stack
● The density distribution of the proton beam is recorded by a stack of
radiochromic films.
● Since protons deposit most of their energy in the Bragg peak, one
film shows the distribution corresponding to only one specific energy.
Munib Amin – ILPP Düsseldorf
34
Detection – proton streak camera (1)
Top view
Slit
Side view
Permanent
magnet
Detector
(MCP)
Munib Amin – ILPP Düsseldorf
Back side – detector
T. Sokollik, et al., to be published
35
Detection – proton streak camera (2)
Top view
● The spectrometer setup can be used
map the time evolution of an electric
field in one dimension.
● In contrast to a film stack this setup
provides a high energy resolution
for lower energetic protons (up to
ca. 5 MeV).
Munib Amin – ILPP Düsseldorf
Side view
Back side – detector
36