Transcript Laser ion acceleration – principle and applications - Heinrich

Laser ion acceleration and
applications
A bouquet of flowers
Munib Amin
Institute for Laser and Plasma Physics
Heinrich Heine University Düsseldorf
Introduction
● You need




Thin foil target
Short pulse
High intensity
High contrast
Munib Amin – ILPP Düsseldorf
● You get

Up to 1013 protons

up to about 60 MeV

high laminarity beam

Small virtual source
size
2
Overview
● Acceleration
● Beam Properties and Control
● Applications
● Conclusion
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How to accelerate protons?
TNSA!
(Target Normal Sheath Acceleration)
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How to accelerate protons (I)
+ + ++
+ ++
+ +
+ + ++
+ ++
+ +
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How to accelerate protons (II)
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Properties (I): Laminarity
● Longitudinal laminarity
● Transversal laminarity
Proton
generation foil
Slow
protons
Fast
protons
Virtual
source
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Borghesi et al. (2004)
Cowan et al. (2004)
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Properties (II): Ion species
● Heating
Ions/MeV
1011
F7+ heated
● Ablation
1010
109
108
F7+ unheated
107
0.0
20.0 40.0
60.0 80.0 100.0 120.0
Energy [MeV]
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Hegelich et al (2002)
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Properties (III): Divergence/spectrum
● Focus
Laser pulse 2
● Collimate
● Select energy
Protons
Metal foil
cylinder
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Toncian et al (2006)
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Properties (IV): Energy
● Energy increase: Laser piston regime?
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Esirkepov et al (2004)
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Applications
● Diagnostics for dense plasmas
● Isochoric heating
Already
done
● Ion source for conventional
particle accelerators
● Fast ignition
● Medical applications
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Maybe
one day
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Probing (I): Principle
Object moving downwards
● Time variation can mapped.
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Borghesi et al (2001)
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Probing (II): Electric field
Higher
density
Displacement
++
+
● Measure: Density
distribution/displacement of
protons having the same
energy
Lower
density
Proton
trajectories
Higher
density
● Find out: Temporal evolution
of the electric field
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Probing (III): Deflectometry
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Probing (IV): Deflectometry
● Identify grid nodes
● Measure their displacement
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Isochoric heating: Creating WDM
● Hemispherical target
Al-foil
320 µm Al
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Patel et al (2003)
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Fast ignition
Petawatt beams
(5ps 6kJ)
Proton beams
Conical shaped
target
Primary driver
Fuel
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Roth et al (2001)
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Medical applications (I): Radioisotopes
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Ledingham et al (2004)
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Medical applications (II): Cancer
therapy
X-rays
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Protons
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Conclusion
● Attractive applications are waiting for
laser accelerated ion beams
● …if we are able to control their
properties.
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Thank you
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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.
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Overview (2)
● 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).
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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.
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Reconstruction of the electric field – an
iterative method
Experiment 1: Streaking
Experiment 2: Imaging
Modelling
Imaging
Streaking
Experimental
result
Experimental
result
Parameter fit
Simulation
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Parameter
transfer
Parameter fit
Simulation
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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
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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).
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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.
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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.
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The target geometry
The one dimensional field distribution
is applied along the dashed lines
x
t3
t2
t1
y
Plain target
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Curved or cylindrical target
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