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High quality, Laser-Accelerated Ion Bunches From Double

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High quality, Laser-Accelerated Ion Bunches From Double
COULOMB’09,
Ions Acceleration with high Power Lasers:
Physics and Applications
June 15-18, 2009, Senigallia (AN), Italy
Laser-Accelerated Ions From
Layered Targets
Leonida A. Gizzi
Intense Laser Irradiation Laboratory, IPCF, CNR,
&
Istituto Nazionale di Fisica Nucleare, INFN, Pisa, Italy
CONSIGLIO NAZIONALE DELLE RICERCHE
ISTITUTO NAZIONALE DI FISICA NUCLEARE
PEOPLE
•
•
•
•
•
IL GRUPPO ILIL-CNR
Antonio GIULIETTI (CNR)*
Danilo GIULIETTI (Univ. Pisa, CNR)*
Leonida A. GIZZI (CNR)*
Luca LABATE (CNR)*
Moreno VASELLI (CNR-Associato)*
http://ilil.ipcf.cnr.it
• Walter BALDESCHI (CNR)
• Antonella ROSSI (CNR)
•
•
•
•
•
•
•
Sergio BETTI (CNR)*, postdoc
Carlo A. CECCHETTI (CNR)*, PhD
Andrea GAMUCCI (CNR & Univ. of Pisa)*, PhD
Petra KOESTER (CNR & Univ. of Pisa)*, PhD
Tadzio LEVATO (CNR & Univ. of Pisa)*, PhD
Naveen PATHAK (UNIPI & CNR), PhD
Orlando CIRICOSTA (UNIPI and CNR), Tesi Laurea sp.
• Francesco VITTORI (UNIPI and CNR), Tesi Laurea sp.
• Francesco MICHIENZI (UNIPI and CNR), Tesi laurea tri.
* Also at INFN
CNR - DIPARTIMENTO MATERIALI E DISPOSITIVI
Progetto: Ottica, Fotonica e Plasmi
Unità (Commessa): FOTONICA DEGLI ALTI CAMPI
Fotonica degli alti campi per la generazione di impulsi
ultracorti di radiazione X e particelle di alta energia;
Sviluppo di laser a larga banda per studi strategici sulla
fusione per confinamento inerziale;
CNR Research Campus, Pisa, Italy
CONSIGLIO NAZIONALE DELLE RICERCHE
ISTITUTO NAZIONALE DI FISICA NUCLEARE
COLLABORATION
L.A. Gizzi, S. Betti, A. Giulietti, D. Giulietti, P. Koester, L. Labate, T. Levato*
ILIL, IPCF-CNR and INFN, Pisa, Italy, * LNF-INFN, Frascati, Italy
T. Kämpfer, I. Uschmann, E. Förster,
IOQ, Univ. Jena, Germany
F. Zamponi, A. Luebcke,
Max Born Institute, Berlin, Germany
A. P. L. Robinson
Central Laser Facility, RAL, UK
CONSIGLIO NAZIONALE DELLE RICERCHE
ISTITUTO NAZIONALE DI FISICA NUCLEARE
UNDERLYING MOTIVATION: FAST
ELECTRON TRANSPORT





The Fast Ignition scheme of Inertial Fusion Energy requires high current,
fast electron beams to propagate efficiently in high solid density collisional
plasmas;
Transient magnetic fields and neutralising plasma return current occur;
Knowledge is needed on the state of the material in which f.e. propagation
occurs;
X-ray spectroscopy is the principal tool for accomplishing this task;
Return current will give rise to resistive thermal heating that will modify the
spectral features of X-ray fluorescence;
Need to investigate PROPAGATION
AND ENERGY DEPOSITION
of fast electron beam inside the
material
CONSIGLIO NAZIONALE DELLE RICERCHE
ISTITUTO NAZIONALE DI FISICA NUCLEARE
FAST ELECTRON PROPAGATION STUDIES
WE USE LARGE AREA, MULTI-LAYER
METALLIC and METAL-INSULATOR
TARGETS
Experiments performed also at the
Jena (IOQ) laser facility within the
LASERLAB access.
Ni
10µm
Optical
spectroscopy
Charged particle
detector
Laser
80 fs; up to 0.6 J
≈ 5x1019 W/cm2
Fe
10µm
“Rear”
pin hole
camera
CONSIGLIO NAZIONALE DELLE RICERCHE
Cr
1.2µm
“Front”
pin hole camera
ISTITUTO NAZIONALE DI FISICA NUCLEARE
X-RAY IMAGING OF FRONT AND REAR SIDE
LASER
Cr
Ni
Fe
1.2 µm
10µm
10µm
50 µm
CONSIGLIO NAZIONALE DELLE RICERCHE
ISTITUTO NAZIONALE DI FISICA NUCLEARE
FORWARD ESCAPING FAST ELECTRONS
Target
Radiochromic
film layers
Laser
Spectrum is obtained matching
dose released in each layer
with predictions of MC
(GEANT4) through an iterative
process.
CONSIGLIO NAZIONALE DELLE RICERCHE
ISTITUTO NAZIONALE DI FISICA NUCLEARE
FORWARD ESCAPING FAST ELECTRONS
Target
Radiochromic
film layers
Laser
Forward
emitted
charged
Particles
(electrons)
CONSIGLIO NAZIONALE DELLE RICERCHE
ISTITUTO NAZIONALE DI FISICA NUCLEARE
FORWARD ESCAPING FAST ELECTRONS
Electron spectrum at E < 1MeV
-2
cm )
Cr+Ni+Fe target
3 108
2.5 108
Electrons (e MeV
-1
y = m1*m0* exp(-(m0+m2)/m3)
Value
Error
m1
1.5738e+05
1.4009e+12
m2
-483.02
1.435e+09
m3
161.33
27.445
Chisq
1.1836e+16
NA
R
0.87822
NA
2 108
1.5 108
Fit with a “relativistic Maxwellian”
8
1 10
5 107
Yields a fast electron temperature of 160 keV
0 100
0
200
400
600
800
1000
Energy (keV)
CONSIGLIO NAZIONALE DELLE RICERCHE
ISTITUTO NAZIONALE DI FISICA NUCLEARE
ION ACCELERATION IN THE TNSA
SHEATH
Acceleration of the target ions
driven by the fast electrons
Fast
Electrons
Foil target
L. Romagnani et al., Phys. Rev. Lett. 95 195001 (2005).
S. Betti et al., Plasma Phys. Contr. Fusion 47, 521-529 (2005).
F. Ceccherini et al., Laser Phys. 16, 594-599 (2006).
J. Fuchs et al. Nature Physics 2, 48 (2006).
CONSIGLIO NAZIONALE DELLE RICERCHE
ISTITUTO NAZIONALE DI FISICA NUCLEARE
Towards High-Quality Ion Bunches
/01
Applications (ICF, Proton Imaging,...) require high quality ion
bunches, with special attention to the spectral and angular features, the
total yield and spatial cross section uniformity.
Quality control of the laser-driven ion bunch might rely on the use of
double-layer targets, as theoretically proposed in T. Esirkepov et al.,
Phys. Rev. Lett. 89, 175003 (2002).
In recent experiments, the employment of custom double-layer
targets resulted in a significant reduction of the energy spread
which typically characterizes laser-accelerated ion bunches (H.
Schwoerer et al., Nature (London) 439, 445 (2006), M. Hegelich et al.,
Nature (London) 439, 441 (2006).).
CONSIGLIO NAZIONALE DELLE RICERCHE
ISTITUTO NAZIONALE DI FISICA NUCLEARE
Towards High-Quality Ion Bunches
/02
Plastic coatings have been found to induce filamentation of the fast electron
current. Such effect has a strong detrimental influence on the ion bunch cross
section by increasing its size and depleting its uniformity:
(RCF image taken from J. Fuchs et al.,
PRL 91, 255002 (2003), shot on a 100 μm
glass foil)
Experimentally, fast electron current filamentation has been observed to occur
with plastic coatings thicker than 0.1 μm (M. Roth et al., PRST-AB 5, 061301
(2002), shot on a 100 μm plastic foil).
CONSIGLIO NAZIONALE DELLE RICERCHE
ISTITUTO NAZIONALE DI FISICA NUCLEARE
IONS FROM LAYERED TARGETS
Dielectric layers are made using
lacquer coating, a dielectric
characterized by a very high
resistivity (1.5 x 107 W/m) and high
adhesion to the substrate;
<0.6 J, 80 fs, 5E19 W/cm2
Targets adopted: μm thick foils
i) single-layer, lacquer-coated
ii) multi-layer, lacquer assembled
iii) single-layer, uncoated
Lacquer chemical composition: C6H7(NO2)3O5
CONSIGLIO NAZIONALE DELLE RICERCHE
ISTITUTO NAZIONALE DI FISICA NUCLEARE
PRELIMINARY RCF DATA
Experimental results:
Ti, 5 μm,
uncoated
10 μm Fe + 1.5 μm Mylar + 10 μm
Ti, lacquer assembled
Fe, 10 μm,
back-coated with
lacquer
Given their more favourable charge-to-mass ratio, ion bunch mainly consists of protons;
Energy ranging between 1.2 and 3.5 MeV (from a radiographic image of a Ta grid & SRIM
calculations), confirmed by 1D, PIC model simulations (S. Betti et al. Technical report, ILILIPCF, CNR, Pisa, Italy, available at http://ilil.ipcf.cnr.it);
Strong effect of the dielectric coating, which increases the uniformity and reduces the
dimensions of the proton bunch spatial cross section;
Protons consistently originate from the lacquer layer, even if lacquer is buried in the target;
CONSIGLIO NAZIONALE DELLE RICERCHE
ISTITUTO NAZIONALE DI FISICA NUCLEARE
PRELIMINARY OBSERVATION
Enhancement of the
spatial
cross section uniformity
Reduction of the
spatial
cross section size
(divergence?)
CONSIGLIO NAZIONALE DELLE RICERCHE
Reduction of fast electron
current filamentation even after
propagation through an
insulating layer (the lacquer)
Modification of the fast electron
Distribution with inhibition of peripheral
portion of the fast electron current
ISTITUTO NAZIONALE DI FISICA NUCLEARE
DEDICATED EXPERIMENT
Systematic comparison between the ion bunches emitted
from uncoated and lacquer-coated metal foils.
Same experimental setup of the first campaign
Targets: 10 μm thick steel and 5 μm thick Ti foils, either
uncoated or back-coated with 1.5 µm thick lacquer.
7 mm
LASER
TARGET
+
+
+
+
+
+
Lacquer coating
5 cm
RCF
Uncoated metal
CONSIGLIO NAZIONALE DELLE RICERCHE
ISTITUTO NAZIONALE DI FISICA NUCLEARE
EXPERIMENTAL - RCF RAW DATA
Experimental results: 10 µm thick steel target
Without dielectric
coating
With lacquer
Coating (1.5 µm thick)
CONSIGLIO NAZIONALE DELLE RICERCHE
ISTITUTO NAZIONALE DI FISICA NUCLEARE
EXPERIMENTAL - RCF RAW DATA
Experimental results: 5 µm Ti
Without dielectric
coating
CONSIGLIO NAZIONALE DELLE RICERCHE
With lacquer
Coating (1.5 µm thick)
ISTITUTO NAZIONALE DI FISICA NUCLEARE
EXPERIMENTAL - RCF DATA
Experimental results: 5 µm Ti
Without dielectric
coating
CONSIGLIO NAZIONALE DELLE RICERCHE
With lacquer
Coating (1.5 µm thick)
ISTITUTO NAZIONALE DI FISICA NUCLEARE
OBSERVATIONS
The results confirm a systematic effect of the dielectric coating which
increases the proton bunch uniformity and reduces the transverse size;
this is in contrast with previous experiments that show that dielectric
coatings thicker than 0.1 μm induce fast electron current filamentation,
which has a detrimental effect on the accelerated proton bunch;
As in the TNSA scenario (which is here the key mechanism) ion
acceleration is driven by the fast electron current, the observations
suggest that modification in the fast electron transport regime;
The different quality/type of dielectric coating (plastic vs. lacquer) and
the quality of the coating-metal interface adopted here might played a role.
Indeed, standard plastic-coated foils (vacuum deposition) may include
uncontrolled vacuum gaps and loose interfaces.
CONSIGLIO NAZIONALE DELLE RICERCHE
ISTITUTO NAZIONALE DI FISICA NUCLEARE
MODELLING APPROACH
An full modeling of our proton acceleration conditions,
including fast electron generation and transport is well beyond
the possibility of presently available numerical codes.
Since the emphasis is on the comparison of two configurations
with identical laser-target interaction conditions, we can
focus on the fast electron transport stage in order to find the
possible origine of differences observed between uncoated and
lacquer-coated targets.
Fast electron transport is thus investigated with the help of the
2D hybrid Vlasov-Fokker-Planck (VFP) numerical Code LEDA
(A. P. L. Robinson and M. Sherlock, Phys. Plasmas 14, 083105
(2007).)
CONSIGLIO NAZIONALE DELLE RICERCHE
ISTITUTO NAZIONALE DI FISICA NUCLEARE
SUMMARY OF SIMULATION RESULTS
LEDA results for the fast electron distribution on the back of the
target after the laser-matter interaction stage:
5.7 μm-thick Al foil,
uncoated
Experimental proton data
Transverse coordinate [μm]
Simulation predict a fine scale filamentation of the fast electron beam that is
expected to affect the proton beam – similar features are observed in our
experimental data;
CONSIGLIO NAZIONALE DELLE RICERCHE
ISTITUTO NAZIONALE DI FISICA NUCLEARE
SUMMARY OF SIMULATION RESULTS
LEDA results for the fast electron distribution on the back of the
target after the laser-matter interaction stage:
5.7 μm-thick Al foil,
back-coated with a
2.3 μm-thick CH layer
(no vacuum gap)
Experimental data
Transverse coordinate [μm]
Simulations of back-coated targets predict reduction of fine scale filamentation that may
originate from the onset of a large scale quasi-static B-field at the interface due to the
resistivity gradient in the dielectric – this is under further investigation
CONSIGLIO NAZIONALE DELLE RICERCHE
ISTITUTO NAZIONALE DI FISICA NUCLEARE
PRELIMINARY CONCLUSIONS
Fast electron transport can be investigated via direct and indirect
techniques. We also use study of ion emission to investigate fast electron
transport phenomena in layered targets;
Our measurements show of an increase of the proton bunch spatial cross
section uniformity together with a reduction of its dimensions.
The simulations show that under our experimental conditions the presence
of the lacquer leads to a suppression of both the fast electron current fine
scale filamentation and of the peripherical portion of the bunch;
The unexpected improved beam quality with dielectric coated targets may
be a consequence of the unique properties of the interface in our dielectric
coating (lacquer)….
CONSIGLIO NAZIONALE DELLE RICERCHE
ISTITUTO NAZIONALE DI FISICA NUCLEARE
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