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Title: Comparative spectra and efficiencies of ions laser-accelerated forward from the front and rear surfaces of thin solid foils

Abstract

The maximum energy of protons that are accelerated forward by high-intensity, short-pulse lasers from either the front or rear surfaces of thin metal foils is compared for a large range of laser intensities and pulse durations. In the regime of moderately long laser pulse durations (300-850 fs), and for high laser intensities [(1-6)x10{sup 19} W/cm{sup 2}], rear-surface acceleration is shown experimentally to produce higher energy particles with smaller divergence and a higher efficiency than front-surface acceleration. For similar laser pulse durations but for lower laser intensities (2x10{sup 18} W cm{sup -2}), the same conclusion is reached from direct proton radiography of the electric fields associated with proton acceleration from the rear surface. For shorter (30-100 fs) or longer (1-10 ps) laser pulses, the same predominance of rear-surface acceleration in producing the highest energy protons is suggested by simulations and by comparison of analytical models with measured values. For this purpose, we have revised our previous analytical model of rear-surface acceleration [J. Fuchs et al., Nat. Phys. 2, 48 (2006)] to adapt it to the very short pulse durations. Finally, it appears, for the explored parameters, that rear-surface acceleration is the dominant mechanism.

Authors:
 [1];  [2];  [3]; ; ;  [1];  [3];  [4];  [3]; ;  [5]; ; ; ;  [4]; ; ;  [1];  [4];  [6] more »; ; ;  [7];  [5];  [6];  [8] « less
  1. General Atomics, San Diego, California 92121 (United States)
  2. (France)
  3. (United States)
  4. LULI, Ecole Polytechnique, CNRS-CEA, UPMC, route de Saclay, 91128 Palaiseau (France)
  5. University of California, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
  6. (Germany)
  7. Technische Universitat Darmstadt, 64289 Darmstadt (Germany)
  8. Max-Planck-Institut fuer Quantenoptik, 85748 Garching (Germany) (and others)
Publication Date:
OSTI Identifier:
20975001
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 5; Other Information: DOI: 10.1063/1.2720373; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; ACCELERATION; COMPARATIVE EVALUATIONS; EFFICIENCY; ELECTRIC FIELDS; FOILS; IONS; LASERS; METALS; PLASMA; PROTON RADIOGRAPHY; PROTONS; PULSES; REFRACTIVE INDEX; SOLIDS; SPECTRA; SURFACES

Citation Formats

Fuchs, J., LULI, Ecole Polytechnique, CNRS-CEA, UPMC, route de Saclay, 91128 Palaiseau, Physics Department, MS-220, University of Nevada, Reno, Nevada 89557, Sentoku, Y., Cowan, T. E., Kemp, A., Physics Department, MS-220, University of Nevada, Reno, Nevada 89557, D'Humieres, E., Physics Department, MS-220, University of Nevada, Reno, Nevada 89557, Cobble, J., Fernandez, J. C., Audebert, P., Antici, P., Gauthier, J.-C., Popescu, H., Nikroo, A., Campbell, E. M., Stephens, R., Brambrink, E., Technische Universitat Darmstadt, 64289 Darmstadt, Blazevic, A., Geissel, M., Roth, M., Hegelich, M., Max-Planck-Institut fuer Quantenoptik, 85748 Garching, and Karsch, S. Comparative spectra and efficiencies of ions laser-accelerated forward from the front and rear surfaces of thin solid foils. United States: N. p., 2007. Web. doi:10.1063/1.2720373.
Fuchs, J., LULI, Ecole Polytechnique, CNRS-CEA, UPMC, route de Saclay, 91128 Palaiseau, Physics Department, MS-220, University of Nevada, Reno, Nevada 89557, Sentoku, Y., Cowan, T. E., Kemp, A., Physics Department, MS-220, University of Nevada, Reno, Nevada 89557, D'Humieres, E., Physics Department, MS-220, University of Nevada, Reno, Nevada 89557, Cobble, J., Fernandez, J. C., Audebert, P., Antici, P., Gauthier, J.-C., Popescu, H., Nikroo, A., Campbell, E. M., Stephens, R., Brambrink, E., Technische Universitat Darmstadt, 64289 Darmstadt, Blazevic, A., Geissel, M., Roth, M., Hegelich, M., Max-Planck-Institut fuer Quantenoptik, 85748 Garching, & Karsch, S. Comparative spectra and efficiencies of ions laser-accelerated forward from the front and rear surfaces of thin solid foils. United States. doi:10.1063/1.2720373.
Fuchs, J., LULI, Ecole Polytechnique, CNRS-CEA, UPMC, route de Saclay, 91128 Palaiseau, Physics Department, MS-220, University of Nevada, Reno, Nevada 89557, Sentoku, Y., Cowan, T. E., Kemp, A., Physics Department, MS-220, University of Nevada, Reno, Nevada 89557, D'Humieres, E., Physics Department, MS-220, University of Nevada, Reno, Nevada 89557, Cobble, J., Fernandez, J. C., Audebert, P., Antici, P., Gauthier, J.-C., Popescu, H., Nikroo, A., Campbell, E. M., Stephens, R., Brambrink, E., Technische Universitat Darmstadt, 64289 Darmstadt, Blazevic, A., Geissel, M., Roth, M., Hegelich, M., Max-Planck-Institut fuer Quantenoptik, 85748 Garching, and Karsch, S. Tue . "Comparative spectra and efficiencies of ions laser-accelerated forward from the front and rear surfaces of thin solid foils". United States. doi:10.1063/1.2720373.
@article{osti_20975001,
title = {Comparative spectra and efficiencies of ions laser-accelerated forward from the front and rear surfaces of thin solid foils},
author = {Fuchs, J. and LULI, Ecole Polytechnique, CNRS-CEA, UPMC, route de Saclay, 91128 Palaiseau and Physics Department, MS-220, University of Nevada, Reno, Nevada 89557 and Sentoku, Y. and Cowan, T. E. and Kemp, A. and Physics Department, MS-220, University of Nevada, Reno, Nevada 89557 and D'Humieres, E. and Physics Department, MS-220, University of Nevada, Reno, Nevada 89557 and Cobble, J. and Fernandez, J. C. and Audebert, P. and Antici, P. and Gauthier, J.-C. and Popescu, H. and Nikroo, A. and Campbell, E. M. and Stephens, R. and Brambrink, E. and Technische Universitat Darmstadt, 64289 Darmstadt and Blazevic, A. and Geissel, M. and Roth, M. and Hegelich, M. and Max-Planck-Institut fuer Quantenoptik, 85748 Garching and Karsch, S.},
abstractNote = {The maximum energy of protons that are accelerated forward by high-intensity, short-pulse lasers from either the front or rear surfaces of thin metal foils is compared for a large range of laser intensities and pulse durations. In the regime of moderately long laser pulse durations (300-850 fs), and for high laser intensities [(1-6)x10{sup 19} W/cm{sup 2}], rear-surface acceleration is shown experimentally to produce higher energy particles with smaller divergence and a higher efficiency than front-surface acceleration. For similar laser pulse durations but for lower laser intensities (2x10{sup 18} W cm{sup -2}), the same conclusion is reached from direct proton radiography of the electric fields associated with proton acceleration from the rear surface. For shorter (30-100 fs) or longer (1-10 ps) laser pulses, the same predominance of rear-surface acceleration in producing the highest energy protons is suggested by simulations and by comparison of analytical models with measured values. For this purpose, we have revised our previous analytical model of rear-surface acceleration [J. Fuchs et al., Nat. Phys. 2, 48 (2006)] to adapt it to the very short pulse durations. Finally, it appears, for the explored parameters, that rear-surface acceleration is the dominant mechanism.},
doi = {10.1063/1.2720373},
journal = {Physics of Plasmas},
number = 5,
volume = 14,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • In the last few years, intense research has been conducted on the topic of laser-accelerated ion sources and their applications. Ultra-bright beams of multi-MeV protons are produced by irradiating thin metallic foils with ultra-intense short laser pulses. These sources open new opportunities for ion beam generation and control, and could stimulate development of compact ion accelerators for many applications, in particular proton therapy of deep-seated tumours. Here we show that scaling laws deduced from fluid models reproduce well the acceleration of proton beams for a large range of laser and target parameters. These scaling laws show that, in our regime,more » there is an optimum in the laser pulse duration of {approx}200 fs-1 ps, with a needed laser energy level of 30 to 100 J, in order to achieve e.g. 200 MeV energy protons necessary for proton therapy.« less
  • We have measured energy spectra of secondary electrons produced by fast-carbon-cluster C{sub n}{sup +} (n=1-4) bombardment of thin carbon foils (3.2, 7.3, 11.9, and 20.3 {mu}g/cm{sup 2}). For clusters of identical velocity, the convoy-electron yield is enhanced with increasing cluster size n, while the yield of secondary electrons is reduced. The yield of convoy electrons normalized to the number of injected atoms increases proportionally with cluster size n. This proportionality suggests that there is only a weak vicinage effect on the number of primary electrons scattered by the projectile. The vicinage effect observed in low-energy secondary electrons must therefore arisemore » from either transport or transmission through the surface.« less
  • No abstract prepared.
  • A new diagnostic method of the thermal transport zone of a laser-created plasma at short wavelength (0.26 {mu}m) is presented. This method uses soft x-ray spectroscopy and allows one to deduce the temperature of the propagating thermal front during the laser interaction. Time-resolved X--UV spectra of the rear side of thin plastic foils coated on their front side with a thin layer of gold of different thicknesses (50--300 A) are presented. The layers of gold must be sufficiently thin in order to avoid the fact that their spectrum perturbs the heating of the foil by radiative effects. The plastic thicknessesmore » are chosen less or equal to the ablation thickness of the material for the laser illumination conditions, i.e., about 6 {mu}m. The spectrum emitted by the gold layer plays the role of a backlighter that probes the plastic heated by the laser. Computer simulations including radiation (MULTI) confirm the weak effect of radiation heating particularly for the thinner layers of gold.« less
  • We present a numerical study of the effect of the laser spot size of a circularly polarized laser beam on the energy of quasi-monoenergetic protons in laser proton acceleration using a thin carbon-hydrogen foil. The used proton acceleration scheme is a combination of laser radiation pressure and shielded Coulomb repulsion due to the carbon ions. We observe that the spot size plays a crucial role in determining the net charge of the electron-shielded carbon ion foil and consequently the efficiency of proton acceleration. Using a laser pulse with fixed input energy and pulse length impinging on a carbon-hydrogen foil, amore » laser beam with smaller spot sizes can generate higher energy but fewer quasi-monoenergetic protons. We studied the scaling of the proton energy with respect to the laser spot size and obtained an optimal spot size for maximum proton energy flux. Using the optimal spot size, we can generate an 80 MeV quasi-monoenergetic proton beam containing more than 10{sup 8} protons using a laser beam with power 250 TW and energy 10 J and a target of thickness 0.15 wavelength and 49 critical density made of 90% carbon and 10% hydrogen.« less