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Title: Emittance growth mechanisms for laser-accelerated proton beams

Abstract

In recent experiments the transverse normalized rms emittance of laser-accelerated MeV ion beams was found to be <0.002 mm mrad, which is at least 100 times smaller than the emittance of thermal ion sources used in accelerators [T. E. Cowan et al., Phys. Rev. Lett. 92, 204801 (2004)]. We investigate the origin for the low emittance of laser-accelerated proton beams by studying several candidates for emittance-growth mechanisms. As our main tools, we use analytical models and one- and two-dimensional particle-in-cell simulations that have been modified to include binary collisions between particles. We find that the dominant source of emittance is filamentation of the laser-generated hot electron jets that drive the ion acceleration. Cold electron-ion collisions that occur before ions are accelerated contribute less than ten percent of the final emittance. Our results are in qualitative agreement with the experiment, for which we present a refined analysis relating emittance to temperature, a better representative of the fundamental beam physics.

Authors:
 [1];  [2]; ;  [1];  [3]; ; ; ;  [1]
  1. Physics Department, University of Nevada, Reno, Nevada 89557 (United States)
  2. (United States)
  3. (France)
Publication Date:
OSTI Identifier:
21072438
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics; Journal Volume: 75; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevE.75.056401; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 43 PARTICLE ACCELERATORS; ACCELERATION; BEAM EMITTANCE; ELECTRON-ION COLLISIONS; ELECTRONS; ION BEAMS; IONS; LASERS; MEV RANGE; PLASMA; PLASMA SIMULATION; PROTON BEAMS

Citation Formats

Kemp, Andreas J., Lawrence Livermore National Laboratory, Livermore, California 94551, Fuchs, J., Antici, P., Laboratoire pour l'Utilisation des Lasers Intenses, UMR 7605 CNRS-CEA-Ecole Polytechnique-Universite Paris VI, Palaiseau, Sentoku, Y., Sotnikov, V., Bakeman, M., and Cowan, T. E.. Emittance growth mechanisms for laser-accelerated proton beams. United States: N. p., 2007. Web. doi:10.1103/PHYSREVE.75.056401.
Kemp, Andreas J., Lawrence Livermore National Laboratory, Livermore, California 94551, Fuchs, J., Antici, P., Laboratoire pour l'Utilisation des Lasers Intenses, UMR 7605 CNRS-CEA-Ecole Polytechnique-Universite Paris VI, Palaiseau, Sentoku, Y., Sotnikov, V., Bakeman, M., & Cowan, T. E.. Emittance growth mechanisms for laser-accelerated proton beams. United States. doi:10.1103/PHYSREVE.75.056401.
Kemp, Andreas J., Lawrence Livermore National Laboratory, Livermore, California 94551, Fuchs, J., Antici, P., Laboratoire pour l'Utilisation des Lasers Intenses, UMR 7605 CNRS-CEA-Ecole Polytechnique-Universite Paris VI, Palaiseau, Sentoku, Y., Sotnikov, V., Bakeman, M., and Cowan, T. E.. Tue . "Emittance growth mechanisms for laser-accelerated proton beams". United States. doi:10.1103/PHYSREVE.75.056401.
@article{osti_21072438,
title = {Emittance growth mechanisms for laser-accelerated proton beams},
author = {Kemp, Andreas J. and Lawrence Livermore National Laboratory, Livermore, California 94551 and Fuchs, J. and Antici, P. and Laboratoire pour l'Utilisation des Lasers Intenses, UMR 7605 CNRS-CEA-Ecole Polytechnique-Universite Paris VI, Palaiseau and Sentoku, Y. and Sotnikov, V. and Bakeman, M. and Cowan, T. E.},
abstractNote = {In recent experiments the transverse normalized rms emittance of laser-accelerated MeV ion beams was found to be <0.002 mm mrad, which is at least 100 times smaller than the emittance of thermal ion sources used in accelerators [T. E. Cowan et al., Phys. Rev. Lett. 92, 204801 (2004)]. We investigate the origin for the low emittance of laser-accelerated proton beams by studying several candidates for emittance-growth mechanisms. As our main tools, we use analytical models and one- and two-dimensional particle-in-cell simulations that have been modified to include binary collisions between particles. We find that the dominant source of emittance is filamentation of the laser-generated hot electron jets that drive the ion acceleration. Cold electron-ion collisions that occur before ions are accelerated contribute less than ten percent of the final emittance. Our results are in qualitative agreement with the experiment, for which we present a refined analysis relating emittance to temperature, a better representative of the fundamental beam physics.},
doi = {10.1103/PHYSREVE.75.056401},
journal = {Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics},
number = 5,
volume = 75,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • Laser pre-pulse is a major issue in experiments on laser-generation of protons, often limiting the performances of laser sources. In this paper, we show how we can actively use a low intensity prepulse (<10{sup 13} W/cm{sup 2}, ns duration) to manipulate the proton beam direction or spatial energy distribution. The prepulse is focused onto the front surface of a thin foil before the arrival of the high intensity pulse ({approx_equal}10{sup 19} W/cm{sup 2}, ps duration). Under oblique high-intensity irradiation and for low prepulse intensities, the proton beam is directed away from the target normal. Deviation is towards the laser forwardmore » direction, with an angle that increases with the level and duration of the ASE pedestal. Also, for a given laser pulse, beam deviation increases with proton energy. The observations are discussed in terms of Target Normal Sheath Acceleration, in combination with a laser-controllable shock wave locally deforming the target surface. Results obtained with an annular intensity distribution of the prepulse show smooth proton beams with a sharp circular boundary at all energies. Potential mechanisms to explain the observations are discussed.« less
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  • Abstract not provided.
  • Small fluctuations in the acceleration sheath change the pointing of a proton beam accelerated from the rear side of a laser irradiated thin aluminum foil. The proton acceleration was produced with 40 fs pulses of a Ti:sapphire laser at an intensity of approximately 10{sup 19} W/cm{sup 2}. This observation has been made with a high spatial resolution Thomson spectrometer. The proton beam pointing has appeared stable in the energy range between the high energy cutoff (3 MeV) and 50% of this value. Deviations of the beam position at lower energies changes in a range of 0-3 mrad. The recorded picturesmore » show wiggled and continuous proton traces which imply a release of the proton beam from the acceleration zone with a velocity chirp.« less