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Title: Proton acceleration by irradiation of isolated spheres with an intense laser pulse

We report on experiments irradiating isolated plastic spheres with a peak laser intensity of 2–3 × 10 20 W cm –2. With a laser focal spot size of 10 μm full width half maximum (FWHM) the sphere diameter was varied between 520 nm and 19.3 μm. Maximum proton energies of ~ 25 MeV are achieved for targets matching the focal spot size of 10 μm in diameter or being slightly smaller. For smaller spheres the kinetic energy distributions of protons become nonmonotonic, indicating a change in the accelerating mechanism from ambipolar expansion towards a regime dominated by effects caused by Coulomb repulsion of ions. The energy conversion efficiency from laser energy to proton kinetic energy is optimized when the target diameter matches the laser focal spot size with efficiencies reaching the percent level. The change of proton acceleration efficiency with target size can be attributed to the reduced cross-sectional overlap of subfocus targets with the laser. Reported experimental observations are in line with 3D3V particle in cell simulations. In conclusion, they make use of well-defined targets and point out pathways for future applications and experiments.
Authors:
 [1] ;  [2] ;  [2] ;  [3] ;  [2] ;  [3] ;  [3] ;  [2] ;  [2] ;  [3] ;  [4] ;  [4] ;  [4] ;  [4] ;  [4] ;  [4] ;  [2] ;  [3] ;  [2] ;  [4] more »;  [4] ;  [4] ;  [3] ;  [2] ;  [3] ;  [4] ;  [4] ;  [1] « less
  1. Ludwig-Maximilians-Univ. Munchen, Garching (Germany); Max-Planck-Institut fur Quantenoptik, Garching (Germany)
  2. Ludwig-Maximilians-Univ. Munchen, Garching (Germany)
  3. Ludwig-Maximilians-Univ. Munchen, Munchen (Germany)
  4. Univ. of Texas at Austin, Austin, TX (United States)
Publication Date:
Grant/Contract Number:
NA0002008
Type:
Published Article
Journal Name:
Physical Review E
Additional Journal Information:
Journal Volume: 94; Journal Issue: 3; Journal ID: ISSN 2470-0045
Publisher:
American Physical Society (APS)
Research Org:
Univ. of Texas, Austin, TX (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
OSTI Identifier:
1326698
Alternate Identifier(s):
OSTI ID: 1435454

Ostermayr, Tobias M., Haffa, D., Hilz, P., Pauw, V., Allinger, K., Bamberg, K. -U., Bohl, P., Bomer, C., Bolton, P. R., Deutschmann, F., Ditmire, T., Donovan, M. E., Dyer, G., Gaul, E., Gordon, J., Hegelich, B. M., Kiefer, D., Klier, C., Kreuzer, C., Martinez, M., McCary, E., Meadows, A. R., Moschuring, N., Rosch, T., Ruhl, H., Spinks, M., Wagner, C., and Schreiber, J.. Proton acceleration by irradiation of isolated spheres with an intense laser pulse. United States: N. p., Web. doi:10.1103/PhysRevE.94.033208.
Ostermayr, Tobias M., Haffa, D., Hilz, P., Pauw, V., Allinger, K., Bamberg, K. -U., Bohl, P., Bomer, C., Bolton, P. R., Deutschmann, F., Ditmire, T., Donovan, M. E., Dyer, G., Gaul, E., Gordon, J., Hegelich, B. M., Kiefer, D., Klier, C., Kreuzer, C., Martinez, M., McCary, E., Meadows, A. R., Moschuring, N., Rosch, T., Ruhl, H., Spinks, M., Wagner, C., & Schreiber, J.. Proton acceleration by irradiation of isolated spheres with an intense laser pulse. United States. doi:10.1103/PhysRevE.94.033208.
Ostermayr, Tobias M., Haffa, D., Hilz, P., Pauw, V., Allinger, K., Bamberg, K. -U., Bohl, P., Bomer, C., Bolton, P. R., Deutschmann, F., Ditmire, T., Donovan, M. E., Dyer, G., Gaul, E., Gordon, J., Hegelich, B. M., Kiefer, D., Klier, C., Kreuzer, C., Martinez, M., McCary, E., Meadows, A. R., Moschuring, N., Rosch, T., Ruhl, H., Spinks, M., Wagner, C., and Schreiber, J.. 2016. "Proton acceleration by irradiation of isolated spheres with an intense laser pulse". United States. doi:10.1103/PhysRevE.94.033208.
@article{osti_1326698,
title = {Proton acceleration by irradiation of isolated spheres with an intense laser pulse},
author = {Ostermayr, Tobias M. and Haffa, D. and Hilz, P. and Pauw, V. and Allinger, K. and Bamberg, K. -U. and Bohl, P. and Bomer, C. and Bolton, P. R. and Deutschmann, F. and Ditmire, T. and Donovan, M. E. and Dyer, G. and Gaul, E. and Gordon, J. and Hegelich, B. M. and Kiefer, D. and Klier, C. and Kreuzer, C. and Martinez, M. and McCary, E. and Meadows, A. R. and Moschuring, N. and Rosch, T. and Ruhl, H. and Spinks, M. and Wagner, C. and Schreiber, J.},
abstractNote = {We report on experiments irradiating isolated plastic spheres with a peak laser intensity of 2–3 × 1020 W cm–2. With a laser focal spot size of 10 μm full width half maximum (FWHM) the sphere diameter was varied between 520 nm and 19.3 μm. Maximum proton energies of ~ 25 MeV are achieved for targets matching the focal spot size of 10 μm in diameter or being slightly smaller. For smaller spheres the kinetic energy distributions of protons become nonmonotonic, indicating a change in the accelerating mechanism from ambipolar expansion towards a regime dominated by effects caused by Coulomb repulsion of ions. The energy conversion efficiency from laser energy to proton kinetic energy is optimized when the target diameter matches the laser focal spot size with efficiencies reaching the percent level. The change of proton acceleration efficiency with target size can be attributed to the reduced cross-sectional overlap of subfocus targets with the laser. Reported experimental observations are in line with 3D3V particle in cell simulations. In conclusion, they make use of well-defined targets and point out pathways for future applications and experiments.},
doi = {10.1103/PhysRevE.94.033208},
journal = {Physical Review E},
number = 3,
volume = 94,
place = {United States},
year = {2016},
month = {9}
}