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Hard X-ray spectroscopy of inner-shell K transitions generated by MeV electron propagation from intense picosecond laser focal spots |
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| Authors: | JF Seely CI Szabo P Audebert E Brambrink E Tabakhoff GE Holland LT Hudson A Henins P Indelicato A Gumberidze |
| Institution: | 1. Naval Research Laboratory, Space Science Division, Washington, DC 20375, USA;2. Laboratoire Kastler Brossel, École Normale Supérieure; CNRS; Université P. et M. Curie – Paris 6 Case 74; 4, place Jussieu, 75252 Paris CEDEX 05, France;3. Laboratoire pour L''Utilisation des Lasers Intenses (LULI), Ecole Polytechnique, France;4. Global Strategies Group North America Inc., Crofton, MD 21114, USA;5. National Institute of Standards and Technology, Gaithersburg, MD 20899, USA |
| Abstract: | The propagation of energetic electrons from the focal spots of intense picosecond laser pulses was studied using targets consisting of planar foils and fine metal wires. High-resolution K-shell spectra of elements with atomic numbers in the range 46–74 (Pd to W) and with energies from 21 keV to 69 keV were recorded by a Cauchois-type spectrometer using a curved transmission crystal. The K-shell spectra resulted from the collisional ionization of 1 s electrons by energetic electrons that were generated in the laser focal spot and propagated into the planar foil region beyond the focal spot or into the metal wires adjacent to an irradiated wire. The lateral spread of the energetic electrons from the focal spot was determined from the source broadening of the K spectral lines and from the relative intensities of the K spectra from an irradiated wire and neighboring wires of different metals. The propagation distances up to 1 mm in a variety of materials indicated electron energies up to 1 MeV were generated in the laser focal spot. Inhibited propagation in an electrically insulating material was observed that results from a weak return current and incomplete space charge neutralization. |
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