Multi-keV x-ray sources from HYBRID targets on GEKKO and OMEGA facilities
1 CEA, DAM, DIF, 91297 Arpajon, France
2 Institute for Laser Engineering, Osaka University, Osaka 565-0871 Japan
3 Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
a e-mail: email@example.com
Published online: 15 November 2013
The feasibility of efficient X-ray sources for radiography on the LMJ (Laser MégaJoule) in the multi-kJ/ns range was demonstrated on the OMEGA laser facility (Univ. Rochester) from 2002 to 2004 [1,2]. We significantly enhanced the conversion efficiency of titanium (4–6 keV), copper (8–10 keV) and germanium (9–13 keV) foils by using an optimized pre-pulse/pulse combination. Since higher X-ray energy and therefore electronic temperature need hydroconfinement, plastic cylindrical hohlraums internally coated with titanium, copper and germanium with various OMEGA beam configurations were successfully tested from 2005 to 2009 [3–5]. In addition, many shots with metal-doped aerogel (Ti, Fe, Ge) were tested on OMEGA .
Recently we tested a new concept of “HYBRID sources” based on the combination of a thin titanium foil at the exit hole of a plastic cylinder filled with very low density SiO2 aerogel (2 and 5 mg/cc). The benefit of the underdense medium is, first, to transport the laser energy to the titanium foil after its conversion into a supersonic ionization front and, second, to prevent foil expansion and excessive kinetic energy losses by longitudinal hydroconfinement.
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