The PHEBUS experimental facility operating at 250 ps and 0·53 μm

Abstract

The experiments reported in this paper demonstrate that the PHEBUS laser facility is now currently being operated with high performances (4 TW with 250 ps pulses at 0-527 jum wavelength).The output energy of the 2-beam PHEBUS laser system can be focused either in a small focal spot (80% of the incident energy is in a 220 /zm diameter focal spot) for high intensity experiments (3=5 x 10 15 W cm" 2 ) or in very large spots (a few mm in diameter) at moderate intensities (10 13 -2-5 x 10 14 WcrrT 2 ), for large scale experiments. It is shown that the spatial intensity distribution in the target plane is primarily due to intensity independent aberrations and to diffraction. Laser light absorption in plane aluminum and gold targets are interpreted in terms of inverse bremsstrahlung absorption that may account for 70 to 90% of absorbed energy. Finally, the plasma expansion is shown to be very planar and comparison with one-dimensional Lagrangian simulations gives flux limiter values of 0-03 and 0-02 respectively for Al and Au targets. G. Thielletal. Pixels 3072 2048 1024 1024 Pixels FIGURE 1. Temporal profile of the oscillator pulse recorded through a Fabry-Perot etalon with a streak camera.

Nuclear diagnostics for Inertial Confinement Fusion (ICF) plasmas

“…The results from these first experiments were very encouraging and led to the development of several new, larger ICF facilities around the world, such as NOVA in the US [12], Gekko-XII in Japan [13], Phebus in France [14], ISKRA-4 (followed by ISKRA-5) in the USSR [15,16], SG-I in China [17] and OMEGA-24 in the US [18]. Hot-spot experiments at Gekko-XII generated impressive results, including ion temperatures of ∼10 keV and neutron yields of ∼10 13 [19].…”

“…In contrast to x-rays, which have been used for decades to radiograph plasma-density distributions, charged particles are sensitive to both matter and electromagnetic fields, where the latter is the physics of main interest in most radiography experiments. To interrogate the electromagnetic fields in an ICF-relevant plasma, a pointprojection backlighter that produces primary fusion products is typically used in combination with a CR-39 detector 14 . The backlighter is generally positioned ∼1 cm from the subject and the CR-39 detector is positioned on the other side of the subject ∼30 cm away, resulting in a magnification of ∼30.…”

Performance of a prototype for a large-aperture multipass Nd:glass laser for inertial confinement fusion

“…A Single-Pass Master-Oscillator, Power-Amplifier Architecture Most large glass lasers designed for inertial fusion experiments have the single-pass master oscillator, power-amplifier ͑MOPA͒ architecture ͑Fig. 1͒: For example, the Nova laser 10 -12 at Lawrence Livermore National Laboratory, U.S.A.; the Omega laser 13 at the Laboratory for Laser Energetics, University of Rochester, U.S.A.; the Gekko XII laser 14 at the Institute of Laser Engineering, University of Osaka, Japan; the Phébus laser 15 at the Commissariat a l'É nergie Atomique, Centre d'É tudes de Limeil-Valenton, France; and the Helen laser 16 at the Atomic Weapons Research Establishment, England, are all based on a single-pass MOPA design.…”