Fusion conference attracts many experts

Roland Roux

PARIS, FRANCE?The second annual Conference on Solid-State Lasers for Applications to Inertial Confinement Fusion (ICF) was held here late last year at the Centre des Congr?s. Organized by the Commissariat ? l?Energie Atomique (CEA; the French Atomic Energy Commission), the meeting attracted a significant number of world experts working in the ICF field, thus emphasizing the degree of interest in this approach to fusion. Many additional attendees from optics, optoelectronics, laser, and electronics companies were interested in the potential technological fallout from ICF research. Members of this grou¥were also hoping to position themselves to participate as subcontractors in any procurement contracts that might emerge and which could lead to large orders over several years.

The first of 14 conference sessions was dedicated to complete laser systems. Other sessions focused on pulse generators, amplifiers, laser components, thin-film coatings, diffractive optics, and damage. The last session addressed ultrashort pulses, fast ignitors, and inertial fusion energy.

In the first session Lawrence Livermore National Laboratories (LLNL; Livermore, CA) reported on the current design status and schedule for the National Ignition Facility (NIF) project (see Laser Focus World, Nov. 1996,

p. 107, and Jan. 1997, p. 55). Installation of laser hardware will begin in January 1999, and the first 4 2-beam bundle is scheduled to be operational by April 2000. Complete activation of the system is expected during October 2002.

The CEA Laser Megajoule (LMJ) project, which is similar to NIF, was also described during this session (see Fig. 1). The LMJ will include 240 beamlines located in the CEA-CESTA laboratory, close to Bordeaux, France. The project was described and compared to NIF in the context of the collaboration established with LLNL in 1994. To validate the LMJ technology, an eight-beam prototype LIL (Ligne d?Integration Laser) will be constructed in advance of LMJ. The building to house LIL is under construction and scheduled for completion in April 1998. Four of the eight LIL beam lines will be operational by the beginning of 2001, and target experiments at the 60-kJ level will start in January 2002. The LMJ itself will be completed in two phases after the building is finished in 2003. To allow activation of phase I, 80 beamlines and experiments at 600 kJ are planned for the end of 2005. Phase II completion with the full 240 beamlines is expected in 2010.

A detailed design study of the 4 2 laser amplifier modules has been completed, and the first module will be delivered in January 1997 for testing in a special laboratory currently under construction at LLNL (see Fig. 2 on p. 44). Michel Andr?, Ma?tre d?oeuvre principal LMJ, CEA (Bruy?res le Chatel, France), says, OThe primary technology development activities [at LMJ] are executed in close collaboration with the NIF project at LLNL. This collaboration provides peer review of critical development and lowers the total technology investment costs. Despite the distance and language differences, the exchange of personnel and specific joint technology, development activities have already proven the collaboration to be extremely cost effective for both projects.O

Other laser systems

Also in the first session, the Russian Federal Nuclear Center?Institut of Experimental Physics reported on its ISKRA-6 project, which includes about 100 amplifiers designed to deliver 300 kJ of output energy in 2?3-ns pulses at a wavelength of 351 nm and with an exit aperture of 20 20 cm.

In the USA, the overall energy and performance goals have been met or exceeded by the 60-beam 40-kJ OMEGA laser system that has been operational for about one year at the Laboratory for Laser Energetics, University of Rochester, (Rochester, NY). A recently installed flexible pulse-shaping system allows a choice of pulse shapes for pulses between 0.1 and 3 ns duration. Variously shaped pulses have been used for target experiments including simultaneous propagation of two different pulse shapes in different arms of the laser.

To meet the future requirements of the AWE Plasma Physics Programme (Aldermaston, Reading, England), design studies are being conducted for a 100-TW Nd:glass laser system operating at the third harmonic. An outline of the system, which is based on technology developed for NIF, was presented at the conference. The proposal is for a

32-beam laser, which is a subset of the 192-beam NIF.

During the last session LLNL reported production of more than a petawatt of peak power with the Nova Petawatt Laser generating more than 500 J in less than 500 fs. The Petawatt Laser Project was initiated to develo¥the capability to test the fast-ignitor concept for ICF. The laser was designed to produce near-kilojoule pulses with a duration adjustable between 0.5 and 20 ps. At the shortest pulse lengths this laser will exceed 1021 W/cm2 when focused later this year.

In Japan during FY1995, supplemental funding of approximately $5 million was authorized for the Institute of Laser Engineering at Osaka University for new beamline construction of GEKKO XII in order to generate a high-intensity short pulse for x-ray backlighting of high-density compressed plasma?part of the fast-ignitor concept. Completion of the system is scheduled for the end of 1996.

The VULCAN high-power laser is a multiple-beam Nd:glass system operating at the Central Laser Facility Rutherford Appleton Laboratory (Didcot, England). This laser can deliver multiterawatt 1-ps pulses; short pulses with high intensities result from chirped-pulse amplification. Design improvements were described that will increase the output to more than 200 TW with 400-fs pulses. Large-aperture diffraction gratings (42 21 cm) will compress the pulses, which will then be focused on the target using an off-axis parabola.