The target chamber from the Nova laser experiment at the Lawrence Livermore National Laboratory in California was last week shipped to France. Physicists there plan to use it as an interim component of the Laser Megajoule, a huge laser facility to be built near Bordeaux.
Officials from the US Department of Energy say the chamber is on loan to France as part of a deepening collaboration between nuclear weapons physicists in France and the United States. In exchange for the loan, French scientists will deliver and develop a diagnostic system for the National Ignition Facility (NIF), the laser experimental facility currently under construction at Lawrence Livermore.
Not everyone at Livermore is happy to see the target chamber go. “It's part of a pattern that makes our people a little uncomfortable,” says one official there. He points out that the dismantling of Nova and of another laser, the Beamlet, which has been sent to the Sandia National Laboratory in New Mexico, means that researchers at Livermore will have no machines to work on until the NIF is completed in 2003 at the earliest.
Many of the researchers are using the Omega laser at the University of Rochester, New York, a facility comparable in size to Nova. Operating time at Omega has been increased to allow more experiments from researchers displaced from Nova, the Department of Energy says.
Nova cost about $150 million to build. But energy department officials say that the scrap value of its 5-metre-diameter target chamber — where ten laser beams converge to heat a tiny target — was only $30,000. A senior official values the radiation-temperature diagnostics system, which France will provide at the NIF in exchange for the chamber, at $1 million.
Unlike the NIF, which was designed to be fully functional by 2003, the Laser Megajoule will be constructed incrementally, starting with a few lasers firing targets in the chamber borrowed from the United States, and later adding lasers and new target chambers to accommodate higher energies.
Both facilities aim to achieve ‘ignition’, at which the fusion of deuterium and tritium fuel inside the target provides enough heat to sustain itself for a short period.
France and the United States have been working increasingly closely on using lasers for nuclear weapons physics since they signed an agreement to collaborate on this in 1994. It has been reported that the French demanded the agreement in exchange for making a commitment to stop nuclear testing.
According to Matt Mckenzie, who monitors nuclear weapons research for the Natural Resources Defense Council, a Washington-based environmental group, the collaboration has moved beyond working together on laser equipment to the design of the targets, called hohlraums, which are heated by the lasers to reproduce conditions inside a detonating nuclear weapon.
Both the Laser Megajoule and the NIF are intended primarily to help train nuclear weapons physicists and to simulate conditions inside nuclear weapons. But they will also be used by plasma physicists to explore the feasibility of inertial confinement fusion as an energy source.