The Omega laser’s 40-kilojoule output is used, among other things, to crush hydrogen pellets and initiate nuclear fusion. The latest presidential budget request proposes shutting down in three years the Rochester, New York, facility housing Omega. Credit: University of Rochester

The US Department of Energy intends to close a premier facility that has long led one of the three principal approaches to initiating nuclear fusion through the use of powerful lasers. DOE plans to initiate a “three-year rampdown” of the University of Rochester’s Laboratory for Laser Energetics (LLE) in the fiscal year that begins in October, according to a summary of the agency’s 2019 budget proposal released on 12 February.

The LLE, which houses the 40-kilojoule Omega laser, is one of three major facilities supported by the inertial confinement fusion (ICF) program of DOE’s National Nuclear Security Administration. Complementing work at the much larger National Ignition Facility at Lawrence Livermore National Laboratory, the research at the LLE focuses on a direct-drive approach to ICF, in which peppercorn-sized capsules of deuterium and tritium are imploded by the 60-beam Omega. The second approach, at NIF, pursues indirect-drive fusion, in which light from the facility’s 192 beams is converted to the x rays that implode capsules. A third approach, centered at Sandia National Laboratories’ Z experimental device, explores implosion driven by electromagnetic fields.

Details of the ICF budget request had yet to be released at press time, but a summary of DOE’s budget request says closure of the “aged” Omega, which has been operational since 1995, would be part of a rebalancing “to strengthen longer term support for [stockpile stewardship] as well as to respond to higher NNSA priorities.” NNSA officials didn’t immediately respond to requests for comment.

The LLE rampdown is part of a larger 20%, or $104 million, reduction proposed for the overall ICF program. The FY 2018 request for the LLE is $66.8 million, an increase from the $62.8 million appropriated in FY 2017. In the coming months Congress will decide whether to endorse the DOE recommendation.

Michael Campbell, LLE director, says he was “completely surprised” by the closure proposal. “I don’t understand how such a decision could be made in the absence of any discussion with the program performers,” he says, referring to the LLE and the other labs in the ICF program.

Campbell says he suspects that with the recent release of the Trump administration’s Nuclear Posture Review, the NNSA decided to place greater emphasis on extending the lifetime of weapons and designing warheads at the expense of the underlying science program. “When these life extension programs are done in the 2030s, where are we going to get the talent that’s going to produce the experts?” he says. “How do you test someone who’s been doing computer codes? You test them by doing experiments in the real world. Omega, Z, and NIF do that.”

Campbell says that two years ago, the directors of the NNSA’s three weapons labs had backed continuing all three ICF programs, and that attaining laboratory fusion was “a critical element” of the science in support of the nuclear weapons stockpile. “What has changed in the past two years to make that statement different?”

Research at LLE and the other facilities has been funded principally to further nuclear weapons science. The ICF program’s main objective has been to achieve ignition, the point at which fusion reactions release more energy than was required to create them. Neither Omega nor Z can produce enough energy to achieve ignition, and NIF has so far failed to achieve the milestone for which it was designed.

The ICF program and facilities also address other topics in high-energy-density physics, such as the behavior of materials under shock and extreme pressures. Richard Petrasso, head of the high-energy-density physics division at MIT’s plasma science and fusion center, says students from 40 universities have performed experiments and theoretical work at Omega in the past 20 years. MIT currently has six PhD students working on projects at the LLE. The DOE budget proposal is “a disaster,” says Petrasso, who’s done experiments for 25 years at Omega.

David Crandall, a former DOE official who now consults for the ICF program, says LLE is “the world-class facility for the development of new science and techniques in high energy density physics, and for the development of new diagnostic capabilities and people.” He says the direct-drive approach, if it were upsized to NIF scale, could increase fusion yield compared to indirect drive. The challenge for both direct and indirect drive has been to achieve the necessary symmetry in the implosions.

Stephen Dean, president of Fusion Power Associates, says the NNSA may have seen an opening to target the LLE in the retirement last year of longtime LLE director Robert McCrory. Dean says McCrory was skilled at keeping DOE funding flowing, both through lobbying the New York congressional delegation and by actively supporting the NIF physics program.

Campbell says Congress has been very strong in its support for LLE, and he expects that in this case it “will react appropriately.”