NS&D Monitor
7/11/2014
Spallation Neutron Source Achieves Designed Beam Power
The Spallation Neutron Source at Oak Ridge National Laboratory has achieved its designed beam power of 1.4 megawatts eight years after construction was completed and operations began,. The milestone took place on June 26, shortly before shutdown for the summer maintenance period, but the plan is to maintain that power level for users when the system restarts in mid-August and for the foreseeable future. Kevin Jones, the director of Oak Ridge National Laboratory’s Research Accelerators Division, said the scale up to 1.4 megawatts took time and was all about making the neutron flux the best possible for research scientists who come to SNS from around the world to do material experiments.
Generally speaking, the higher the beam power, the more neutrons that are available for scientists to do neutron-scattering experiments, and the more neutrons the better the science opportunities. A higher concentration of neutrons allows researchers to do more experiments or to do experiments using smaller samples than otherwise would be possible. Over the past couple of years, the SNS beam power had been topped at about 1 megawatt in order to achieve consistency and, during some time periods, to conserve power costs.
Jones said the ramp up began earlier this year. The system was upped to 1.1 megawatts, then ran at 1.2 for about four weeks and then achieved 1.3 megawatts for a while before going to more than 1.4 megawatts in late June, he said. Meeting the milestone also means satisfying the Department of Energy’s demands for the research facility, which was constructed at a cost of about $1.4 billion.
Work Underway to Increase Target Lifetime
In addition to upping the power level, ORNL is trying to maximize the lifetime of the mercury target that’s used to produce the neutrons for science. The SNS has had problems in the past with premature failures of the stainless-steel target vessel. Jones said the SNS team has installed a new design of the vessel that will be tested when operations resume next month. There were some design changes in the internal part of the vessel that will change how the mercury flows through the area where the proton beam hits the target. The hope is that it will reduce the internal damage from cavitation—bubbles in the mercury collapsing and sending energy against the walls.
Overall, the accelerator-based research facility is working very, very well, Jones said. In the current fiscal year, the SNS availability to researchers has exceeded 91 percent, he said. That’s above DOE’s expectation of 90 percent, he said.
