Researchers in the Applied Nuclear Physics Group at Lund University in Sweden have built a compact accelerator-driven neutron source and are now moving it into commissioning at the university's Nuclear Applications Laboratory. The facility gives Swedish scientists a neutron beam close to home at a time when access to European research reactors is shrinking.
The core of the system is a 3 MV Pelletron accelerator first installed in 1990 and now repurposed for the project. It fires a beam of deuterons at 2.8 MeV onto a thin beryllium target, producing neutrons through a beryllium deuteron reaction. At the outset the beam current will be 10 microamps, which the team expects to yield roughly 10 billion neutrons per second. A planned upgrade to 100 microamps would raise that output to about 100 billion neutrons per second, although reaching that level depends on an ion-source upgrade that has not yet been completed.
The neutrons produced span energies up to about 9 MeV, with most clustered near 5 MeV. A nine-meter vacuum beamline with magnets shapes and pulses the beam into bursts as short as 25 nanoseconds. Downstream, a 3,000-litre tank of deionized water acts as a moderator, slowing the neutrons. The tank was built in cooperation with the Swedish firm Cipax AB. Three extraction ports at 0, 30 and 150 degrees let users pick the balance they need: forward ports deliver more fast neutrons, while the backward port favours thermal ones.
The planned applications include neutron activation analysis, testing of detectors used to monitor spent nuclear fuel for safeguards purposes, and general detector development. Local access to such a beam would reduce the group's dependence on shared international facilities, whose beam time has become harder to secure.
Credit. Based on reporting by Katie Riggs for Science. Is this your work? Write to us.
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