Neutron facility to open at CERN

2 November 1999


A new facility is set to join the CERN experimental programme from April 2000. The neutron time-of-flight (nTOF) system will support a range of experiments that study neutron-induced reactions. They will cover subjects as diverse as stellar nucleosynthesis and basic nuclear physics, and they will be complementary to experiments already under way at the laboratory’s ISOLDE radioactive beam facility.

Taking its cue from the recent TARC experiment at CERN, which studied the transmutation of elements using neutrons moderated in lead, the facility will also study the neutron-induced transmutation of radioactive isotopes found in nuclear waste.

The nTOF facility’s strong point is its extremely high resolution for neutron capture cross-sections over the 1 eV to 250 MeV energy range. Neutrons, produced by spallation in a lead target that was recycled from TARC, will travel to an experimental area 200 m downstream. It is this distance that gives nTOF its unprecedented neutron energy resolution, which is expected to be of the order 10-4 over the entire energy range.

The facility is currently under construction and, when it starts up next year, it will have been commissioned in record time. One reason for this is the extensive use made of the existing infrastructure. The facility will be installed in an existing tunnel leading from the Proton Synchrotron accelerator, which will provide the protons driving the spallation process in the lead target, to CERN’s west experimental area. Moreover, this tunnel passes 7 m below another that formerly housed the Intersecting Storage Rings collider. The experimental target will be situated below this tunnel, which will be adapted to provide target-handling facilities.

The first experiments at the nTOF will be designed to test its performance. Known neutron capture cross-sections will be evaluated before the nTOF programme moves on to a range of new measurements.

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