Single crystal CVD diamonds as neutron detectors at JET

Abstract

This paper reports on the three new Single Crystal Diamond (SCD) detectors installed at JET for the 2008 Restart campaign. The yields of total neutrons produced during DD plasma pulses as well as the time dependent neutron emission have been measured. The three detectors present some main new developments as for their fabrication characteristics, embeddings and electronic chains. The first detector is 200 μm thick and is embedded in paraffin. The second detector is 104 μm thick and is covered by a thermally evaporated 3 μm thick 6LiF film in order to detect the total and the 14-MeV neutrons. In addition, it is surrounded by a 2.5-cm thick polyethylene shield to enhance its thermal neutron response. The third detector is operated in an innovative way that is with a single low capacitance super-screened cable and its whole electronic chain put outside the JET Torus Hall. Furthermore it uses fast electronics, suitable to the fast diamond response pulse (<1 ns). It is 75 μm thick, covered by a 3 μm thick 6LiF film and surrounded by a 2.5-cm-thick layer of polyethylene. All the detectors have been previously tested and qualified at the ENEA-FNG with 2.5 and 14.7 MeV neutron beams. After the description of their main features, the results of the measurements, so far performed, are reported showing a very good matching with other standard detectors, such as fission chambers, routinely used at JET.