Capabilities of a Diamond Detector matrix for neutron spectroscopy measurements at JET

Single-crystal Diamond Detectors (SDDs) feature high radiation hardness, fast response and
compact size. This makes SDDs ideal candidates for fast neutron detectors in environment
where high neutron flux is an issue such as the next generation burning plasmas experiments.
Neutron detection in SDD is based on the collection of electron-hole pairs produced by charged
particles generated by neutron interaction with 12C nuclei. For neutron energies above about 7
MeV neutron spectroscopy is possible by measuring the deposited energy into the detector via
the reaction 12C(n,a)9Be. This is indeed the cases of SDD measurements of 14 MeV neutrons of
DT plasmas. A single pixel SDD (4.5x4.5x0.5 mm^3) prototype was installed at JET in 2013
and the achieved results allowed to assess also the neutron spectroscopic capability of
deuterium plasmas. A 12-pixels SDD matrix has been recently realized and will be installed in
2015 at JET for DT plasmas as part of the Vertical Neutron Spectrometer project.
In this paper calibration of the SDD matrix with alpha particles in the laboratory and 14 MeV
neutrons performed at the ENEA Frascati Neutron Generator will be presented. These
calibrations have been performed with a fast charge preamplifier combined to a fast digital data
acquisition, which allows for neutron spectroscopy measurements with simultaneously high
energy resolution and high count rate capability. Both requirements are essential for neutron
spectroscopy of high power fusion plasmas. The calibrations results achieved extrapolate
favourably in view of future neutron spectroscopy measurements at JET using diamond
detectors.