Evaluation of the energy calibration of diamond detectors for fast neutrons applications

The radiation hardness, the chemical resistance, and the capabilities to operate at high temperature conditions make diamond detectors a good option for carrying out fast neutron measurements on fusion plasma experiments or facilities using accelerator-driven neutron sources. A correct energy calibration of pulse-height spectra acquired through diamond detectors allows to perform fast neutron spectrometry. As a general rule, energy calibration of diamond detectors is performed using an alpha source, e.g. ²³⁹Pu, ²⁴¹Am, ²⁴⁴Cm, whose characteristic emission energies are in the range from 5 to 6 MeV. Calibration at higher energies, such as those related to charged particles (about 8.4 MeV) produced by the ¹²C(n,alpha)⁹Be induced by fast neutrons coming from D-T fusion reaction, is traditionally extrapolated with the hypothesis of linearity for the energy calibration curve. In this work an evaluation of the diamond detector energy calibration based on alpha source emissions is performed at higher energies by means of a compact D-T neutron generator, able to produce neutrons within a broad energy range, by changing the accelerator voltage and the neutron emission angle. A relative deviation less than 2% between experimental and theoretical energies was observed, showing that the energy calibration through alpha sources could be still valid for fast neutrons coming from D-T fusion reactions.