Development and irradiation test of lost alpha detection system for ITER

We developed a lost alpha detection system to use in burning plasma experiments. The scintillators of Ag:ZnS and polycrystalline Ce:YAG were designed for a high-temperature environment, and the optical transmission line was designed to transmit from the scintillator to the port plug. The required optical components of lenses and mirrors were irradiated using the fission reactor with the initial result that there was no clear change after the irradiation with a neutron flux of 9.6× 10¹⁷ nm^-2 s^-1 for 48 h. We propose a diagnostic of alpha particle loss, so-called alpha particle induced gamma ray spectroscopy. The initial laboratory test has been carried out by the use of the Ce doped Lu₂SiO ₅ scintillator detector and an Am-Be source to detect the 4.44 MeV high energy gamma ray due to the ⁹Be (α,nγ) ¹²C reaction.