Speaker
Marco Riva
(Fusion)
Description
The Neutron Camera is a Joint European Torus (JET) diagnostic with the main function of measuring the 2.5 MeV (DD) and 14 MeV (DT) neutron emissivity profile over a poloidal plasma cross-section using line-integrated measurements along a number of collimated channels (lines-of-sight, LOS). Measurements are performed using two detectors: NE213 liquid scintillators (DD, low power DT) and BC418 plastic scintillators (high power DT, low intensity DT in strong DD).
The BC418 detectors work using old analog electronics, suffering limitations:
No raw data storage.
No accurate pulse height spectra (PHS).
Complex calibration procedure.
Moreover, as during the 1997 DTE1 campaign the BC418 detectors worked up to ~1.2 × 1066 cps (above 10 MeV threshold) , higher NBI power in the future DT campaign might imply even higher rates.
The NE213 detectors are coupled to an Field Programmable Gated Array (FPGA)-based digital system. This overcomes the BC418 limitations, but off-line processing is limited to ~9×1055 cps (lab. tests), with limited pile-up management.
To address those limitations, in view of JET DT campaigns, an enhancement project (Neuron Camera Upgrade, NCU) was launched with two main objectives: i) to increase the performance and reliability of the14 MeV neutron measurements performed by BC418 detectors; ii) to assess the possibility of increasing the counting rate capabilities of the NC detection system based on NE213 detectors. The first objective will be achieved by installing at JET a new FPGA-based digital system. The new units will include:
o High throughput digital acquisition for BC418 detectors performing on-line preprocessing.
o Raw data storage, in the NC cubicles.
o Off-line processing (pile-up, DT neutron count rates, PHS, calibration).
The present paper describes the hardware architecture and the FPGA processing selected for the new NCU system and the tests carried out at JET for its design.
Co-author
Marco Riva
(Fusion, ENEA, Frascati, Italy)
