Neutron measurements on Joint European Torus using an NE213 scintillator with digital pulse shape discrimination

Abstract

A digital pulse shape discrimination system (DPSD) has been used in conjunction with collimated NE213 scintillators for neutron spectroscopic measurements at high count rates (MHz range) in Joint European Torus discharges (DD and DT fueled, neutral beam injection and rf heated). The system, developed at ENEA-Frascati, is based on a commercial 200 MHz 12-bit analog to digital transient recorder card, which digitizes the direct output signal from the anode of a photomultiplier. Among the unique features of this DPSD system are the possibility of postexperiment data reprocessing, high count rate operation, and simultaneous neutron and gamma (γ) spectroscopy. Separation between γ and neutron (n) events is performed by means of dedicated software exploiting the charge comparison method; separate n and γ pulse height distributions are obtained and an example of neutron spectrum unfolding is shown. Implications of the DPSD in future neutron diagnostic systems on large and next step tokamaks are discussed.

ITER relevant developments in neutron diagnostics during the JET Trace Tritium campaign

“…An NE213 scintillator was installed in the JET roof lab and connected to the DPSD hardware. Measurements were carried out during TTE with satisfactory performance of the DPSD system: total count rates up to MHz level were detected as well neutron and gamma pulse height spectra were acquired (up to 300 kHz) under different plasma scenarios [16].…”

JET diagnostic enhancements in preparation for DT operations

“…It was led by ENEA who built a Digital Pulse Shape Discrimination (DPSD) board, coupled to a NE213 scintillator detector (diameter 2.5 cm x 2.5 cm thick) with LED for photomultiplier gain variation corrections, built by Physikalisch-Technische Bundesanstalt (PTB) [5].…”

Status of ITER neutron diagnostic development

“…ρ on x-axis is minimum ρ on respective line of sight. [19,20] for 100 ms time window) /monitor [27] 100 (digital monitor) Natural diamond detector The optimal VNC arrangement will be decided on the basis of on-going analysis. Unscattered neutron fluxes at the detector positions integrated over the respective viewing cones of the external and internal channels of the RNC and the lower VNC collimators [25] are shown in figure 2.…”