Fast response neutron emission monitor for fusion reactor using Stilbene Scintillator and Flash-ADC

Abstract

The stilbene neutron detector which has been used for neutron emission profile monitoring in JT-60U has been improved, to respond to the requirement to observe the high-frequency phenomena in megahertz region such as toroidicity-induced Alfvén Eigen mode in burning plasma as well as the spatial profile and the energy spectrum. This high-frequency phenomenon is of great interest and one of the key issues in plasma physics in recent years. To achieve a fast response in the stilbene detector, a Flash-ADC is applied and the wave form of the anode signal stored directly, and neutron/gamma discrimination was carried out via software with a new scheme for data acquisition mode to extend the count rate limit to MHz region from 1.3 x 10(5) neutron/s in the past, and confirmed the adequacy of the method.

High repetition rate neutron flux array using digital-signal processing and scintillators for study of high performance plasma at JT-60U

“…Therefore, it is important to evaluate the population of energetic ion in developing high performance plasmas. 10 This system achieved successfully the counting rate higher than 1 ϫ 10 5 counts/ s and also observation of d-T neutrons from deuterium-tritium reaction. Therefore, neutron measurement is one of the most important diagnostics for the control of burning plasmas for future fusion devices such as ITER.…”

Research and Development of Neutron Detection System using Scintillator and Digital-Signal Processing

“…The flash ADCs and a computer for the ADC control are installed in a basement room on the downstairs of the torus hall to guard from the strong neutron radiation. The hardwired cable between detectors and the ADCs is about 20 m long for oblique chords and about 30 m long for a vertical chord [15][16][17]. The sampling rate of the ADCs was 200 M samples/s, which was chosen as a compromise between the pulse shape discrimination quality, and the time period covered by the system due to the limitation of the memory in ADC.…”

“…To overcome the defects, a system using a fast flash analog-to-digital converter (flash ADC) was developed [15,16]. In this system, output pulses from an anode of a photomultiplier tube (ELT 9266B type manufactured by Electron Tube Ltd.) for the detector are recorded as a continuous waveform using a fast flash ADC with 200 MS/s permitting pulse pile-up, and the recorded data is analyzed with software off-line.…”

A study on fast digital discrimination of neutron and gamma-ray for improvement neutron emission profile measurement

“…The DSP system is applicable for measurement under high-counting-rate conditions in which analog processing is impossible to use. 1,8,10,11 A charge comparison method was applied to pulse signals from the scintillation detector, where neutrons and γ -rays are discriminated through comparison of pulse shape attenuation. [3][4][5][6][7][8]11 In the conventional pulse comparison method, each pulse signal is integrated in two time intervals.…”