Directional detection of fast neutrons by the Timepix pixel detector coupled to plastic scintillator with silicon photomultiplier array

Abstract

Fast neutrons are conventionally detected by scintillators of large volume, low spatial resolution and poor, if any, directional sensitivity. In this paper we present a detection technique based on the tracking of protons recoiled by fast neutrons. In this approach we use the silicon pixel detector Timepix attached in contact planar geometry to a fast plastic scintillator. The protons recoiled by neutrons in the scintillator are detected by the pixel detector while scintillation light is sensed by a 4 × 4 array of silicon photomultipliers (SiPM). Each photomultiplier is equipped with an independent amplifier and discriminator providing a fast trigger signal to the pixel detector. Variable threshold level allows adjustment of the trigger sensitivity. Single events in the pixel detector can be tagged and triggered by the scintillating detector. Position and energy sensitivity of the scintillator together with the position and the energy sensitivity of the pixel detector allow obtaining information about the position and the spectrum of the neutron source. The Timepix detector is operated with the FITPix readout interface and the Pixelman software package providing control, DAQ and online visualization. The assembled prototype has been tested with fast neutrons from a laboratory radioactive source (AmBe) and a Van de Graaff accelerator (D-T reaction). The detector architecture, comprising the Timepix device, the scintillator and the segmented SiPM, allows stacking several such units for increased detection efficiency and enhanced directional sensitivity.

Semi-insulating GaAs detectors with HDPE layer for detection of fast neutrons from D–T nuclear reaction

“…The resistivity of GaAs is about 1.1×10 8 Ωcm, and the Hall mobility is 5280 cm 2 /Vs at room temperature. The wafer was polished from both sides to a thickness of 270 μm.…”

“…1 Conversion layers for fast neutrons are attached to the detector in contact planar geometry and are usually based on polyethylene (PE) 2,3,4 and high density polyethylene (HDPE), 5,6,7 but also on fast plastic scintillator. 8 We have optimized our bulk semi-insulating (SI) GaAs detectors for fast-neutron detection by a multi-pixel structure of a Schottky contact. 7 Neutrons are converted by (n,p) elastic nuclear collisions in an HDPE layer covering the Schottky contact.…”

Fast neutron detector based on surface-barrier VPE GaAs structures

“…Nowadays semiconductor based neutron detectors are widely adopted [1][2][3][4][5][6]. The operating principle of such detectors is based on the detection of secondary particles produced by (n, α)-, (n, γ)or (n, p)-reactions using a semiconductor sensor.…”