Evaluation of two thermal neutron detection units consisting of ZnS/ 6 LiF scintillating layers with embedded WLS fibers read out with a SiPM

Abstract

Two single channel detection units for thermal neutron detection are investigated in a neutron beam. They consist of two ZnS/ 6 LiF scintillating layers sandwiching an array of WLS fibers. The pattern of this units can be repeated laterally and vertically in order to build up a one dimensional position sensitive multi-channel detector with the needed sensitive surface and with the required neutron absorption probability. The originality of this work arises from the fact that the WLS fibers are read out with SiPMs instead of the traditionally used PMTs or MaPMTs. The signal processing system is based on a photon counting approach. For SiPMs with a dark count rate as high as 0.7 MHz, a trigger efficiency of 80% is achieved together with a system background rate lower than 10 −3 Hz and a dead time of 30 µs. No change of performance is observed for neutron count rates of up to 3.6 kHz.

A 16-ch module for thermal neutron detection using ZnS:6LiF scintillator with embedded WLS fibers coupled to SiPMs and its dedicated readout electronics

“…Independent of how many SiPM cells are triggered simultaneously due to the SiPM crosstalk, the discriminator creates only one standard SD-pulse. This "digitization" which suppresses the crosstalk allows to reduce the quiet background rate of the detector [9]. The analog output signals from the front-end board are readout by the WaveDREAM board, a 16-ch FPGA-based readout board (Fig.…”

Neutron detectors for the ESS diffractometers

“…With this technology, pixel sizes as small as 1 mm 2 became possible due to the advances made in the commercial production of high-efficiency, low dark-rate multi-anode photomultiplier tubes (PMTs) or silicon photo-multipliers (SiPMs) [40,42]. The efficiency of a scintillator-based detector can now reach 65% at 1.2 Å [43]. The maximum count rate capability of a scintillator module depends upon the type and thickness of the scintillator material, as well as the fiber-photosensor coupling or encoding scheme.…”

“…The intense efforts carried out over the last years into increasing the performance of scintillatorbased detectors in terms of efficiency and counting rate capability showed positive results from the perspective of operation under the intense neutron fluxes expected at spallation neutron sources. The combined neutron imaging and neutron diffraction beamline IMAT, currently under construction at the ISIS facility [14], and the POLDI diffractometer operational at the Swiss spallation source SINQ at PSI [42,43,45], are examples of instruments that will be populated with scintillator modules combining the latest achievements in the field of photosensors or signal readout. WISH (ISIS), NOMAD (SNS), TAIKAN and SuperHRPD (J-PARC) are examples of diffractometers operated with hundreds of 3 He-filled position-sensitive tubes surrounding the sample [8,10,46,47,48].…”

Digital signal processing for a thermal neutron detector using ZnS(Ag):6LiF scintillating layers read out with WLS fibers and SiPMs

“…A 1-D position sensitive detector for thermal neutrons is currently under development [1,2,3] for upgrading the POLDI instrument, a strain-scanning diffractometer installed at the Swiss neutron spallation source (SINQ) at PSI. This detector is based on ZnS(Ag): 6 LiF scintillating layers read out with wavelength shifting fibers (WLS) and silicon photomultipliers (SiPM).…”