A new two-dimensional scintillation detector system for small-angle neutron scattering experiments

Abstract

Abstract-A new two-dimensional position-sensitive detector system for small-angle neutron scattering experiments is under development. It is based on a 60 60 cm 2 large 6 Li-glass scintillator for the neutron capture and dispersion of the emitted light on an array of photomultiplier tubes for the derivation of the event position. For subthermal neutrons of 8 Å, an efficiency of 96% and a spatial resolution of 8 mm are to be achieved. Major improvements have been made in the signal-and data-processing branch, which aims at an electronical dead time of 1 s. A fast digitalization method using free-running analog-to-digital converters for each photomultiplier combined with field-programmable gate arrays for a parallel event detection in all channels has been applied. A subsequent farm of up to 16 floating-point digital signal processors is used to provide enough computing power for an improved reconstruction of the event position according to a maximum likelihood method.

Design and performance of a large area neutron sensitive anger camera

“…The primary purpose of the glass spacer is to allow expansion of the light cone to span the tube gaps. As described in other designs, gaps between optically active elements have a major impact on the performance of the detector [5,6]. All glass interfaces are coupled using silicone gel.…”

Position-sensitive detectors of the detector group at Jülich

“…2) at the research reactor FRJ-2, the 15-yr-old detector system has been replaced [6]. While the Anger camera-based concept of the detector remained unchanged, the signal-and data-processing branch has been completely revised.…”

“…Excellent gamma discrimination of about 10 À6 has been obtained with a 6 LiI crystal scintillator. However, 6 LiI must be single crystalline, strongly hygroscopic and needs to be encapsulated. The sensitive size of the plane detector is different and based on 1) were developed in our institute.…”

“…The detector design is based on a modified Anger technology [2,3], where the sensitive detector area is formed by a planar 6 Li scintillator on the front side of a rectangular transparent light disperser. The scintillator light is transferred to a linear row of photomultiplier (PM) with photocathodes facing the backside of a glass disperser.…”

Performance measurements of a new large-area neutron scintillation detector system

“…Due to the pulse processing inside the FPGAs, the appropriate model to describe the dead time behavior of this detector is the paralyzable dead time model, in which at high counting rates the dead period of the detector may be multiply extended. In this model the measured counting rate m of the detector is obtained by the true rate through (3) where denotes the dead time. By curve fitting a value of s is obtained for the new detector, which is only about half of the dead time of the former detector.…”