11 research outputs found
Time-resolved fast-neutron imaging with a pulse-counting image intensifier
A new imaging method that combines high-efficiency fast-neutron detection with sub-ns time resolution is presented. This is achieved by exploiting the high neutron detection efficiency of a thick scintillator and the fast timing capability and flexibility of light-pulse detection with a dedicated image intensifier. The neutron converter is a plastic scintillator slab or, alternatively, a scintillating fibre screen. The scintillator is optically coupled to a pulse counting image intensifier which measures the 2-dimensional position coordinates and the Time-Of-Flight (TOF) of each detected neutron with an intrinsic time resolution of less than 1 ns. Large-area imaging devices with high count rate capability can be obtained by lateral segmentation of the optical readout channels
Low-Afterglow, High-Refractive-Index Liquid Scintillators for Fast-Neutron Spectrometry and Imaging Applications
For ion and neutron spectrometry and imaging applications at a high intensity
pulsed laser facility, fast liquid scintillators with very low afterglow are
required. Furthermore, neutron imaging with fiber (or liquid-core) capillary
arrays calls for scintillation materials with high refractive index. To this
end, we have examined various combinations of established mixtures of fluors
and solvents, that were enriched alternatively with nitrogen or oxygen.
Dissolved molecular oxygen is known to be a highly effective quenching agent,
that efficiently suppresses the population of the triplet states in the fluor,
which are primarily responsible for the afterglow. For measuring the glow
curves of scintillators, we have employed the time-correlated single photon
counting (TCSPC) technique, characterized by high dynamic range of several
orders of magnitude in light intensity. In this paper we outline the
application for the fast scintillators, briefly present the scintillation
mechanism in liquids, describe our specific TCSPC method and discuss the
results.Comment: 5 pages, Contribution to SORMA WEST 2008. To be published in IEEE
TNS, 200
Progress with Xenon Liquid Hole Multipliers
The bubble-assisted Liquid Hole Multiplier (LHM) is a recently-proposed
concept for the combined detection of ionization electrons and primary
scintillation photons in noble-liquid time projection chambers. The LHM
comprises a perforated micro-pattern electrode (e.g. Thick Gas Electron
Multiplier - THGEM, or Gas Electron Multiplier - GEM) immersed in the liquid,
with a bubble of the noble gas supported underneath. Ionization electrons and
scintillation-induced photoelectrons extracted from a cesium iodide
photocathode drift through the electrode's holes and induce electroluminescence
(EL) signals in the bubble; these are recorded by photon detectors located
closely below the electrode. We present recent results in the development of
LHMs, comparing the response of different electrodes to ionization and
photon-induced electrons.Comment: Presented at 2016 IEEE NSS/MIC, Strasbourg, France, 29 October - 5
November 201
Detectors for the Gamma-Ray Resonant Absorption (GRA) Method of Explosives Detection in Cargo: A Comparative Study
Gamma-Ray Resonant Absorption (GRA) is an automatic-decision radiographic
screening technique that combines high radiation penetration with very good
sensitivity and specificity to nitrogenous explosives. The method is
particularly well-suited to inspection of large, massive objects (since the
incident gamma-ray probe is at 9.17 MeV) such as aviation and marine
containers, heavy vehicles and railroad cars. Two kinds of gamma-ray detectors
have been employed to date in GRA systems: 1) Resonant-response nitrogen-rich
liquid scintillators and 2) BGO detectors. This paper analyses and compares the
response of these detector-types to the resonant radiation, in terms of
single-pixel figures of merit. The latter are sensitive not only to detector
response, but also to accelerator-beam quality, via the properties of the
nuclear reaction that produces the resonant gamma-rays. Generally, resonant
detectors give rise to much higher nitrogen-contrast sensitivity in the
radiographic image than their non-resonant detector counterparts and
furthermore, do not require proton beams of high energy-resolution. By
comparison, the non-resonant detectors have higher gamma-detection efficiency,
but their contrast sensitivity is very sensitive to the quality of the
accelerator beam. Implications of these detector/accelerator characteristics
for eventual GRA field systems are discussed.Comment: 11 page