J.C. Lund

Thallium bromide radiation detectors

Crystals of highly purified thallium bromide were used to fabricate radiation detectors. These detectors were rested with isotopic photon sources and successfully detected gamma and X-rays in the 0.01- to 1 MeV energy range. The detectors were tested at and below room temperature, and their performance approaches that of other semiconductor detector materials which have been under development. The performance of TlBr detectors is due to the similarity in the transport characteristics of electrons and holes in TlBr and the relatively large number of charge carriers produced per unit of energy of detected particle. The performance of these detectors is currently limited by shot noise induced by the leakage current in the TlBr. >

Properties of lead iodide semiconductor radiation detectors

Abstract Semiconductor radiation detectors have been fabricated from melt grown crystals of lead iodide (PbI 2 ) and the performance of these detectors as room temperature X-ray spectrometers has been measured. These detectors exhibit good energy resolution (915 eV FWHM for the 5.9 keV peak of 55 Fe at 20°C). Preliminary results indicate they are more stable than HgI 2 detectors and capable of operating at temperatures over 100°C.

Lead iodide X-ray detection systems

Recent progress in the development of room-temperature lead iodide (Phi,) X-ray detectors is reported. Progress has been made in the areas of detector fabrication and preamplifier electronics, and this has resulted in improved detection performance. An energy resolution of 415 eV (FWHM) has been reported for 5.9 keV X-rays (“Fe source) with 1 mm’ detector at room temperature. A better estimation of the Fano factor in PbIz has been carried out and the upper limit of the Fano factor is calculated to be 0.19. Larger lead iodide detectors (up to 2.5 mm*) have been fabricated and their spectroscopic performance has been evaluated. The timing characteristics of lead iodide detectors have been investigated. A compact, portable lead iodide probe assembly has been designed and built for X-ray spectroscopic applications. Finally, optical and charge particle detection properties of lead iodide detectors have also been characterized.

Experimental Results from an Antineutrino Detector for Cooperative Monitoring of Nuclear Reactors

Our collaboration has designed, installed, and operated a compact antineutrino detector at a nuclear power station, for the purpose of monitoring the power and plutonium content of the reactor core. This paper focuses on the basic properties and performance of the detector. We describe the site, the reactor source, and the detector, and provide data that clearly show the expected antineutrino signal. Our data and experience demonstrate that it is possible to operate a simple, relatively small, antineutrino detector near a reactor, in a non-intrusive and unattended mode for months to years at a time, from outside the reactor containment, with no disruption of day-to-day operations at the reactor site. This unique real-time cooperative monitoring capability may be of interest for the International Atomic Energy Agency (IAEA) reactor safeguards program and similar regimes.

Thallium bromide semiconductor X-ray and γ-ray detectors

Abstract Over the last few years, thallium bromide (TlBr) has been investigated for use as a semiconductor radiation detection material. This article reviews the history of TlBr detector development and describes the fabrication of state-of-the-art TlBr γ-ray detectors. Studies of TlBr detectors of different chemical purity indicate that their performance is no longer limited by chemical purity, as was true previously. This is a result of our purification methods, which employ multipass zone-refining. We also report on the performance of vacuum-deposited (by sublimation, ≅ 100 μm thick) TlBr films as single photon detectors. They have surprisingly high μτ for sublimed films, and X-ray detectors made from these films may find use in some X-ray imaging applications, including xeroradiography.

Lead iodide nuclear spectrometers

The preparation of radiation detectors from semiconducting lead iodide is discussed, and the performance of these devices as X-ray and gamma-ray spectrometers is evaluated. Detectors prepared from melt-grown crystals exhibit good energy resolution for low-energy ( >

Boron Phosphide on Silicon for Radiation Detectors

We report on radiation detectors fabricated from boron phosphide (BP) layers. These devices were fabricated by growing 1 to 10 {mu}m thick layers of BP by chemical vapor deposition (CVD) on (100) oriented n-type silicon substrates. Ohmic contacts were applied to the Si (Au--Sb). Schottky barrier contacts (also Au--Sb) were applied to the BP layer. The devices were tested as radiation detectors and were found to be capable of detecting individual 5.5 MeV alpha particles. With some improvements we hope to fabricate neutron detectors from these devices, making use of the very high cross-section of boron for thermal neutrons. 10 refs., 2 figs.

Indium phosphide particle detectors for low energy solar neutrino spectroscopy

Abstract Semiconductor radiation detectors have been constructed from indium phosphide to investigate the feasibility of using them in a solar neutrino detector. The 115 In (76% by mass) in an InP detector is expected to undergo the reverse beta decay reaction induced by the solar neutrino flux. This reaction produces energetic photons and electrons which might be used to identify and measure the energy of low energy neutrinos. InP detectors up to 1.0 cm 3 in volume capable of detecting individual electrons and photons have been constructed.

Characterization of thallium bromide nuclear detectors

Abstract We report on the performance of T1Br nuclear detectors fabricated on crystals grown from highly purified material. The detectors are characterized in terms of their energy and timing resolution. In addition, parameters important to detector performance are presented. Finally, the effect of material processing on device performance is addressed.

CHARACTERIZATION OF LEAD IODIDE FOR NUCLEAR SPECTROMETERS

Abstract We report on the results of a number of investigations into the material properties of lead iodide and their relation to x- and gamma-ray spectrometers. The effectiveness of zone refining as determined by inductively coupled plasma optical emission spectroscopy is demonstrated. We show that zone refining is effective in producing lead iodide with a higher degree of purity in terms of extrinsic dopants and we determine the segregation coefficients for a number of these impurities. Low temperature photoluminescence also indicates an improvement in the material properties of the purified lead iodide. The chemical etching characteristics, including etch rates, of lead iodide are presented for a number of etching solutions. Triple axis x-ray diffraction measurements have been employed to determine the structural perfection of the lead iodide after diamond sawing and etching and recovery of the crystallinity of the material is seen after Nal etching.