A method for detecting Special Nuclear Materials (SNM) or Radiological dispersion Devices (RDD), comprising: conveying an object along a predetermined path; imaging a distribution of radioactive sources associated with the object as it passes along said path; determining the presence and location of one or both of an RDD or SNM radioactive source within the object.

Detection of nuclear materials

A detector for detecting radiation, the detector comprising: a plurality of elongate scintillator segments arranged in a side by side array; and at least one pair of light sensors optically coupled to ends of each of the elongate scintillator such that they receive light from scintillations produced in the scintillator and generate electrical signals responsive thereto.

Nuclear Threat Detection

A method of improving energy determination of a Gamma event which interacts with a segmented scintillation detector, the method comprising: identifying radiation events detected by a detector that are likely not to have deposited their full energy in the detector, based only on characteristics of said detected events; and treating the identified radiation events differently from other radiation events that are likely to have deposited their full energy in the detector.

Methods and apparatus for improved gamma spectra generation

Indirect imaging systems such as SPECT have three essential components: an image-forming element, an image detector, and a reconstruction algorithm. These components act together to transfer information about the object to the end user or observer, which can be a human or a computer algorithm. As we shall see in Chapter 5, the efficacy of this information transfer can be quantified and used as a figure or merit for the overall imaging system or for any component of it. Fundamentally, image quality is defined by the ability of some observer to perform some task of medical or scientific interest.

Detectors for Small-Animal SPECT II

The performance of high Z solid state detectors has been significantly improved over the last decade: one of the most promising materials for X and gamma ray detectors is CdTe/CdZnTe, which combines high detection efficiency, no requirement for cooling to cryogenic temperatures, good spectroscopic performances, good time response and imaging capabilities. Unfortunately some important features of semiconductor detectors (pulse height, energy resolution, photopeak efficiency) are affected by the charge collection efficiency: the low mobility of the charge carriers (particularly the holes) and trapping/detrapping phenomena can degrade the CdTe/CdZnTe detectors' response, depending on the distance between the charge formation position and the collecting electrodes. The deterioration of the spectroscopic performances can be reduced by using either hardware or software techniques. The biparametric method herein described is based on a hybrid HW and SW technique that utilizes a twin pulse shaping active filter (one "slow" and one "fast") to analyze the same signal. This technique could be particularly suitable for implementation in a readout integrated circuit for multipixel detectors. The experimental results obtained with the application of this biparametric technique with CdZnTe detectors are presented in order to assess the reliability and the efficiency of this compensation method as a function of bias voltage, primary photon energy and shaping time pairs.

Compensation of CdZnTe signals using a twin shaping filter technique

A gamma ray detector (50) comprises a plastic scintillation body (52) arranged to receive incident gamma rays to be detected. Photons are generated in response to the gamma rays by excitation and de-excitation processes in the scintillation body. The photons are detected using at least one photodetector (56) which generates an output signal representative of the energy of the gamma rays. The scintillation body has a detection surface to receive the gamma rays and a thickness in a direction substantially orthogonal to the detection surface that is not greater than 5 cm. Deconvolution techniques can be used to improve the output signal; the thinness of the scintillation body allows sufficiently accurate results to be obtained that individual isotopes can be readily identified. The detector can be usefully employed in portal radiation monitors.

Gamma Ray Detectors

Gamma ray spectrometers

A method of identifying radioactive components in a source comprising (a) obtaining a gamma-ray spectrum from the source; (b) identifying peaks in the gamma-ray spectrum; (c) determining an array of peak energies and peak intensities from the identified peaks; (d) identifying an initial source component based on a comparison of the peak energies with a database of spectral data for radioactive isotopes of interest; (e) estimating a contribution of the initial source component to the peak intensities; (f) modifying the array of peak energies and peak intensities by subtracting the estimated contribution of the initial source component; and (g) identifying a further source component based on a comparison of the modified array of peak energies with the database of spectral data. Thus a method for identifying radioactive components in a source is provided which does not rely on comparing template spectra with an observed spectrum.

David Ramsden

Papers

Gamma Ray Detectors

Gamma ray spectrometers

Radioactive isotope identification