Comparison Between Digital and Analog Pulse Shape Discrimination Techniques For Neutron and Gamma Ray Separation

Recent advancement in digital signal processing (DSP) using fast processors and computer makes it possible to be used in pulse shape discrimination applications. In this study, we have investigated the feasibility of using a DSP to distinguish between the neutrons and gamma rays by the shape of their pulses in a liquid scintillator detector (BC501), and have investigated pulse shape-based techniques to improve the resolution performance of room-temperature cadmium zinc telluride (CZT) detectors. For the neutron/gamma discrimination, the advantage of using a DSP over the analog method is that in analog system two separate charge-sensitive ADC's are required. One ADC is used to integrate the beginning of the pulse risetime while the second ADC is for integrating the tail part. Using a DSP eliminates the need for separate ADCs as one can easily get the integration of two parts of the pulse from the digital waveforms. This work describes the performance of these DSP techniques and compares the results with the analog method

Technical description of candidate fluorescence compounds and radioisotopes for a nuclear smuggling deterrence tag (IL500E)

This report summarizes the efforts completed in identifying candidate fluorescence compounds and radioisotopes for a developing tagging system. The tagging system is being developed as a deterrent to nuclear smuggling, by providing a means of: (1) tracing materials and pilferers to the facility of origin for any recovered special nuclear materials; (2) inventory control of long-term stored items containing special nuclear materials; and (3) tracking materials transferred between facilities. The tagging system uses four types of tagging materials to cover a range of applications intended to prevent the pilfering of special nuclear materials. One material, fluorescent compounds which are invisible without ultraviolet or near-infrared detection systems, is marked on controlled items with a tracking pattern that corresponds to a specified item in a specified location in the data control system. The tagging system uses an invisible, fluorescent dusting powder to mark equipment and personnel who inappropriately handle the tagged material. The tagging system also uses unique combinations of radionuclides to identify the facility of origin for any special nuclear material. Currently, 18 long-lived radioisotopes, 38 short-live radioisotopes and 10 fluorescent compounds have been selected as candidate materials for the tagging system

Preliminary evaluation of a fluorescence and radioisotope nuclear smuggling deterrence tag - final report (IL500E)

This report summarizes the efforts completed in identifying candidate fluorescence compounds and radioisotopes for a developing tagging system. The tagging system is being developed as a deterrent to nuclear smuggling, by providing a means of: (1) tracing materials and pilferers to the facility of origin for any recovered special nuclear materials, (2) inventory control of long-term stored items containing special nuclear materials, and (3) tracking materials transferred between facilities. The system uses three types of materials to cover a range of applications intended to prevent the pilfering of special nuclear materials. One material, fluorescent compounds which are invisible without ultraviolet or near-infrared detection systems, is marked on controlled items with a tracking pattern that corresponds to a specified item in a specified location in the data control system. The tagging system uses an invisible, fluorescent dusting powder to mark equipment and personnel who inappropriately handle the tagged material. The tagging system also uses unique combinations of radionuclides to identify the facility of origin for any special nuclear material. This report also summarizes the efforts completed in identifying hardware that will be used for the tagging system. This hardware includes the devices for applying the tagging materials, the commercially available fluorescence detection systems, and gamma ray detection systems assembled from existing, commercially available technologies

Optimization Studies of a Compton Suppression Spectrometer Using Experimentally Validated Monte Carlo Simulations

Recent developments associated with room temperature semiconductor detectors and inorganic scintillators suggest that these detectors may be viable alternatives for the primary detector in a Compton Suppression Spectrometer (CSS). The room temperature operation of these detectors allows removal of a substantial amount of material from between primary and secondary detector and if properly designed and should afford substantially better suppression factors than can be achieved by germanium-based spectrometers. We have chosen to study the optimum properties of a CSS with a LaX3:Ce scintillator (where X is chloride or bromide) as the primary gamma ray detector. A Monte Carlo photon transport model is used to determine the optimum geometric properties of this spectrometer. To validate the assumptions and basic design of the Monte Carlo simulations, the energy distribution of a 137Cs point source is measured and simulated for two experimental systems. Comparison of the suppression factors for the measured and simulated data validates the model accuracy. A range of CSS physical parameters are studied to determine optimal detector geometry and to maximize the Compton suppression factor. These physical parameters and their optimum values are discussed

INL Capabilities For Nuclear Data Measurements Using The Argonne Intense Pulsed Neutron Source Facility

The relevant facts concerning the Argonne National Laboratory – Intense Pulsed Neutron Source (ANL/IPNS) and the Idaho National Laboratory (INL) apparatus for use at the ANL/IPNS facility to measure differential neutron interaction cross sections of interest for advanced reactor physics applications are presented. The INL apparatus, which consists of an array of multiple types of multiple detectors operated in coincidence, signal electronics, and a data acquisition system, is presented as an application of new means and methods to measure the relevant parameters described. The immediate measurement goals involve measurement of neutron induced interaction cross sections for 240Pu and 242Pu with 241Pu, 241Am, with measurements for other nuclides of interest for advanced reactor physics applications to follow later. Specific uncertainties and error limits are presented and methods for controlling these uncertainties are described. The post experiment analysis using data sorts and data selection from a large, self-consistent data set to produce spectra that will be analyzed for direct results and used to determine cross sections is also discussed

Using the Cockroft-Walton voltage multiplier design in handheld devices

Abstract--A variation of the basic Cockroft-Walton (C-W) Voltage Multiplier circuit design may be used to generate multiple voltages at sufficient currents to drive the dynodes of a photomultiplier tube. In a battery-operated handheld device, the current draw on the batteries must be kept to a minimum. Several other parameters must be considered carefully during the design as well. Components must be chosen based on size restrictions, expected load current, expected output voltage range, and the maximum allowable ripple in the output voltage. A prototype surface mount C-W board was designed and tested to power two photomultipliers. The whole system, including the detectors, draws less than 15mA of supply current with the outputs at 1000VDC

Optimization Studies of a Compton Suppression Spectrometer Using Experimentally Validated Optimization Studies of a Compton Suppression Spectrometer Using Experimentally Validated Monte Carlo Simulations

Abstract--Recent developments associated with room temperature semiconductor detectors and inorganic scintillators suggest that these detectors may be viable alternatives for the primary detector in a Compton Suppression Spectrometer (CSS). The room temperature operation of these detectors allows removal of a substantial amount of material from between primary and secondary detector and, if properly designed should afford substantially better suppression factors than can be achieved by germanium-based spectrometers. We have chosen to study the optimum properties of a CSS with a LaX 3 :Ce scintillator (where X is chloride or bromide) as the primary gamma ray detector. A Monte Carlo photon transport model is used to determine the optimum geometric properties of this spectrometer. To validate the assumptions and basic design of the Monte Carlo simulations, the energy distribution of a 137 Cs point source is measured and simulated for two experimental systems. Comparison of the suppression factors for the measured and simulated data validates the model accuracy. A range of CSS physical parameters are studied to determine optimal detector geometry and to maximize the Compton suppression factor. These physical parameters and their optimum values are discussed