D.W. MacArthur

Long-range alpha detector.

Historically, alpha-particle detectors have been limited by the very short range of alpha particles in air. This results in a number of problems inherent to alpha contamination detectors, such as relatively poor sensitivity, geometry limitations, and inefficient monitoring techniques. In this paper, we document tests of a new long-range alpha detector. The charges generated by the interaction of alpha particles with air can be transported over significant distances (several meters) in a moving current of air generated by a small fan. An ion chamber located in front of the fan measures the current carried by the moving ions and, hence, detects the alpha decays.

Alpha contamination monitoring of surfaces, objects, and enclosed areas

The usefulness of traditional alpha detectors for contamination monitoring is limited by the size and sensitivity of the detectors and by the short range of alpha particles in air. The long-range alpha detector (LRAD) detects the ions produced by the alpha particles passing through air, rather than the alpha particles themselves, limiting LRAD detection by the range of the ions (tens of meters), rather than the range of the alpha particles (a few centimeters). Since the LRAD collects all ions simultaneously, an LRAD monitor is sensitive to all of the sources of contamination contained within it. The electronic noise within the LRAD can be reduced so that better sensitivity than traditional detectors is also possible. These advantages are used in the object, pipe, and duct, floor, and soil surface monitors discussed. The design of these monitors and field test results are presented. >

Long-range alpha detector (LRAD) for contamination monitoring

The authors describe a novel long-range alpha detector (LRAD) in which alpha particles interact with the ambient air, producing ionization in the air at the rate of about 30000 ion pairs per megaelectronvolt of alpha energy. These charges can be transported over significant distances (several meters) in a moving current of air generated by a small fan. An ion chamber located in front of the fan measures the current carried by the moving ions. The LRAD-based monitor is more sensitive and more thorough than conventional monitors. The authors present current LRAD sensitivity limits and results, practical monitor designs, and proposed uses for LRAD monitors.<<ETX>>

Long-range alpha detector (LRAD) sensitivity to beta contamination and soil moisture

Long-range alpha detector (LRAD) systems are designed to monitor alpha contamination by measuring the ionization in air formed by the alphas. Recent tests have been performed to determine the sensitivity of LRAD systems to beta contamination and soil moisture levels. These results and the general technology are discussed in this paper. >

LRAD-based alpha-particle contamination monitoring of personnel and equipment

Traditional alpha-particle contamination monitors are limited in usefulness because of the short range of alpha particles in air. This range limitation makes it impossible to adequately monitor for alpha-particle contamination on uneven surfaces and inside equipment. Personnel must be scanned manually, a procedure that is comparatively uncertain. The long-range alpha detector eliminates many of the difficulties associated with equipment and personnel monitoring by detecting the ions produced by the alpha particles interaction with the air, rather than detecting the alpha particle itself. The personnel and equipment monitors are described in detail, and other potential applications are suggested.

New generation enrichment monitoring technology for gas centrifuge enrichment plants

We report our progress toward development of new generation on-line enrichment monitoring technology for UF6 gas centrifuge plants based on a transmission source and a NaI spectrometer. We use an X-ray tube with transmission filters instead of a decaying isotopic transmission source to eliminate the costly replacement of this source. The UF6 gas density measurement is based on the energy dependency of the mass attenuation for two characteristic X-ray lines generated by the transmission filters. An analytical expression for the UF6 density is derived and criteria for the selection of transmission energies are discussed. Because of the differential method of measurement, the UF6 gas density does not depend on the intensity of the X-ray source. We describe a design of a sealed UF6 gas test stand for development testing and calibration of various on-line enrichment monitoring instruments. The sealed source is intended to replace a UF6 gaseous loop currently used for calibration.

Long-range alpha detector sample monitoring

Abstract Long-range alpha detector (LRAD) systems are designed to monitor alpha sources and contamination by measuring the number of ions created in air by ionizing radiation. Traditional alpha detectors are designed to detect alpha particles directly and must be passed slowly within about 3 cm of an alpha source to operate effectively. LRAD detectors collect the ions created from alpha interactions with air. Therefore, they are better able to monitor equipment and complex surfaces and can be operated at a much greater distance from an alpha source than traditional alpha detectors. Furthermore, because LRAD detectors remain stationary during monitoring, they are less subject to operator error than traditional alpha detectors. This paper will discuss the basic operation as well as recent advances that have been made to LRAD Sample Monitors.

Long-range alpha detector (LRAD) technology, results, and applications

The usefulness of traditional alpha detectors for contamination monitoring is limited by the size and sensitivity of the detectors and by the short range of alpha particles in air. The long-range alpha detector (LRAD) detects the ions produced by the alpha particles passing through air, rather than the alpha particles themselves. Thus, LRAD detection is limited by the range of the ions (tens of meters), rather than the range of the alpha particles (a few centimeters). Since it collects all ions simultaneously, an LRAD monitor will be sensitive to all of the sources of contamination contained within it. In addition, the electronic noise within the LRAD can be reduced so that better sensitivity than that of traditional detectors is possible. Both soil surface and object monitors incorporate these advantages in their designs. Field-test results for these monitors are discussed.<<ETX>>

Fast integrating multiware beam profile monitor with digital readout

Abstract A beam position and size monitor is described for use with pulsed beams with an intensity above 105 particles/(pulse cm2). It uses a standard multiwire chamber, but the current on each wire is integrated, digitized, and stored for each beam pulse. For optimum determination of beam size, the wire spacing in the chamber should be small compared to the beam size; the present system has 2-mm wire spacing.

Development of a Liquid Scintillator Neutron Multiplicity Counter (LSMC)

A new neutron multiplicity counter is being developed that utilizes the fast response of liquid scintillator detectors. The ability to detect fast (vs. moderated) fission neutrons makes possible a coincidence gate on the order of tens of nanoseconds (vs. tens of microseconds). A neutron counter with such a narrow gate will be much less sensitive to accidental coincidences making it possible to measure items with a high single neutron background to greater accuracy in less time. This includes impure Pu items with high (alpha,n) rates as well as items of low mass HEU where a strong active interrogation source is needed. Liquid scintillator detectors also allow for energy discrimination between interrogation source neutrons and fission neutrons, allowing for even greater assay sensitivity. Designing and building a liquid scintillator multiplicity counter (LSMC) requires a symbiotic effort of simulation and experiment to optimize performance and mitigate hardware costs in the final product. We present preliminary Monte Carlo studies using the GEANT toolkit along with analysis of experimental data used to benchmark and tune the simulation.