Wireless neutron and gamma ray detector modules for dosimetry and remote monitoring (original) (raw)

Perforated Semiconductor Neutron Detector Modules for Detection of Spontaneous Fission Neutrons

2007 IEEE Conference on Technologies for Homeland Security, 2007

Compact neutron detectors are being designed and tested for use as low-power real-time personnel dosimeters and for remote neutron sensing. The neutron detectors are pin diodes that are mass produced from high-purity Si wafers. Each detector has thousands of circular perforations etched vertically into the device. The perforations are backfilled with 6 LiF to make the pin diodes sensitive to thermal neutrons. The prototype devices delivered over 3.8% thermal neutron detection efficiency while operating on only 15 volts. The highest efficiency devices thus far have delivered over 12% thermal neutron detection efficiency. Devices moderated with high density polyethylene (HDPE) can be used for fast neutron detection. Compact packages with or without remote readout electronics are under construction and characterization.

Integrated Neutron Detector for Handheld Systems

IEEE Transactions on Nuclear Science, 2013

This paper describes detectors comprised of (CLYC) scintillators coupled to silicon photomultipliers (MPPC, Hamamatsu). CLYC has been developed for dual gamma ray and thermal neutron detection. MPPCs are compact detectors with a very thin profile (2 mm), but also a small active area (6 mm 6 mm). The combination of both can create a compact replacement of a He-3 tube. Three different crystal sizes were tested: a cube, a cuboid, and a cylinder. All three detectors showed a well-resolved thermal neutron peak with energy resolution of 5.4%, 7%, and 11% (FWHM), respectively. The degradation in larger crystals is due to a mismatch between the coupled crystal face and the active area of the light detector. All detectors showed the 662 keV gamma ray peak from a Cs-137 source, indicating capability for limited gamma ray spectroscopy, with energy resolutions of 10%, 17%, and 26%, respectively. The capability for pulse shape discrimination was shown as well. The efficiency of the detectors was measured against a 10 atm He-3 tube (9 volume). The best absolute efficiency was shown by the cylinder detector, next by the He-3 tube (almost the same as the cylinder detector), and finally by the cuboid detector. The latter showed the best neutron count per , twice as high as the two other detectors.

Perforated diode neutron detector modules fabricated from high-purity silicon

Radiation Physics and Chemistry, 2009

Compact neutron detectors are being designed and tested for use as low-power real-time personnel dosimeters. The neutron detectors are pin diodes that are mass produced from high-purity Si wafers. Each detector has thousands of circular perforations etched vertically into the device. The perforations are backfilled with 6 LiF to make the pin diodes sensitive to thermal neutrons. The prototype devices deliver 4.7% thermal neutron detection efficiency while operating on only 15 V, showing a 9% increase in efficiency over identical planar devices.

Neutron dosimeters employing high-efficiency perforated semiconductor detectors

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007

A technology that makes use of recently developed high-efficiency, low-power semiconductor detectors for neutron dosimetry is described. Silicon semiconductor material is perforated using plasma etching techniques; the surface is then coated and the perforations are filled with neutron reactive material. These perforated detectors appear to be capable of greater than 40% efficiency when used in a sandwich design. Devices incorporating bare and cadmium-filtered perforated semiconductor detectors with micro-controller hardware to process and readout the detectors can be made small enough to function as portable neutron dosimeters. Monte Carlo modeling that relates the detector responses to phantom dose equivalent at various positions on an elliptical water phantom is discussed.

Low-cost fabrication of high efficiency solid-state neutron detectors

Proceedings of SPIE, 2016

The development of high-efficiency solid state thermal neutron detectors at low cost is critical for a wide range of civilian and defense applications. The use of present neutron detector system for personal radiation detection is limited by the cost, size, weight and power requirements. Chip scale solid state neutron detectors based on silicon technology would provide significant benefits in terms of cost, volume, and allow for wafer level integration with charge preamplifiers and readout electronics. In this paper, anisotropic wet etching of (110) silicon wafers was used to replace deep reactive ion etching (DRIE) to produce microstructured neutron detectors with lower cost and compatibility with mass production. Deep trenches were etched by 30 wt% KOH at 85°C with a highest etch ratio of (110) to (111). A trench-microstructure thermal neutron detector described by the aforementioned processes was fabricated and characterized. The detector-which has a continuous p +-n junction diode-was filled with enriched boron (99% of 10 B) as a neutron converter material. The device showed a leakage current of ~ 6.7 × 10-6 A/cm 2 at-1V and thermal neutron detection efficiency of ~16.3%. The detector uses custom built charge pre-amplifier, a shaping amplifier, and an analogto-digital converter (ADC) for data acquisition.

A hand-held neutron detection sensor system

2006 IEEE International Symposium on Circuits and Systems, 2006

Osberg, K.; Schemm, N.; Balkir, S.; Brand, J.I.; Hallbeck, S.; and Dowben, Peter A., "A hand-held neutron detection sensor systems" (2006). Peter Dowben Publications. Paper 112.

Passive detectors for neutron personal dosimetry: state of the art

Radiation protection dosimetry, 2004

Passive, solid-state detectors still dominate the field of neutron personal dosimetry, mainly thanks to their low cost, high reliability and elevated throughput. However, the recent appearance in the market of several electronic personal dosemeters for neutrons presents a challenge to the exclusive use of passive systems for primary or official dosimetry. This scenario drives research and development activities on passive dosemeters towards systems offering greater accuracy of response and lower detection limits. In addition, further applications and properties of the passive detectors, which are not met by the electronic devices, are also being explored. In particular, extensive investigations are in progress on the use of solid-state detectors for aviation and space dosimetry, where high-energy neutron fields are encountered. The present situation is also stimulating an acceleration in the development of international standards on performance and test requirements for passive dosi...

GAMBE: GAMma Blind neutron Efficient detector

Gamma Blind neutron Efficient detector, 2018

Thermal neutron detectors, which are based on semiconductor material such as silicon coated with neutron reactive material like 10B and 6Li have been discussed for many decades. The performance of the thermal neutron detector system, GAMBE, which is based on two silicon sensors in a sandwich configuration is investigated. The results show that a single sandwich design with 6LiF film of (1.5 ± 0.6) mg/cm2 thick can achieve a total ("tn) and a coincidence ("cn) detection efficiency of 4% and 1% respectively. While, 6Li foil of (40 ± 10) μm thick is able to attain a ("cn) of (1.5 ± 0.9)% and a ("tn) of (9.2 ± 1.4)%. The coincidence that defines a true neutron hit is the simultaneous signal recorded by the two sensors facing the conversion layer. These coincidences provide a very good method for rejecting spurious hits coming from gamma-rays, which are usually present in the neutron field under measurement. This methodology results in a high gamma-ray rejection factor of 108. However, the price to pay is a reduction of the detection efficiency of the single sandwich detector. The thermal neutron detection efficiency of the detector is enhanced by using a stacked detector configuration and highdensity polyethylene (HDPE) sheets, as neutron moderators and reflectors. The GAMBE detector is positioned inside a box of HDPE with a lead window in the direction of the neutron flux for neutron moderation and a reduction of the effect of gamma-rays on the detector. The experimental layout was modeled in MCNP4C to investigate the contribution of HDPE to the thermal neutron flux (n/s/cm2). In this research a stack of 4 silicon semiconductor sensors with two 6LiF films of an average thickness of (2.8 ± 0.6) mg/cm2 in a configuration of two sandwiches is shown to achieve a total and a coincidence detection efficiency of (27 ± 3)% and (4 ± 1)% respectively. This represents a significant improvement compared to a single detector. The effect of these stacked detectors for the development of a handheld thermal neutron detector, using 4 coated Si detectors is shown to have a 22% efficiency. Finally, this information is used to inform the optimised design of the handheld detector. The results based on GEANT4 and MCNP4C simulations indicate that the total detection efficiency of this portable detector with a stack of 7 sandwich detectors will increase up to 52% by using an optimal thickness of a 6LiF film of 17 μm (3.95 mg/cm2). This handheld detector has a highest total detection efficiency of 69% when using a 6Li foil of 36 μm thick.

Characterization of prototype perforated semiconductor neutron detectors

Radiation Physics and Chemistry, 2010

Semiconductor detectors whose surfaces are coated with neutron-reactive material can be made to detect thermal neutrons, but with efficiencies only of a few percent. However, perforating the semiconductor material, filling the perforations with neutron-reactive material, and then coating the detector surface can lead to neutron detectors of much higher thermal neutron detection efficiencies, perhaps approaching or exceeding 50%. Several perforated semiconductor neutron detectors have been constructed, both for dosimetry and for position-sensitive neutron detection. The characterization of prototype devices based on these detectors is described.