This paper provides a brief overview of radiation detector history, a summary of the present state of the art, and some
speculation on future developments in this field. Trends in the development of radiation detectors over the years are
analyzed. Rapid progress in detection technology was experienced between WWII and the 1970s. Since then, fewer
dramatic improvements have been seen. The authors speculate about the reasons for this trend and where the technology
might take us in the next 20 years. Requirements for radiation detection equipment have changed drastically since 9/11;
this demand is likely to accelerate detector development in the near future.
This paper describes a gamma detector employing an array of eight cadmium-zinc-telluride (CZT) crystals configured as a high resolution gamma ray spectrometer. This detector is part of a more complex instrument that identifies the isotope, displays this information, and records the gamma spectrum. Various alarms and other operator features are incorporated in this battery operated rugged instrument.
The CZT detector is the key component of this instrument and will be described in detail in this paper. We have made extensive spectral measurements of the usual laboratory gamma sources, common medical isotopes, and various Special Nuclear Materials (SNM) with this detector. Some of these data will be presented as spectra. We will also present energy resolution and detection efficiency for the basic 8-crystal array. Additional data will also be presented for a
32-crystal array.
The basic 8-crystal array development was completed two years ago, and the system electronic design has been improved recently. This has resulted in significantly improved noise performance. We expect to have a much smaller detector package, using 8 crystals, in a few months. This package will use flip-chip packaging to reduce the electronics physical size by a factor of 5.
Simultaneous detection of gamma rays and neutrons emanating from an unknown source has been of special significance and importance to consequence management and first responders since the earliest days of the program. Bechtel Nevada scientists have worked with 6LiI(Eu) crystals and 6Li glass to develop field-operable dual sensors that detect gamma rays and neutrons simultaneously. The prototype 6LiI(Eu) counter, which has been built and tested, is designed to collect data for periods of one second to more than eight hours. The collection time is controlled by thumbwheel switches. A fourpole, high pass filter at 90 KHz reduces microphonic noise from shock or vibration. 6LiI(Eu) crystals generate completely separable gamma-ray and thermal neutron responses. The 6LiI(Eu) rate meter consists of a single crystal 3.8 x 3.8 cm (1.5 x 1.5 in) with a 2.54-cm-(1-in-) thick, annular, high-density, polyethylene ring around the cylinder. Special
features are (1) thermal and epithermal neutron detection (0.025eV to 250keV) and (2) typical gamma resolution of 8% at 661.6 keV. Monte Carlo N-Particle calculations for characteristics of gamma spectral behavior, neutron attenuation length, relative neutron and gamma detection efficiency are reported.
Conference Committee Involvement (6)
Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XIV
30 April 2013 | Baltimore, Maryland, United States
Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XIII
24 April 2012 | Baltimore, Maryland, United States
Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XII
26 April 2011 | Orlando, Florida, United States
Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XI
6 April 2010 | Orlando, Florida, United States
Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing X
14 April 2009 | Orlando, Florida, United States
Chemical Biological Radiological Nuclear and Explosives (CBRNE) Sensing IX
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