Nuclear Radiation Detectors – Past, Present and Future
The need to develop and harness advanced technology to detect nuclear materials is now in vivid focus. Many national-security users of radiation detectors must obtain and deliver fast and accurate information to intercept radioactive/nuclear materials and respond to a variety of threats. Ideally, the detectors would be compact, light weight, low maintenance, low power, able to identify radioactive isotopes, possess high signal-to-noise ratios, and capable of stand-off operation. Practically all of the proposed approaches have been limited by the quality of the materials used to produce the detectors, and resolution of the material problems has not been amenable to a quick and easy fix. For gamma detectors, the most promising approaches have involved the development of room-temperature semiconductor detectors based on cadmium zinc telluride (CZT) and scintillators based on the lanthanum halides. Because of deficiencies in the quality of the material, high energy-resolution CZT gamma spectrometers are still limited to relatively small dimensions, which makes them inefficient at detecting high photon energies and somewhat ineffective for weak radiation signals except in proximity. Scintillators based on lanthanum halides have also been limited to relatively small sizes. Both detectors are very attractive for a broad range of gamma-ray detector applications; however, increases in their efficiencies are needed without sacrificing the ability to operate at room temperature and to spectrally resolve isotopes of interest. To fully exploit these emerging technologies, it will be necessary to develop a detailed understanding of the underlying problems limiting the performance of devices and to apply this knowledge to improve the material quality. Progress is required in the following areas: growth of large uniform single crystals, reductions in carrier trapping, and improved device fabrication procedures. Despite the current material constraints, several types of new room-temperature gamma-ray detectors have been developed, some of which are now addressing important applications. This talk will summarize the material factors limiting the performance of solid-state detectors and scintillators and discuss ways to overcome them through appropriate corrections. Comments on the material limitations for advanced neutron detectors will also be discussed.
Solid-State Cadmium-Zinc-Telluride Gamma Ray Detectors
Cadmium zinc telluride (CZT) is the most promising semiconductor material today for production of X-ray and gamma detectors and imaging arrays operable at room temperature. The performance of CZT devices, the global capacity for growth of detector-grade crystals, and the size of the commercial market have progressed steadily over the past few years. Concurrently, the cost for CZT gamma-ray spectrometers has decreased. Unfortunately, because of deficiencies in the quality of the material, high-resolution CZT spectrometers are still limited to relatively small dimensions (< 1 cm3), which makes them inefficient at detecting high photon energies and somewhat ineffective for weak radiation signals except in near proximity. Despite the current constraints on efficiency of the devices, CZT detectors have been increasingly deployed in medical, space, environment, and national security applications for monitoring and imaging radiation in the energy range of 2-2000 keV. The detectors could be attractive for a much broader range of applications; however, increases in their efficiency are needed without sacrificing the ability to spectrally resolve X-ray and gamma energies. Achieving the goal of low-cost efficient CZT detectors requires progress in the following areas: growth of larger crystals, reductions in carrier trapping, increases in the electrical resistivity, better uniformity of device response, and improved device fabrication procedures. This talk will summarize the material factors limiting the performance of CZT gamma-ray detectors and discuss ways to overcome them through appropriate corrections in the crystal growth and device fabrication processes.
Brookhaven National Laboratory's R&D on Advanced Sensor Technology for Homeland Security Applications
The need to harness advanced sensor technology to detect chemical, biological, radiological and nuclear, and explosives (CBRNE) agents is now in vivid focus. This presentation discusses Brookhaven National Laboratory’s new sensor approaches designed to obtain and deliver fast and accurate information to intercept CBRNE materials and respond to a variety of homeland security threats. The talk will cover basic research related to the development of advanced detector materials, applied development of prototype instruments, and the deployment of technology in real-life environments.
Dr. Ralph B. James was born in Nashville, TN in 1953. He received a B.S. degree in Engineering Physics with highest honors from the University of Tennessee in 1976, a M.S. degree in Physics from Georgia Institute of Technology in 1977, and M.S. and Ph.D. degrees in Applied Physics from California Institute of Technology in 1978 and 1980. From 1981 to 1983 he was a Eugene P. Wigner Fellow at Oak Ridge National Laboratory. He then moved to Sandia where he held an appointment as Distinguished Member of the Technical Staff until 2001. In 2001 Ralph became the Associate Laboratory Director for the Energy, Environment and National Security Directorate with the U.S. Department of Energy’s Brookhaven National Laboratory. The Directorate encompassed Brookhaven’s Department of Environmental Sciences, Department of Energy Sciences & Technology, Department of Nonproliferation & National Security, Center for Data-Intensive Computing, and Research and Business Operations. In this position, James oversaw a wide range of basic and applied research with annual funds-in of approximately $100 million. For example, the work includes such programs as aerosol chemistry and how it relates to global warming and air pollution, research in biological and chemical processes to develop better cleanup technologies, safety of nuclear facilities, advanced ultra-clean fuels to increase energy supply and lower costs, development of optical and photonic devices, and new sensors to detect and image more minute quantities of nuclear, chemical, biological and explosive materials. He also chaired Brookhaven’s Homeland Security Working Group, which is conceptualizing and coordinating Laboratory efforts to develop technologies to support national and homeland security. In 2016, Dr. James accepted the position as Chief Research Officer and Associate Laboratory Director for Science and Technology at Savannah River National Laboratory.
Dr. Ralph James has conducted transformational research in the area of nuclear detectors for over 3 decades. His research results have been extensive and fundamental, and the impact of his work has been lasting. Dr. James has authored more than 600 scientific publications, served as editor of 29 books, and holds 26 patents related to semiconductor detectors. Among his many prestigious honors, Dr. James won Discover magazine’s “Innovator of the Year” award for his contributions to develop radiation detectors, particularly CZT devices. He is a six-time winner of R&D Magazine’s R&D 100 Award, which honors the top 100 inventions of the year. Dr. James received the Room-Temperature Semiconductor Detector Scientist Award in 2004 and the IEEE Outstanding Radiation Instrumentation Achievement award in 2005. He was recognized as Long Island’s Person of the Year in science for 2010, Gordon Battelle Award for Technology Innovation, and Frost & Sullivan’s Inventor of the Year for development of instrumentation for detecting prostate cancer. He won these awards, among many others, for pioneering research to understand and design compound semiconductor radiation detectors, improve the growth of materials for advanced nuclear detectors, and develop innovative nuclear spectroscopy and imaging instrumentation. Dr. James is a Fellow of the APS, SPIE, IEEE, OSA, MRS and AAAS in honor of his accomplishments in the area of nuclear detectors and materials research.
He is also recognized for a long history of dedicated leadership to accelerate the development of high-performance nuclear detectors. For example, Dr. James has diligently worked to rally the assets and talents of academia, government labs, and U.S. industry toward the common goal of developing advanced sensors. He also played pivotal roles to establish over 24 CRADAs with industry to co-develop and commercialize semiconductor radiation detectors and instruments, and he served as chairman of approximately 33 international scientific conferences devoted to development of nuclear detectors and their applications.
The output of his research and leadership in the field of semiconductor radiation detectors continues to lead to new products and applications in the fields of gamma-ray spectroscopy, astrophysics, and high-resolution imaging for security and medical uses.
Top of Form
Contact Dr. Ralph B. James at Ralph.James@SRNL.DOE.gov, 803-725-2362