The Collimated Directional Radiation Detection System (CDRDS) is capable of imaging radioactive sources in two dimensions (as a directional detector). The detection medium of the CDRDS is a single Cs2LiYCl6:Ce3+ scintillator cell enriched in 7Li (CLYC-7). The CLYC-7 is surrounded by a heterogeneous high-density polyethylene (HDPE) and lead (Pb) collimator. These materials make-up a coded aperture inlaid in the collimator. The collimator is rotated 360° by a stepper motor which enables time-encoded imaging of a radioactive source. The CDRDS is capable of spectroscopy and pulse shape discrimination (PSD) of photons and fast neutrons.
The measurements of a radioactive source are carried out in discrete time steps that correlate to the angular rotation of the collimator. The measurement results are processed using a maximum likelihood expectation (MLEM) algorithm to create an image of the measured radiation.
This collimator design allows for the directional detection of photons and fast neutrons simultaneously by utilizing only one CLYC-7 scintillator. Directional detection of thermal neutrons can also be performed by utilizing another suitable scintillator. Moreover, the CDRDS is portable, robust, and user friendly. This unit is capable of utilizing wireless data transfer for possible radiation mapping and network-centric applications. The CDRDS was tested by performing laboratory measurements with various gamma-ray and neutron sources.
The problem of accurately detecting extremely low levels of nuclear radiation is rapidly increasing in importance in nuclear counter-proliferation, verification, and environmental and waste management. Because the 239Pu gamma signature may be weak, for instance, even when compared to the natural terrestrial background, coincidence counting with the 239Pu neutron signature may improve overall 239Pu detection sensitivity. However, systems with sufficient multiple-particle detectors require demonstration that the increased sensitivity be sufficiently high to overcome added cost and weight. We report the results of measurements and calculations to determine sensitivity that can be gained in detecting low levels of nuclear radiation from use of a relatively new detector technology based on elpasolite crystals. We have performed investigations exploring cerium (Ce3+)-doped elpasolites Cs2LiYCl6:Ce3+0.5% (CLYC) and Cs2LiLa(Br6)90%(Cl6)10%:Ce3+0.5% (CLLBC:Ce). These materials can provide energy resolution (r(E) = 2.35σ(E)/E) as good as 2.9% at 662 keV (FWHM). The crystals show an excellent neutron and gamma radiation response. The goals of the investigation were to set up the neutron/gamma pulse shape discrimination electronics for elpasolite detectors; perform limited static source benchmarking, testing, and evaluation to validate system performance; and explore application of a maximum likelihood algorithm for source location. Data were measured and processed through a maximum likelihood estimation algorithm, providing a direction to the radioactive source for each individual position. The estimated directions were good representations for the actual directions to the radioactive source. This paper summarizes the maximum likelihood results for our elpasolite system.
In investigations of Ce3+-doped Cs2LiLa(Br6)90%(Cl6)10% (CLLBC) elpasolite crystals, the crystals show an excellent neutron and gamma (n/γ) radiation response. The results of our studies on the scintillation properties of CLLBC viz. radioluminescence, energy resolution, light yield, decay times, and nonproportionality are discussed. The CLLBC detector can provide energy resolution as good as 4.1% at 662 keV (FWHM), which is better than that of NaI:Tl. Because the crystal contains 6Li, CLLBC can also detect thermal neutrons. In the energy spectra, the full energy thermal neutron peak appears near or above 3 MeV gamma equivalent energy. This high-energy signature for the thermal neutron peak means that very effective pulse height discrimination is possible. Unfortunately, because the core-to-valence luminescence observed in other elpasolites that can be exploited for effective pulse shape discrimination (PSD) is not observed in the CLLBC, other strategies for obtaining the PSD of CLLBC are needed. The n/γ discrimination capability of CLLBC detectors may be optimized by tuning the cerium doping content for maximum effect on n/γ pulse shape differences. The value of adding a chlorine component to the nominal CLLB crystal is discussed. Because the crystal contains chlorine, its sensitivity to fast neutrons is better than that of Cs2LiLaBr6 (CLLB). Further, an array of three of these CLLBC detectors may be able to perform directional detection in both the neutron and gamma channels simultaneously.
Improvised explosive devices (IEDs) are an important concern to coalition forces during the conflicts in the Middle East.
These devices are responsible for many casualties to American armed forces in the Middle East. These explosives are
particularly dangerous because they are improvised with materials readily available to the designer, and there is no
systematic way of explosive ordinance disposal. IEDs can be made from things such as standard military ammunition
and can be detonated with common electronic devices such as cell phones and garage door openers. There is a great
need for a low cost solution to neutralize these IEDs. At the Applied Physics Institute we are building a single function
disrupter robot whose sole purpose is to neutralize these IEDs. We are modifying a toy remote control car to control it
either wirelessly using WI-FI (IEEE 802.11) or wired by tethering the vehicle with an Ethernet cable (IEEE 802.3). The
robot will be equipped with a high velocity fuze disrupter to neutralize the IED as well as a video camera for inspection
and aiming purposes. This robot utilizes commercial-off-the-shelf (COTS) components which keeps the cost relatively
low. Currently, similar robot systems have been deployed in Iraq and elsewhere but their method of operation is such
that it is impractical to use in non-combat situations. We will discuss our design and possible deployment scenarios.
Pressurized rail tank cars transport large volumes of volatile liquids and gases throughout the country, much of which is
hazardous and/or flammable. These gases, once released in the atmosphere, can wreak havoc with the environment and
local populations. We developed a system which can non-intrusively and non-invasively detect and locate pinhole-sized
leaks in pressurized rail tank cars using acoustic sensors. The sound waves from a leak are produced by
turbulence from the gas leaking to the atmosphere. For example, a 500 μm hole in an air tank pressurized to 689 kPa
produces a broad audio frequency spectrum with a peak near 40 kHz. This signal is detectable at 10 meters with a
sound pressure level of 25 dB. We are able to locate a leak source using triangulation techniques. The prototype of the
system consists of a network of acoustic sensors and is located approximately 10 meters from the center of the rail-line.
The prototype has two types of acoustic sensors, each with different narrow frequency response band: 40 kHz and 80
kHz. The prototype is connected to the Internet using WiFi (802.11g) transceiver and can be remotely operated from
anywhere in the world. The paper discusses the construction, operation and performance of the system.
The paper describes the design and development of a network of wireless gamma-ray sensors based on cell phone or
WiFi technology. The system is intended for gamma-ray detection and automatic identification of radioactive isotopes
and nuclear materials. The sensor is a gamma-ray spectrometer that uses wireless technology to distribute the results. A
small-size sensor module contains a scintillation detector along with a small size data acquisition system, PDA, battery,
and WiFi radio or a cell phone modem. The PDA with data acquisition and analysis software analyzes the accumulated
spectrum on real-time basis and returns results to the screen reporting the isotopic composition and intensity of detected
radiation source. The system has been programmed to mitigate false alarms from medical isotopes and naturally
occurring radioactive materials. The decision-making software can be "trained" to indicate specific signatures of
radiation sources like special nuclear materials. The sensor is supplied with GPS tracker coupling radiological
information with geographical coordinates. The sensor is designed for easy use and rapid deployment in common wireless networks.
Northwest Nuclear, LLC (NWN), the Applied Physics Institute (API) at Western Kentucky University, and Crisis Prep Services, LLC (CPS) have developed a tracking technology for first responders and security personnel based upon the AeroScout system (a product of AeroScout, Inc.) and technologies developed independently by NWN, API, and CPS. These systems provide location information using 802.11XXX architecture by measuring the time of arrival of packets from a set of active radio frequency (RF) tags to a set of location receivers. The system can track and graphically display the location on maps, drawings, floor plans or photographs of tagged items on any 802.11-compliant devices (PDAs, laptops, computers, WiFi telephones) situated both outside and inside structures. This location information would be vital for tracking the location of first responders, security, and other emergency personnel during rescue operations; particularly, under adverse conditions (e.g., fires). NWN, API, and CPS have been improving the precision of the location measurement to an uncertainty of 20 cm or 8 inches (under certain conditions) and also developing algorithms to increase the accuracy. NWN and API personnel have developed: 1) special tags which indicate tampering or sudden movement and transmit briefly under these conditions, and 2) permanent and portable systems which can be deployed rapidly. Additional software created by Crisis Prep Services, LLC allows response force personnel to be tracked and located inside a building in real time as well as use the software and tags as a training and rehersal system. The location of each person is depicted on a drawing of the building and is displayed on a laptop computer or any other browser capable device.
PELAN (Pulsed ELemental Analsys with Neutrons) is a man-portable system for the detection of explosives and chemical warfare agents, weighing 40 kg. It is based on the principle that explosives and other contraband contain various chemical elements such as H, C, N, O, etc. in quantities and ratios that differentiate them from ot her innocuous substances. The pulsed neutrons are produced with a pulsed 14 MeV (d-T) neutron generator. Separate gamma-ray spectra from fast neutron, thermal neutron and activation reactions are accumulated and analyzed to determine elemental content. Data analysis is performed in an automatic manner and a final result of whether a threat is present is returned to the operator. Since 1999, PELAN has undergone several field trials and demonstrations, including in 2001, demonstrations in Belgium andin the US of its ability to identify chemical warfare agents. We will review the results of these tests and also discuss the modifications made to the system.