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Improvements to a Java based software package developed at Pacific Northwest National Laboratory (PNNL) for display and analysis of radioxenon spectra acquired by the International Monitoring System (IMS) are described here. The current version of the Radioxenon JavaViewer implements the region of interest (ROI) method for analysis of beta-gamma coincidence data. Upgrades to the Radioxenon JavaViewer will include routines to analyze high-purity germanium detector (HPGe) data, Standard Spectrum Method to analyze beta-gamma coincidence data and calibration routines to characterize beta-gamma coincidence detectors. These upgrades are currently under development; the status and initial results will be presented. Implementation of these routines into the JavaViewer and subsequent release is planned for FY 2011-2012., Published in Proceedings of the 2010 Monitoring Research Review - Ground-Based Nuclear Explosion Monitoring Technologies, 21-23 September 2010, Orlando, FL. Volume II. Sponsored by the Air Force Research Laboratory (AFRL) and the National Nuclear Security Administration (NNSA). U.S. Government or Federal Rights License

Traditional radioxenon measurements have been done by ground-based fixed systems, however in recent years there has been an increased need for systems capable of quick deployment or even complete mobility. Using the Pixie-4 data acquisition (DAQ) system can help reduce the electronics footprint of both current systems, like the radioxenon Radionuclide Laboratory 16 (RL-16) and the Swedish Automatic Unit for Noble Gas Acquisition (SAUNA), as well as future systems. Pacific Northwest National Laboratory (PNNL) has developed a Linux based Nyx graphical user interface (GUI) for Pixie-4 cards. The Nyx software can be installed on various Linux platforms and is written in C++. This software offers a rich user interface for configuring and operating the Pixie4 card and PNNL designed high voltage (HV) cards. Nyx allows one to quickly get a nuclear detector operational by maintaining the core diagnostic features built into the Pixie-4 cards. First, Nyx maintains the multitude of adjustable parameters accessible in the Pixie-4 cards, which allows one to customize settings to take full advantage of a particular detector. Nyx also maintains an oscilloscope feature which is extremely useful to optimize settings and to verify proper detector behavior and is often the first feature used in Nyx during detector setup. Finally, Nyx allows the user to collect data in several formats including full pulse shapes to basic histograms. Overall, it is the corner stone for the transition of beta-gamma systems to a state-of-the-art digitizing DAQ system., Published in Proceedings of the 2010 Monitoring Research Review - Ground-Based Nuclear Explosion Monitoring Technologies, 21-23 September 2010, Orlando, FL. Volume II. Sponsored by the Air Force Research Laboratory (AFRL) and the National Nuclear Security Administration (NNSA). U.S. Government or Federal Rights License

Detecting radioactive xenon isotopes in air is one of the methods employed in nuclear explosion monitoring. Using scintillator detectors, the xenon signal is distinguished from background via coincidence spectroscopy. The resulting detectors are complex instruments, with up to 12 scintillators, requiring specialized data acquisition (DAQ) electronics. Bridgeport Instruments, in collaboration with Pacific Northwest National Laboratory is developing a compact, lowcost DAQ solution. The DAQ module produces raw data, such as energies, arrival times, triggers, etc in real time using digital signal processing embedded in FPGAs. These raw data are available immediately and can be combined in real time by an event builder to form complex events and to check for trigger patterns. It is a unique characteristic of the DAQ module, that the event builder can be implemented by the customer in an open-source FPGA. In a similar manner, multiple DAQ modules can be connected to a backplane that contains programmable units, such as a trigger FPGA and a communication and control FPGA. All programmable logic on the backplane will be completely open-source. With this approach we are creating a very versatile platform that uses proprietary code only to generate raw data from the scintillator detector pulses (energies, triggers, etc.). All other aspects, especially those that create a unique instrument from the combination of scintillator detectors are completely under customer control. In this paper we present the architecture of this new nuclear instrumentation platform., Presented at the Conference on Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies (30th), held in Portsmouth, VA, on 23-25 Sep 2008. Published in the proceedings of the conference, p802-809, 2008. Prepared in cooperation with Pacific Northwest National Laboratory. Sponsored in part by the National Nuclear Security Administration (NNSA) and by the Army Space and Missile Defense Command. Proposal no. BAA07-48.

Several of the radioxenon detection systems developed for the International Monitoring System use beta/gamma coincidence detection to achieve high sensitivity. These systems use an arrangement of separate beta and gamma detectors to detect beta/gamma coincidence events characteristic of the different radioxenon isotopes. While very sensitive to small amounts of radioxenon, they also require careful calibration and gain matching of several detectors and photomultiplier tubes. An alternative approach is the use of a single phoswich detector in which beta-gamma coincidences are detected by pulse shape analysis (PSA). We previously reported on prototype phoswich well detectors, consisting of a fast plastic scintillator (absorbing betas) optically coupled to a slower CsI(Tl) scintillator (absorbing gammas). These detectors require only a single photomultiplier tube and an electronics readout channel. Beta/gamma coincidences create characteristic "fast/slow" signals that can easily be distinguished from "slow only" or "fast only" non-coincident interactions. We describe the development of a commercial off-the-shelf (COTS) radioxenon detector system based on such phoswich detectors. The PSA functions were implemented using the digital signal processor in a set of commercial readout electronics that is also compatible with ARSA and SAUNA detectors. These functions detect coincidences in real time and accumulate 2D histograms in on-board memory. The acquisition and the PSA functions can also be integrated into larger-scale acquisition and control software. Several phoswich detectors have been characterized for energy resolution, separation of coincidence events in 2D beta/gamma energy histograms, and detection efficiency. A test pulser module has been developed to support monitoring and testing of the electronics for state of health during operation. The phoswich detector, readout electronics, and software are now available as a COTS product package., Proceedings of Monitoring Research Review(30th): Ground-Based Nuclear Explosion Monitoring Technologies, Portsmouth, VA, 23-25 Sep 2008, sponsored by the National Nuclear Security Administration (NNSA) and the Air Force Research Laboratory (AFRL). Prepared in collaboration with Pacific Northwest National Laboratory, and PhotoPeak, Inc.. The original document contains color images.

Monitoring changes in atmospheric radioxenon concentrations is a major tool in the detection of an underground nuclear explosion. Ground-based systems like the Automated Radioxenon Sampler /Analyzer (ARSA), the Swedish Unattended Noble Gas Analyzer (SAUNA) and the Automatic portable radiometer of isotopes Xe (ARIX), can collect and detect several radioxenon isotopes by processing and transferring samples into a high-efficiency beta-gamma coincidence detector. The high-efficiency beta-gamma coincidence detector makes these systems highly sensitive to the radioxenon isotopes 133Xe, 131mXe, 133mXe, and 135Xe. The standard analysis of the 2-dimensional beta-gamma energy spectra uses regions of interest (ROI) to determine the amount of a particular radioxenon isotope present by summing the counts in region. This method relies on the peaks of interest falling within energy limits of the region. Some potential problems inherent in this method are the reliance on stable detector gains and a fixed resolution for each energy peak. In addition, when a high activity sample is measured, there will be more interference among the ROI, in particular within the 133Xe, 133mXe, and 131mXe regions. A solution to some of these problems can be obtained through spectral fitting of the data. Spectral fitting is simply the fitting of the peaks using known functions to determine the number and relative peak positions and widths. By knowing this information it is possible to determine which isotopes are present. The area under each peak can then be used to determine an overall concentration for each isotope. Using the areas of the peaks, several key detector characteristics can be determined: efficiency, energy calibration, energy resolution, and ratios between interfering isotopes (Radon daughters)., Published in Proceedings of Monitoring Research Review (30th): Ground-Based Nuclear Explosion Monitoring Technologies, Portsmouth, VA, on 23-25 Sep 2008, p733-738 sponsored by the National Nuclear Security Administration (NNSA) and the Air Force Research Laboratory (AFRL). The original document contains color images.