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  • Author or Editor: T. Hakulinen x
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Abstract  

The electromagnetic calorimeter of the CMS detector at CERN, Geneva will consist of PbWO4 crystals and be exposed to a hadron flux of 106 cm-2·s-1, mostly pions, during its operation. We have used FLUKA and DETRA codes for advance prediction of the activation of the detector. To assess the accuracy of these calculations, a small PbWO4 crystal was irradiated in a 345 MeV/c pion beam of the PSI to a fluence of 1.6·1012 cm-2. The resulting activation was measured using an HPGe-detector after cooling times varying from a few minutes to 14 months. The spectra were analyzed using the SAMPO 90 code for peak search and area determination and the SHAMAN code for radionuclide identification and quantification. The spectra were extremely complex and the first ones measured not useful due to violent peak overlap and pile-up. The number of found peaks in the spectra we analyzed varied between 841 and 128 peaks depending on the cooling time. The corresponding number of nuclides identified per spectrum varied between 116 and 15. The comparisons between the predicted time-development of the nuclide composition by FLUKA/DETRA and the analyzed results show that the activities of nuclides agree excellently for the most important nuclides and very well even for the less abundant ones. The total dose rate in the vicinity of the activated crystals, including its time dependence, is very well reproduced by the FLUKA/DETRA calculations.

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Abstract  

Radionuclide identification from a measured gamma-spectrum is an iterative process, where the analyst aims to find correct nuclides by decreasing the amount of possibilities by trial and error. Although the process of identification is quite complex, it can be formulated using rules of thumb combined with exact mathematical analysis. Thus, an expert system can be built, where the knowledge of a human expert is converted to explicit rules. In this paper expert system SHAMAN is presented, which carriess out the qualitative nuclide identification and activity determination with minimum of user intervention. The reasoning process is performed by an inference engine written in C-language. The system uses a database containing over 2000 radionuclides with about 48 000 gamma-transitions. Spectra are provided in preprocessed format, where peak energies, intensities and backgoounds with respective error estimates have been calculated by a separate analysis program.

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Abstract  

A set of 100 gamma-ray spectra with known traces of anthropogenic nuclides was utilized in the First System-Wide Performance Test (SPT1) of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) in June 2005. The spectrum set was very realistic, since it is based on real measured spectra. Yet, the correct spectrum contents are known, when anthropogenic peaks with known areas have been synthesized into the spectra. This paper investigates the key performance indicators for the UniSampo-Shaman software package when applied to these spectra, concentrating on results from automated pipeline analysis. In summary, the UniSampo-Shaman performance is very satisfactory and fully in line with previous evaluations.

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Abstract  

We present a framework for a multi-user server-based installation of the Shaman gamma-ray spectrum identification software. It allows users to access centrally managed Shaman and UniSampo software packages in a laboratory-wide multi-workstation environment. The server-based framework allows coordinated management of the software packages themselves as well as analysis parameter sets and analysis results either in a file system-based data vault or in an SQL-database based on the Linssi gamma-ray spectrometry database definition. Hierarchical management of analysis parameter sets allows full control of the individual analysis runs yet maintaining flexibility when analyzing a variety of sample types.

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Abstract  

SHAMAN is an expert system for qualitative and quantitative radionuclide identification in gamma spectrometry. SHAMAN requires as input the calibrations, peak search, and fitting results from reliable spectral analysis software, such as SAMPO. SHAMAN uses a comprehensive reference library with 2600 radionuclides and 80 000 gamma-lines, as well as a rule base consisting of sixty inference rules. Identification results are presented both via an interactive graphical interface and in the form of configurable text reports. An organization has been established for monitoring the recent Comprehensive Test Ban Treaty. For radionuclide monitoring, 80 stations will be set up around the world. Air-filter gammaspectra will be collected from these stations on a daily basis and they will need to be reliably analyzed with minimum turnaround time. SHAMAN is currently being evaluated within the prototype monitoring system as an automated radionuclide identifier, in parallel with existing radionuclide identification software. In air-filter monitoring, very low concentrations of radionuclides are measured from bulky sources in close geometry and with long counting time. In this case true coincidence summing and self-absorption become important factors. SHAMAN is able to take into account these complicated phenomena, and the results it produces have been found to be very reliable and accurate.

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Abstract  

Using gamma-spectrometry systems on mobile units with accurate position information is a convenient means for surveying large areas for radioactive fallout or finding hot spots due to misplaced sources or releases from nuclear installations. Traditionally, large (tens of litres) high efficiency NaI(T1) detectors have been used for the purpose. HPGe detectors, however, offer certain advantages which can often compensate for their lower efficiency. This kind of remote sensing, regardless of detector type, requires specialized software. In order to provide accurate position information, the integration times must be kept as short as possible. This is especially true for fast air-borne measurements where counting periods below one second are desirable. We have constructed a special version of SAMPO software which controls data acquisition and runs real-time gamma-spectrum analysis including peak determination, nuclide identification, activity calculations, and reporting. The measurement/analysis cycle can be reduced down to 0.5 seconds on a standard Pentium-based PC. The analysis results are combined with accurate co-ordinates from a differential GPS system on a color coded map. The system is also able to give alarms based on different criteria. We have already measured and analyzed more than 500 000 spectra in field applications using jets, helicopters, cars, and also on-foot.

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Abstract  

SHAMAN is an expert system for radionuclide identification and spectrum peak interpretation in gamma-ray spectrometry. SHAMAN utilizes a comprehensive reference library with 2616 radionuclides and 81,642 gamma-ray lines, as well as a rule base consisting of sixty inference rules. Identification results are presented both via a graphical user interface and as configurable text reports. SHAMAN has been installed as an automated radionuclide identifier, handling the last phase of the gamma-ray spectrum analysis of air filter samples in the Comprehensive Nuclear-Test-Ban Treaty (CTBT) environment, both at the International and National Data Centre level. SHAMAN is a powerful tool in this environment: it is shown to reach a peak explanation percentage above 99% for routine CTBT air filter spectra. However, SHAMAN's true capabilities are revealed when anything unusual is detected in a spectrum.

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Abstract  

Gamma spectrum analysis is a standard tool in many fields today. Often the task is to find out the exact composition and concentrations of radionuclides in a measured spectrum. A full manual identification of a complex spectrum requires considerable expertise on the part of the laboratory personnel and takes usually several hours.An expert system coupled with the gamma spectrum analysis system SAMPO has been developed for automating the qualitative identification of radionuclides as well as for determinating the quantitative parameters of the spectrum components. The program is written in C-language and runs in various environments ranging from PCs to UNIX workstations. The expert system utilizes a complete gamma library with over 2600 nuclides and 80 000 lines, and a rule base of about fifty criteria including energies, relative peak intensities, genesis modes, half-lives, parent-daughter relationships etc. The rule base is furthermore extensible by the user.The performance of the expert system has been evaluated using test cases from environmental samples, sets of standard sources and activation analysis measurements, which have been carefully analyzed manually. Also. synthesized spectra have been used, where the exact composition of the sample is known in advance. Results from these tests show that the expert system performs very well, even for difficult spectra.

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Summary  

{\rtf1\ansi\ansicpg1250\deff0\deflang1038\deflangfe1038\deftab708{\fonttbl{\f0\froman\fprq2\fcharset238{\*\fname Times New Roman;}Times New Roman CE;}} \viewkind4\uc1\pard\scaps\f0\fs24 UniSampo\scaps0 and \scaps Shaman\scaps0 are well-established analytical tools for gamma-ray spectrum analysis and the subsequent radionuclide identification. These tools are normally run locally on a Unix or Linux workstation in interactive mode. However, it is also possible to run them in batch/non-interactive mode by starting them with the correct parameters. This is how they are used in the standard analysis pipeline operation. This functionality also makes it possible to use them for remote operation over the network. We have developed a framework for running \scaps UniSampo\scaps0 and \scaps Shaman\scaps0 analysis using the standard WWW-protocol. A WWW-server receives requests from the client WWW-browser and runs the analysis software via a set of CGI-scripts. Authentication, input data transfer, and output and display of the final analysis results is all carried out using standard WWW-mechanisms. This WWW-framework can be utilized, for example, by organizations that have radioactivity surveillance stations in a wide area. A computer with a standard internet/intranet connection suffices for on-site analyses. \par }

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Summary  

Some environmental xenon sampling like the Automated Radioxenon Sampler-Analyzer (ARSA) and the Swedish Automated Noble Gas Unit (SAUNA), use &-& coincidence detectors that are energy dispersive on both the & and & axes. Applying conventional region-of-interest (ROI) analysis algorithms to such 3-D spectra is problematic due to spectral interferences in the low-resolution spectra. Deconvolving the 3-D sample spectra into the most probable combination of signals using non-negative least-squares results shows promise to robustly resolve the spectral interferences. This paper describes the multiple isotope component analysis (MICA) algorithm developed for analysis of 3-D &-& spectra from xenon sampling and measurement units.

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