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  • Author or Editor: P. Aarnio x
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Abstract  

UNISAMPO is a new member of the SAMPO family of gamma-spectrum analysis programs running on Linux. Its portable graphical user interface relies on Tcl/Tk running an X-client, which obtains services from an X Window System server, allowing natural access to UNISAMPO over the Internet. UNISAMPO features a scripting ability for analyses of thousands of spectra. Peak search is based on stringent statistical criteria and peak fitting has optional step function under each peak of a multiplet. UNISAMPO will analyze 32K spectra with up to 2500 peaks, and 32 peaks in a single multiplet extending over a fitting interval of 1024 channels. It has an interface to the expert system SHAMAN for extensive peak interpretation and radionuclide identification.

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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  

SAMPO for Windows is a high performance gamma spectrum analysis program. All the measurement, analysis and NAA phases can be done either under full interactive user control or user defined tasks can be used for automated measurement and analysis sequences including control of MCAs and sample changers. High resolution gamma-ray spectroscopy together with the possibility to resolve complex multiplets with high accuracy makesSAMPO very suitable for INAA. On the other hand, the possibility to automate analysis sequences allows its use effectively also in all routine NAA measurements.NAA inSAMPO is accomplished using comparative methods. Spectra of standards, flux monitors, controls and actual samples are analyzed normally to obtain the peak areas which are optionally corrected for decay. In the comparison the flux monitor results are used to correct for variations in the effective neutron flux. An optional irradiation position correction can also be applied. The controls are used to alarm for possible deviations in the results.The sophisticated spectrum analysis methods used together with the comparative NAA and monitors give accurate results limited by the systematic effects only. The Windows environment provides ease of use and further processing power is available through the interface to expert system identification of nuclides.

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Abstract  

The widely used SAMPO Ge(Li) and HPGe gamma spectrum analysis program has been adapted to IBM Personal Computers in a thoroughly revised version MicroSAMPO. The program is intended for peak search, peak fitting, nuclide identification and activity calculations. The use of calibrated peak shape functions for peak area determination makes it possible to resolve complex multiplets with strongly overlapping peaks. Menu-driven user interface, colour graphics diplays, semi-automatic calibrations and interactive options have been designed to make the program more user-friendly. It is well suited for both spectroscopic research and routine analysis.

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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  

SAMPO 90 is a high performance gamma-spectrum analysis program for personal computers. It uses color graphics to display calibrations, spectra, fitting results as multiplet components, and analysis results. All the analysis phases can be done either under full interactive user control or macros and programmable function keys can be used for completely automated measurement and analysis sequences including the control of MCAs and sample changers. Accurate peak area determination of even the most complex multiplets, of up to 32 components, is accomplished using linear, non-linear and mixed mode fitting. Nuclide identification is done using associated lines techniques allowing interference correction for fully overlapping peaks. Peaked Background Subtraction can be performed and Minimum Detectable Activities calculated. The analysis reports and program parameters are fully customizable.

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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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