The spectrometry of promptly emitted /spl gamma/ rays after thermal neutron capture is used for a complete, nondestructive, isotopic material analysis developed at the Physikalisch-Technische ...Bundesanstalt (PTB). This method is independent of the sample dimensions and its state of aggregation. Furthermore all isotopes are detected by multichannel analysis, simultaneously. Isotopic mass differences have been determined up to now with a relative uncertainty of 3/spl times/10/sup -10/ 1.
Within its occupational radiation protection programme, the International Atomic Energy Agency (IAEA) initiated and funded an international intercomparison exercise of personal dosemeters to ...determine the quantity personal dose equivalent in mixed neutron-photon radiation. The objectives of the intercomparison are to assess the capabilities of the dosimetry services in measuring the quantity Hp(10) in mixed neutron-gamma fields; to assist IAEA member states in achieving sufficiently accurate dosimetry; and, if necessary, to provide guidelines for improvements (not simply a test of the performance of the existing dosimetry service). The intercomparison is directed to passive dosemeters to determine, in mixed neutron-gamma radiation fields, either these two components separately or the total personal dose equivalent. The intercomparison consists of two phases: Phase I--Type-test intercomparison: irradiation in selected calibration fields and results used to improve dosimetric procedures of participating laboratories, where needed. Phase II--Simulated workplace field intercomparison: irradiation in radiation fields similar to those in workplaces as a final check of performance. The exercise revealed clear deficiencies in the methodology used by several laboratories and necessitated a detailed analysis of the existing discrepancies. This papers summaries the finding and conclusions for radiation fields similar to those found in nuclear industry.
The Compact Neutron Spectrometer (CNS) is a Joint European Torus (JET) Enhancement Project, devoted to measure the neutron emission spectra in different plasmas scenarios. The results obtained by CNS ...during next JET campaigns will contribute to the development of neutron spectrometers suitable for applications in the International Thermonuclear Experimental Reactor (ITER). The main components of the instrument are a liquid scintillation detector (BC501A) for neutron (n) and gamma-ray (¿) detection and a Digital Pulse Shape Discrimination (DPSD) acquisition system. The CNS will enable recording and discrimination of n and ¿ pulse height spectra up to total count rates of ~10 6 s -1 . After unfolding the neutron spectra can be determined with energy resolution <2% at 14 MeV and <4% at 2.5 MeV. The work done in the last two years by ENEA-Frascati and Physikalisch-Technische Bundesanstalt (PTB) respectively in the assembly of DPSD and scintillation detector, along with the preliminary tests and results performed on both the components and the assembled spectrometer are presented.
CONUS is a novel experiment aiming at detecting elastic neutrino nucleus scattering in the fully coherent regime using high-purity Germanium (Ge) detectors and a reactor as antineutrino (\(\bar\nu\)) ...source. The detector setup is installed at the commercial nuclear power plant in Brokdorf, Germany, at a very small distance to the reactor core in order to guarantee a high flux of more than 10\(^{13}\bar\nu\)/(s\(\cdot\)cm\(^2\)). For the experiment, a good understanding of neutron-induced background events is required, as the neutron recoil signals can mimic the predicted neutrino interactions. Especially neutron-induced events correlated with the thermal power generation are troublesome for CONUS. On-site measurements revealed the presence of a thermal power correlated, highly thermalized neutron field with a fluence rate of (745\(\pm\)30)cm\(^{-2}\)d\(^{-1}\). These neutrons that are produced by nuclear fission inside the reactor core, are reduced by a factor of \(\sim\)10\(^{20}\) on their way to the CONUS shield. With a high-purity Ge detector without shield the \(\gamma\)-ray background was examined including highly thermal power correlated \(^{16}\)N decay products as well as \(\gamma\)-lines from neutron capture. Using the measured neutron spectrum as input, it was shown, with the help of Monte Carlo simulations, that the thermal power correlated field is successfully mitigated by the installed CONUS shield. The reactor-induced background contribution in the region of interest is exceeded by the expected signal by at least one order of magnitude assuming a realistic ionization quenching factor of 0.2.
Prompt (n,/spl gamma/)-spectrometry is an on-line measurement for the determination of characteristics of nuclei (atomic masses, cross sections, level schemes, etc.) and nondestructive investigation ...of the isotopic composition (and, therefore, of the element composition) of any sample. The thermal neutrons are captured in the sample according to their isotope-specific cross sections and cause an high internal excitation of the nuclei concerned. This leads to an immediate rearrangement of the nucleons in a new state most favourable with respect to energy, and the excess energy is dissipated by prompt emission of electromagnetic radiation in the form of characteristic /spl gamma/-quanta. The process takes place for all isotopes (contrary to the neutron activation analysis), is nondestructive and has no need for sample preparation (contrary to the mass spectrometry). Moreover it is independent of the sample dimensions and its state of aggregation.
The Compact Neutron Spectrometer (CNS) is a Joint European Torus (JET) Enhancement Project, designed for fusion diagnostics in different plasma scenarios. The CNS is based on a liquid scintillator ...(BC501A) which allows good discrimination between neutron and gamma radiation. Neutron spectrometry with a BC501A spectrometer requires the use of a reliable, fully characterized detector. The determination of the response matrix was carried out at the Ion Accelerator Facility (PIAF) of the Physikalisch-Technische Bundesanstalt (PTB). This facility provides several monoenergetic beams (2.5, 8, 10, 12 and 14 MeV) and a 'white field'(Emax ~17 MeV), which allows for a full characterization of the spectrometer in the region of interest (from ~1.5 MeV to ~17 MeV. The energy of the incoming neutrons was determined by the time of flight method (TOF), with time resolution in the order of 1 ns. To check the response matrix, the measured pulse height spectra were unfolded with the code MAXED and the resulting energy distributions were compared with those obtained from TOF. The CNS project required modification of the PTB BC501A spectrometer design, to replace an analog data acquisition system (NIM modules) with a digital system developed by the 'Ente per le Nuove tecnologie, l'Energia e l'Ambiente' (ENEA). Results for the new digital system were evaluated using new software developed specifically for this project.
We characterize the neutron output of a deuterium-deuterium plasma fusion neutron generator, model 35-DD-W-S, manufactured by NSD/Gradel-Fusion. The measured energy spectrum is found to be dominated ...by neutron peaks at 2.2 MeV and 2.7 MeV. A detailed GEANT4 simulation accurately reproduces the measured energy spectrum and confirms our understanding of the fusion process in this generator. Additionally, a contribution of 14.1 MeV neutrons from deuterium-tritium fusion is found at a level of~\(3.5\%\), from tritium produced in previous deuterium-deuterium reactions. We have measured both the absolute neutron flux as well as its relative variation on the operational parameters of the generator. We find the flux to be proportional to voltage \(V^{3.32 \pm 0.14}\) and current \(I^{0.97 \pm 0.01}\). Further, we have measured the angular dependence of the neutron emission with respect to the polar angle. We conclude that it is well described by isotropic production of neutrons within the cathode field cage.
The spectrometry of promptly emitted /spl gamma/-rays after thermal neutron capture is used for a complete, nondestructive, isotopic material analysis developed at the PTB. This method is independent ...of the sample dimensions and its state of aggregation. Furthermore all isotopes are detected by multi-channel analysis, simultaneously. Isotopic mass differences have been determined with an uncertainty of 10/sup -10/.
The compact neutron spectrometer project was initiated to develop a device able to study fast neutrons produced by fusion reactions in a tokamak. The goal is to provide a fully characterized BC501A ...detector using a digital acquisition system developed by ENEA. The pulse height resolution and the response matrix of the detector are determined using experimental data acquired at the PTB facility. To achieve this goal, methods of data analysis involving entropy maximization and new software were developed. The methods are described and the current results for the pulse height resolution are presented.
