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[en] Gas-filled proton recoil proportional counters have been used extensively for the measurement of neutron spectra in degraded fission-spectrum environments. Some considerations relating to the use of these counters for personnel dosimetry are here described. High sensitivity and good accuracy in the determination of dose-equivalent can be obtained if relatively high pressure hydrogen-filled proportional counters are used as the active element in a dosimeter system

[en] Although new work has generally reinforced the previous conclusions (1985), recent sheets of commercial grade CR-39 have exhibited both good neutron sensitivity, and low backgrounds, which, unlike those of earlier batches, have not increased with time. This improvement is believed to be associated with changes in the manufacturing process. In addition, this work has confirmed that a revised and simplified processing schedule produces equivalent results to the original processing schedule, and there are indications that further changes may improve the low-energy neutron response without increasing the backgrounds. Some studies of the effect of time and environment on the neutron sensitivity and background in the plastic have been undertaken. These have shown that, although slow changes take place in the plastic with time and environment, simple precautions minimise these effects, and they are not a serious obstacle to the introduction of an operational dosimeter. The most important remaining problem is that of the acceptability of the poor angular response of a single planar detector, and the possible need for an operational dosimeter to use multiple detectors with different orientations. (author)

[en] A magnetic proton recoil (MPR) spectrometer has been designed and constructed for use at the Joint European Torus (JET) tokamak. It was installed at JET in October 1996 and has subsequently been in continuous use during the first main deuterium-tritium (DT) operation in 1997, which culminated in the production of a record plasma generating 16.1 MW fusion power. This thesis describes the MPR spectrometer, including calibration and characterization procedures, and the JET experiments. Special emphasis is given to the focal plane detector and its response to radiation, which is a part of the total spectrometer response function. The result from this development and characterization work is presented. The data taking and reduction procedures are also described. Results from the first measurements in D-plasmas on the triton burnup neutron energy distribution are presented and compared with calculations. Examples of results obtained for DT-plasmas are reported which represent the first use of neutron spectrometry for measurements of plasma rotation and fast ion components in radio frequency heated plasmas. The forthcoming use of neutron spectrometry, especially for studies of ignited plasmas, is outlined in view of gained operating experience of the new technique and the achieved results

[en] A method to unfold neutron spectra from experimental proton recoil data in form of a multichannel pulse height analyzer is developed and tested. The method takes into account, distortions due to multiple scattering and edge effects. It has been applied to a stilbene scintillation spectrometer using experimentally determined response functions but should equally well be applicable to other types of proton recoil spectrometers. The method is tested by application to experimental data produced with a stilbene fast neutron spectrometer system. Spectra of reactor neutron and that transmitted through water and iron barriers are unfolded. The unfolded measured spectra are compared with that calculated and a reasonable agreement was found between the two. Moreover, the maxima and depths which are observed in the spectra behind these barriers are checked against the depths and maxima in the total cross sections

[en] The ²³⁹Pu fission cross section was measured with the proton recoil detector in order to test the possibilities of this detector. It is shown that the resolution and the background sensitivity are particularly good

[en] The report describes measurements performed for the energy calibration of the TANSY neutron detectors (two arrays of 16 detectors each one). The calibration procedure determines four calibration parameters for each detector. Results of the calibration measurements are given and test measurements are presented. A relation of the neutron detector calibration parameters to producer's data for the photomulipliers is analysed. Also the tests necessary during normal operation of the TANSY neutron spectrometer are elaborated (passive and active tests). A method how to quickly get the calibration parameters for a spare detector in an array of the neutron detectors is included

[en] Absolute measurements of neutron fluence are an essential prerequisite of neutron-induced cross section measurements, dosimetric investigations and neutron beam lines characterisation. Independent and precise neutron flux measurements can be performed with respect to the H(n,p) elastic cross section. However, the use of silicon proton recoil detectors is not straightforward below incident neutron energy of 1 MeV, due to a high background in the detected proton spectrum. A new gaseous proton-recoil detector based on a double ionisation chamber, has been designed to answer the challenge. The detector is constituted by a H-rich deposit (polypropylene, mylar foil or tristearin deposit), and a segmented ΔE-E ionization chamber (4*4*12 cm³), read by a 64 pads Micromegas-based detection plane. The chamber is filled with gas (CF₄ or N₂-CO₂) at an adjustable pressure, from few tens of mbar to few tens of 100 mbar, to reduce as much as possible the detector sensitivity to Compton electrons. Tests have confirmed the low electron sensitivity of the detector, making it well suited for neutron energies down to 200 keV in a gammas and electrons dense environment. The ΔE-E coincidences, coupled to a 3D proton track analysis, enables the disentanglement between direct and scattered neutrons

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No abstract available