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Communication Dans Un Congrès Année : 2023

Methodology for an experimental drift velocity determination using a mTPC. Example in a 700mbar 95%He+5%CO2 mixture

Méthodologie pour une détermination expérimentale de la vitesse de dérive en utilisant une microTPC; appilcation a une mélange 95%He+5%CO2 à 700 mbar

Résumé

The Laboratory for micro-irradiation, neutron metrology and dosimetry (LMDN) is responsible for establishing metrological references in France for neutron fluence energy distributions and associated dosimetric quantities. LMDN work on a project of neutron primary detector based on Time Projection Chamber technology and called “µTPC”. The neutron detection principle is based on the neutron/ion elastic scattering. Each track of recoil nuclei is detected by a pixelated Micromegas anode with a readout system (a slice each 20 ns) coupled to the charge measurement via a dedicated preamplifier. The detector can be adapted to different energy ranges from a few keV to several MeV using different gas types with specific pressure and preamplifiers adapted to the signal. The off-line data analysis process enables the energy and trajectory of the recoil particle produced to be reconstructed in three dimensions, event by event. The determination of the third dimension of the trajectory requires the knowledge of the drift velocity of the electrons in the gas. However, this quantity remains largely theoretical and is generally given by simulations, notably those of the Magboltz program proposed by the European Organization for Nuclear Research (CERN). However, an experimental measurement of this quantity is mandatory. The exploitation of two experimental measurements in monoenergetic neutron fields at 5 and 1.2 MeV allowed us to develop an experimental methodology to determine the drift velocity in the mixture used for the measurement (i.e. 700mbar 95%He+5%CO2). The methodology is self-supporting and uses the elastic scattering properties of neutrons on the gas nuclei with only a few point corrections related to the Quenching factor. The results have been compared with theoretical predictions from Magboltz simulations. The quantities are in good agreement even if the measurement is systematically slightly higher about 5% than the theoretical values. Sensitivity studies are proposed to lead to a consolidated estimate of the drift velocity in this mixture. The transposability of this approach to various gas mixtures is then studied. We will present at ANIMMA 2023 the methodology, the preliminary results and the sensitivity study. A large discussion about the drift gas properties will be presented.
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hal-04136743 , version 1 (29-06-2023)

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  • HAL Id : hal-04136743 , version 1

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Thibaut Vinchon, Michael Petit. Methodology for an experimental drift velocity determination using a mTPC. Example in a 700mbar 95%He+5%CO2 mixture. ANIMMA2023 - 8th International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications, Jun 2023, Lucca, Italy. ⟨hal-04136743⟩

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