There has been an increasing demand over the past few years for a precise knowledge of beta spectra, coupled with well-established uncertainties. Recently, a theoretical study has been led off for calculating beta spectra, but these theoretical predictions can only be validated by a systematic comparison with new measurements. A dedicated experimental setup has already been developed during a previous PhD thesis using a silicon PIPS detector, and was tested with success. However, many developments are still needed to achieve the desired results.

The main objective of the hereby thesis will be to evolve this setup with the use of thicker Si(Li) detectors for high energy transitions and of a 4pi geometry, but also to improve and to evolve the raw data treatment, the Monte Carlo simulations, and the analysis of the measured spectra. These spectra can be distorted by the detection (detector efficiency, non-linearity of the electronics) and by physical phenomenons (thickness and homogeneity of the sources, detector dead zones, incident angle, scattering and backscattering, bremsstrahlung). It will be necessary to study precisely all the sources of distortion, and then to perform a deconvolution of these effects from the measured spectrum in order to extract the experimental shape factor. The deconvolution of the photonic contribution will be a major challenge. The measurement of pure beta emitters will allow a direct comparison between experiment and theory.

The applicant must be motivated by the experimental work, and he must possess some knowledge in ionizing radiation detection as well as in programming (C/C++, Fortran). Some experience with Monte Carlo simulations would be appreciated. If the applicant is interested, the subject may also include a theoretical part on the calculation of beta spectrum shapes.

This position is open until it is filled.

Department: DM2I (LIST)
Laboratory: Cellule de Données Fondamentales
Start Date: 01-10-2015
ECA Code: SL-DRT-15-0548
Contact: xavier.mougeot<στο>cea.fr