Characterisation of fast transient phenomena using X-ray phase contrast imaging
The aim of this post-doctorate is to develop a measurement chain dedicated to the observation and characterisation of Rapid Transient Phenomena (RTP) using X-ray phase contrast imaging (XPCI). The challenge is to provide a measurement system that can be deployed in the laboratory on a wide range of experiments that cannot be moved to the synchrotron. The performance targets are justified by the problems associated with additive manufacturing, the propagation of shock waves in low-density polymers, and the diagnosis of carbon composite materials impacted by an electric arc.
For objects with low absorption, such as low-density polymers, liquids or plasmas, conventional X-ray imaging, which provides contrast due to the absorption cross-sections variations, is insufficient. To complete absorption, it is possible to exploit the phase of X-rays, which provides better detection of inhomogeneities and interfaces. The method used here to measure the phase is the multilateral shearing interferometry (IDML). It uses a single two-dimensional checkerboard phase grating that generates a reference interference pattern on the detector. The introduction ofan object between the grating and the detector modifies the reference interference pattern, which is then analysed by Fourier transform to reconstruct the phase image. By requiring only a single phase grid and exhibiting minimal X-ray flux loss, this method has favourable intrinsic characteristics in terms of sensitivity, robustness, ease of alignment and versatility, for application to dynamic imaging.
Calibration of the high dose rate flash therapy beam monitor of the IRAMIS facility
Ultra-flash beams are pulsed beams of high-energy electrons (over a hundred MeV) with pulse durations in the femto-second range. The IRAMIS facility (CEA Saclay) uses laser acceleration to produce this type of beam, with a view to their application in radiotherapy. The LNHB is in charge of establishing dosimetric traceability for the IRAMIS facility, and to do this it has to calibrate the facility's monitor. Current radiotherapy facilities are based on medical linear accelerators operating at energies of up to 18 MeV in electron mode. LNHB has such equipment. It is used to establish national references in terms of absorbed dose to water, under the conditions of the IAEA protocol TRS 398.
Establishing dosimetric traceability involves choosing the measurement conditions, knowing the transfer dosimeter characteristics used and any corrections to be applied to the measurements taking into account the differences between the IRAMIS Facility and those of LNHB.
Optimization of a metrological approach to radionuclide identification based on spectral unmixing
The Laboratoire national Henri Becquerel (LNE-LNHB) at CEA/Saclay is the laboratory responsible for French references in the field of ionizing radiations. For several years now, it has been involved in the development of an automatic analysis tool for low-statistics gamma spectra, based on the spectral unmixing technique. This approach makes it possible to respond to metrological constraints such as robust decision-making and unbiased estimation of counts associated with identified radionuclides. To extend this technique to field measurements, and in particular to the deformation of spectra due to interactions in the environment of a radioactive source, a hybrid spectral unmixing model combining statistical and automatic learning methods is currently being developed. The aim of this mathematical solution is to implement a joint estimation of the spectra measured and the counts associated with the radionuclides identified. The next step will be to quantify the uncertainties of the quantities estimated from the hybrid model. The aim is also to investigate the technique of spectral unmixing in the case of neutron detection with a NaIL detector. The future candidate will contribute to these various studies in collaboration with the Laboratoire d'ingénierie logicielle pour les applications scientifiques (CEA/DRF).
Environmental dosimetry: study, design and implementation of a calibration facility for low dose equivalent rates
In order to meet the calibration needs of the European radioactivity monitoring network, the Laboratoire national Henri Becquerel, part of CEA List, is installing a calibration facility for low dose equivalent rates, below 1 µSv/h. The work includes a study of the performance of the existing radiation beams and the design, installation and dosimetric characterization of a shielded facility to reduce the radiative background, in which low activity photon sources will be installed.
Eco-innovation of insulating materials by AI, for the design of a future cable that is long-lasting, resilient, bio-sourced and recyclable.
This topic is part of a larger upcoming project for the AI-powered creation of a new electrical cable for future nuclear power plants. The goal is to design cables with a much longer lifetime than existing cables in an eco-innovative approach.
The focus is on the cable insulation because it is the most critical component for the application and the most sensitive to aging. The current solution is based on adding additives (anti-rad and antioxidants) to the insulation to limit the effects of irradiation and delay aging as much as possible. However, there is another solution that has never been tested before: self-repairing materials.
The project to which this topic is attached aims to design and manufacture several test model of insulation specimens. With several test characterization protocols, in order to verify the gain in terms of reliability and resilience. The results obtained will begin to fill a future database for the AI platform Expressif, developed at CEA List, which will be used to design the future cable.
Contribution to the metrological traceability of emerging alpha-emitting radiopharmaceuticals in the framework of the european AlphaMet project (Metrology for Emerging Targeted Alpha Therapies)
The Laboratoire national Henri Becquerel (LNE-LNHB) at CEA/Saclay is the laboratory responsible for the french references in the field of ionizing radiation. The LNHB is involved in the european EPM AlphaMet (Metrology for Emerging Targeted Alpha Therapies) submitted under the Metrology support for Health call (2022) to provide metrological support for clinical and preclinical studies; it began in September 2023 for a total duration of three years. The project comprises four Work Packages (WP) targeting different issues, with WP1 in particular dedicated to activity metrology and nuclear data measurements for imaging and dosimetry. This project aims at to improve the metrological traceability of emerging alpha-emitting radiopharmaceuticals such as 211At, 212Pb/212Bi, 225Ac.
The candidate will participate in the various tasks defined as part of the European AlphaMet project in which the LNHB is involved. Radiation-matter simulations will be carried out to study the response of the laboratory's ionisation chambers in various situations concerning: (i) the evolution of the response during the in-growth of the ?-emitting progeny of 225Ac, (ii) the quantification of the influence of the 210At impurity in the case of the measurement of 211At, and (iii) the search for a long-lived radionuclide surrogate of 212Pb for the quality control of dose calibrators. The candidate will also be involved in setting up a new device aimed at improving the linearity of the measurement of half-life with an ionization chamber. During the post-doctoral stay at LNHB, the candidate will interact with the various partners in the AlphaMet project (activity metrology laboratories, hospitals, clinical study centres).
The initial duration of the post-doctorate is 12 months (renewable) at the Laboratoire National Henri Becquerel (CEA/Saclay). It is hoped to start in the first half of 2024.