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.

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.

Development of a modular multi-detector instrumentation for the measurement of atomic and nuclear parameters

The LNE PLATINUM project (PLATFORM OF MODULAR NUMERICAL INSTRUMENTATION) aims to develop a modular platform, in order to test new instrumentation using two or more detectors in coincidence. The principle implemented in this project is based on the simultaneous detection of interactions taking place in two different detectors, by collecting information on the type of particle and its energy (spectroscopy). This principle is the basis for absolute measurements of activity or active continuous background reduction systems to improve detection limits. But it also allows the measurement of parameters characterizing the decay scheme, such as internal conversion coefficients, X-ray fluorescence yields or angular correlations between photons emitted in cascade.

Thanks to its expertise in atomic and nuclear data, the LNHB has noted for many years the incompleteness of decay schemes for certain radionuclides. These schemes, established at the time of evaluation from existing measured data, sometimes present inconsistencies or poorly known transitions, in particular in the presence of highly converted gamma transitions or very low intensity (for example, recent studies on 103Pa, 129I and 147Nd have revealed such inconsistencies). It therefore appears important for LNHB to better master the technique of coincidence measurement, taking advantage of the new possibilities in terms of data acquisition and time stamping to provide additional information on decay scheme and contribute to their improvement.

Compressed Sensing Electron Tomography: Quantitative Multi-dimensional Characterization of Nanomaterials

Electron tomography (ET) is a well-established technique for the 3D morphological characterization at the nanoscale. ET applied to spectroscopic modes for 3D structural and chemical analysis has become a hot topic but necessitates long exposure times and high beam currents. In this project, we will explore advanced compressed sensing (CS) approaches in order to improve the resolution of spectroscopic ET and reduce significantly the dose. More precisely, we will focus on the following two tasks: 1. Comparison of total variation minimization, orthogonal or undecimated wavelets, 3D curvelets or ridgelets and shearlets for nano-objects with different structures/textures; 2. Comparison of PCA and novel CS-inspired methods such as sparse PCA for dimensionality reduction and spectral un-mixing. The code will be written in Python, using Hyperspy ( and PySAP ( libraries.
The project follows a multidisciplinary approach that involves the strong expertise of the coordinator in ET and the input of two collaborators with complementary skills: Philippe Ciuciu with expertise in MRI (DRF/Joliot/NEUROSPIN/Parietal) and Jean-Luc Starck with expertise in cosmology, signal processing and applied maths (DRF/IRFU/DAP/CosmoStat). The three communities share a strong interest in compressed sensing algorithms.

Study of a transient regime of helium dispersion to simulate an accidental release of hydrogen from a fuel cell.

CEA and industrial partners want to improve their knowledge, models and risk mitigation means for the conséquences of an accidental release of hydrogen from a H2 Fuel Cell. The dispersion of helium as a replacement for hydrogen takes place in a private garage and the transient state will be studied. Different scenarios of release are considered: from a cubic idealized fuel cell, then with different aspect ratios and finally with varying main dimension. The goal is to study some scaling effects. For the first case, we will measure helium concentration with katarometres and possibly velocity fields with PIV methods. Then mitigation processes will be tested. At last comparisons with models and numerical simulations will be performed.

Developpment of a control quality method for radiotherapy treatments based on dosimetric gels

In the field of dosimetry for radiotherapy, chemical dosimetry, and in particular gel dosimeters, are good candidates for dose distribution measurements for the quality control of treatment plans. Actually, these gels are radiosensitive and, thus, enable measurements of the dose in 3 dimensions when read by adapted imaging methods.

This post-doctoral project deals with the development of gel dosimetry methods, using two types of reading devices: Optical tomography and Magnetic Reading Imaging. For gel-MRI dosimetry, the aim will be to adapt and validate the method used at LNHB (Laboratoire National Henri Becquerel) for quality control applications for MR-guided-radiotherapy devices. For this purpose, specific phantoms will have to be designed and produced using 3D printing. The reading method will also have to be optimized and transposed on partnering hospital devices.

Concerning the gel-optical CT dosimetry method, the whole method will have to be developed. This involves an adaptation of the composition for the gel, a characterization of the reading device and a validation of the method established.

New reference radiation field for radioprotection in the range of Cs-137 et Co-60 using an electrostatic electron accelerator

During the last years, LNHB has started and realized a research program in order to produce a reference photon radiation field for the radioprotection needs at high energies (~6 MeV) using its medical electron accelerator Saturne 43. For this purpose, a target and its appropriate flattering-attenuating filter have been designed by LNHB in order to produce the required photon field.

Nowadays there is no existing device able to produce radiation fields from an accelerator in the Cs-137 and Co-60 equivalent energy range. In order to achieve this, one needs the technology to construct and properly use absolute dosemeters for photons (cavity ionization chambers), to determine the right target-filter assembly allowing the production of the required photon field and to accurately calculate the conversion factors from air-kerma to operational quantity which is the dose-equivalent using the spectral distribution at the calibration position.

The candidate will participate in the construction of cavity ionization chambers needed for the characterization in terms of dose-equivalent of radiation field obtained from the electron accelerator and to the on-site measurements. He(She) will also be in charge with Monte-Carlo simulations in order to optimize the target-filter assembly used to produce the reference photon field from an electrostatic accelerator.

Design and implementation of a bio-inspired sense, application to offshore teleoperation and to operator assistance

In recent years, the Bio-inspired Robotics Group of Robotics team IRCCyN has developed an artificial bio-inspired electric fish sense. To emulate the electrical sense, resistive probes were used for piloting the IRCCyN submarine autonomous robot.
For its part, within the Interactive Robotics Laboratory (LRI), the CEA LIST has been pursuing for several years a research activity in the field of force feedback telerobotics. The operator manipulates a slave robot located in hostile environments via a master arm located in a safe area and a computer system.
The candidate’s work will take place in a CEA- IRCCyN project running in parallel over a first project whose purpose is to demonstrate the concept of electro- haptic loop on a Cartesian arm carrying an electric probe with a fixed and known geometry. The postdoc will be in charge of implementing the loop on a "marinized" manipulator arm with a complex geometry. To do this, with the assistance of CEA and IRCCyN , he/she will support the preparation of this arm and adaptation of electrical sensor (emitter electrodes , receiver , electronic) architecture considered , as well as the adaptation of the monitoring / control of the haptic interface at the base of the electro-haptic loop. In addition to the technological challenges of this adaptation, the candidate must also consider different strategies to exploit the electric field on a multi-body system of variable geometry.
Experimental validation and proof of concept of this new offshore teleoperation system will be carried out on scenarios, to be defined, representative of the final application.