Fast-scintillator-based device for on-line FLASH-beam dosimetry

New cancer treatment modalities aim to improve the dose delivered to the tumor while sparing healthy tissue as much as possible. Various approaches are being developed, including the temporal optimization of the dose delivered with very high dose rate irradiation (FLASH).
In this particular case, recent studies have shown that FLASH irradiation with electrons was as effective as photon beam treatments for tumor destruction while being less harmful to healthy tissue. For these beams, the instantaneous doses are up to several orders of magnitude higher than those produced by conventional beams. Conventional active dosimeters saturate under irradiation conditions at very high dose rates per pulse, therefore on-line dosimetry of the beam is not possible.
We propose to develop a dosimeter dedicated to the measurement of beams in FLASH radiotherapy based on an ultra-fast plastic scintillator coupled with a silicon photomultiplier sensor (SiPM). The novelty of the project lies both in the chemical composition of the plastic scintillator which will be chosen for its response time and its wavelength emission to have a response adapted to the impulse characteristics of the beam, and in the final sensor with the possibility of coupling the plastic scintillator to a miniaturized SiPM matrix.
The final goal is to be able to access, with a reliable methodology, the dosimetry and in-line geometry of FLASH beams.

Measurement of active cell nematics by lensless microscopy

At CEA-Leti we have validated a video-lens-free microscopy platform by performing thousands of hours of real-time imaging observing varied cell types and culture conditions (e.g.: primary cells, human stem cells, fibroblasts, endothelial cells, epithelial cells, 2D/3D cell culture, etc.). And we have developed different algorithms to study major cell functions, i.e. cell adhesion and spreading, cell division, cell division orientation, and cell death.
The research project of the post-doc is to extend the analysis of the datasets produced by lens-free video microscopy. The post-doc will assist our partner in conducting the experimentations and will develop the necessary algorithms to reconstruct the images of the cell culture in different conditions. In particular, we will challenge the holographic reconstruction algorithms with the possibility to quantify the optical path difference (i.e. the refractive index multiplied by the thickness). Existing algorithms allow to quantify isolated cells. They will be further developed and assessed to quantify the formation of cell stacking in all three dimensions. These algorithms will have no Z-sectioning ability as e.g. confocal microscopy, only the optical path thickness will be measured.
We are looking people who have completed a PhD in image processing and/or deep learning with skills in the field of microscopy applied to biology.

IMPROVING OPTICALLY PUMPED MAGNETOMETERS FOR BIOMEDICAL IMAGING

Our lab works on optically pumped magnetometers (OPM) based on helium-4 metastable atoms. Our main achievement in last years has been the design and space qualification of the most advanced OPMs available for spatial exploration, which were launched on ESA Swarm mission [1]. With this very same species we have developed OPMs for medical imaging of brain (MEG) and heart (MCG), which have the advantage of operating at room temperature. The development of these two imaging techniques is an opportunity to better understand and diagnose pathologies like epilepsy, Alzheimer or arrhythmia.
A few years ago we performed proof of concept measurements of both MCG and MEG with primitive versions of our sensors [2,3]. After getting a better understanding of our sensors physics [4] and implementing substantial improvements, we are now developing arrays of OPMs and collaborating with several clinical teams in order to test them for different applications and environments. The purpose of this post-doctoral position is to contribute to the development of magnetometer arrays. It involves experimental work to improve the current prototypes of medical OPM arrays: the post-doc will be notably in charge of improving the intrinsic noise of the sensor and identifying the best way to build robust, reproducible architectures that could be replicated in arrays of several hundreds of sensors.
This work is aimed at bringing this technology to the medical imaging market, in collaboration with a start-up currently prepared by CEA-Leti. It will be carried out in a multidisciplinary team, composed of researchers, experienced engineers, PhD students and post-docs, specialized in the fields of optics, lasers, magnetism and electronics. It will also rely on collaborations with medical research teams in neurology and cardiology.

[1] http://smsc.cnes.fr/SWARM
[2] S. Morales et al.,
[3] E. Labyt et al., IEEE Transactions on Medical Imaging (2019).
[4] F. Beato et al. Physical Review A (2018)

LAB AND FIELD WORK ON OPTICALLY PUMPED MAGNETOMETERS

The purpose of this post-doctoral position is to contribute to the development of magnetometer arrays. It involves mainly the deployment of OPM arrays in the clinical environments where they are going to be tested by several of our partner medical research teams in both neurology and cardiology. The post-doc should be able to deploy and operate the sensors in these environments, solve the practical issues, and bring feedback on all kind of improvements that are needed. He or she will also participate in the implementation of some of these improvements, and their tests in lab environment.
This work is aimed at bringing this technology to the medical imaging market. It will be carried out in a multidisciplinary team, composed of researchers and experienced engineers.

[1] http://smsc.cnes.fr/SWARM
[2] S. Morales et al., Phys. Med. B
[3] E. Labyt et al., IEEE Transactions on Medical Imaging (2019).
[4] F. Beato et al. Physical Review A (2018)

Analysis of low abundance 144Ce and 106Ru isotopes by mass spectrometry

The aim of this project is to develop the high precision analysis of 144Ce and 106Ru by mass spectrometry in irradiated samples for the qualification of neutronic calculation codes. These two isotopes are present at low abundances in the samples of interest and display significant isobaric interferences with 144Nd and 106Pd respectively. To complete this project, the candidate will carry out the appropriate analytical developments in conventional laboratory on inactive samples. Then the procedure will be transposed in the active laboratory for validation with the analysis of real samples. In the case of 144Ce, the implementation of a coupling between high performance liquid chromatography (HPLC) and ICPMS-MC, combined with the isotope dilution technique for the precise determination of atomic contents is envisaged. For 106Ru, the 101Ru concentration will first be determined by ICPMS-Q and the 101Ru/106Ru ratio will be determined by HPLC/ICPMS-Q or HPLC/ICPMS-MC coupling to remove the 106Pd/106Ru interference.

Development of femtosecond Fiber Bragg Grating acoustic receivers for the Structural Health Monitoring using passive acoustic tomography

The proposed post-doctoral fellowship is part of a transverse project initiated by the CEA and which consists in developing a prototype of a continuous monitoring system of a metallic structure (pipe for example) using fiber Bragg gratings acoustic receivers and passive imaging (or passive tomography). It aims to demonstrate the relevance of the SHM (Structural Health Monitoring) concept for nuclear facilities using optical fiber sensors operating in continuous and in extreme environment. This project is based on two recent developments: new generation of fiber Bragg gratings developed for severe environments and defect imaging algorithms based on ambient noise analysis. A demonstration of elastic wave reconstruction from passive algorithm applied to fiber Bragg gratings was carried out at the CEA in 2015, which is a world first, patented. The project aims more particularly to produce a demonstrator and to equip a pipeline on a test loop. It will provide input data relating to the ability of a moving fluid to generate elastic waves that can be analyzed in passive tomography.

Atomic sensors based on metastable 4He

Detection of weak magnetic fields opens the way to new techniques of medical imaging, geophysics and chemistry. Optically pumped magnetometers are currently the most accurate and precise sensors for magnetic fields [1]. Our lab works on optically-pumped magnetometers based on a thermal gas of helium-4 metastables, a spin-one electronic species. Our main achievement in last years has been the design and space qualification of the most recent generation of magnetometers available for spatial exploration, which were launched by ESA Swarm mission [2].
We are now starting a new project in order to explore further applications of magneto-optical effects of metastable helium. Indeed, dichroism and birefringence have been observed on 4He from the very first times of optical pumping [3] but, in strong contrast with alkali [4], the nonlinear regimes which can be reached from the introduction of 1083 nm lasers have been hardly studied. These regimes open new possibilities for realizing not only magnetometers but also other kind of useful sensors which address a broader range of industrial applications.
We are looking for a motivated postdoc candidate willing to work towards a better understanding of these effects but also towards harnessing them for building ultra-precise sensors. The applicant should have a PhD in physics, ideally with a good background in experimental atomic physics and/or laser physics. Our lab is well equipped and staff engineers will be available to assist the post doc on technical aspects related to optics, design of electronics and magnetic materials. The results will be divulgated in form both of journal publications and of patents.
[1] Kominis et al., Nature 422 (2003)
[2] http://smsc.cnes.fr/SWARM
[3] Laloë, Leduc, Minguzzi, Journal de Physique, 30 (1969)
S. Pancharatnam, J. Phys. B: At. Mol. Phys. 1 (1968).
[4] Budker et al., Rev. Mod. Phys. 74 (2002)

Wireless biological sensor using 2D materials (Graphene , Molybdenium disulfide)

The main goal of the post-doctoral position is the fabrication of a biological sensor using 2D materials and that can be remotely addressed thanks to a RF antenna simultaneously fabricated alongside the biosensor.
The post-doctoral associate will be in charge of the fabrication and characterization of the prototype. Starting from well-designed modelling, he/she will first establish a design architecture for the sensor and RF antenna. Once designed and sized, the post-doctoral associate will adapt existing transfer protocol of 2D materials to develop an innovative fabrication process for the sensor. He/she will then fabricate the first prototypes of the sensors. Consecutively he/she will validate first the remote addressing of the sensor via the RF antenna. Secondly he/she will lead biodétection tests to assess the sensitivity of the fabricated sensors. Finally, he/she will try to integrate Transition Metal Di-chalcogenides 2D materials (such as MoS2) to graphene sensors inside a hybrid 2D materials biological sensor. The goal here will be to boost operational sensitivity.

Nonlinear ultrasonic testing for the assessment of adhesive bonding properties

The CEA-LIST carries out Non Destructive Testing (NDT) projects in partnership with various industrial sectors. A strong collaboration with Airbus Group Innovations (AGI) had led to a common entity through the NDT laboratory for Aeronautics Applications (LC2A).
With the increasing portion of composite materials in the aerospace industry, assessment of the adhesive bonding properties of such composite structures is a key issue. Various aspects could decrease the quality of bonding, such as the surface contamination, non-optimal thermal cycle or external mechanical stresses. However, conventional NDT techniques are often not sensible to such damages in the adhesive bonds.
Non-linear ultrasonic methods such as wave mixing, harmonic generation or non- linear imaging appear as promising techniques to detect kissing bonds and pre-damaging that could occur in adhesive bonds. The objective of this postdoc position is to develop NDT innovative solutions for the assessment of the adhesion quality by means of experimental techniques based on such non-linear methods.
This post-doc position will be carried out in the framework of an international research program on the adhesion bonding. The candidate will work in the NDE laboratory for Aeronautics Applications located in Toulouse. Strong skills in experimental physics, instrumentation, and non-linear ultrasonics would be appreciated.

Development of a compact XRF for online analysis dedicated to process monitoring.

X-ray fluorescence (XRF) spectrometry is a well-known analytical technique for elemental analysis in an industrial context. In a simplified way, this technique is based on the measurement of X-radiation characteristics that are emitted by the atoms rearranging their electron cloud following an external stimulus. This is a non-destructive measurement relevant for the determination of chemical elements within liquid and solid mixture. In the 90s, the work conducted by the CEA has shown the relevance of XRF for the measurement of heavy elements using L-edge, (U, Pu, Am, Np, Cm, Pb) as well as lighter ones (Zr, Mo, Sr) using K-edge. Low detection limits (few mg/l) have been reached and the method has been implemented industrially for monitoring several processes (for instance at La Hague plant). However, operating a XRF requires heavy and cumbersome equipment, especially a nitrogen-cooled detector and a large X-Ray generator.
Recently the technology has been significantly improved on two key issues:
• The X-rays sources, which were miniaturized,
• The detectors thanks to new type of semiconductor of small volumes, operating at room temperature with a convenient spectral resolution (CdZnTe crystals for instance).
In this framework, the proposed subject concerns new R&D studies on potentialities offered by these improvements, regarding two application fields:
• On-line monitoring in reprocessing process.
• Screening of the contaminant in the polluted soils before remediation in a decommissioning context