4 sujets IRFU/DEDIP

Dernière mise à jour : 13-12-2018


• Astrophysics

• Mathematics - Numerical analysis - Simulation

• Particle physics

 

Integration of high impedance transition edge sensors (TES) for X-ray spectro-imagers for spatial astrophysics, and development of the associated multiplexing cryogenic microelectronics

SL-DRF-19-0555

Research field : Astrophysics
Location :

Département d'Electronique, des Détecteurs et d'Informatique pour la physique (DEDIP)

Laboratoire d’Intégration des Systèmes Electroniques de Traitement et d’Acquisition

Saclay

Contact :

Xavier de la BROÏSE

Jean-Luc SAUVAGEOT

Starting date : 01-10-2019

Contact :

Xavier de la BROÏSE

CEA - DSM/IRFU/SEDI/STREAM

0169084093

Thesis supervisor :

Jean-Luc SAUVAGEOT

CEA - DRF/IRFU/DAP/LSIS

0169088052

Laboratory link : irfu.cea.fr

Astrophysical research requires the development of very high performance cameras embedded in space observatories. The observation of the universe in the X-ray range (X-ray spectro-imagery) needs detectors made of matrices of micro-calorimeters operating at very low temperature (50 mK). The absorption by the detector of an X-ray photon coming from the observed celestial object causes a micro-rise in the temperature of the detector. The measurement of this temperature rise, which makes possible to determine the energy of the photon, requires ultra-sensitive micro-thermometers, and a cryogenic electronics, with very low noise, capable of reading them.

Two technologies of thermometers have been used so far : high-impedance silicon-doped metal insulator sensors (MIS), and very low impedance transition edge sensors (TES). Each requires a very specific electronics, either based on HEMT transistors for adapting to high impedances, or based on SQUIDs for adapting to very low impedances. The high impedances have the advantage of an extremely reduced heat dissipation on the detection stage, which allows a large number of pixels, while the very low impedance TES, more sensitive than the MIS, make easier to obtain excellent spectral resolutions.

A few years ago, a new type of thermometer has been developed by the CNRS/CSNSM : this is high impedance TES, potentially allowing to combine the advantages of one and the other types of detectors. A first thesis was carried out in our laboratory (2016 - 2019), with the aim of evaluating this new path by implementing it for the first time, and by associating it with an innovative readout electronics architecture that performs an active electro-thermal feedback. This thesis has highlighted the extremely promising nature of the device, by obtaining very interesting first experimental measurements.

The objective of the new thesis, proposed here, is to continue this exploratory work by going one new major stage further : validate from this new technology the feasibility of a matrix of several thousand pixels. For this, the work will focus on two parallel axes : on the one hand carry out a complete work of improvement and optimization, in order to draw from the device its best performances, and on the other hand design and test the integrated electronic system (ASIC) essential for the realization of the future large matrices.

The main difficulty lies in the conditions of implementation of the system : the detector must be placed in a cryo-generator to be cooled to very low temperature (50 mK), and equipped with a cryogenic electronics, to be designed, operating at 4 K. This one will have to ensure not only the multiplexing and the amplification of the signal but also, despite this multiplexing, the maintenance of the active electro-thermal feedback of the detectors, and this while satisfying the extremely severe noise and thermal dissipation constraints required by space cryogenics.

Component separation from multi-frequency radio-interferometric data, with application to the Epoch of Reionization (EoR) signal

SL-DRF-19-0119

Research field : Mathematics - Numerical analysis - Simulation
Location :

Département d'Electronique, des Détecteurs et d'Informatique pour la physique (DEDIP)

Laboratoire de cosmologie et statistiques (LCS)

Saclay

Contact :

Jérôme Bobin

Starting date : 01-10-2019

Contact :

Jérôme Bobin

CEA - DRF/IRFU/SEDI/LCS

0169084463

Thesis supervisor :

Jérôme Bobin

CEA - DRF/IRFU/SEDI/LCS

0169084463

Personal web page : http://jbobin.cosmostat.org

Laboratory link : http://www.cosmostat.org

With the forthcoming large-scale radio-telescopes, the need for dedicated methods to analyse radio-interferometric data is paramount in signal processing as well as in astrophysics. In this context, the quest for the cosmological signal at the epoch of reionisation mandates the use of tailored component separation methods, whose role is to decompose multi-frequency data into elementary components. Nevertheless, standard methods are not adapted to cope with radio-interferometric data: i) the data are composed of incomplete measurements in the Fourier domain and ii) the sought-after signal is overwhelmed with foreground galactic sources as well as instrumental noise. Consequently, the extraction of the EoR signal mandates the development of dedicated methods that have to tackle both a separation problem and a compressed sensing problem to deal with incomplete measurements. Furthermore, recovering such a weak signal requires designing highly precise component separation methods that account for precise physical models, which are generally parametric and non-linear. Machine Learning methods will be considered to learn complex non-linear models. Finally, as astrophysics enters the Big Data era, a particular attention will be paid to the development of computationaly efficient algorithms.

Development of an innovative muon tomography instrument for societal applications

SL-DRF-19-0246

Research field : Particle physics
Location :

Département d'Electronique, des Détecteurs et d'Informatique pour la physique (DEDIP)

DÉtecteurs: PHYsique et Simulation

Saclay

Contact :

David Attié

Starting date : 01-10-2018

Contact :

David Attié

CEA - DRF/IRFU/SEDI/DEPHYS

(+33)(0)1 69 08 11 14

Thesis supervisor :

David Attié

CEA - DRF/IRFU/SEDI/DEPHYS

(+33)(0)1 69 08 11 14

More : https://www.sciencedirect.com/science/article/pii/S0168900217308495

Muon tomography, or muography, consists in using cosmic muons to perform deep imaging of structures. These highly energetic muons, produced in showers generating from the interaction of cosmic rays with the atmosphere, can indeed cross several hundred meters of stones before being absorbed. The outstanding progress achieved in the last years on particle detectors (spatial resolution, robustness, electronics, etc.) have recently elicited a high interest for muography in many different fields.



A first muon telescope prototype was built and tested in 2015, using Micro-Pattern Gaseous Detectors (Micromegas) with a patented multiplexing scheme. The next year, three new telescopes were deployed around the Khufu's pyramid in Egypt, showing their robustness in extreme conditions (temperature, dust, etc.). Their detection of the "ScanPyramids Big Void" in combination with Japanese instruments located inside the pyramid are a world premiere for outdoors instruments.



These developments triggered the interest of many industrials and researchers for this technology. But like an optical telescope, muon telescopes are quite directional and still not very compact. An elegant solution consists in using a Time Projection Chamber (TPC), which allows for a full trajectory reconstruction with better precision and in a quasi-isotropical way.



The goal of this PhD is then to design, build and test in real conditions such an instrument. One of the main key points concerns the TPC autonomy, in particular the gas consumption, but also its overall stability in outside conditions. A sealed or semi-sealed TPC with a gas purification system, easily transportable and resistant to environmental variations would be a major breakthrough in muon tomography and for gaseous detectors in general.



Through this project, the PhD student will have the opportunity to cover a large spectrum of activities (design, integration, detector characterization, electronics, data analysis, simulation, etc.) and will then acquire skills in multiple aspects of experimental physics. The small size of the team (~6 people) will also ensure a great visibility to his/her work.

Improvement of the muon spectrometer and Z boson physics in ATLAS

SL-DRF-19-0671

Research field : Particle physics
Location :

Département d'Electronique, des Détecteurs et d'Informatique pour la physique (DEDIP)

DÉtecteurs: PHYsique et Simulation

Saclay

Contact :

Fabrice Balli

Esther FERRER RIBAS

Starting date : 01-10-2019

Contact :

Fabrice Balli

CEA - DRF/IRFU/SPP/Atlas

+33169081715

Thesis supervisor :

Esther FERRER RIBAS

CEA - DRF/IRFU/DEDIP/DEPHYS

0169083852

Laboratory link : http://irfu.cea.fr/en/Phocea/Vie_des_labos/Ast/ast_technique.php?id_ast=2225&id_unit=537

More : http://irfu.cea.fr/Pisp/esther.ferrer-ribas/

ATLAS, one of the major experiment at the LHC, is starting the preparation for the expected increase of luminosity for Run3 and HL-LHC. The work of this thesis will initially consist of analysing qualification data for the new muon detectors, which will integrate the experiment from 2020 onwards. The thesis will be followed by a measurement of precision physics in the field of the Z boson with ATLAS data.



In the first year, the student will focus on analyzing the cosmic data from the test bench for a future ATLAS detector at the LHC, the new small wheel (NSW). This detector, based on the Micromegas technology, should be installed from 2020. These new modules are necessary to monitor the expected improvement in the performance of the LHC accelerator by 2020, in terms of brightness and particle flux. Micromegas detectors, for MICRO MEsh GAseous Structure, are gaseous particle detectors, resulting from the development of wire chambers, but allowing high flow operation and simplified construction using processes derived from printed circuit board technology. Invented in 1992 by Georges Charpak and Ioannis Giomataris, Micromegas detectors are mainly used in experimental physics (particle physics, nuclear physics, astrophysics, etc.) but also for imaging projects of large structures or dense objects with cosmic rays. The work will consist in validating the modules by analyzing data on the Saclay cosmic bench and participating in the test beams at CERN.

For the other two years, the subject is focused on electroweak precision physics in ATLAS. The aim is to measure with the best possible precision the electroweak mixing angle, as well as the mass of the Z boson, using Run2 (and possibly Run3) data. The explored channel is that of the Z boson decaying into a muon-antimuon lepton pair. The student will work on muon momentum calibration using J/Psi as the standard candle, and will also reduce, through advanced fitting methods, the uncertainties related to the parton distributions functions (PDFs). These measurements should lead to a high improvement in the electroweak fit and thus significantly constrain the Standard Model, as well as Beyond Standard Model physics.

 

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