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Phd Towards a next generation of CMB experiments based on KID technology (M/W)

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Français - Anglais

Date Limite Candidature : lundi 11 juillet 2022

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General information

Reference : UMR5821-CHRVEL-119
Workplace : GRENOBLE
Date of publication : Monday, June 20, 2022
Scientific Responsible name : Andréa Catalano
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2022
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly

Description of the thesis topic

New generation of mm and sub-mm experiments requires high-throughput and large fields of view optical designs to increase the mapping speed. From the instrumental point of view, this implies basically four axis of development in the case of the KID technology:
1) Large scale focal plane development with tens of thousands of photon noise limited detectors.
2) Developments of low power consumption readout electronics with very high multiplexing factors.
3) Large optical elements (mirrors and lenses).
4) Very good control of systematics errors induced by the technology.
To better follow each of these points, we have recently reinforced the KID-GIS activities by equipping a new millimeter laboratory at LPSC. This laboratory is installed in the LPSC project hall and it is expected to work in parallel with the one already operating at the Institut Néel and IRAM. In this new laboratory we plan to focus our activities on items 2), 3), 4) thanks to fundings from CNES, Labex Focus and Labex ENIGMASS. Although Point 2) will be managedby the LPSC electronics service (see companion Focus proposal DMM-LTC-2022-CH), the millimeter laboratory will be used as support for cold tests. For the next two years the main R&Ds will be focused on:
1) Silicon Lenses : Anti reflection coating (AR) techniques dedicated to big lenses. This can be performed via the use of a specific milling machine that we will acquire in 2022 thanks to a Labex ENIGMASS funding. Once designed and fabricated, these optical elements have to be tested and validated in the laboratory prior to the integration in new instruments and installation in situ. This milling equipment can be used for instruments in different fields, other than related to the KID's technology. In particular, these developments can represent a mandatory step to a participation in large CMB collaborations such as CMB-S4 and Litebird.
2) Control of the Systematic effects for polarisation measurements:
LEKID detectors used on photometers have shown strong performance potential in the wavelength range between 200μm and 3mm (100GHz to 1.5THz). On the contrary, the problem of controlling the beam in polarisation and the associated systematic effects have arisen. In addition, the control of instrumental cross-polarization is an open point. In the framework of a CNES R&T we proposed to study the performance in polarisation and the systematics related to a particular configuration which consists in placing 2 LEKID arrays perpendicular to each other where each of these matrices allows polarization measurement at 90° relative to each other. A 45° polarizer plate works in transmission or in reflection on one or the other of the matrices. There is no loss of photons during the detection process. In order to make this characterisation we need to develop a test bench that must lower and control systematic effects (control of the lobe, absence of source polarization effects,....). The results of this study will be compared with other polarimeter configurations which are used (or plan to be used) in current or future experiments.
Description of the PhD work:
The main objective of the proposed PhD thesis is to mitigate in any possible way limiting systematics effects for the next generation of CMB experiments. This will require identification and modeling of systematics, detailed high precision in-lab measurements, careful characterization of instrumental properties related to these systematics, and development of calibration procedures during operations.
In this context the proposed work consists of previous two key R&Ds but more in general in most of the activities of the GIS. The candidate will help the design and test of the new prototype of the Silicon lenses. She/he will test new arrays of detectors and she/he studies in detail the problem to qualify LEKIDs and annex optics for future experiments. The student will participate also in the design and evolution of the new high resolution instrument devoted to CMB observations, which are under study within the GIS.
Finally, the student will be introduced to the "LiteBIRD" collaboration by participating in the design of the ground calibrations. LPSC is responsible for the spectral and polarization ground characterization of MFT and HFT instruments.

- Description détaillée des objectifs et des tâches considérées :
The person recruited as a PhD student will join the LPSC cosmology group and will work in close collaboration with our local colleagues from Institut Néel. He will be in charge of specific tasks as:
1) She/He will actively participate in the experimental activities of the group listed before through daily work in the millimeter laboratory at the LPSC and at the Institut Néel.
2) Based on the previous work, she/he will define the main scientific requirements for the new instrument in close collaboration with the instrumental and analysis teams. He/she will proceed also to the optimization of key instrumental and survey parameters like overall sensitivity and observation time, frequency coverage and sampling, polarization capabilities, and sky coverage.

3) She/He will also join the LiteBIRD collaboration. Other promoting our instrumental and scientific solutions, she/he will gain expertise in accurate systematic characterization and modelling. She/he will be able to apply the development of the test bench for spectral and polarisation ground characterisation. The project has already finished Phase A1 at CNES, and it is today in a Phase A2 expected to last until the end 2022. The timing for the student will be therefore perfect for the student. Furthermore, within the framework of the LiteBIRD collaboration she/he will have the opportunity to interact and collaborate with best CMB scientists all around the world

Work Context

The Laboratory of Subatomic Physics and Cosmology of Grenoble (LPSC) (http://lpsc.in2p3.fr) is a joint research unit associating CNRS-IN2P3, the University of Grenoble Alpes (UGA) and Grenoble INP, for an average staff of about 230 people.
The researcher will be assigned to the COSMO-ML team composed of 4 researchers, 2 PhD students and 1 postdoc, under the responsibility of Frédéric Mayet
His thesis director will be Andréa Catalano, Alessandro Monfardini (Institut Néel) will be the co-supervisor.

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