PhD CIFRE for cryogenic RF absorbers studies

High-frequency microwaves (MW) have various applications in fundamental science from particle accelerators, axion dark matter search, cosmic microwave background (CMB), radio astronomy, precision measurement of quantum electrodynamics, etc. In this wide spectrum over different research domains, MW absorbers play an essential role to reduce external and internal MW noises that could be harmful for the operation of the experiment. One yet-to-be explored research objective is cryogenic MW absorbers. The future high-luminosity particle colliders (FCCee/PERLE) may not be functional without properly designed cryogenic absorbers. Reducing noise and unwanted interference with parasitic modes in cryogenic environment will be crucial in a new axion dark matter experiment MADMAX. The LiteBird satellite for CMB measurement needs to have appropriate MW absorbers in the space i.e. 3 K cryogenic environment. Despite the pressing needs of cryogenic MW absorbers, few studies have been performed to understand the materials to be used as such absorbers. IJCLab and IAS are developing a common test-stand to perform qualification of cryogenic MW absorbers.

The test-stand will be composed of a set of commercial horn antennas and a Vector Network Analyzer to reconstruct material parameters (ϵ',ϵ'') from the scattering parameters (S11,S21). The measurement of different absorber materials is of critical importance in this project. Depending on the applications, the candidate materials are different from ceramic to more porous sponge-like materials; however, the underlined physics and testing procedure would be the same and this is exactly the new field of material research.

For the accelerator applications, one must handle high RF power of the order of 10-100 W in 70 K and particle-free environment. The historically adopted solutions are ferrite, graphite, SiC, and recently AlN. The practical issue is that the property of such materials would vary quite a lot depending on the vendors. For example, the same SiC sample of the same catalog spec of previous project does not work in the same way (RF absorption at 70 K, brazing properties, etc). One may even need to study charging up phenomenon and its mitigation by using some specific thin-film coating (TiN?) on the ceramic. The student will work the material in the test-stand to answer these fundamental questions.

For dark matter applications, one must achieve excellent RF noise level equivalent to less than 10 K noise temperature. This corresponds to noise power spectral density of 1.38e-22 W/Hz = -188.6 dBm/Hz in 4 K environment. In the so-called “open booster” system of the next MADMAX experiment by 2029, such a low-noise environment is a highly non-trivial challenge inside a cryostat under fabrication. Unlike the above accelerator applications, one does not need to cope with high-power RF and particle-free vacuum so that the more conventional RF absorbers, such as ECOSOBEs or carbon nanotubes glued on a support (options developed for CMB experiments), can be employed. Still, the mechanical and RF performances in cryogenic environment are in general with a big question mark. The student will measure the materials around 20 GHz and suggest the best option for the dark matter experiment.

All these applications are blue ocean of applied material science. The companies do not have clear answers on their products in such specific environment, i.e. cryogenics, high-frequency microwaves, and either high power of 100 W (for accelerators) or 1e-22 W/Hz (dark matter). This is the niche of the research domain.

Accelerators and Cryogenic Systems (ACS) is a company specializing in the development of particle gas pedals, superconducting technologies and cryogenic systems and equipment.

ACS was founded by members of the Institut of Physics Nuclear of Orsay (IPNO, CNRS), who previously worked at the IJClab laboratory, where the PhD student will be based. Since its inception in 2009, its engineers and scientists have developed expertise in particle gas pedals that has earned them worldwide recognition.

Profile required for the CIFRE thesis which will be involved in the field of Applied Physics & Cryogenic RF Absorbers must be : 

Education:
- Master 2 or engineering degree in applied physics, electronics, materials engineering, or a related discipline.
- In-depth technical knowledge in electromagnetism, cryogenics, and materials physics.

Technical skills :

- Solid knowledge of the principles of radiofrequency wave propagation and associated techniques.
- Good understanding of thermodynamic phenomena at low temperatures and the challenges associated with cryogenic environments.
- Knowledge of high-performance materials under extreme conditions (high thermal conductivity, low RF loss, etc.).

Experimental experience:

- Cryogenic laboratory work (handling liquid nitrogen, helium, etc.).
- Materials fabrication or characterization (micro/nanofabrication, spectroscopy, etc.).
Plus :
- Knowledge of quantum physics or statistical mechanics applied to innovative materials.
- First experience in an industrial environment or academic/industrial collaboration is an asset.