arXiv subjects

M. Moulin

Publications and source records attributed to M. Moulin.

4 recordsLinked to original sources

arXiv2026

Status of the COSmological Microwave Observations CALibrator

As the sensitivity of CMB telescopes increases, the need for precise calibration becomes critical. Started in 2022, the COSMOCal project aims to place an artificial polarized source in geostationary orbit, which will serve as a reference for CMB telescopes. This source will emit at 90, 150 and 270 GHz and will be linearly polarized with a highly precise orientation smaller than 0.1 deg. This proceeding presents the scientific motivations for the project, the current status of the development of the instrument and the results of a calibration campaign performed in March 2026 at the Institut d'Astrophysique Spatiale.

astro-ph.IM↗

arXiv2018

Added mass: a complex face of tidal conversion

This paper revisits the problem of tidal conversion at a ridge in a uniformly stratified fluid of limited depth using measurements of complex-valued added mass. When the height of a sub-marine ridge is non negligible with respect to the depth of the water, the tidal conversion can be enhanced in the supercritical regime or reduced in the subcritical regime with respect to the large depth situation. Tidal conversion can even be null for some specific cases. Here, we study experimentally the influence of finite depth on the added mass coefficients for three diffierent ridge shapes. We first show that at low forcing frequency the tidal conversion is weakly enhanced by shallow depth for a semi-circular ridge. In addition, added mass coefficients measured for a vertical ridge show strong similarities with the ones obtained for the semi-circular ridge. Nevertheless, the enhancement of the tidal conversion at low forcing frequency for the vertical ridge has not been observed, in contrast with its supercritical shape. Finally, we provide the experimental evidence of a lack of tidal conversion due to the specific shape of a ridge for certain depth and frequency tuning.

physics.flu-dyn↗

arXiv2014

Flow dynamics and magnetic induction in the von-Karman plasma experiment

The von-Karman plasma experiment is a novel versatile experimental device designed to explore the dynamics of basic magnetic induction processes and the dynamics of flows driven in weakly magnetized plasmas. A high-density plasma column (10^16 - 10^19 particles.m^-3) is created by two radio-frequency plasma sources located at each end of a 1 m long linear device. Flows are driven through JxB azimuthal torques created from independently controlled emissive cathodes. The device has been designed such that magnetic induction processes and turbulent plasma dynamics can be studied from a variety of time-averaged axisymmetric flows in a cylinder. MHD simulations implementing volume-penalization support the experimental development to design the most efficient flow-driving schemes and understand the flow dynamics. Preliminary experimental results show that a rotating motion of up to nearly 1 km/s is controlled by the JxB azimuthal torque.

physics.plasm-ph↗

arXiv2007

Generation of magnetic field by dynamo action in a turbulent flow of liquid sodium

We report the observation of dynamo action in the VKS experiment, i.e., the generation of magnetic field by a strongly turbulent swirling flow of liquid sodium. Both mean and fluctuating parts of the field are studied. The dynamo threshold corresponds to a magnetic Reynolds number Rm \sim 30. A mean magnetic field of order 40 G is observed 30% above threshold at the flow lateral boundary. The rms fluctuations are larger than the corresponding mean value for two of the components. The scaling of the mean square magnetic field is compared to a prediction previously made for high Reynolds number flows.

physics.flu-dyn↗