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Louis-Joseph Alain

Toutes les versions de cet article : English , français

Groupe Irrégularités

Contact :
alain.louis-joseph-AT-polytechnique.edu

+33 (0)1 69 33 46 63

Supervision of a student in MASTER 2 of physic

FT & Statiscals processing of stochastic NMR datas
The Nuclear Magnetic Resonance spectroscopy1 (NMR) is a technique widely used nowadays to determine the structure of biological or organic molecules. The NMR technique usually used is pulse Fourier transform (FTNMR). NMR stochastic2 (STONMR) is an alternative method which may offer advantages in terms of compromise between resolution and sensitivity. It consists in exciting the spin system randomly then processing the data by combining temporal Fourier transforms averaging. To deepen the limits and possibilities of STONMR, we want to model and simulate a spin system subjected to stochastic excitation and perform various treatments (frequency analysis and / or statistical…) on the simulated data. The objective of this work is to develop original ways of STONMR digital data processing for obtaining relevant 1D and 2D NMR spectra.
1) A. Abragam, The Principle of Nuclear Magnetism, Oxford university press, 1982
2) Ernst R. R. and Primas H., Helv. Phys. Acta., vol. 36, 583-600 (1963)

Scientific instruments : Low Field NMR Spectrometer

We have designed and built several NMR spectrometers, compact, wideband, high resolution, capable of operating with permanent magnets and therefore without cryogenic maintenance.

They include all radio frequency electronics (RF transmission/reception/demodulation), the low noise pre-amplification chain (LNA), programmable components (FPGA, DDS) to generate pulse sequences and frequency synthesis up to about 300MHz.

They integrate an ARM microprocessor and an FPGA to interface the spectrometer with a PC.

These NMR spectrometers are dedicated to the pedagogical teaching of NMR&MRI through their open block functional modules and their applications : for example quantification, measurement of relaxation parameters (T1, T2) or low field diffusion coefficients.

These NMR units are mobile, portable, autonomous and therefore adaptable to multiple physics experiments. A unit is used for fundamental research in relaxation experiments in the presence of light and dynamic polarization by optical pumping.

Shared liquid NMR spectrometer

I am in charge of a shared liquid nuclear magnetic resonance spectrometer for the physics and chemistry laboratories of the École Polytechnique (LCM, LSO, PICM, PMC, PMC,).

I manage, maintain and troubleshoot the instrument. I provide support to the subjects of the chemistry groups in the different laboratories.

I train students or research staff in NMR. I also work with other NMR spectrometers in laboratories for advice and/or troubleshooting.

Supervision of a PhD student -
Using a controlled NMR MASER to access Dynamic Nuclear Polarization mechanisms

Collaboration between :
Laboratoire des biomolécules - UMR7203, Département de chimie, Ecole Normale Supérieure, 24, rue Lhomond Paris
and
Laboratoire de Physique de la Matière Condensée, Ecole Polytechnique, CNRS, IP Paris, 91128 Palaiseau, France
Co-Encadrement d’un doctorant

Using a controlled NMR MASER to access Dynamic Nuclear Polarization mechanisms
Nuclear magnetic Resonance (NMR) spectroscopy is a powerful and versatile technic that is used worldwide in many fields in research, health and industry. It can provide quantitative information on structures and dynamics of a molecule. Combined with Dynamic nuclear polarization (DNP) techniques, NMR give rise to a huge increase in the sensitivity of the NMR experiments.
One of the intriguing aspects of NMR/DNP at such very high polarizations is the occurrence of strongly nonlinear effects that are directly related to the associated extremely large magnetization and interaction between the coil and a phenomenom called Radiation damping (RD).
Our project aims at investigating fundamental aspects of Dynamic Nuclear Polarization (DNP) and Nuclear Magnetic Resonance (NMR) in high magnetic fields at liquid Helium temperatures using controlled sustained maser oscillations.
Our objectives are to realize and utilize an electronic instrumentation in order to control the Radiation Damping and to develop a methodology that will allow one to access the details of the DNP mechanisms.
We propose to study in details the unconventional phenomena and characterize the erratic spin dynamics caused by the entangled RD (or its alteration using the electronic instrumentation) and dipolar field effects at cryogenic temperatures.