Nuclear Magnetic Resonance

S. Holé, J. Lucas

With the progressive insertion of LEG researchers in LPEM from 2008 to 2011, we have worked on potential collaborative subjects with other LPEM teams. Since particularly efficient magnetic sensors were developed at LPEM we began to work on Nuclear Magnetic Resonance (NMR) at very low magnetic field (more or less the earth magnetic field) in a complete open instrumentation. That is a very challenging project since NMR signals are very small at earth field which requires high sensitive magnetic sensors, and noise is very important in open environment requiring particularly well suited instrumentation. We started from scratch with a commercial magnetic sensor (SQUID) working in liquid helium at about 4 K keeping in mind that it is a first step before using sensors developed at LPEM. We have designed a dedicated controllable superconducting switch to protect the SQUID during the magnetic polarization phase. That switch is currently under patent application consideration. We have also studied particular gradiometer in order to optimize the signal capture while reducing the noise. Figure below presents our developed instrumentation and the first NMR signal obtained few month ago in the environment shown.

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(a) Our low field Nuclear Magnetic Resonance instrumentation. (b) First observed signal in a completely open environment. (c) Part of the signal on a larger scale. The relaxation field is about 69 µT.


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