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Adiabatic Pulses to Improve MRS Measurements
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 24th European Meeting of Environmental and Engineering Geophysics, Sep 2018, Volume 2018, p.1 - 5
Abstract
The Magnetic Resonance Sounding (MRS) Method allows for the direct quantification and characterization of non or weakly bounded water in near surface soil. MRS measurements in densely populated areas, like almost everywhere in central Europe, frequently cause S/R ratios of less than 1. This is why last year we have added a transmitter for the pre-polarization (PP) of the soil to our MRS apparatus MRS-MIDI-III. A field of 500 □T can be generated for several seconds within the 2 metre PP-Loop. In doing so, the nuclear magnetisation of the water within the upper 1–2 metres increases up to one magnitude. The directly following “conventional” MRS measurement then stimulates an up to 10 times greater response signal (FID). Recently we have added a further innovation to our instrument: an adiabatic pulse (AP). A Tx pulse to deviate the protons in the soil is normally constant in regards to frequency and amplitude. The specific characteristic of adiabatic pulses is that the frequency and/or current change during the pulse. Through this, the distribution of the sensitivity in the soil can be advantageously influenced and the signal amplitude increases by a factor of up to 3.