|
Descripción
|
|
|---|---|
| The application of MRS to shallow studies, particularly in the vadose zone, requires a significant improvement in the signal to noise ratio. Several turns small dimensions loops have to be used in order to achieve a high vertical and lateral resolution. This increases the loop impedance, limiting the current intensity and making more critical the need of producing excitation pulses with a good shape. Due to the high current intensity needed to create the excitation field, the tuning system used in MRS equipment is achieved by a variation in discrete steps in the capacitive reactance, with several fixed configurations depending on the cable length and frequency. For high impedances that means a great range in the tuning frequency, which must be reduced to fit the required Larmor frequency. Finally, to improve the resolution in the very first part of the underground, the distance of the excited zone from the plane of the antenna should be optimized, to validate the dipolar approximation. Several techniques have been developed as an aid to optimize the recording parameters for shallow MRS: - A quantitative index has been derived to define the quality of the shape of the excitation pulse, as an aid to decide whether the design of the antenna should be modified. - A methodology which allows improving the tuning through an optimized configuration of the transmitter antenna. - The design and construction of a portable, low-cost device to use above ground antennas. This development has been derived using a NumisLITE Iris Instrument, though it can be applied to any other instrument. Field experiments have shown the validity of the proposed field techniques. | |
|
Internacional
|
Si |
|
Comentarios Mérito
|
POSTER PRESENTADO EN EL "4TH INTERNATIONAL WORKSHOP ON MAGNETIC RESONANCE SOUNDING". GRENOBLE (FRANCIA), 20-23 OCTUBRE DE 2009. PROCEEDING PP:53-58 (DE MOMENTO SIN ISSN/ISBN) |