| 摘要 |
<p>Subject of the invention is a polarisation amplified two-channel NQR/NMR (PA NQR/NMR) detection of solid and liquid explosives by using multi- pulse series, this means a two-channel detection of solid and liquid explosives based on the polarisation amplified nuclear quadruple resonance (NQR) and proton nuclear quadruple resonance (NMR). According to the invention it is possible to detect solid and liquid explosives in dug (land) mines with small metal content, in the magnitude of 0.5 g per igniter and with only 50 - 100 g of explosive. Typical of the detection of solid and liquid explosives according to the invention is that by using a magnet for previous magnetic polarization of hydrogen nuclei in the explosive in a high magnetic field B0 is not equal to zero by using fast NMR radio-frequency (RF) Carr-Purcell pulse series of the NMR channel I or can be verified whether the NMR spin-spin relaxation time T2 of the nuclei 1H is short (us) or long (ms) which is typical for liquid explosives, while in the first case for solid explosive, and in this case by using the NQR channel II by previous polarization of hydrogen nuclei at B0 does not equal zero by using a multi-pulse "spin-locking" radio-frequency series alpha 0 (tau - alpha 90 degrees - tau)n, where alpha 90 degrees means, that this pulse is phase-staggered by 90 degrees regarding the previous pulse alpha 0 and n is the number of repetitions of the basic series of the RF pulses and alpha the width of the RF pulse which optimizes the detected NQR signal in the field B0 = 0, a series of spin echoes by a single composite pulse series is obtained, and by averaging the spin echoes within one series the detection and specification time is shortened even for solid explosives through low NQR resonance frequencies by a factor of 100 and more.</p> |
