| 摘要 |
<p>A method for detecting the presence within a larger article of a specific substance containing quadrupolar atomic nuclei includes performing tests of parts of the article by placing the article adjacent to an array of coils (10), energising with an rf source (20) the coils (10) in periods within a cyclic sequence to irradiate parts of the article with rf pulses of one or more frequencies at or close to a resonant frequency of quadrupolar atomic nuclei within the substance to be detected, connecting the coils (10) in other periods within the cyclic sequence to a phase-sensitive detecting and measuring circuit (15, 24-26) to measure response signals due to nuclear quadrupole resonances, and summing the response signals detected at corresponding instants over a number of cyclic sequences. Apparatus for detecting the presence of a specific substance analogous to the above method is also disclosed.</p> |
