| 摘要 |
<p>The present invention relates to an analytic head which is intended for detecting vapours of explosive substances and comprises the following members: a housing (1) used as an outer electrode; a central electrode (2) isolated from the housing by a fluoroplastic insert (3); a fluoroplastic wall (4) for tightly dividing a drifting gap into two annular segments of a main (5) channel and a reference (6) channel; and an ionisation source (7) for the main channel. The central electrode (2) comprises a blind axial opening (8) having its bottom connected by a side channel (9) to the cavity of the reference channel drifting gap (6). The blind axial opening (8) includes, on the one hand, a vapour source of the reference substance (10) which is made in the shape of a mesh impregnated with one of the explosive substances to be detected, essentially TNT, and on the other hand, an ionisation source for the reference channel (11). The end of the drifting gap in the main (5) and reference (6) channels includes an ion collecting system of said channels or collector, wherein said collector comprises two semi-annular electrodes electrically isolated from one another (12, 13), an ionic current regulator in the shape of an electrode (14) mounted in the reference channel, and an ion trap in the shape of an electrode (15) mounted in the main and reference channels. The collector electrodes (12, 13) are connected respectively to electrometric amplifiers (16, 17) of the main and reference channels. The electrodes (1, 2) of the drifting gap are connected to an asymmetric-polarity alternating voltage generator (18) and to a compensation direct voltage generator (19) as well as to a control and signal-recording device (20). The device is connected to the outputs of the electrometric amplifiers (16, 17) and to the control inputs of the generators (18, 19). A pump (21) is further mounted at the outlet of the main and reference flow channels.</p> |
