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621.396.67In the present article, the design of a two-spiral flat coil intended for detecting NQR signals is described. Results of calculations of its magnetic fields and field non-uniformities are presented for windings of different types. It is demonstrated that the two-spiral coil field is localized in the near-field zone and has more uniform structure than the field of the conventional spiral coil with the same radius and winding type. It is emphasized that the two-spiral coil has higher sensitivity than the analogous conventional flat coil. Results of experiments on detecting the 14 N NQR signal of urotropine C 6 H 1 N 4 with this coil are presented.

Abstraet. The data of the observation of the nuclear quadrupole resonance signal in trinitrotoluene C6H2(NO2)3CH 3 are reported. The measurements are carried out on a crude industrial sample of the Chinese manufacturing at 293 K. It is shown that the lines of the monoclinic form and probably orthorhombic forms are present in our spectra, but the most suitable lines for the detection of trinitrotoluene belong to the monoclinic form. The results of our experiments specify an opportunity of application of the pulse method of nuclear quadrupole resonance for the detection of trinitrotoluene in crude industrial samples.As it is known [1], one of the basic explosives used in industry and for military purposes is trinitrotoluene (TNT) C6H2(NO2)3CH 3. TNT has a wide range of applications in industry, especially in the mining industry. Hence, the industrial TNT is more accessible for probable terrorists in comparison with other explosives. However, the quality and parameters of the military and industrial TNT may differ [2] depending on the manufacturer. The detection of TNT by different methods is an important problem for humanitarian mine clearing and struggle against terrorism. One of the detection methods may be nuclear quadrupole resonance (NQR) [3]. One can use two methods for the NQR detection of TNT. The first meth0d is the pure pulse NQR method [1,4]. The other is the double nuclear magnetic-nuclear quadrupole resonance (double NMR-NQR) [3].For the application of double NMR-NQR the presence of the static magnetic field for proton polarization is necessary. During this experiment in the field of 0.8 T the longitudinal relaxation time of protons is T~ ~ 30 s [5]. The duration of the registration of signals for a 0.5 g sample is large despite the high sensitivity of the method [5]. However, the main defect is the necessity of the creation of a strong homogeneous magnetic fiel& These features set limits on the application of the double NMR-NQR for the purposes mentioned above.

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