No abstract

The wide use of electrical explosions of conductors (EEC) in science and engineering [1, 2] is making it necessary to develop new experimental methods of diagnosing the accompanying physical processes (shock waves, pulses of electromagnetic radiation, etc.). The microwave (MW) method has recently been intensively studied in connection with this need, since the propagation of microwave radiation (MWR) in various media has been the subject of much research and since the method provides accurate and reliable information. Knowledge gained thus far from studies of the main mechanisms responsible for the generation of electromagnetic radiation in low-temperature plasmas makes it possible to solve inverse problems which establish the main parameters characterizing the formation of plasmas by unsteady sources from the characteristics of recorded electromagnetic radiation [3].For example, data on the recording of electromagnetic radiation in EEC within the optical and infrared ranges was presented in [4].Use of the MW method to diagnose impulsive plasma processes in EEC requires the use of low-inertia radiometers. In connection with this, we developed a compensation-type wide-band radiometer [5] for an 8-mm wavelength (working frequency 36 Hz, band width -2% of the working frequency) to record 10-6-10 -3 see pulses of MW radiation. Decay time ranges from 10 -7 to 10 -4 see, which allows recording of the time dependence of the spectral intensity of the MWR.Here, we report experimental data obtained on this dependence for MWR from the electrical explosion of wires and contacting metallic surfaces.Copper wires 0.15 mm in diameter were electrically exploded with an initial supply voltage of 5 kV. The capacitance of the capacitor that discharged onto the wire was 2 #F. The distance from the edge of the waveguide of the radiometer to the wire was 3 cm. Figure 1 shows the experimental setup. The dashed lines outline components containing either (a) the wire 2 or (b) a hard-alloy electrode 3 and a steel plate 4. The MWR 1 from the electrical explosion of the conductor was recorded by a radiometer. The signal from the latter was then sent to a separate system for analysis. Figures 2 and 3 show signals recorded by the radiometer in the explosion of wires with lengths of 1 and 2 cm, respectively. Maximum MWR intensity in Figs. 2 and 3 corresponded to an antenna temperature -180 kK.Analysis of the resulting signals leads to the conclusion that they represent electromagnetic radiation from a discharge current, the maximum intensity of the MWR corresponding to the highest rate of current change. It is evident from Figs. 2 and 3 that the MWR from the explosion itself is separate from the MWR from the discharge associated with the radiation pause --which coincides roughly with the time of the current pause [1]. The earlier pulse is the MWR current flowing in the stillintact wire and starts the radiometer, which is operating in the slave mode. Figure 2 shows the amplitude of this pulse to be greater than the amplitude of the pulse in Fig...