Abstract
Microwave emission was found when materials were destroyed by a hypervelocity impact or by a static pressure. This paper describes the experimental setup to observe the phenomena, the obtained terms and results, and the possibility to apply the phenomena to geophysical explorations. As this field may not be familiar to most readers and the special techniques to receive and measure impulsive microwaves are required, the overall understanding is pursued instead of detailed description. In the receiving system, microwave signal is first amplified by a low noise amplifier, digitized in a sampling frequency high enough for the observed frequency, and then stored as data. The observed frequency was 22GHz, 2GHz, 300MHz and 1MHz. If the data storage capacity is too small to keep the data, namely at 22GHz and 2GHz, the signal is converted to a lower frequency by a heterodyne receiver and then processed to data.
In the impact experiment, the velocity is 7 km/sec at maximum. Target material was selected from metal such as aluminum or iron, ceramic, brick or rubber. In the destruction experiment due to a static pressure, four kinds of rocks were pressed with a compressor. The observed microwave is intermittent quite narrow pulses in every destruction mode. In the rock destruction due to a static pressure, 22 GHz was detected only from quartzite. As the waveforms thus obtained are almost sinusoidal in shape, we can calibrate the power through the receiving system. As a result, the average emitted power at 2 GHz was 2.7x10-5mW and 2.7x10-8mW in the hypervelocity and static pressure experiments, respectively. The cause of microwave emission is inferred to be the dissociation of atoms or molecules, but is not yet completely confirmed. Currently, the phenomena are expected to be applied to geophysical explorations in the following fields:
(1) Research of material characteristics: celestial body impacts, material science, space debris issues.
(2) Change of the underground structure: rock crush.
(3) Earthquake detection.
