Penetrating rock with intense millimeter-waves

The use of directed energy millimeter-waves to bore into hard rock is being investigated in the laboratory as an advanced drilling technology. Experiments at 28 GHz show that with peak intensities of 1-2 kW/cm
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granite, basalt, and limestone can be melted and vaporized to over 3000 °C in a few minutes. Heating is limited by radiative heat transfer loss. Key features for practical field implementation of a gyrotron drilling system have been shown on a small scale in the laboratory.