Millimeter-Wave Heating, Radiometry, and Calorimetry of Granite Rock to Vaporization

Abstract

Abstract:Millimeter-wave (MMW) technologies can provide unique heating and diagnostic capabilities to research the thermal dynamics of materials to extreme temperatures. The MMW properties of rocks in the molten state up to their vaporization temperatures are not well known. Using a 28 GHz gyrotron beam collinear with a 130 GHz radiometry view in a calorimetric chamber, the transitions of granite rock specimens through solid phases, melting, and vaporization were observed, including release of trapped trace gas (< 0.07%). The 28 GHz emissivity of molten granite was observed to be approximately constant at 0.66 ± 0.03 up to vaporization where it increased to 0.70 ± 0.03 at an equilibrated temperature of 2710 ± 120 °C. An analysis of the thermal power balance during a 76 s steady state vaporization time period indicates that the MMW emissivity of the molten granite is larger than in the infrared. The observations support the possibility that MMW thermal ablative penetration into hot crystalline rock formations could be a more practical approach than infrared laser drilling to access deep resources.

Design and high‐power test of the transmission line for millimeter wave deep drilling

“…Comparing with the conventional drilling methods, the millimeter wave is more convenient and effective, which is transmitted to the drilling face through the waveguide, and the working face rock is heated to vaporize it. The gasified rock is carried away from the working surface by the high‐pressure airflow introduced by the hollow waveguide and deposited on the well wall to form a vitreous or ceramic body for cementing purposes.…”

System Development and Performance Testing of a W-Band Gyrotron

“…Furthermore, new and interesting ideas, such as the use of a medium power gyrotron for advanced drilling technology as suggested by Woskov et al, have been proposed recently [21]. In this application, the researchers demonstrated that granite, basalt, and limestone can be melted and vaporized at temperatures over 3000 °C in a few minutes using a 28 GHz, 10 kW gyrotron [22,23].…”