Automated induction heating of quartz for in situ cosmogenic 14C measurements
Miss Cody Paige1, Dr. John Gosse1, Mr. Jim Wilson2, Dr. Liam Kiesler3, Dr. Maarten Lupker4
1Dalhousie University, Halifax, Canada, 2Aeon Laboratories, Tuscon, USA, 3A. E. Lalonde Laboratory, Ottawa, Canada, 4ETH Zurich, Zurich, Switzerland
A new C-14 extraction line laboratory at Dalhousie University (DCELL) builds on recent innovations from other labs and introduces two additional features to improve process blank levels and reproducibility. DCELL is an automated, ultra-high vacuum stainless steel extraction system that uses induction heating to extract C-14 from quartz. A 10-kW induction furnace is used to heat cleaned fine quartz sand in one or more platinum tubes within a sapphire combustion chamber so that masses >5 g may be possible. Heating is controlled with two system-integrated pyrometers with overlapping temperature ranges (200-1500°C and 800-2300°C). The pyrometers are safely positioned 30 cm from the induction coil for an off-axis sensing with a radius of ~2 mm on the surface of the tubes. Tests with different platinum boat geometries inside a test sapphire tube (ID 3 cm) appear to suggest that Pt-tubes are optimal. Safe ramp speeds of 50°C/s and platinum boat surface temperatures of >1600°C were achieved (STP, no quartz) with less than 25% of available power. While tests are required to verify the complete transformation of quartz to cristobalite for carbon diffusion from the quartz, DCELL may be able to achieve the complete extraction in less than 1 hour at temperatures above the commonly cited 1650°C threshold. The released gasses are purified to CO2 using an automated process through a stainless steel line which uses only metallic fittings (no carbon-bearing seals, only copper gaskets in conflat fittings and copper tips in the pneumatically operated valves). Liquid nitrogen variable temperature traps, an optional quartz bead heater, an Ag-Cu furnace, and helical LN trap are all automated, and system parameters are logged during the complete run. We will report results of induction furnace experiments to determine if there is any real improvement in sample throughput rate, process blank, and experiment reproducibility.
Cody completed her undergraduate degree at Queen’s University, Canada, in Engineering Physics. She holds a Master of Applied Science from the University of Toronto in Aerospace Engineering and is currently completing a Ph.D. in Earth Science at Dalhousie University focusing on improving Carbon-14 extraction methods and the use of C-14 for erosion rate calculations in Panamint Valley, California. Cody is concurrently completing a Ph.D. in Astronautics at MIT with a focus on enabling a permanent human presence on the Moon.