Development of a High Performance Arc-Heater Which Can Provide High Atomic Oxygen Density Flow

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A zirconia-coated cathode was applied to our arc-heater to achieve a flow containing high number density of atomic oxygen. In addition, multi-pass cell type highly sensitive laser absorption spectroscopy system with an external cavity was developed to enhance its sensitivity by two to three orders.1.Development of an arc-heater with a zirconia-coated zirconium cathodeThe arc-heater with an oxygen injection port located at the center of cathode (a hollow cathode) showed high erosion rate at the cathode tip and could survive only for several minuets. Therefore, we tested a zirconia-coated zirconium cathode instead and the oxygen was supplied from the cathode base via premixed gas with argon. As a result, it could operate for more than 3 hours without serious erosion. Furthermore, almost perfect dissociation of the oxygen was achieved.2.multi-pass cell type highly sensitive laser absorption spectroscopy systemTo optically access relatively low temperature but high degree of dissociation flow by the laser absorption spectroscopy method, we tested the multi-pass type sensitivity enhancement method. Although, last year, we tried the intra-cavity method, mode-hopping during the laser frequency scanning occurred too often to have the meaningful line shape of the absorbers. Therefore, this year, we tested the cavity-enhanced method, resulting in the enhancement by 400 times.