Hydrogen atom density in narrow-gap microwave hydrogen plasma determined by calorimetry

The density of hydrogen (H) atoms in the narrow-gap microwave hydrogen plasma generated under high-pressure conditions is expected to be very high because of the high input power density of the order of 104 W/cm3. For measuring the H atom density in such a high-pressure and high-density plasma, powe...

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Veröffentlicht in:Journal of applied physics 2016-02, Vol.119 (6)
Hauptverfasser: Yamada, Takahiro, Ohmi, Hiromasa, Kakiuchi, Hiroaki, Yasutake, Kiyoshi
Format: Artikel
Sprache:eng
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Zusammenfassung:The density of hydrogen (H) atoms in the narrow-gap microwave hydrogen plasma generated under high-pressure conditions is expected to be very high because of the high input power density of the order of 104 W/cm3. For measuring the H atom density in such a high-pressure and high-density plasma, power-balance calorimetry is suited since a sufficient signal to noise ratio is expected. In this study, H atom density in the narrow-gap microwave hydrogen plasma has been determined by the power-balance calorimetry. The effective input power to the plasma is balanced with the sum of the powers related to the out-going energy per unit time from the plasma region via heat conduction, outflow of high-energy particles, and radiation. These powers can be estimated by simple temperature measurements using thermocouples and optical emission spectroscopy. From the power-balance data, the dissociation fraction of H2 molecules is determined, and the obtained maximum H atom density is (1.3 ± 0.2) × 1018 cm−3. It is found that the H atom density increases monotonically with increasing the energy invested per one H2 molecule within a constant plasma volume.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4941821