High-Power Pure Steam Plasma Torch and Its Temperature Measurements

We report the generation of a high-power pure steam torch plasma operated by a 915-MHz microwave and its temperature measurements. Steam from a steam generator enters the discharge tube as a swirl gas at a temperature of ~140 °C. This steam becomes a plasma forming gas and produces a stable steam torch plasma. The torch volume is almost linearly proportional to the microwave power. The temperature of the torch flame was measured with an optical spectroscopy, analyzing the optical emissions of hydroxyl molecules ~309 nm. The plasma torch showed two distinctive regions: 1) a bright, whitish region of a high-temperature zone and 2) a reddish, dimmer region of a relatively low-temperature zone. The maximum temperature in a microwave-driven region was measured to be ~6720 K. We also investigated the plasma temperatures at the axial distances of plasma torch column.