Diagnostics of high-density hydrogen plasmas by diode laser absorption spectroscopy. Temperature and density of the n=2 state

Diode laser absorption spectroscopy at the Balmer-α line was applied to high-density hydrogen plasmas for detecting the n=2 state of atomic hydrogen. We evaluated the density and the temperature of the n=2 state from the broadening and the amplitude of the absorption line profile, respectively. We examined the temperature variation of the n=2 temperature after the ignition and the termination of the discharge. From the time constant of the temporal variation, we evaluated the power consumed for gas heating. We also compared the temperatures of hydrogen and deuterium. In addition, we examined the density ratio of hydrogen and deuterium at the n=2 state as a function of the mixing ratio of the feedstock H2 and D2. Based on this experiment, we propose diode laser absorption spectroscopy as a method for monitoring the D/T fuel ratio in nuclear fusion plasmas. (author)