Hydrogen Recycling Study with a High Temperature Target in the Divertor Simulation Experiment in GAMMA 10/PDX

Abstract

Hydrogen recycling with a high-temperature W target has been studied in GAMMA 10/PDX. The V-shaped target with W plates was heated up to 573 K and then exposed to the end-loss plasma. When the target temperature was increased from room temperature to 573 K, the intensities of the H α and H β lines almost doubled even though the electron density increased from ∼ 2.3×10 16 m −3 to ∼ 2.6×10 16 m −3 , an increase of ∼ 12%. On the contrary, the electron temperature did not change at approximately 30 eV. The vibrational temperature was ∼ 3400 K and did not change, thus suggesting that the hydrogen molecules were highly vibrationally excited and that the vibrational level did not change. The intensities of the Q1-branch of the Fulcher-α band almost doubled, thus indicating that the molecular density of hydrogen also doubled. The increase of the Balmer-line intensities with increasing target temperature may be caused by the increase in the excited hydrogen atoms produced by the dissociation of vibrationally excited molecules desorbed from the high-temperature target. This increase in excited hydrogen atoms enhances the overall hydrogen recycling.