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

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 Hα and Hβ lines almost doubled even though the electron density increased from ∼ 2.3×1016 m−3 to ∼ 2.6×1016 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.