Development of hydrogen storage electrode for plasma biasing in the Tohoku University Heliac

In the Tohoku University Heliac (TU- Heliac), a new type of hydrogen storage electrode made of a palladium (Pd) was developed. This new gold (Au)-coated palladium electrode can produce high-density plasma up to ∼40 shots per hydrogen gas charge. The Pd-Au electrode is the most useful tool for production of high-density plasma, compared with previous electrodes (Ti, V, and Pd). A reduced-size Au-coated palladium electrode was also developed. The electrode current was controllable in the lower voltage region and the controllability of electrode current in the small electrode current range was confirmed in only one discharge. Compared with the hot cathode experiments, the reduced-size Pd-Au electrode had the ability to produce a biased plasma, which was similar to the characteristics of the biased plasma by the hot cathode made of LaB₆, even though the surface area of the electrode for the plasma was much smaller than that the hot cathode.