Multiple-electrode triggered vacuum gaps

Since the design criteria for reliable operation of a single gap at 300 kV are not well known, multiple-electrode triggered vacuum gaps were constructed. A six-gap structure was initially studied. It had excessive time delay in the initiation of the arc. Subsequently, a three-gap structure was built. Time delays in initiation of the arc were satisfactory, but the rate of rise of current was slow. In addition, voltage hold-off capability was marginal. To improve these characteristics, a low pressure of hydrogen, 7 to 25 mtorr, was added. Considerably improved firing characteristics and reliable voltage hold-off at 320 kV were obtained.