Preliminary test of the azimuthal uniformity of feed currents of a 1-MV prototype induction voltage cavity

Summary form only given. The azimuthal uniformity of feed currents would produce great effects on the output parameters and operating performance of magnetically induction voltage adder (MIVA). Thus, achieving an azimuthal uniform feed current is of great matter for MIVA cavity design. Preliminary tests of feed uniformity had been done on a 1-MV prototype induction cavity. It is noted that, the cavity was not driven by traditional pulse forming lines (PFLs). Instead, it was fed by an incorporated discharge brick, which is consisted of two 12 nF capacitors and one gas spark switch. It could provide about 5 kA pulse current with a pulse width about of 100 ns at charge of ± 20kV. The prototype cavity was tested under two different cases, with one current pulse fed alone or two pulses fed symmetrically, respectively. In each case, several different connection configurations between the azimuthal line and the cathode plate were tested in order. The results indicated that, in the case of the cavity fed just by one pulse, the best current uniformity with an azimuthal variation of 19% is acquired when the azimuthal line connects the cathode plate just at the low half circumference. When the cavity is fed by two pulses, the current uniformity become well, and a current uniformity with an azimuthal variation of 11% is easily attained. The tests results were also compared with the simulation results from a 3D transient electromagnetic model, which showed good agreements with each other. In addition, derived from the experiment waveforms, the electrical parameters of this cavity such as the geometry inductance were evaluated, to provide more information to circuit models.