Analysis of the ZR Vacuum Insulator Stack

Sandia National Laboratories (SNL) is developing ZR, a 26-MA driver for z-pinch experiments, by replacing most of the pulsed power hardware presently on Z with hardware of a new design. The accelerator was modeled using the transmission line code, Bertha, to determine the time-dependent voltage and current waveforms between stages in each of 36 modules. Bertha is an NRL-developed transmission line code. The design of the vacuum insulator stack was dictated by the drive voltages on each of four levels, the electric field stresses on the grading rings, insulator rings, and A-K rings, the field grading on each level, the interface requirements of the water lines and magnetically insulated transmission lines (MITLs), and the machine operations and maintenance requirements. The electrostatic analysis codes, ELECTRO (2D/RS) and MAXWELL (3D), were used to optimize the shape of the grading rings, insulator rings, anode and cathode conductors, and the MITL anode and cathode flares. The dynamic 3D computer codes, QUICKSILVER and EMPHASIS/NEVADA were used to optimize the designs of the stack interface at the MITL and water convolute connections, respectively. This paper will describe the insulator stack design and present the results of the electrostatic analyses.