3-D PIC simulations of the convolute and inner MITL on the Z accelerator
The Z accelerator at Sandia National Laboratories delivers current pulses rising up to {approximately}20 MA in {approximately}100 ns to a Z-pinch load. The accelerator is cylindrical, with power flowing radially inward through a water pulse-forming section to the insulator stack at r {approximately} 2 m. Inside the stack, power flows along four conical, vacuum, magnetically-insulated transmission lines (MITL's) to the convolute, at r {approximately} 10 cm. The convolute couples the feed MITL currents, in parallel, into the inner MITL that drives the load. The convolute is a critical area of the vacuum power flow, because it necessarily has magnetic field nulls, which could potentially result in large electron losses. The authors have been using the 3-D, electromagnetic particle-in-cell (PIC) code QUICKSILVER to simulate the convolute and inner MITL region of Z. The simulations are done in cylindrical coordinates and accurately model the Z geometry (to stair-step accuracy). Several convolute simulations have been done, using a fixed load impedance and a 20 ns rise time on the drive pulse. They study different convolute geometries: 6-post versus 12-post, and changing post diameters. The authors have very detailed information on electron losses to the anode, both current and energy. Although they cannot yet simulate realistic pulse lengths and time-dependent load impedances, qualitative comparisons with features of some Z shots have been instructive.
- Research Organization:
- Sandia National Lab., Albuquerque, NM (US)
- Sponsoring Organization:
- US Department of Energy
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 20050995
- Country of Publication:
- United States
- Language:
- English
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