The Design of Magnetically Insulated Transmission Lines

The design of vacuum power feeds for high-power accelerators requires the use of magnetically insulated transmission lines (MITLs) for efficient power coupling. In MITLs, the self-magnetic field is strong enough to trap field emitted electrons near the cathode and prevent catastrophic electron losses. This requires a low enough impedance to have sufficient current to give the needed magnetic field. Analytic design tools have been developed over the last 25 years that are now being complemented by multi-dimensional E&M PIC calculations. We will describe the evolution of vacuum feed design starting with non-emissive vacuum power feeds and ending up with MITLs. We provide a heuristic, analytic approach to MITL design for high-power accelerators. The design tools have been benchmarked against 2-D E&M PIC codes. We will use the Screamer circuit code to model a high-power accelerator and show how Screamer provides the necessary information to design a high-power MITL.