Development of a 30 kV ferrite line pulse-sharpening system

Using saturating (soft magnetic) ferrite beads, coaxial transmission lines may be operated to give output rise-times in the range 100 ps-1 ns. A particular characteristic of the shock wave produced in the ferrite-loaded coaxial line is that the rise-time is amplitude-dependent. This is expected theoretically and is observed experimentally both in ferrite lines operated with DC current bias as well as in lines operated with an axial (e.g. solenoid-driven) magnetic bias. For a particular design of line using polyethylene heatshrink insulation, and with a solenoidal bias, the rise-time obtainable with a 50 n pulse feed falls from around 500 ps at 3 kV to around 110 ps at 1O kV. The basic question is whether the rise-time obtained using a given ferrite type continues to reduce as the pulse amplitude is increased above 1O kV. This is the principal justification for development of a 30 kV pulse system. The presentation outlines aspects of the system requiring development for operation at 30 kV, e.g. cabling, connectors, D-dot pick-offs, and the load termination