Inductive Adder for Nanosecond-Scale High Voltage Pulses into Low-Impedance Loads

Enclosure for the 35-kV inductive adder constructed for ONR.

EHT inductive adders allow for high voltage pulses into 50 Ω loads with nanosecond-scale rise times. This topology offers many advantages:

  • All drive components are ground referenced eliminating switching jitter issues and the complexity associated with floating gate drive.
  • Output pulses defined by input pulses to gates (pulse width and pulse repetition frequency agility).
  • Modular design: Identical modules all switch same voltage and current are triggered simultaneously.
  • Scalable to higher voltage by adding more modules.
  • Can drive wide range of loads.
  • Load voltage is almost completely independent of the load.

EHT has built an inductive adder for the Office of Naval Research (ONR) that is designed for driving nonlinear transmission lines (NLTLs) for high power microwave production.  The initial unit could produce 35 kV pulses with adjustable pulse width (40 – 100 ns) and fast rise times (11 ns). This unit could do short bursts at pulse repetition frequencies up to 1 MHz.

35 kV output pulses into 50 load (700 A) with 11 ns rise time with 40 ns (left) and 100 ns (right) pulse widths.

The next generation unit for ONR is under construction and will have the following specs:

  • Output voltage: At least 30 kV into a 50 Ω load
  • Adjustable output pulse width: 25-100 ns
  • Output rise time: 12 ns or less
  • Energy per pulse: 1.8 J at 30 kV
  • Input power: 15 kW DC supply provided by EHT
  • PRF at 12 kW and 100 ns PW: 6 kHz
  • PRF at 12 kW at 25 ns PW: 25 kHz
  • Duty cycle: pulser will operate at least 2 seconds continuously, once every 2 minutes

Applications for inductive adders:

  • High power microwave production
  • Radar applications
  • Stripline kickers and pickups for accelerators
  • Klystron driving