Pulse-forming network

They have been used to produce nanosecond-length pulses with voltages of up to 106–107 volts and currents up to 106 amperes, with peak power in the terawatt range, similar to lightning bolts.

In a simple charged transmission-line pulse generator (animation, right) a length of transmission line such as a coaxial cable is connected through a switch to a matched load RL at one end, and at the other end to a DC voltage source V through a resistor RS, which is large compared to the characteristic impedance Z0 of the line.

High-power PFNs generally use specialized transmission lines consisting of pipes filled with oil or deionized water as a dielectric to handle the high power stress.

[1][2] A transmission line circuit which circumvented the above problem, producing an output pulse equal to the power-supply voltage V, was invented in 1937 by British engineer Alan Blumlein[3] and is widely used today in PFNs.

[1] To trigger the pulse, a switch short-circuits the line at the power-supply end, causing a negative voltage step to travel toward the load.

When the switch "fires" (closes), the network of capacitors and inductors within the PFN creates an approximately square output pulse of short duration and high power.

The combination of a high-voltage source, PFN, HV switch, and pulse transformer (when required) is sometimes called a "power modulator" or "pulser".

A pulse-forming network for an Nd:YAG laser rangefinder
The Shiva Star device at Air Force Research Laboratory , USA, which generates pulsed power for high-energy fusion power experiments. Each of the 6 radial arms is a pulse-forming line delivering a pulse of energy to the center, whose capacitors store a total of 10 MJ of energy and can create microsecond pulses of 120 kV and 6 million amperes.
Simple charged transmission-line pulse generator
Blumlein generator has the advantage that it can generate a pulse equal to the charging voltage V