Design of pulse power supply for klystron and its noise characterization

At SAMEER, extensive developments are being carried out in the field of high energy electron linear accelerator technology primarily for medical applications. In linacs, electrons are accelerated to fractions of light speed and such energy is derived through interaction with high power microwaves generated by Klystron in a specialized accelerating structure. These high power RF klystrons employed as RF amplifier in turn derive this energy from high voltage pulsed dc power supply commonly called as Modulator. Currently, we have our expertise in development of 15 MV linear accelerators which requires a 6 MW high power RF Klystron. The pulse generator driving this Klystron has maximum peak power rating of 14.4 MW; average power rating of 14.68 kW and discharges 74.59 Joules of energyinto the Klystron tube during each pulse.

High power pulse generator employs line type topology i.e., an E-type PFN is used as lumped equivalent of transmission line to generate the desired pulse width of 6 μs. The energy stored in PFN is discharged using a high voltage switch namely, Thyratron. This high voltage switching produces a large transient noise that is coupled with many other local electronic circuits. Apart from thyratron there are many other sources that may generate noise, so a study has been carried out to identify the noise sources in pulse generator in which exhaustive data has been collected and analyzed. This paper provides the design of discharge section of power pulse generator, data acquisition setup, noise waveforms at different locations of modulator and the interpretation of data in identifying the problem posed by high voltage systems on low voltage control systems.