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PHIL Modulator; waveform optimization

The HV waveform of the klystron has approxiumately a trapezoidal shape, and flat top uniformity is essential to minimize the electron bunches enegy dispersion, from the gun. At PHIL, for the moment, the mode is monopulse at 5Hz, but for most operational accelerators in particle physics, the gun is operating in burst mode, so a huge bunch number is emitting during the flat top. The unwanted wave amplitude, or ripple is to reduce. We are searching for ripple of some per mille of the voltage, ie less than 200V peak to peak for 200kV measured at the klystron cathode.

Among leading parameters, the Pulse Forming Network tuning of the modulator has become important. The future tuning of the PFN needs a theoretical study of coupling mecanisms of the PFN cells.

Otherwise, an automation project of the tuning is in course, planned to be achieved in 2014. A soft kernel is also to study, based on observation and signal processing of modulator waveforms.