Frequency-segmented power amplification using multi-band radio frequency amplifiers to produce a high-voltage pulse.

A method of frequency-segmented power amplification using multiband radio frequency (RF) amplifiers was proposed to generate stable and arbitrary high-voltage pulses. The concept behind this method is that an arbitrary pulse with a specified duration and sharp edges can be reconstructed using only several frequencies, and most of the power is concentrated on the fundamental frequency. The high-voltage pulse can, therefore, be obtained by amplifying each segmented frequency and then combining it with the RF power combiners. To correct the frequency-dependent group delays and gain of the amplifier circuit and to perform fine-tuning of the pulse structure, a seed pulse is divided into several lines that have bandpass filters, variable delay lines, variable power attenuators, and main RF amplifiers. A prototype pulse amplifier was designed and fabricated based on this method to generate rectangular pulses for the electron beam chopper of an x-ray free-electron laser injector. Flat and stable pulses with a 2 ns width of 0.2 kV height, peak-to-peak flat top of 0.8%, and route-mean-squared peak jitter of less than 0.2% were successively generated in both single- and multi-bunch structures. In the future, this type of pulse generator will play an important role in accelerators that require complicated and precise beam handling at high repetition rates of kHz or MHz.