Two pulsed power amplifiers operating at a nominal 250 MHz, with a minimum 400 W peak power, were designed to meet the specifications for an application in a pulsed EPR (electron paramagnetic resonance) spectrometer. A thorough search revealed that there was no commercial, off-the-shelf amplifier available that would meet the specifications. Two vendors, Communication Power Corporation of Hauppauge, New York and Tomco Technologies of Norwood, South Australia, built amplifiers to the meet the specifications, and these were extensively tested, both as stand-alone units and in the spectrometer application. A summary of the specifications and performance of both amplifiers is presented.
ABSTRACT:A pulsed power amplifier operating at a nominal 250 MHz with 2 kW (ϩ63 dBm) output was designed to meet the specifications for an application in a pulsed EPR (electron paramagnetic resonance) spectrometer and was built by Tomco Technologies of Adelaide, South Australia. Key design features were pulse fidelity for short (e.g., 40 ns) RF pulses, output noise blanking after the pulse, and output power linear with input power from very low levels up to 2 kW output. A summary of the specifications, design, and performance of the amplifier is presented. The 2 kW RF amplifier tested has approximately 12 ns rise times and 15 ns fall times, permitting the formation of approximately 40 ns RF pulses. It has negligible amplitude droop over microsecond-long pulses and negligible phase change over microsecond long pulses. There was observable but small phase change during the rise and fall times of the pulse. Even for input pulses as short as 16 ns, the output pulse peaks at more than half of the rated power output. Application to measuring the free induction decays of triaryl methyl radicals in aqueous solution was demonstrated.
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