High-power low-Q RF ESR resonator for pulse techniques

A new type RF ESR resonator for pulse techniques was developed. The resonat or is an LC circuit that consists of a single turn coil (inner diameter, 45 mm) and ceramic capacitors. A two-turn coil-shaped polyethylene tube is lo cated inside of the loop and an aqueous sodium chloride solution is perfuse d into the tube at a rate of 6 cm(3)/min. Its resonant frequency is approxi mately 300 MHz, with a Q of less than 70. Using this resonator, pulsed-long itudinally detected ESR measurements of a phantom (inner diameter, 20 mm) c ontaining a triaryl methyl spin probe were performed. The Q value was suffi ciently low for irradiation over wide frequency band in the pulsed radiowav e where the pulse width was 200 ns. The apparatus tan handle a sufficient h igh power (maximum, 100 W) adjusted according to the sample size.