High Power, Frequency Tunable, Submillimeter Wave ESR Device Using a Gyrotron as a Radiation Source

ESR device using a submillimeter wave gyrotron as a radiation source and a pulse magnet for high field up to 30 T has been constructed. Our gyrotrons (Gyrotron FU series) were developed as millimeter and submillimeter wave radiation sources and have attractive advantages for ESR spectroscopy, for example, high power and frequency tunability over broad range. The ESR device has been successfully applied to three cases of ESR measurements. In the first case, the temperature dependence of ESR was measured for a typical antiferromagnetic material MnO at the frequency of 301 GHz. In the second case, the dependence of the fine structure constant of the ruby on the magnetic field intensity was measured in the millimeter to submillimeter wave region. In these two cases, the gyrotron was operated by complete cw mode. In the final case, a pulse technique was applied to the ESR, the gyrotron was operated in pulse mode and the pulsed magnetic field was generated in the synchronized phase with the gyrotron operation.