A MODIFIED MIMS-STYLE TRANSMISSION RESONATOR FOR LOW-FREQUENCY PULSEDELECTRON-SPIN-RESONANCE

The Mims cavity is an effective sample resonator for pulsed ESR at low temperature because of its low quality factor and high filling factor . Its size, however, is inherently linked to the waveguide dimensions of the frequency band of operation, and the operation of such a conven tional unit below X-band is therefore impractical because the entire s tructure must reside within a helium cryostat (Dewar flask), A modifie d version of the Mims cavity is described that is based on ridged wave guide transmission line feeds while retaining the lambda/2 resonant st rip. The modified transitions reduce the cavity dimensions to 4 cm x 4 cm, thereby greatly facilitating compatibility with a liquid helium i mmersion Dewar flask while extending the operating frequency range dow nwards to 4.75 GHz.