CONSTRUCTION AND PERFORMANCE OF RIBBON-WOUND TE(011) CYLINDRICAL EPR ENDOR CAVITIES/

A robust yet sensitive Q-band (35 GHz) cavity has been designed for ro utine variable temperature electron paramagnetic resonance and electro n nuclear double-resonance measurements down to 2 K, The cavity withst ands repeated temperature cycling as well as providing high microwave energy density and magnetic-field modulation at the sample, It consist s of an aluminum or brass (plain, silver, or gold-plated) ribbon imbed ded in a cylindrical epoxy or epoxy/quartz composite with a tunable pi ston at the bottom, The cavity has all the advantages of the tradition al silver wire-wound cavity often used for Q-band measurements but is much more robust and easier to construct, The cavity suppresses degene rate resonant modes and minimizes wall eddy currents induced by field modulation, With standard Varian Q-band modulation coils, a 100 kHz mo dulation field of 27 G peak-to-peak is obtained at the sample, The cav ity Q(L)(approximate to 2500) and weak pitch signal/noise (approximate to 1000:1) with a Varian/E-110 microwave bridge are comparable to tho se obtained with either a traditional wire-wound cavity or a cavity co nstructed with a thin silver wall on an epoxy/quartz substrate, A set of parallel posts along the axis of the cavity (bidirection) form the ENDOR coil. The ''ribbon-wound'' design should be useful in EPR and EN DOR applications at frequencies higher than Q band as well. (C) 1995 A cademic Press, Inc.