W BAND EPR SPECTROMETER DEVELOPMENT

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Multi-purpose variable temperature setup (2.5-300K) for wide-scan (up 7 T) W-band EPR spectroscopy has been engineered, tested, and is in operation. It is frequently improved and upgraded. Setup utilizes a vertically movable remotely controlled platform with a 95 GHz microwave bridge, a modified continuous flow Oxford cryostat CF 1200 outfitted with custom-implemented microwave, electrical and mechanical feedthroughs, modified I TC-4 Oxford temperature controller, and a multi-purpose W-band probehead with a remote tuning and a goniometer for one-axis sample rotation. The setup is suitable for High Frequency EPR spectroscopy of metalloproteins at cryogenic temperatures, including studies of single crystals of metalloproteins with submillimeter sizes. The setup is available for outside users. During the 1996 year we have designed and manufactured a new resonator for low-temperature measurements which does not show any detectable impurities signal compared with previous design. This year, progress includes 1) development of the next version of the probehead with built-in goniometer allowing 0.1 degree accuracy in sample positioning. 2) Implementing dielectric waveguide section to cut microwave and thermal losses during cryogenic EPR experiments. 3) Development of the probehead for sub-helium work.