Ultra-fast MM-WAVE detectors for observation of microbunching instabilities in the Diamond storage ring

The operation of the Diamond storage ring with short electron bunches using low alpha optics for generation of Coherent THz radiation and short X-ray pulses for time-resolved experiments is limited by the onset of microbunching instabilities. We have installed two ultra-fast (time response is about 250 ps) Schottky Barrier Diode Detectors sensitive to radiation within the 3.33-5 mm and 6-9 mm wavelength ranges. Bursts of synchrotron radiation at these wavelengths have been observed to appear periodically above certain thresholds of stored current per bunch. The fast response allows a bunch-by-bunch and turn-by-turn detection of the burst signal, which facilitates study of the bursts structure and evolution. In this paper we present our first results for various settings of alpha and also discuss future plans.