The measurement of sub-Brownian lever deflections

A micromechanical lever that deflects in response to the impacts of charged particles has previously been proposed as a means of improving upon the capabilities of existing radiation detection technology. The momentum detector offers promise as a highly discriminating, high-resolution tool for ion sensing. Advances required to successfully realize a spectroscopic capability has been completed; specifically, techniques for reproducibly fabricating micromechanical structures have been optimized, and an instrument that measures miniscule deflections has been developed. Even without substantial refinement efforts, the novel coupled-cavity optical detector can resolve lever motions on the order of 1-10 picometers. A method by which the Brownian motion of the lever can be stilled has been proven which elicits reductions sufficient to measure heavy-ion impact, the deflections from which may be several orders of magnitude below the thermal vibration amplitude. Using active forcing techniques, the Brownian vibration of the microlevers has been reduced from room temperature (288 K) to sub-Kelvin temperatures, for levers vibrating in air. The mechanical factors that limit the noise reduction magnitude are discussed and methods of surmounting those limitations are identified.