Recent Progress with the KWISP Force Sensor

Abstract

The KWISP opto-mechanical force sensor has been built and calibrated in the INFN Trieste optics laboratory and is now under off-beam commissioning at CAST. It is designed to detect the pressure exerted by a flux of solar Chameleons on a thin (100 nm) Si3N4 micromembrane thanks to their direct coupling to matter. A thermally-limited force sensitivity of 1.5 10-14 N/pHz, corresponding to 7.5 10-16 m/pHz in terms of displacement, has been obtained. An originally developed prototype chameleon chopper has been used in combination with the KWISP force sensor to conduct preliminary searches for solar chamaleons.