Recent Progress with the KWISP Force Sensor

TL;DR

The paper reports on the development, calibration, and initial testing of the KWISP force sensor designed to detect solar Chameleons via their pressure on a micromembrane, achieving high sensitivity and conducting preliminary searches.

Contribution

It introduces a new opto-mechanical force sensor with high sensitivity for detecting solar Chameleons and presents initial experimental results and a novel chameleon chopper prototype.

Findings

Force sensitivity of 1.5 x 10^{-14} N/√Hz achieved

Successful calibration and initial off-beam testing

Preliminary searches for solar Chameleons conducted

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) Si$_3$N$_4$ micromembrane thanks to their direct coupling to matter. A thermally-limited force sensitivity of $1.5 \cdot 10^{-14}~\mbox{N}/\sqrt{\mbox{Hz}}$, corresponding to $7.5 \cdot 10^{-16}~\mbox{m}/\sqrt{\mbox{Hz}}$ 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.