Development of the Liquid Level Meters for the PandaX Dark Matter Detector

TL;DR

This paper details the design and testing of precise liquid level meters for the PandaX dark matter detector, achieving sub-millimeter accuracy crucial for detector operation.

Contribution

It introduces a novel design of cylindrical capacitive level meters with high stability and precision for two-phase xenon detectors.

Findings

Achieved less than 0.02 mm fluctuation for short level meters.

Achieved less than 0.2 mm fluctuation for long level meter.

Demonstrated stable long-term operation during testing.

Abstract

The two-phase xenon detector is at the frontier of dark matter direct search. This kind of detector uses liquid xenon as the sensitive target and is operated in two-phase (liquid/gas) mode, where the liquid level needs to be monitored and controlled in sub-millimeter precision. In this paper, we present a detailed design and study of two kinds of level meters for the PandaX dark matter detector. The long level meter is used to monitor the overall liquid level while short level meters are used to monitor the inclination of the detector. These level meters are cylindrical capacitors custom-made from two concentric metal tubes. Their capacitance values are read out by a universal transducer interface chip and recorded by the PandaX slow control system. We present the developments that lead to level meters with long-term stability and sub-millimeter precision. Fluctuations (standard deviations) of less than 0.02 mm for the short level meters and less than 0.2 mm for the long level meter were achieved during a few days of test operation.