Results from a Calibration of XENON100 Using a Source of Dissolved Radon-220

Understand

A Rn-220 source is deployed on the XENON100 dark matter detector in order to address the challenges in calibration of tonne-scale liquid noble element detectors.

• We show that the Pb-212 beta emission can be used for low-energy electronic recoil calibration in searches for dark matter.
• The isotope spreads throughout the entire active region of the detector, and its activity naturally decays below background level within a week after the source is closed.
• We find no increase in the activity of the troublesome Rn-222 background after calibration.