Characterization of XIA UltraLo-1800 Response to Measuring Charged Samples for Dark Matter Backgrounds

Radon daughter plate-out and subsequent alpha particle measurements are distorted by embedded charge in polyethylene, influencing dark matter studies. We characterized an XIA UltraLo-1800 Alpha Particle Counter to study and mitigate the response of measured alpha energy peaks and alpha detection efficiency to embedded charge. We found no correlation between measurements and electrostatic potential directly below the alpha source, but a high granularity electric field map could be used to model the effects of the energy peak within the ~-70 V/cm to ~0 V/cm region. A correlation for alpha detection efficiency remains unclear. We showed that predicting such effects was possible in a Geant4-based simulation framework to varying degrees of effectivity. We also demonstrated the effectiveness of an anti-static fan to eliminate the charge and bring measurements of energy peak and alpha detection efficiency to within 3.74% and 0.695% of the control, respectively. A 97.73% efficiency was recovered.