Abstract:
Alpha decays in the EXO-200 detector are used to measure the fraction of charged ²¹⁸Po and ²¹⁴Bi daughters created from α and β decays, respectively. ²²²Rn α decays in liquid xenon (LXe) are found to produce ²¹⁸Po+ ions 50.3 ± 3.0% of the time, while the remainder of the ²¹⁸Po atoms are neutral. The fraction of ²¹⁴Bi+ from ²¹⁴Pb β decays in LXe is found to be 76.4 ± 5.7%, inferred from the relative rates of ²¹⁸Po and ²¹⁴Po α decays in the LXe. The average velocity of ²¹⁸Po ions is observed to decrease for longer drift times. Initially the ions have a mobility of 0.390 ± 0.006 cm²/(kVs), and at long drift times the mobility is 0.219 ± 0.004 cm²/(kVs). Time constants associated with the change in mobility during drift of the ²¹⁸Po+ ions are found to be proportional to the electron lifetime in the LXe.
