As an example, radon concentrations are known to fluctuate seasonally, as has been noted in Ref. [10], and it was suggested that the decay of 222 Rn could lead to a seasonally dependent charge distribution on the experimental apparatus. However, this effect is extremely small given the low counting rates that typically arise from radon background [11], and in any case, the PTB data shown in Fig. 3 were corrected for background.
As an example, radon concentrations are known to fluctuate seasonally, as has been noted in Ref. [10], and it was suggested that the decay of 222 Rn could lead to a seasonally dependent charge distribution on the experimental apparatus. However, this effect is extremely small given the low counting rates that typically arise from radon background [11], and in any case, the PTB data shown in Fig. 3 were corrected for background.