Table 1.

Summary of the parameters used to identify delayed coincidences and the corresponding numerical results. As discussed in Sect. 5, the ratio between $N_P$ and $N_C$ depends on the contaminant position. Moreover, in the ${}^{232}$Th chain, the daughter selection is further constrained to detect 3 consecutive $\alpha$-decays, the third occurring with a $\Delta t>80$ ms

Decay chain	${}^{238}$U	${}^{232}$Th
Parent	${}^{222}$Rn	${}^{224}$Ra
Daughter	${}^{218}$Po	${}^{220}$Rn − ${}^{216}$Po
Parent range (keV)	$5590\pm 30$	$5789\pm 30$
Daughter range (keV)	$6115\pm 60$	–
$\Delta t_w$ (s)	930	278
$N_P$ (parent candidates)	4938	3133
$N_C$ (delayed coincidences)	4442	2030
$N_{\mathit{PP}}$/$N_{\mathit{PP}}^{\mathit{obs}}$	$48\pm 7$ / 47	$6\pm 2$ / 4