Current Status and Future Prospects of the SNO+ Experiment

Table 3

²³⁸U- and ²³²Th-chain levels for external background sources. Shown are measured levels and expected decay rates.

Source	Measured levels	Decays/yr
Internal ropes	^214Bi:  /g [37]	4966
	^208Tl: <2.0 × 10^−10 /g [37]	<418
Hold-down ropes	^214Bi:  /g [37]
	^208Tl:  /g [37]
Hold-up ropes	^214Bi:  /g [37]
	^208Tl:  /g [37]
Water shielding	^214Bi:  /g [38]
	^208Tl:  /g [38]
Acrylic vessel	^214Bi: <1.1 × 10^−12 /g [7]
	^208Tl: <1.1 × 10^−12 /g [7]
Acrylic vessel external dust	^214Bi:  /g [39]
	^208Tl:  /g [39]
Acrylic vessel internal dust	^214Bi:  /g [39]
	^208Tl:  /g [39]
PMTs	^214Bi: 100 ×  /PMT [7]
	^208Tl: 100 ×  /PMT [7]

Assumed  g/g.
It is assumed that the top hemisphere of the external AV surface is not cleaned, while the bottom hemisphere is at target level.