Table 2.

Measured activities of radioactive isotopes in the selected cryostat and TPC materials for XENONnT as well as the cleaning agents used during assembly. Measured values are given with $\pm 1\sigma$ uncertainties, and upper limits are set at 95% C.L. The facility, sample mass, and lifetime are provided for each measurement (as applicable). Samples 18–20 are the averaged results from measurements of different sets of 10-15 PMTs fitting into the germanium spectrometer at once

Sample	Component	Manufacturer	Facility	Mass [kg]	Livetime [d]	Units	${}^{238}$U	${}^{235}$U	${}^{226}$Ra	${}^{228}$Ra (${}^{232}$Th)	${}^{228}$Th	${}^{40}$K	${}^{60}$Co	${}^{137}$Cs
Stainless Steel (304)
0	Bell/Vessel	Nironit	GeMPI	7.8	11.7	mBq/kg	13(7)	0.7(3)	0.3(1)	0.6(2)	0.5(1)	1.6(6)	2.4(2)	$<0.2$
0	Bell/Vessel	Nironit	ICP-MS	–	–	mBq/kg	3.7(6)	–	–	0.10(8)	–	–	–	–
1	Bell/Vessel	Nironit	GeMPI	7.8	57.1	mBq/kg	4(2)	$0.2{(1)}^{\ast }$	1.3(1)	0.9(1)	0.57(6)	1.4(2)	0.61(5)	0.03(2)
1	Bell/Vessel	Nironit	ICP-MS	–	–	mBq/kg	8.6(4)	–	–	$<8.1$	–	–	–	–
2	Bell/Vessel/Electrodes	Nironit	GeMPI	8.4	27.5	mBq/kg	$<11$	$<0.6$	0.6(1)	0.4(1)	0.4(1)	$<2.4$	0.4(1)	$<0.2$
2	Bell/Vessel/Electrodes	Nironit	ICP-MS	–	–	mBq/kg	2.5(3)	–	–	0.4(2)	–	–	–	–
3	Welding Rods (Vessel)	Nironit	GeMPI	2.6	30.6	mBq/kg	$<5.7$	$<0.3^{\ast }$	3.1(3)	2.9(4)	11.4(7)	7(1)	1.6(2)	$<0.3$
Oxygen-free high-conductivity copper
4	Field Shaping Rings	Luvata	Gator	71.7	32.5	mBq/kg	$<0.33$	$<0.02$	$<0.18$	$<0.22$	0.18(5)	0.45(14)	0.03(1)	$<0.05$
4	Field Shaping Rings	Luvata	ICP-MS	–	–	mBq/kg	0.03(1)	–	–	0.010(4)	–	–	–	–
5	Guard Rings	Niemet	GeMPI	56.5	42.1	mBq/kg	$<1.6$	$<0.14$	0.13(3)	$<0.06$	$<0.04$	0.6(2)	0.05(1)	$<0.03$
6	Wires	-	GeMSE	12	–	mBq/kg	$<2.3$	–	$<0.1$	$<0.06$	$<0.04$	0.55(2)	0.43(3)	$<0.04$
7	Array Support Plate	Niemet	GeMSE	93.4	35.6	mBq/kg	$<1.06$	–	$<0.21$	$<0.08$	$<0.01$	$<0.42$	0.08(1)	$<0.011$
7	Array Support Plate	Niemet	ICP-MS	–	–	mBq/kg	0.0014(4)	–	–	0.004(1)	–	–	–	–
8	Array Support Pillar	Luvata	GeMPI	57.3	26.2	mBq/kg	$<2.7$	$<0.23$	$<0.06$	$<0.08$	$<0.04$	$<0.27$	0.10(2)	$<0.05$
Plastics
9	PTFE Reflectors	Amsler and Frey	GeMPI	15.4	25.0	mBq/kg	$<2.4$	$<0.08$	$<0.03$	0.11(4)	$<0.09$	8(1)	–	$<0.07$
9	PTFE Reflectors	Amsler and Frey	ICP-MS	–	–	mBq/kg	$<0.06$	–	–	0.05(2)	–	–	–	–
10	PTFE Reflectors	Amsler and Frey	GeMPI	25.0	19.7	mBq/kg	$<1.0$	$<0.07$	0.15(3)	$<0.1$	$<0.08$	0.08(3)	–	$<0.05$
10	PTFE Reflectors	Amsler and Frey	ICP-MS	–	–	mBq/kg	0.15(7)	–	–	0.03(2)	–	–	–	–
11	PTFE Pillars	Amsler and Frey	GeMPI	15.1	45.0	mBq/kg	$<0.8$	$<0.05$	0.04(1)	$<0.06$	$<0.04$	$<0.42$	–	$<0.01$
11	PTFE Pillars	Amsler and Frey	ICP-MS	–	–	mBq/kg	0.26(9)	–	–	0.10(2)	–	–	–	–
12	PTFE PMT Holders	Amsler and Frey	GeMSE	18.2	19.9	mBq/kg	$<1.9$	–	$<0.1$	$<0.08$	$<0.04$	$<1.0$	$<0.05$	$<0.03$
13	PTFE PMT Holders	Amsler and Frey	ICP-MS	–	–	mBq/kg	$<0.1$	–	–	$<0.04$	–	–	–	–
14	Torlon Reflectors	Drake Plastics	ICP-MS	–	–	mBq/kg	1.8(5)	–	–	0.2(1)	–	–	–	–
15	Torlon Reflectors	Drake Plastics	ICP-MS	–	–	mBq/kg	2.2(6)	–	–	0.4(1)	–	–	–	–
16	PEEK Array Spacers	Spalinger	ICP-MS	–	–	mBq/kg	0.4(1)	–	–	0.12(3)	–	–	–	–
17	PEEK Screws	Solidspot	GeMPI	0.27	23.1	mBq/kg	$<20$	$<1.4$	10(1)	7(1)	6(1)	30(10)	–	$<0.8$
Photosensors and components
18	R11410 PMTs (average 180 PMTs)	Hamamatsu	Gator	–	–	mBq/PMT	9(2)	0.4(1)	0.47(2)	0.47(7)	0.46(2)	14.2(5)	1.05(3)	$<0.14$
19	R11410 PMTs (average 60 PMTs)	Hamamatsu	GeMPI	–	–	mBq/PMT	14(7)	0.5(1)	0.52(4)	0.6(1)	0.45(5)	18.6(9)	1.27(6)	$<0.13$
20	R11410 PMTs (average 99 PMTs)	Hamamatsu	GeMSE	–	–	mBq/PMT	6.5(3)	–	0.32(4)	0.33(5)	0.19(1)	11.1(4)	0.71(3)	$<0.06$
21	Ceramic Stem	Hamamatsu	GeMPI	1.5	20.7	mBq/kg	2.7(5)	0.13(2)	0.29(2)	0.17(2)	0.12(1)	2.7(3)	$<0.003$	$<0.009$
22	Ceramic Stem	Hamamatsu	GeMPI	1.6	22.8	mBq/kg	3.4(5)	0.12(2)	0.22(1)	0.20(2)	0.07(1)	0.13(2)	$<0.002$	$<0.01$
23	Bases/components	Fralock/various	GeMSE	1.9	7.0	mBq/piece	1.5(1)	–	0.7(3)	0.14(1)	0.053(3)	0.29(5)	$<0.003$	$<0.002$
24	HV Connectors/PTFE/Copper	Accu-Glass/custom	GeMSE	1.0	27.5	$\mathrm{\mu }$Bq/piece	$<310$	–	$<37$	$<42$	$<14$	140(90)	50(10)	$<3.3$
25	Coaxial Cables	Huber and Suhner	GeMPI	1.5	22.6	mBq/kg	$<74$	$<1.4$	2.4(5)	$<1.5$	1.4(5)	40(8)	$<0.2$	$<0.6$
26	Kapton Cables	Accu-glass	GeMPI	0.1	29.3	mBq/kg	$<56$	$<11$	8(2)	$<9.0$	$<3.4$	110(30)	$<3.3$	$<4.2$
27	Optical Fiber	Ratioplast	ICP-MS	–	–	mBq/kg	7(3)	–	–	7(2)	–	340(90)	–	–
Miscellaneous
28	M5 Screws (Ag), TPC	U-C Components	GeMPI	0.5	27.6	mBq/kg	$<43$	$<1.4$	$<1.1$	3(1)	3.3(6)	12(3)	53(4)	$<0.6$
29	M6 Screws (Ag), TPC	U-C Components	GeMPI	1.0	23.9	mBq/kg	$<15$	$<3.4$	$<1.6$	$<3.0$	2.7(7)	18(5)	6.7(7)	$<0.9$
30	M8 Screws (Ag), TPC	U-C Components	GeMPI	0.9	22.8	mBq/kg	50(20)	$<2.1$	2.0(5)	3.4(8)	3.9(6)	13(3)	52(4)	$<0.8$
31	M8 Screws (Ag), Bell	ALCA	GeMPI	1.2	21.6	mBq/kg	$<29$	$<0.8$	0.8(3)	2.0(5)	7.6(6)	5(2)	4.9(4)	$<0.3$
32	SMD Resistors	OHMITE	GeDSG	0.01	6.9	$\mathrm{\mu }$Bq/piece	110(50)	2.3(5)	29(2)	13(2)	15(1)	60(10)	$<1.1$	$<0.6$
Cleaning solutions
33	HARO Clean 100	HAROSOL	Corrado	1.0	9.8	mBq/kg	$<710$	$<20$	11(6)	$<18$	$<21$	4600(300)	$<8$	$<7$
34	HARO Clean 188	HAROSOL	Corrado	1.5	6.0	mBq/kg	$<24400$	–	$<35$	520(310)	$<18$	$5.8(4)\times {10}^6$	$<175$	$<133$
35	HARO Clean 106	HAROSOL	Corrado	0.6	3.1	mBq/kg	$2.1(1)\times {10}^3$	–	$<20$	$<77$	$<16$	750(160)	$<9$	$<15$
36	P3-Almeco 36	Henkel	Bruno	0.1	3.9	mBq/kg	$14(3)\times {10}^3$	790(160)	98(27)	$<91$	$<113$	$15(2)\times {10}^3$	$<19$	$<21$
37	Tickopur R33	Dr. H. Stamm	Giove	1.0	5.0	mBq/kg	$<7400$	–	36(13)	$<429$	$<11$	$1.55(9)\times {10}^6$	$<49$	$<65$
38	Elma clean 65	Elma	Giove	1.0	7.1	mBq/kg	430(200)	–	6(3)	$<12$	$<8$	1190(90)	$<1.6$	$<4$
39	Elma clean 70	Elma	Giove	1.1	2.7	mBq/kg	$<17100$	–	53(18)	$<340$	19(9)	$1.45(9)\times {10}^6$	$<65$	$<156$
40	${\text{HNO}}_3$ (69%)	Roth	Corrado	0.5	5.1	mBq/kg	$<970$	–	$<19$	$<22$	$<27$	$<80$	$<4$	$<7$