Table 6.

Results of ${}^{222}$Rn emanation measurement to identify and replace the dominant ${}^{222}$Rn sources in the QDrive pump

#30	Bare magnets	6 pieces: 1.55 cm $\times$ 1.88 cm $\times$ 1.88 cm each Total surface: 112 cm${}^2$	$<0.021$ mBq $<1.9$ mBq/m${}^2$
#31	Magnets with epoxy coating	8 pieces: 1.55 cm $\times$ 1.88 cm $\times$ 1.88 cm each Total surface: 150 cm${}^2$	(0.37 ± 0.04) mBq (24.8 ± 2.9) mBq/m${}^2$
#32	Alternative epoxy coating for magnets (from Magnet Coating Engineering)	Cured on Cu substrate Surface: 618 cm${}^2$	(0.093 ± 0.017) mBq (1.51 ± 0.28) mBq/m${}^2$
#33	1.1mm copper wire for magnet winding	1.68 kg	$<0.097$ mBq
#34	Wingard & Co. silicon steel	6 plates (9.3 cm $\times$ 8.9 cm $\times$ 0.05 cm) Fulfills ASTM A677 standard Total: 167 cm${}^2$/29.4 g	(0.240 ± 0.040) mBq (14.1 ± 2.2) mBq/m${}^2$
#35	Dolphon CC-1105 HTC	Solventless polyester resin 396 cm${}^2$/95.4 g	(0.70 ± 0.05) mBq (17.7 ± 1.2) mBq/m${}^2$
#36	Elantas GRC 59-25 (alternative to Dolphon CC-1105 HTC)	Low viscosity hermetic varnish 398 cm${}^2$/51.9 g	(0.027 ± 0.012) mBq (0.76 ± 0.30) mBq/m${}^2$