Sudbury, Canada Workshop in Low Radioactivity Techniques December 2004 Highly sensitive measurements of 222 Rn emanation and diffusion Grzegorz Zuzel Max Planck Institute for Nuclear Physics Heidelberg

Sudbury, Canada Grzegorz ZuzelLRT 2004 Outline Detection of 222 Rn Detection of 222 Rn Investigations of 222 Rn emanation Investigations of 222 Rn emanation Measurements of 222 Rn diffusion Measurements of 222 Rn diffusion Some results Some results Summary Summary

Sudbury, Canada Grzegorz ZuzelLRT 2004 Detection of 222 Rn Low-level proportional counters

Sudbury, Canada Grzegorz ZuzelLRT 2004 Developed for the GALLEX experiment Developed for the GALLEX experiment Handmade at MPI-K (ultra-pure quartz) Handmade at MPI-K (ultra-pure quartz) Active volume ~1 cm 3 Active volume ~1 cm 3 α- detection in case of 222 Rn measurements α- detection in case of 222 Rn measurements Background ~0.5 cpd for E > 50 keV Background ~0.5 cpd for E > 50 keV Detection efficiency 50% Detection efficiency 50% Special filling procedure is required Special filling procedure is required Detection of 222 Rn – counters

Sudbury, Canada Grzegorz ZuzelLRT 2004 Detection of 222 Rn – filling line Sample purification Mixing with counting Mixing with counting gas (P10) gas (P10) Counter filling Counter filling Absolute detection limit:~30 µBq limit: ~30 µBq (15 atoms) (15 atoms)

Sudbury, Canada Grzegorz ZuzelLRT 2004 Outline Detection of 222 Rn Detection of 222 Rn Investigations of 222 Rn emanation Investigations of 222 Rn emanation Measurements of 222 Rn diffusion Measurements of 222 Rn diffusion Some results Some results Summary Summary

Sudbury, Canada Grzegorz ZuzelLRT 2004 Investigations of 222 Rn emanation Emanation chambers Made out of electro-polished stainless steel Made out of electro-polished stainless steel Two of them are available: 20 l and 80 l Two of them are available: 20 l and 80 l Detection limits: 60/150 µBq Detection limits: 60/150 µBq Glass vials For small samples (up to 1 l) glass vials connected directly to the glass line can be used For small samples (up to 1 l) glass vials connected directly to the glass line can be used Detection limit: 40 µBq Detection limit: 40 µBq Emanation from “stand-alone” units or systems Tanks, purification columns, filters etc. Tanks, purification columns, filters etc. Extracted 222 Rn is collected in the charcoal traps Extracted 222 Rn is collected in the charcoal traps Detection limit: 50 µBq Detection limit: 50 µBq

Sudbury, Canada Grzegorz ZuzelLRT 2004 Investigations of 222 Rn emanation – emanation chambers

Sudbury, Canada Grzegorz ZuzelLRT 2004 Outline Detection of 222 Rn Detection of 222 Rn Investigations of 222 Rn emanation Investigations of 222 Rn emanation Measurements of 222 Rn diffusion Measurements of 222 Rn diffusion Some results Some results Summary Summary

Sudbury, Canada Grzegorz ZuzelLRT 2004 Measurements of 222 Rn diffusion Thin membranes are required Thin membranes are required Measurements can be performed for samples under different conditions Measurements can be performed for samples under different conditions Simultaneous measurements of diffusion- and solubility coefficients Simultaneous measurements of diffusion- and solubility coefficients Sensitivity for D ~ cm 2 /s Sensitivity for D ~ cm 2 /s

Sudbury, Canada Grzegorz ZuzelLRT 2004 Measurements of 222 Rn diffusion – the apparatus

Sudbury, Canada Grzegorz ZuzelLRT 2004 Diffusion profile

Sudbury, Canada Grzegorz ZuzelLRT 2004 Outline Detection of 222 Rn Detection of 222 Rn Investigations of 222 Rn emanation Investigations of 222 Rn emanation Measurements of 222 Rn diffusion Measurements of 222 Rn diffusion Some results Some results Summary Summary

Sudbury, Canada Grzegorz ZuzelLRT 2004 Selected results – 222 Rn emanation Sample description Emanation rate Stainless steel foil (4.6 ± 0.9) µBq/m 2 Teflon foil < 9 µBq/m 2 Borexino PMT < 40 µBq Activated Carbon - CarboAct (0.3 ± 0.1) mBq/kg Silicon rubber (196 ± 4) mBq/m 2 Polyurethane (< 0.3 – 40) mBq/m 2 Nitrogen stripping column (2.3 ± 0.3) mBq PC storage tank TK4 (~30 m 3 ) (25 ± 3) mBq

Sudbury, Canada Grzegorz ZuzelLRT 2004 Selected results – 222 Rn diffusion RH standard saltRH [%] D [cm 2 /s] S Permeability P [cm 2 /s] Effective permeability P eff [cm 2 /s] Mg(ClO 4 ) 2  0(2.1  0.4)×  0.7(9.5  2.3)× (5.8  1.4)× H 3 PO 4 · ½H 2 O 9  1(2.3  0.3)×  0.3(5.8  1.1)× (3.7  0.7)× LiCl 2 · H 2 O 12  1(2.2  0.3)×  0.3(4.8  0.9)× (3.0  0.6)× CaCl 2 · 6H 2 O 32  2(4.3  0.5)×  0.2(7.7  1.2)× (6.0  1.1)× Na 2 Cr 2 O 7 · 2H 2 O 52  2(1.9  0.3)×  0.2(2.7  0.6)× (2.5  0.6)× Na 2 S 2 O 3 · 5H 2 O 76  2(6.5  0.9)×  0.2(9.8  1.9)× (9.6  1.9)× K 2 CrO 4 88  3(1.3  0.2)×  0.2(2.0  0.4)× (1.9  0.4)× Na 2 SO 4 · 10H 2 O 93  3(3.3  0.4)×  0.1(3.3  0.6)× H 2 O vapors 100  3(1.3  0.2)×  0.1(9.1  2.0)× Rn diffusion, solubility and permeability coefficients as a function of relative humidity for a mm-thick nylon foil (Nylon 6, H[HN(CH 2 ) 5 CO]n OH)

Sudbury, Canada Grzegorz ZuzelLRT 2004 Selected results – 222 Rn diffusion (2)

Sudbury, Canada Grzegorz ZuzelLRT 2004 A combination of 222 Rn diffusion and emanation measurements Applied for investigations of 222 Ra content in a foil used for the construction of the Borexino Inner Vessel Applied for investigations of 222 Ra content in a foil used for the construction of the Borexino Inner Vessel Emanation from ~10 kg (~140 m 2 ) of material performed under „dry“ and „wet“ conditions Emanation from ~10 kg (~140 m 2 ) of material performed under „dry“ and „wet“ conditions Mathematical model of 222 Rn production and emanation allowed to distinguish between the surface and bulk 226 Ra contamination Mathematical model of 222 Rn production and emanation allowed to distinguish between the surface and bulk 226 Ra contamination

Sudbury, Canada Grzegorz ZuzelLRT 2004 Nylon foil in the emanation chamber

Sudbury, Canada Grzegorz ZuzelLRT 2004 Obtained 226 Ra concentrations (Sniamid) Sensitivities: Sensitivities: - surface 226 Ra conc. ~0.5 µBq/m 2 - surface 226 Ra conc. ~0.5 µBq/m 2 - bulk 226 Ra conc. ~10 µBq/kg - bulk 226 Ra conc. ~10 µBq/kg Measured: Measured: - surface 226 Ra conc. < 0.8 µBq/m 2 - surface 226 Ra conc. < 0.8 µBq/m 2 - bulk 226 Ra conc. < 21 µBq/kg - bulk 226 Ra conc. < 21 µBq/kg - total 226 Ra content: (16 ± 4) µBq/kg - total 226 Ra content: (16 ± 4) µBq/kg -> 1.3 ppt 238 U-equivalent -> 1.3 ppt 238 U-equivalent

Sudbury, Canada Grzegorz ZuzelLRT 2004 Outline Detection of 222 Rn Detection of 222 Rn Investigations of 222 Rn emanation Investigations of 222 Rn emanation Measurements of 222 Rn diffusion Measurements of 222 Rn diffusion Some results Some results Summary Summary

Sudbury, Canada Grzegorz ZuzelLRT 2004 Summary Measurements of a few 222 Rn atoms Measurements of a few 222 Rn atoms Emanation studies for sample volume up to 80 l (?00 m 2 ) with the sensitivity at the level of 40 – 150 µBq (< 0.5 µBq/m 2 ) Emanation studies for sample volume up to 80 l (?00 m 2 ) with the sensitivity at the level of 40 – 150 µBq (< 0.5 µBq/m 2 ) Measurements of 222 Rn diffusion coefficient for thin membranes at the sensitivity of ~10 13 cm 2 /s Measurements of 222 Rn diffusion coefficient for thin membranes at the sensitivity of ~10 13 cm 2 /s Several different samples are under investigations for Borexino/GERDA/GeMPI‘s... Several different samples are under investigations for Borexino/GERDA/GeMPI‘s...