1. GERDA General meeting, 18-22.02.2008 Krakow, Poland 222 Rn measurements H. Richter, H. Simgen, G. Zuzel Max-Planck-Institut für Kernphysik, Heidelberg

2. GERDA General meeting, 18-22.02.2008 Krakow, Poland Outlook Short introduction Emanation from the cryostat – Hardy’s talk Samples measured in Heidelberg: - Kalrez gaskets - Coaxial cables - Padova HV-feedthrough - Solders - Welds - Cryogenic valves - Others Future tests:

3. GERDA General meeting, 18-22.02.2008 Krakow, Poland Introduction Absolute detection limit 30 – 100 µBq (15 – 50 atoms)

4. GERDA General meeting, 18-22.02.2008 Krakow, Poland Introduction A Ra – emanation rate ( 226 Ra activity seen via 222 Rn emanation) Saturation value

5. GERDA General meeting, 18-22.02.2008 Krakow, Poland Cryostat 222 Rn emanation A tot ~ 30 mBq

6. GERDA General meeting, 18-22.02.2008 Krakow, Poland Different cryo-containers Tank from Quality of stored gas Vol. [m 3 ] 222 Rn activity in saturation [mBq] specific 222 Rn act. [mBq/m 3 ] Westfalen AGtechnical3 177  659  2 Westfalen AG6.00.67 42  263  3 SOL6.016 65  64.1  0.4 LINDE7.03 2.7  0.30.9  0.1 Air Liquidetechnical0.67 1.8  0.42.7  0.6 LINDEtechnical6.3 3.5  0.20.56  0.03 B OREXINO 114~60~ 0.5 GERDAHP65~ 30~ 0.5

7. GERDA General meeting, 18-22.02.2008 Krakow, Poland Kalrez gaskets (lock) A = (0.05  0.03) mBq

8. GERDA General meeting, 18-22.02.2008 Krakow, Poland Coaxial cables Sample descriptionEmanation rateOthers Habia teflon cable, 514 g, 346 m (0.34  0.09) mBq/kg (0.50  0.13)  Bq/m Ra: < 1.8 mBq/kg U: < 59 mBq/kg Th: < 4.7 mBq/kg Teledyne Reynolds HV cable (teflon coated) 292 g, 197 m (1.9  0.5) mBq/kg (1.8  0.5)  Bq/m Ra: < 1.3 mBq/kg U: < 9 mBq/kg Th: 6 mBq/kg

9. GERDA General meeting, 18-22.02.2008 Krakow, Poland Padova HV-feedthrough A < 0.05 mBq (vessel-side only)

10. GERDA General meeting, 18-22.02.2008 Krakow, Poland Solders 8 Cu strips 2  20 cm with solders (some tens of grams) A < 0.04 mBq

11. GERDA General meeting, 18-22.02.2008 Krakow, Poland Welds

12. GERDA General meeting, 18-22.02.2008 Krakow, Poland Welds SampleDescription Emanation rate [mBq/m] Comments 7 plates Total surface (both sides): 1.5 m 2 Weld length: 2.53 m 0.36  0.04 Standard workshop cleaning procedure (alkaline bath), optically clean. A lot of gas in the Rn samples 2 plates Total surface (both sides): ~0.4 m 2 Weld length: ~0.8 m < 0.1 After 2-hour etching (20 % *) HNO 3 + 1.7 % HF + water) and 30-min passivation (15 % HNO 3 + water). Not much gas in the Rn samples 4 platesWeld length: ~1.2 m 0.10  0.04 Electropolished (3 zones) 4 platesWeld length: ~1.2 m< 0.04Electropolished and etched

13. GERDA General meeting, 18-22.02.2008 Krakow, Poland Welds Etched and passivated plate

14. GERDA General meeting, 18-22.02.2008 Krakow, Poland Welds SampleDescription Emanation rate [mBq/m] Comments 7 plates Total surface (both sides): 1.5 m 2 Weld length: 2.53 m 0.36  0.04 Standard workshop cleaning procedure (alkaline bath), optically clean. A lot of gas in the Rn samples 2 plates Total surface (both sides): ~0.4 m 2 Weld length: ~0.8 m < 0.1 After 2-hour etching (20 % HNO 3 + 1.7 % HF + water) and 30-min passivation (15 % HNO 3 + water). Not much gas in the Rn samples 4 platesWeld length: ~1.2 m 0.10  0.04 Electropolished (3 zones) 4 plates Weld length: ~1.2 m < 0.04Electropolished and etched

15. GERDA General meeting, 18-22.02.2008 Krakow, Poland Welds Electropolished / etched plate

16. GERDA General meeting, 18-22.02.2008 Krakow, Poland Welds electropolished stainless steel etched stainless steel

17. GERDA General meeting, 18-22.02.2008 Krakow, Poland Welds electropolished stainless steelelectropolished weld

18. GERDA General meeting, 18-22.02.2008 Krakow, Poland Welds SampleDescription Emanation rate [mBq/m] Comments 7 plates Total surface (both sides): 1.5 m 2 Weld length: 2.53 m 0.36  0.04 Standard workshop cleaning procedure (alkaline bath), optically clean. A lot of gas in the Rn samples 2 plates Total surface (both sides): ~0.4 m 2 Weld length: ~0.8 m < 0.1 After 2-hour etching (20 % *) HNO 3 + 1.7 % HF + water) and 30-min passivation (15 % HNO 3 + water). Not much gas in the Rn samples 4 platesWeld length: ~1.2 m 0.10  0.04 Electropolished (3 zones) 4 platesWeld length: ~1.2 m< 0.04Electropolished and etched

19. GERDA General meeting, 18-22.02.2008 Krakow, Poland Welds SampleDescription Emanation rate [mBq/m] Comments 7 plates Total surface (both sides): 1.5 m 2 Weld length: 2.53 m 0.36  0.04 Standard workshop cleaning procedure (alkaline bath), optically clean. A lot of gas in the Rn samples 2 plates Total surface (both sides): ~0.4 m 2 Weld length: ~0.8 m < 0.1 After 2-hour etching (20 % *) HNO 3 + 1.7 % HF + water) and 30-min passivation (15 % HNO 3 + water). Not much gas in the Rn samples 4 platesWeld length: ~1.2 m 0.10  0.04 Electropolished (3 zones) 4 platesWeld length: ~1.2 m< 0.04Electropolished and etched Etching works !

20. GERDA General meeting, 18-22.02.2008 Krakow, Poland Consequences for cryostat Emanation of stainless steel: ~ 5  Bq/m 2 -----------> ~ 0.4 mBq ~80 m 2 Not treated welds: 0.36 mBq/m -----------> ~ 20 mBq 100 m Etched welds: < 2 mBq 100 m Rather conservative The aim, but probably difficult to achieve by cryostat cleaning The same range as measured activity, other sources should still be considered (flange and its components, residual dust)

21. GERDA General meeting, 18-22.02.2008 Krakow, Poland Cryogenic valves - WEKA O-ring gasket 222 Rn source Stamp gasket Emanation rate [  Bq]Diffusion rate [  Bq] Comments Teflon 75  15 < 13Original gasket PCTFE- 37  13 TRCH 1000- 43  16 222 Rn source: A = 150 mBq C ~ 1 kBq/m 3

22. GERDA General meeting, 18-22.02.2008 Krakow, Poland Cryogenic valves - KAMMER NPT / VCR connections Connection Emanation rate [  Bq]Diffusion rate [  Bq] Comments NPT 111  23 -Teflon sealed VCR ½” 53  1528  14 Full metal sealed

23. GERDA General meeting, 18-22.02.2008 Krakow, Poland Cryogenic valves - WTA “Kammprofil” gasket Teflon / In gaskets Valve statusEmanation rate [mBq] Open 2.0  0.2 Closed 0.64  0.15 Valve statusEmanation rate [mBq] Open 2.2  0.2 Closed 0.79  0.11 Teflon: In:

24. GERDA General meeting, 18-22.02.2008 Krakow, Poland Cryogenic valves - WTA Body statusEmanation rate [mBq] Not treated 1.8  0.2 Etched (BAMA) 0.11  0.04 Reduction by a factor of ~ 20 !

25. GERDA General meeting, 18-22.02.2008 Krakow, Poland Other samples SampleEmanation rate Glass wool (142 g) (20.6  0.2) mBq/kg Perbunan O-ring SIMIC (5 mm, 3.2 m) (1.8  0.4) mBq Induction sensors (10 pieces) (16  3)  Bq/piece “Micro-camera” (1 piece) < 70  Bq/piece

26. GERDA General meeting, 18-22.02.2008 Krakow, Poland Future tests Next cryostat emanation tests: in present state and after copper mounting (GS) Emanation of the lock (Munich) Routine material checks on requests Systematic investigation of different welding procedures and welds cleaning