222 Rn measurements

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

2. 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: GERDA General meeting, 18-22.02.2008 Krakow, Poland

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

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

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

6. Different cryo-containers GERDA General meeting, 18-22.02.2008 Krakow, Poland

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

8. Coaxial cables GERDA General meeting, 18-22.02.2008 Krakow, Poland

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

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

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

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

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

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

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

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

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

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

19. Welds Etching works ! GERDA General meeting, 18-22.02.2008 Krakow, Poland

20. Consequences for cryostat ~80 m2 Emanation of stainless steel: ~ 5 Bq/m2 -----------> ~ 0.4 mBq 100 m Not treated welds: 0.36 mBq/m -----------> ~ 20 mBq 100 m Etched welds: < 0.04 mBq/m -----------> < 2 mBq 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) Rather conservative GERDA General meeting, 18-22.02.2008 Krakow, Poland

21. Cryogenic valves - WEKA 222Rn source: A = 150 mBq C ~ 1 kBq/m3 O-ring gasket 222Rn source GERDA General meeting, 18-22.02.2008 Krakow, Poland

22. Cryogenic valves - KAMMER NPT / VCR connections GERDA General meeting, 18-22.02.2008 Krakow, Poland

23. “Kammprofil” gasket Teflon / In gaskets Cryogenic valves - WTA Teflon: In: GERDA General meeting, 18-22.02.2008 Krakow, Poland

24. Cryogenic valves - WTA Reduction by a factor of ~ 20 ! GERDA General meeting, 18-22.02.2008 Krakow, Poland

25. Other samples GERDA General meeting, 18-22.02.2008 Krakow, Poland

26. 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 GERDA General meeting, 18-22.02.2008 Krakow, Poland