Water Purification and Radium and Radon assay techniques (SNO)

1. Water Purification and Radium and Radon assay techniques (SNO) Time concentration factor: ~ 2 x 10-6 s (talk-equiv.)/s (R+D work) Jacques Farine Laurentian University LRT04 13 December 2004 Sudbury MnOx Bassam Aharmim HTiO Xiongxin Dai Radon Richard Lange

2. nReactions in SNO n + Þ + + - CC d p p e e • Good measurement of ne energy spectrum • Weak directional sensitivity1-1/3cos(q) • ne only. n + Þ + + n NC d p n x x • Measure total 8B n flux from the sun. • Equal cross section for all n types ES - - + Þ + n e n e x x • Low Statistics • Mainly sensitive to ne,, some sensitivity to n and n • Strong directional sensitivity

3. 1. Pure D2O Good CC sensitivity 2. Added Salt in D2O Enhanced NC sensitivity 3. Neutral Current Detectors 3He proportional counters in the D2O SNO Run Sequence Neutron Detection Method Capture on D CC: PRL 87, 7 (2001) NC: PRL 89, 011301 (2002) Capture on Cl PRL 92, 181301 (2004) Capture on 3He Event by event separation of CC and NC events About to start production DAQ The Three Phases n d  t g …  e (Eg = 6.3 MeV) n35Cl 36Cl g …  e (Eg = 8.6 MeV) n3He  p  t

4. Low Energy Backgrounds Daughters in U or Th chain • b decays • bg decays 24Na “Photodisintegration” (pd) g+ d  n + p Indistinguishable from NC ! Technique:Radiochemical assay Light isotropy 24Na “activation” “Cherenkov Tail” Cause: Tail of resolution, or  Mis-reconstruction Technique: U/Th calib. source  Monte Carlo Must know U and Th concentration in D2O

5. Low Energy Background: Target levels

6. Measuring the U and Th Concentration I.Ex-situ (Radiochemical Assays) • Extract parents to 208Tl, 214Bi and count progenies’ decay: 224Ra, 226Ra, 222Rn Pros: better statistics Cons: overlap with neutrino data (r,t) II.In-situ (Low energy PMT data) • Statistical separation of 208Tl and 214Bi using light isotropy Pros/cons: opposite to ex-situ III. Merge

7. Analysis Flow (Simplified) — Phase II Data Instrumental Bkg Cut Energy, isotropy, neutron calibrations Residual Background Signal Decomposition: CC, NC, ES

8. Part I. EX-situ techniques

10. The Radon assay technique NIM A 517 1-3 139-153

11. D2O Radon monitor degassers H2O 58+-10% at 19 LPM 62+11-9% at 21 LPM

12. SNO’s Lucas Cell Bgnd: 5 counts/day Cntg eff: 74% per alpha The Radon Collection and Concentration Apparatus To concentrator: 100.5+-2.3% Concentrator to LC: 62+-3%

13. Count rate spectrumRn from D20

14. Radon systematics (in %)

15. Kd = [Ra] solid/[Ra] aqueous ~= 106 contradicting requirements ! The MnOx Radium assay technique NIM A 501 2-3 399-417 0.01

16. TEM of the MnOx coating on acrylic beads Top view (width 7.7 mm) Side view (w=0.8 mm)

18. Radon and thoron detection efficiency versus pressure Radon and thoron detection efficiency versus high voltage Compared to simulation

19. MnOx Data Analysis Time spectrum is a linear combination of contributions from supported and unsupported components (Bateman) The combined likelihood function to maximize is the product of the functions: j=1,2,3,4 for 218Po, 216Po, 214Po, 212Po Lj (i) : number of counts in interval i for isotope j

20. MnOx Data Analysis, continued 212Po 216Po

21. MnOx Sensitivity Thorium chain (224Ra): 5 x 10-16 gTh/g Uranium chain (226Ra): 2 x 10-16 gU/g Sensitivity to the Actinium chain demonstrated (223Ra):

22. MnOx Systematics

23. R&D : Reduction of the ESC’s Background Replace all joints with custom-made teflon gaskets Surface contamination removal Some counters used for development Strip 3 mm by chemical attack • 85 liters of EDTA, 0.1 M, pH=10 • Disassemble the chamber, wipe with methanol and cover with PP bolts the threads to avoid contact with EDTA • Put the chamber in the 18” OD tank • Fill the 18” OD tank with UPW (Rinse the chamber 2 times) • Fill with EDTA and let the chamber to soak in for 2h, agitate • Rinse the chamber with UPW, 3 times • Use Methanol to wash and dry the chamber • Assemble the chamber and start a BGND”C”.

24. R&D : Reduction of the ESC’s Background ESC#9 ESC#7

25. R&D : Calibration of the ESC’s using Th spike

26. R&D : Calibration of the ESC’s using Th spike

27. Assay and Purification of Ultra-low Level Radioactivity usingHydrous Titanium Oxide Adsorbent(HTiO) Xiongxin Dai University of Carleton

28. Extraction Ra: 95%; Th: 95% ~ 200T D2O (or 30T H2O) Ra Th HTiO coated ultrafilters Ra Th Elution Ra: 90%; Th: 65% 15 L 0.1M HCl Ra Th Secondary Concentration 12.0 g of Dowex 50WX8 resin Ra: 58%; Th: 45% Th Ra 100 ml 0.25M EDTA (pH 10) 50 ml 4M H2SO4 Th Ra Co-precipitation with HTiO Co-precipitation with HTiO Th 4.0 g of Dowex 1X8 resin Ra Th Dissolve in 2 ml conc. HCl 80 ml 0.5M HCl, and evaporate Ra Th Counting - delayed coincidence liquid scintillation counter Th chain: 455% U chain: 6010% Modified HTiO procedure for 228Th, 224Ra and 226Ra in SNO water Total chemical efficiencies: Ra: 508%; Th: 28% Total efficiencies:307% for 226Ra; 224% for 224Ra; 12% for 228Th

29. Extraction < 15 L of water sample Ra: 982% Th: 955% Add 1-2 ml of 15% Ti(SO4)2 solution Titrate with NaOH to pH 9; Ra and Th co-precipitate with HTiO Elution Trap HTiO precipitate onto small ultrafilter Ra: 9010% Th: 9010% Elute Ra and Th into 10 ml of 0.5M HCl - delayed coincidence liquid scintillation counter Th chain: 455% U chain: 6010% Counting Radium and thorium assay for leaching test Total chemical efficiencies: Ra: 8610%; Th: 88 10% Total efficiencies:5111% for 226Ra; 386% for 224Ra; 40 6% for 228Th Procedural blanks:0.30.1 cph for 226Ra; <0.05 cph for 224Ra and228Th

30. Extraction 955% Water sample HTiO coated ultrafilters Elution Elute U into 0.03M HNO3 9010% Detection ICP-MS analysis Measurement of 238U in water sample Detection limit (200-tonne assay): < 10-16 g/g

31. Purification of radioactivities using HTiO adsorbent - Targets: Ra, Pb, U and Th isotopes - Sample types: Water, salt and liquid scintillator etc - Purification methods: • HTiO co-precipitation • HTiO loaded-ultrafiltration • HTiO loaded-resin

32. Link Assays Results to n data • Multiple sources model • Identify other sources in the systems • System’s history (flow rate, flow path, times ...) • Reconstruct time profile of activityin fiducial volumen DAN • Identify other sources: “Peristaltic assays” • D2O systems idle for long periods - all valves closed • Study Ra leach rate of isolated components • Procedure: • drain/vents on closed subsystem - use to draw/return D2O • mount a MnOx column + use a peristaltic pump - no contact with D2O

34. Subsystem Salt Phase After desalination Exp- ID 224Ra @ EOE (dpd) Exp- ID 224Ra @ EOE (dpd) UFR-01 030710 040129 <11 HX-91 030729_1 031125 031208_1 UFR-05 030729_2 031208_2 <24 P-01 030730 031208_4 PDG 030731 031202 <27 FR-09 030813 <36 031208_3 Peristaltic Assays - Results Prior to salt addition < 16 dpd Salt brine assayed - no Th added Most of the activity is gone with the salt Cl and Na in water changed [Ra]bd/[Ra]aq at sources in systems

35. Phase I: • CC, NC, ES: Single e • Phase II: • CC, ES: Single e • NC: Mostly multiple e’s gmultiplicity means PMT hit pattern for neutron events more isotropic than for single Cherenkov electrons Part II. in-situ analysesLight isotropy

36. ith PMT Reconstructed event position ij jth PMT More Isotropic • The rotationally invariant “Legendre Polynomial Isotropy Parameter”: • where • was chosen for its good separation of the CC and NC signal and the ease of systematic characterization

37. Calibrating the Light Isotropy Parameter

38. Cherenkov Tail New technique: Rn ‘Spikes’

39. Merging ex-situ and in-situ results Merging ex- and in-situresults Good agreement Th (224Ra) concentration at the level of 4 atoms/ton Levels below targets