Water Purification and Radium and Radon assay techniques (SNO) Jacques Farine Laurentian University LRT04 13 December 2004 Sudbury Time concentration factor:~ 2 x s (talk-equiv.) /s (R+D work) MnOxBassam Aharmim HTiOXiongxin Dai RadonRichard Lange

Reactions in SNO - Good measurement of e energy spectrum - Weak directional sensitivity  1-1/3cos(  ) - e only. - Measure total 8 B flux from the sun. - Equal cross section for all types NC xx  npd ES --  e e xx - Low Statistics - Mainly sensitive to e,, some sensitivity to  and  - Strong directional sensitivity CC - eppd  e

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

Low Energy Backgrounds “Photodisintegration” (pd)  + d  n + p Indistinguishable from NC ! Technique:  Radiochemical assay  Light isotropy  24 Na “activation” “Cherenkov Tail” Cause:  Tail of resolution, or  Mis-reconstruction Technique:  U/Th calib. source  Monte Carlo Daughters in U or Th chain  decays  decays 24 Na Must know U and Th concentration in D 2 O

Low Energy Background: Target levels Target levels gTh/ggU/g D 2 O (0.4 n/T/y) H2OH2O

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

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

Part I. EX-situ techniques

The Radon assay technique NIM A

Radon monitor degassers H2OH2O D2OD2O % at 19 LPM % at 21 LPM

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

Count rate spectrum Rn from D 2 0

Radon systematics (in %)

K d = [Ra] solid /[Ra] aqueous ~= 10 6 contradicting requirements ! The MnOx Radium assay technique NIM A

TEM of the MnOx coating on acrylic beads Top view (width 7.7  m) Side view (w=0.8  m)

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

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: L j (i) : number of counts in interval i for isotope j j=1,2,3,4 for 218 Po, 216 Po, 214 Po, 212 Po MnOx Data Analysis

MnOx Data Analysis, continued 212 Po 216 Po

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

MnOx Systematics

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  m 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”.

R&D : Reduction of the ESC’s Background DateType+ Pressure mb Counting time d CPD 214PoCPD 216Po224Ra dpd226Ra dpd Reference values before actions 08/04/2004 BGND"C" NF (P=26  26)   (8-10)60 (57-62) After EDTA cleaning 28/08/2004 BGND"C" NF (P=24  39)   (5-7)29 (26-33) After Teflon conversion 17/09/2004 BGND"C" NF (P=26  28)   (4-6)18 (15-21) ESC#9 ESC#7 DateType+ Pressure mb Counting time d CPD 214PoCPD 216Po224Ra dpd226Ra dpd Reference values before actions 19/05/2004 BGND"C" (P=34  39)   (36-44)292 ( ) After Teflon conversion 08/10/2004 BGND"C" (P=34  35)   (40-46)117 ( ) After EDTA cleaning 10/11/2004 BGND"C" (P=34  35)   (43-49)97 (90-105)

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

Assay and Purification of Ultra-low Level Radioactivity using Hydrous Titanium Oxide Adsorbent (HTiO) Xiongxin Dai University of Carleton

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

Radium and thorium assay for leaching test Total chemical efficiencies: Ra: 86  10%; Th: 88  10 %  -  delayed coincidence liquid scintillation counter Elution < 15 L of water sample Add 1-2 ml of 15% Ti(SO 4 ) 2 solution Trap HTiO precipitate onto small ultrafilter Elute Ra and Th into 10 ml of 0.5M HCl Titrate with NaOH to pH 9; Ra and Th co-precipitate with HTiO Extraction Counting Th chain: 45  5% U chain: 60  10% Ra: 98  2% Th: 95  5% Ra: 90  10% Th: 90  10% Total efficiencies: 51  11% for 226 Ra; 38  6% for 224 Ra; 40  6 % for 228 Th Procedural blanks: 0.3  0.1 cph for 226 Ra; <0.05 cph for 224 Ra and 228 Th

Measurement of 238 U in water sample Detection limit (200-tonne assay): < g/g ICP-MS analysis Elution Water sample HTiO coated ultrafilters Elute U into 0.03M HNO 3 Extraction Detection 95  5% 90  10%

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

Link Assays Results to data Multiple sources model –Identify other sources in the systems –System’s history (flow rate, flow path, times...) –Reconstruct time profile of activity in fiducial volume  DAN Identify other sources: “Peristaltic assays” –D 2 O 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 D 2 O mount a MnOx column + use a peristaltic pump - no contact with D 2 O

031208_3< FR-09 < PDG _ P-01 < _ _2UFR _ _1HX-91 < UFR EOE (dpd) Exp- ID 224 EOE (dpd) Exp- ID After desalinationSalt PhaseSubsystem 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

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

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 More Isotropic Reconstructed event position i th PMT j th PMT  ij

Calibrating the Light Isotropy Parameter

Cherenkov Tail New technique: Rn ‘Spikes’

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