water purification and radium and radon assay techniques (sno) jacques farine laurentian university...
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Water Purification and Radium and Radon assay techniques (SNO)
Jacques Farine
Laurentian University
LRT04 13 December 2004 Sudbury
Time concentration factor: ~ 2 x 10-6 s (talk-equiv.)/s (R+D work)
MnOx Bassam AharmimHTiO Xiongxin DaiRadon Richard Lange
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Reactions in SNO
- Good measurement of e energy spectrum- Weak directional sensitivity 1-1/3cos()- e only.
- Measure total 8B flux from the sun.- Equal cross section for all types
NCxx
npd
ES -- ee x x
- Low Statistics - Mainly sensitive to e,, some sensitivity to and
- Strong directional sensitivity
CC-eppd e
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SNO Run Sequence
1. Pure D2O
– Good CC sensitivity
2. Added Salt in D2O
– Enhanced NC sensitivity
3. Neutral Current Detectors– 3He proportional counters in the
D2O
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
n 3He p t
n 35Cl 36Cl … e (E = 8.6 MeV)
n d t … e (E = 6.3 MeV)
The Three Phases
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Low Energy Backgrounds
“Photodisintegration” (pd)
+ d n + pIndistinguishable from NC !Technique: Radiochemical assay
Light isotropy 24Na “activation”
“Cherenkov Tail”Cause: Tail of resolution, or
Mis-reconstructionTechnique: U/Th calib. source
Monte Carlo
Daughters in U or Th chain •decays• decays
24Na
Must know U and Th concentration in D2O
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Low Energy Background: Target levels
Target levels
gTh/g gU/g
D2O(0.4 n/T/y)
3.7 10-15 4.5 10-14
H2O 3.7 10-14 4.5 10-13
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Measuring the U and Th ConcentrationI. 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
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Analysis Flow (Simplified) — Phase II
Data
Instrumental Bkg Cut
Energy, isotropy, neutron
calibrations
Signal Decomposition: CC, NC, ES
Residual Background
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Part I. EX-situ techniques
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The Radon assay techniqueNIM A 517 1-3 139-153
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Radon monitor degassers
H2O
D2O
58+-10% at 19 LPM 62+11-9% at 21 LPM
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The Radon Collection and Concentration Apparatus
SNO’s Lucas Cell
Bgnd: 5 counts/dayCntg eff: 74% per alpha
To concentrator:100.5+-2.3%
Concentrator to LC:62+-3%
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Count rate spectrumRn from D20
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Radon systematics (in %)
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Kd = [Ra] solid/[Ra] aqueous ~= 106
contradicting requirements !
The MnOx Radium assay techniqueNIM A 501 2-3 399-417
0.01
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TEM of the MnOx coating on acrylic beads
Top view (width 7.7 m) Side view (w=0.8 m)
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Radon and thorondetection efficiencyversus pressure
Radon and thorondetection efficiencyversus high voltage
Compared to simulation
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∏ −=i j
ilj
jj il
imimLF
j
)!(
)())(exp(
)(
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:
Lj (i) : number of counts in interval i for isotope j
j=1,2,3,4 for 218Po, 216Po, 214Po, 212Po
∏∑≠=
−−
= −−=
i
jKK jk
ktti
jiEBiEj
Bj
eeA
ttm1
11
1 )()0(
),(λλ
λ
λε λλ
MnOx Data Analysis
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MnOx Data Analysis, continued
212Po
216Po
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MnOx SensitivityThorium chain (224Ra): 5 x 10-16 gTh/g
Uranium chain (226Ra): 2 x 10-16 gU/g
Sensitivity to the Actinium chain demonstrated (223Ra):
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MnOx Systematics
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R&D : Reduction of the ESC’s Background
Replace all joints with custom-made teflon gaskets
Surface contamination removal
Some counters used for developmentStrip 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”.
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R&D : Reduction of the ESC’s Background
Date Type+ Pressure mbCounting time
dCPD 214Po CPD 216Po 224Ra dpd 226Ra dpd
Reference values before actions
08/04/2004BGND"C" NF
(P=2626)19.25 13.90.8 2.50.4 9 (8-10) 60 (57-62)
After EDTA cleaning
28/08/2004BGND"C" NF(P=2439)
17.75 12.50.9 1.20.3 6 (5-7) 29 (26-33)
After Teflon conversion
17/09/2004BGND"C" NF(P=2628)
13.03 6.10.7 1.50.3 5 (4-6) 18 (15-21)
ESC#9
ESC#7
Date Type+ Pressure mbCounting time d
CPD 214Po CPD 216Po 224Ra dpd 226Ra dpd
Reference values before actions
19/05/2004BGND"C" (P=3439)
19.25 61.12.2 9.10.8 40 (36-44) 292 (283-301)
After Teflon conversion
08/10/2004BGND"C" (P=3435)
9.67 26.51.7 8.20.9 43 (40-46) 117 (109-125)
After EDTA cleaning
10/11/2004BGND"C" (P=3435)
10.88 27.21.6 10.21.0 46 (43-49) 97 (90-105)
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R&D : Calibration of the ESC’s using Th spike
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0
100
200
300
400
500
Counts/3h
Time (d)
212Po 216Po 212Bi
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R&D : Calibration of the ESC’s using Th spike
0 10 20 30 40 50 60 70 80 90
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
Relative efficiency vs. 26 mbar
N2 pressure (mbar)
216Po 212Po
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Assay and Purification of Ultra-low Level Radioactivity using
Hydrous Titanium Oxide Adsorbent(HTiO)
Xiongxin Dai
University of Carleton
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Modified HTiO procedure for 228Th, 224Ra and 226Ra in SNO water
Total chemical efficiencies: Ra: 508%; Th: 28%Total efficiencies: 307% for 226Ra; 224% for 224Ra; 12% for 228Th
- delayed coincidence liquid scintillation counter
Ra: 95%; Th: 95%
SecondaryConcentration
Elution
~ 200T D2O (or 30T H2O)
HTiO coated ultrafilters
15 L 0.1M HCl
100 ml 0.25M EDTA (pH 10) 50 ml 4M H2SO4
12.0 g of Dowex 50WX8 resin
4.0 g of Dowex 1X8 resin
Dissolve in 2 ml conc. HCl
Extraction
Counting
ThRa
Ra
Ra
Ra
Ra
Ra
Ra
Th
Th
Th
Th
Th
ThRa: 90%; Th: 65%
Ra: 58%; Th: 45%
Th chain: 455%U chain: 6010%
Co-precipitation with HTiO
Co-precipitation with HTiO
80 ml 0.5M HCl, and evaporateTh
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Radium and thorium assay for leaching test
Total chemical efficiencies: Ra: 8610%; Th: 88 10
%- delayed coincidence liquid
scintillation counter
Elution
< 15 L of water sample
Add 1-2 ml of 15% Ti(SO4)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: 455%U chain: 6010%
Ra: 982%Th: 955%
Ra: 9010%Th: 9010%
Total efficiencies: 5111% for 226Ra; 386% for 224Ra; 40 6 % for 228Th
Procedural blanks: 0.30.1 cph for 226Ra; <0.05 cph for 224Ra and 228Th
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Measurement of 238U in water sample
Detection limit (200-tonne assay): < 10-16 g/g
ICP-MS analysis
Elution
Water sample
HTiO coated ultrafilters
Elute U into 0.03M HNO3
Extraction
Detection
955%
9010%
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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
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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”– 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
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28 2723
+−
233 5048
+−
7634
31
+
−
7142
37
+
−
39 2622
+−
72 3330
+− 15
28
26
+
−
75 3129
+−
2629
26
+
−031208_3<36030813FR-09
<27031202030731
PDG
031208_4030730P-01
<24031208_2030729_2UFR-05
031208_1
031125
030729_1HX-91
<11040129030710UFR-01
224Ra @ EOE (dpd)
Exp- ID224Ra @ 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 waterchanged [Ra]bd/[Ra]aqat sources in systems
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Part II. in-situ analysesLight 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 moreisotropic than for single Cherenkov electrons
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• 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
MoreIsotropic
Reconstructed event position
ith PMT
jth PMT
ij
€
l =2
N (N −1)Pl
j =i +1
N
∑i =1
N −1
∑ (cosθij )
€
1 +4β4
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Calibrating the Light Isotropy Parameter
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Cherenkov Tail
New technique: Rn ‘Spikes’
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Merging ex- and in-situ
results
Merging ex-situand in-situ results
Good agreement
Th (224Ra) concentrationat the level of 4 atoms/ton
Levels below targets