Transcript Document

Water Purification and Radium and
Radon assay techniques (SNO)
Jacques Farine
Laurentian University
Time concentration factor:
MnOx
HTiO
Radon
LRT04
~ 2 x 10-6 s (talk-equiv.)/s (R+D work)
Bassam Aharmim
Xiongxin Dai
Richard Lange
13 December 2004
Sudbury
n Reactions in SNO
CC
n e + d  p + p + e-
- Good measurement of ne energy spectrum
- Weak directional sensitivity  1-1/3cos(q)
- ne only.
NC
n x + d  p + n +n x
- Measure total 8B n flux from the sun.
- Equal cross section for all n types
ES
nx + e -  nx + e -
- Low Statistics
- Mainly sensitive to ne,, some sensitivity to n and n
- Strong directional sensitivity
SNO Run Sequence
The Three Phases
1. Pure D2O
– Good CC sensitivity
Neutron Detection Method
Capture on D
n + d  t + g …  e (Eg = 6.3 MeV)
CC: PRL 87, 7 (2001)
NC: PRL 89, 011301 (2002)
2. Added Salt in D2O
– Enhanced NC sensitivity
Capture on Cl
n + 35Cl  36Cl + g …  e (Eg = 8.6 MeV)
PRL 92, 181301 (2004)
3. Neutral Current Detectors
–
3He
proportional counters in the
D2O
Capture on 3He
n + 3He  p + t
Event by event separation of CC and NC
events
About to start production DAQ
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
Low Energy Background: Target levels
Target
levels
D2O
gTh/g
gU/g
3.7 10-15 4.5 10-14
(0.4 n/T/y)
H2O
3.7 10-14 4.5 10-13
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
Analysis Flow (Simplified) — Phase II
Data
Instrumental Bkg Cut
Energy, isotropy,
neutron
calibrations
Residual
Background
Signal Decomposition:
CC, NC, ES
Part I. EX-situ techniques
The Radon assay technique
NIM A 517 1-3 139-153
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Radon monitor degassers
D2O
H2O
58+-10% at 19 LPM
62+11-9% at 21 LPM
The Radon Collection and Concentration Apparatus
SNO’s Lucas Cell
Bgnd: 5 counts/day
Cntg eff: 74% per alpha
To concentrator:
100.5+-2.3%
Concentrator to LC:
62+-3%
Count rate spectrum
Rn from D20
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Radon systematics (in %)
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
The MnOx Radium assay technique
NIM A 501 2-3 399-417
Kd = [Ra] solid/[Ra] aqueous ~= 106
contradicting requirements !
0.01
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
MnOx Data Analysis
Time spectrum is a linear combination of
contributions from supported and
unsupported components (Bateman)
mi (t B , t E )   i
A1 (0)
1
 j 1 (e
i
 j t B
e
 j t E
i
)
K 1
K j
k
k   j
The combined likelihood function to
maximize is the product of the functions:
LF j   exp(  m j (i ))
i
l (i )
m j (i ) j
l j (i )!
j=1,2,3,4 for 218Po, 216Po, 214Po, 212Po
Lj (i) : number of counts in interval i for
isotope j
MnOx Data Analysis, continued
212Po
216Po
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):
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
MnOx Systematics
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
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
ESC#9
Date
Type+ Pressure mb
Counting time
d
CPD 214Po
CPD 216Po
224Ra dpd
226Ra dpd
19.25
13.90.8
2.50.4
9 (8-10)
60 (57-62)
17.75
12.50.9
1.20.3
6 (5-7)
29 (26-33)
13.03
6.10.7
1.50.3
5 (4-6)
18 (15-21)
Counting time
d
CPD 214Po
CPD 216Po
224Ra dpd
226Ra dpd
19.25
61.12.2
9.10.8
40 (36-44)
292 (283-301)
9.67
26.51.7
8.20.9
43 (40-46)
117 (109-125)
10.88
27.21.6
10.21.0
46 (43-49)
97 (90-105)
Reference values before actions
08/04/2004
BGND"C" NF
(P=2626)
After EDTA cleaning
28/08/2004
BGND"C" NF
(P=2439)
After Teflon conversion
17/09/2004
BGND"C" NF
(P=2628)
ESC#7
Date
Type+ Pressure mb
Reference values before actions
19/05/2004
BGND"C"
(P=3439)
After Teflon conversion
08/10/2004
BGND"C"
(P=3435)
After EDTA cleaning
10/11/2004
BGND"C"
(P=3435)
R&D : Calibration of the ESC’s using Th spike
500
Counts/3h
400
300
200
212Po
216Po
212Bi
100
0
0.0
0.5
1.0
1.5
2.0
Time (d)
2.5
3.0
3.5
4.0
R&D : Calibration of the ESC’s using Th spike
Relative efficiency vs. 26 mbar
1.05
1.00
0.95
216
Po
212
Po
0.90
0.85
0.80
0.75
0.70
0
10
20
30
40
50
60
N2 pressure (mbar)
70
80
90
Assay and Purification of Ultra-low Level
Radioactivity using
Hydrous Titanium Oxide Adsorbent
(HTiO)
Xiongxin Dai
University of Carleton
Modified HTiO procedure for 228Th, 224Ra and 226Ra in SNO water
Extraction
~ 200T D2O (or 30T H2O)
Ra
Th
Ra
Th
Ra: 95%; Th: 95%
HTiO coated ultrafilters
Elution
Ra: 90%; Th: 65%
15 L 0.1M HCl
Ra
Th
Secondary
12.0 g of Dowex 50WX8 resin
Concentration
Th
Ra
100 ml 0.25M EDTA (pH 10)
Ra
Co-precipitation with HTiO
Ra
Dissolve in 2 ml conc. HCl
Ra
Ra: 58%; Th: 45%
50 ml 4M H2SO4
Th
Co-precipitation with HTiO
Th
4.0 g of Dowex 1X8 resin
Th
80 ml 0.5M HCl, and evaporate
Th
b- delayed coincidence liquid Th chain: 455%
U chain: 6010%
scintillation counter
Total chemical efficiencies: Ra: 508%; Th: 28%
Counting
Total efficiencies: 307% for 226Ra; 224% for 224Ra; 12% for 228Th
Radium and thorium assay for leaching test
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
Total chemical efficiencies:
Ra: 8610%; Th: 88 10 %
Counting
b- delayed coincidence liquid
scintillation counter
Th chain: 455%
U chain: 60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 and 228Th
Measurement of 238U in water sample
Extraction
Water sample
955%
HTiO coated ultrafilters
Elution
Elute U into 0.03M HNO3
Detection
9010%
ICP-MS analysis
Detection limit (200-tonne assay): < 10-16 g/g
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 n 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  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
Peristaltic Assays - Results
Subsystem
Salt Phase
Exp- ID
UFR-01
After desalination
224Ra
030710
@ EOE
(dpd)
Exp- ID
+27
040129
2823
031125
224Ra
@
EOE (dpd)
<11
+34
76
 31
HX-91
030729_1
+50
23348
+26
031208_2
+33
031208_4
UFR-05
030729_2
3922
P-01
030730
7230
+31
PDG
FR-09
031208_1
+42
71
 37
<24
+28
15
 26
7529
031202
030731
030813
<36
031208_3
<27
+29
26
 26
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
g multiplicity means PMT hit
pattern for neutron events more
isotropic than for single
Cherenkov electrons
• The rotationally invariant “Legendre
Polynomial Isotropy Parameter”:
ith PMT
Reconstructed
event position
b1 + 4 b 4
qij
where
jth PMT

More
Isotropic

2
bl 
N (N 1)
N 1 N
 P (cosq
l
ij
)
i 1 j i +1
was chosen for its good separation of the
CC and NC signal and the ease of
systematic characterization
Calibrating the Light Isotropy
Parameter
Cherenkov Tail
New technique: Rn ‘Spikes’
Merging ex-situ
and in-situ results
Good agreement
Merging exand in-situ Levels below targets
results
Th (224Ra) concentration
at the level of 4 atoms/ton