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Purity and purification of Ar with respect to 222Rn
Hardy Simgen / Grzegorz Zuzel
Max-Planck-Institut für Kernphysik Heidelberg
Introduction
� 3 subprojects:
1: Measurement of 222Rn in commercial Ar
2: Search for clean storage tanks (no news)
3: Design, construction and test of a dedicated 222Rn purification column for LArGe (and for GERDA)
Initial 222Rn concentration in commercial argon
0.8Ar 4.6Westfalen AG
1.6Ar 4.6Westfalen AG
8.4Ar 5.0Westfalen AG
0.009Ar 4.6Westfalen AG
0.4Ar 4.6Westfalen AG
0.7Ar 4.6Westfalen AG
0.4Ar 6.0Westfalen AG
0.4Ar 5.0LINDE AG
0.3Ar 4.8Air Liquide
222Rn [mBq/m3 (STP)]QualityCompany
Ar production and distribution: Example Westfalen AG
Hörstel
Ludwigshafen
Air separation
plant
Storage in Ludwigshafen:
Distribution center for south-west Germany
222Rn emanation of storage tanks for cryogenic liquids
3.5 +- 0.2
1.8 +- 0.4
2.7 +- 0.3
65 +- 6
42 +- 2
177 +- 6
222Rn activity in saturation [mBq]
technical
technical
7.0
6.0
6.0
technical
Quality of stored gas
63 +- 30.67Westfalen
AG
4.1 +- 0.416SOL
0.9 +- 0.13LINDE
0.56 +- 0.036.3LINDE
2.7 +- 0.60.67Air Liquide
59 +- 23Westfalen
AG
specific 222Rn act. [mBq/m3]
Vol. [m3]
Tank from
Expected breakthrough curve
Volume of argon
rela
tive
222 R
n co
ncen
trat
ion Breakthrough
Small fractionleaks through
Results for liquid phase adsorption (60 g carbon trap)
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0 50 100 150 200 250
Volume of argon [m^3]
rela
tive
222
Rn
co
nce
ntr
atio
n
Leakingthrough
Breakingthroughat 5 bar
(-166 °C)
at 1 bar(-178 °C)
Results for liquid phase adsorption (60 g carbon trap)
10
135
5
8
40
20
22
25
44
Red. fact.
20 ± 230 mBq120 mBq1939.8.07
12 ± 242 mBq13 mBq18826.7.07
0.7 ± 0.20.5 mBq60 mBq22218.7.07
4.6 ± 1.10.2 mBq4.3 mBq926.6.07
2.2 ± 0.50.2 mBq6.9 mBq5824.4.07
4.0 ± 1.00.1 mBq3.3 mBq804.6.07
5.1 ± 0.60.6 mBq11 mBq12513.6.05
9.9 ± 0.4120 mBq1100 mBq2408.6.05
2.5 ± 0.30.7 mBq28 mBq16819.4.07
Leaking fract. 1/R [%]
ARn in analyzer
ARn in purifier
Volume [liter LAr]
Date
Results for liquid phase adsorption (60 g carbon trap)
0,0%
5,0%
10,0%
15,0%
20,0%
25,0%
0 50 100 150 200 250 300
Amount of argon [liter LAr]
rela
tive
222
Rn
co
nce
ntr
atio
n
old data
new data
Results for liquid phase adsorption (60 g carbon trap)
� Overall picture is unclear� 60g trap is too small for these tests
� No clear indication of breakthrough� Some hints of “leaking through”
� Same reduction for different temperature
� If breakthrough, it happens at ~175 liters LAr
⇒ 10x bigger column should be able to purify >1 m3 of LAr
New 5l column
� Filled with 600 g activated carbon
� To be used for Arpurification for filling of LArGe
� Minor modifications required
Results for liquid phase adsorption (600 g carbon trap)
490
11
130
Red. fact.
0.2 ± 0.10.1 mBq65.7 mBq20316.10.07
0.8 ± 0.50.1 mBq10.3 mBq6411.10.07
9.0 ± 3.70.1 mBq1.1 mBq19831.10.07
Leaking fract. 1/R [%]
ARn in analyzer
ARn in purifier
Volume [lit. LAr]
Date
Only statistical errors. Large systematic uncertainty, because of very low activity ⇒ Unknown blank contributions have strong impact!
Results for liquid phase adsorption (600 g carbon trap)
0%
2%
4%
6%
8%
10%
12%
14%
0 50 100 150 200 250
Amount of argon [liter LAr]
Rel
ativ
e 22
2Rn
co
nce
ntr
atio
n
Leaking fractions ~0.5%~10 times better than for the 60g column
Conclusions
�222Rn concentration in LAr depends very much on delivery chain� Intermediate storage or direct delivery?
� Large differences in tank purities� Pure 6 m3-tank identified (WARP tank)
� 60g carbon column able to� reduce 222Rn by factor ≥20� purify ~170 liters of LAr
� 600g carbon column (for LArGe) able to� reduce 222Rn by factor ~200