purity and purification of ar with respect to rn

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)

Low-level proportional counter

Background for 222Rn: ~1 count/day

Mobile Radon Extraction Unit

222Rn detection limit: ~0.5 µBq/m3

Air separation plantBoilingpoints

Rn

O2

Ar

N2

Initial 222Rn concentration in commercial argon

0.8Ar 4.6Westfalen 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

Adsorption in pores

Column purification

Expected breakthrough curve

Volume of argon

rela

tive

222 R

n co

ncen

trat

ion Breakthrough

Small fractionleaks through

Experimental setup for liquid phase adsorption tests

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)


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


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


� 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

Experimental setup for liquid phase adsorption tests

New 5l column:600 g activated carbon inside

New 5l column

� Filled with 600 g activated carbon

� To be used for Arpurification for filling of LArGe

� Minor modifications required


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!


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

Extra slides

Column purification

Results for gas phase adsorption (150 g carbon trap)

26000.70.278012.4.07

>2700<0.50.201414.11.04

Reduction factor [1/kg]

Final conc. [µBq/m3]

Initial conc. [mBq/m3]

Volume[m3]

Date

222Rn removal in gas phase is very efficient

purity and purification of ar with respect to rn

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