Update on 222 Rn emanation measurements
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GERDA general meeting, Padova Italy, 11- 13.03.2009 Update on 222 Rn emanation measurements S. Lindemann, H. Richter, H. Simgen, G. Zuzel MPI für Kernphysik, Heidelberg
description
Update on 222 Rn emanation measurements. S. Lindemann, H. Richter, H. Simgen, G. Zuzel MPI für Kernphysik, Heidelberg. Outlook. 222 Rn detection technique New results – laboratory samples New results – GERDA cryostat Conclusions and future activities. 222 Rn detection technique. - PowerPoint PPT Presentation
Transcript of Update on 222 Rn emanation measurements
GERDA general meeting, Padova Italy, 11-13.03.2009
Update on 222Rn emanation measurements
S. Lindemann, H. Richter, H. Simgen, G. Zuzel
MPI für Kernphysik, Heidelberg
GERDA general meeting, Padova Italy, 11-13.03.2009
Outlook
222Rn detection technique New results – laboratory samples New results – GERDA cryostat Conclusions and future activities
GERDA general meeting, Padova Italy, 11-13.03.2009
222Rn detection technique
Töpler pump
PusherHg diff.pump
P10Ar
Charcoal trap for He purification
with flowmeter
He
Getter pump
Molecular sieve trap
Si-Getrap
Chromo-sorb trap
Radon transport
trap
NaOHtrap
To the pump
To the bubbler
Counter flange
Ma
in li
ne
Pressure gauge
- Developed for the GALLEX/GNO experiment- Hand-made at MPI-K (~ 1 cm3 active volume)- In case of 222Rn only α-decays are detected 50 keV threshold - bcg: 0.1 – 2 cpd - detection efficiency of ~ 50%- Special filling line needed (blank value of ~10 µBq)- Absolute detection limit ~ 30 µBq (15 Rn atoms)
GERDA general meeting, Padova Italy, 11-13.03.2009
222Rn detection technique
Emanation chambers
MoREx
GERDA general meeting, Padova Italy, 11-13.03.2009
New results – laboratory samples
Sample Emanation rate Remarks
Steel plates without welds < 0.1 mBq
<0.4 mBq/m2
4 plates, ~0.26 m2
(brushed, acetone wiping)
Steel plates with welds< 0.1mBq
<0.03 mBq/m4 plates, 3.2 m, 62 A
(brushed, acetone wiping)
Delrin < 50 µBq Cylinder, 380 cm2, 43 g
PT100 sensors (6.6 0.5) Bq/piece Steel encaps., 10 pieces
Lenght measuring device (0.36 0.03) mBq Cryostat
CF-40 flange with a glass window < 20 µBq Cryostat
Shutter valve (0.92 0.03) mBq Cryostat
Three-axial cryo-line (LN2/LAr) (0.25 0.04) mBq Cryo-infrastructure
Molecular sieve zeolite Z10* (2.2 0.1) Bq/kg WARP, air prepurification
Molecular sieve zeolite Z4** (0.12 0.01) Bq/kg WARP, air dehydrattion
*) CRa226 = (5.4 0.2) Bq/kg**) CRa226 = (7.8 0.3) Bq/kg – only small 222Rn fraction is emanated
GERDA general meeting, Padova Italy, 11-13.03.2009
New results – laboratory samples
PT100Welds
MS
Welds
GERDA general meeting, Padova Italy, 11-13.03.2009
New results – laboratory samples
Delrin
MS
GERDA general meeting, Padova Italy, 11-13.03.2009
New results – laboratory samples
Three-axial line
Shutter
GERDA general meeting, Padova Italy, 11-13.03.2009
New results – GERDA cryostat
Sample description
Single results [mBq]
Av. value [mBq]
Comments
1st test, SIMIC in Nov. 2007
16.9 1.6stat 3.0sys
29.8 2.4stat 5.8sys
23.3 3.6Empty cryostat after cleaning, no N2 mixing prior to extractions
2nd test, SIMIC/GS in March 2008
13.6 0.7stat 2.4sys
13.7 0.7stat 2.7sys
13.7 1.9 Empty cryostat, after additional cleaning performed at SIMIC
4th test, GS in June 2008
33.0 2.8stat 7.0sys
35.7 2.9stat 8.8sys
34.4 6.06 weeks after the 3rd test. Results indicate residual air-born Rn present in the cryostat during 3rd test.
Goal: ARn 14 mBq
It has been decided to clean the cryostat (wiping)
GERDA general meeting, Padova Italy, 11-13.03.2009
New results – GERDA cryostat
Cryostat after cleaning
Sampling on the top and from the bottom (polyamide tube 8 m 81mm, ARn < 71 µBq)for 222Rn (in)homogeneity check
Precise pressure drop (after sampling) measurement -> systematic error reduction
MoREx
Cryostat
P
GERDA general meeting, Padova Italy, 11-13.03.2009
New results – GERDA cryostat
Measurement procedure: Taking a small sample (4 m3) from the bottom Taking a small sample (4 m3) from the top Adding cold, 222Rn-free nitrogen (mixing) Taking a small sample (4 m3) from the bottom Taking a big sample (26 m3) from the top
To compare obtained concentrations and finally to find the total emanation rate of thecryostat one has to calculate back and normalize the measured activities taking intoaccount the amount of extracted gas and changes in the activities in the remaining 222Rn (extractions/decay/production). Doing so one gets:
Cb = (0.28 ± 0.03) mBq/m3
Ct = (0.42 ± 0.05) mBq/m3
Cb = (0.27 ± 0.05) mBq/m3
Ct = (0.23 ± 0.03) mBq/m3
A1 = (33.2 ± 4.0) mBq
A3 = (31.3 ± 5.7) mBqA4 = (27.3 ± 2.5) mBq----------------------------Aav = (30.6 ± 2.4) mBq
GERDA general meeting, Padova Italy, 11-13.03.2009
New results – GERDA cryostat
Sample description
Single results [mBq]
Av. value [mBq]
Comments
1st test, SIMIC in Nov. 2007
16.9 1.6stat 3.0sys
29.8 2.4stat 5.8sys
23.3 3.6Empty cryostat after cleaning, no N2 mixing prior to extractions
2nd test, SIMIC/GS in March 2008
13.6 0.7stat 2.4sys
13.7 0.7stat 2.7sys
13.7 1.9 Empty cryostat, after additional cleaning performed at SIMIC
4th test, GS in June 2008
33.0 2.8stat 7.0sys
35.7 2.9stat 8.8sys
34.4 6.06 weeks after the 3rd test. Results indicate residual air-born Rn present in the cryostat during 3rd test.
5th test GS in Nov. 2008
33.2 3.5stat 1.9sys
31.3 4.6stat 3.4sys
27.3 2.4stat 0.7sys
30.6 2.4After wiping of Cu / steel surface. Precise pressure reading. In the last extraction the biggest gas volume was processed
GERDA general meeting, Padova Italy, 11-13.03.2009
Conclusions
Most of the samples show acceptable 222Rn emanation rates (shutter valve, three-axial line, ...)
The impact of the last cryostat cleaning on its emanation rate was very minor (solutions -> talk of B. Schwingenheuer)
It has been shown that 222Rn was homogeneously distributed in the cryostat volume
The systematic uncertainties were significantly reduced
Further tests with a completed cryogenic infrastructure foreseen
222Rn emanation measurements of the commissioning lock (hall di montaggio)
Investigation of “cold” 222Rn emanation
