Sudbury, Canada Workshop in Low Radioactivity Techniques 12-13. December 2004 Highly sensitive...

Workshop in Low Radioactivity TechniquesWorkshop in Low Radioactivity Techniques12-13. December 200412-13. December 2004 Sudbury, CanadaSudbury, Canada

Highly sensitive Highly sensitive measurements of measurements of 222222Rn Rn emanation and diffusionemanation and diffusion

Grzegorz ZuzelGrzegorz ZuzelMax Planck Institute for Nuclear PhysicsMax Planck Institute for Nuclear Physics

HeidelbergHeidelberg

Grzegorz ZuzelGrzegorz Zuzel LRT 2004LRT 2004 Sudbury, CanadaSudbury, Canada

OutlineOutline

• Detection of Detection of 222222RnRn

• Investigations of Investigations of 222222Rn emanationRn emanation

• Measurements of Measurements of 222222Rn diffusionRn diffusion

• Some resultsSome results

• SummarySummary


Detection of Detection of 222222RnRn

Low-level proportional counters


• Developed for the GALLEX experimentDeveloped for the GALLEX experiment

• Handmade at MPI-K (ultra-pure quartz)Handmade at MPI-K (ultra-pure quartz)

• Active volume ~1 cmActive volume ~1 cm33

• α-α-detection in case of detection in case of 222222Rn Rn measurementsmeasurements

• Background ~0.5 cpd for E > 50 keVBackground ~0.5 cpd for E > 50 keV

• Detection efficiency 50%Detection efficiency 50%

• Special filling procedure is requiredSpecial filling procedure is required

Detection of Detection of 222222Rn – Rn – counterscounters


Detection of Detection of 222222Rn – filling lineRn – filling line

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

Mai

n li

ne

Pressure gauge

• Sample purificationSample purification

• Mixing with counting Mixing with counting gas (P10)gas (P10)

• Counter fillingCounter filling

Absolute detectionAbsolute detectionlimit:limit: ~30 µBq~30 µBq (15 atoms)(15 atoms)


OutlineOutline





• SummarySummary


Investigations of Investigations of 222222Rn emanationRn emanation

Emanation chambersEmanation chambers• Made out of electro-polished stainless steel Made out of electro-polished stainless steel • Two of them are available: 20 l and 80 lTwo of them are available: 20 l and 80 l• Detection limits: 60/150 µBqDetection limits: 60/150 µBq

Glass vialsGlass vials• For small samples (up to 1 l) glass vials connected directly For small samples (up to 1 l) glass vials connected directly

to the glass line can be usedto the glass line can be used• Detection limit: 40 µBqDetection limit: 40 µBq

Emanation from “stand-alone” units or systemsEmanation from “stand-alone” units or systems• Tanks, purification columns, filters etc. Tanks, purification columns, filters etc. • Extracted Extracted 222222Rn is collected in the charcoal trapsRn is collected in the charcoal traps• Detection limit: 50 µBqDetection limit: 50 µBq


Investigations of Investigations of 222222Rn emanation – Rn emanation – emanation chambersemanation chambers

Sample

Pump

Si-Getrap

Rn trap

Gas exit

Gas flowmeter

Trap for Hepurification

Emanationchamber

He bottle


OutlineOutline





• SummarySummary


Measurements of Measurements of 222222Rn diffusionRn diffusion

• Thin membranes are requiredThin membranes are required

• Measurements can be performed for Measurements can be performed for samples under different conditions samples under different conditions

• Simultaneous measurements of Simultaneous measurements of diffusion- and solubility coefficientsdiffusion- and solubility coefficients

• Sensitivity for D ~10Sensitivity for D ~10-13 -13 cmcm22/s/s


Rnsource

Pump

Humiditystandard (gas)

Apparatus forRn diffusion

measurements

Salt

PMT PMT

PMT PMT

Vd

Membrane filter

Investigated foil

Constant Rn flux

Rn chamber

Measurements of Measurements of 222222Rn diffusion – the Rn diffusion – the apparatusapparatus


0 20 40 60 80 100 120Timeh0

0.0001

0.0002

0.0003

0.0004

evitaleR

tnuoC

etaR

n 2 n 1

Dry nylonD = (2.0 ± 0.5)×10-12 cm2/sS = 4.0 ± 0.8

0 20 40 60 80 100 120Timeh0

50000

100000

150000

200000

n 1hpc

Diffusion profileDiffusion profile


OutlineOutline





• SummarySummary


Selected results – Selected results – 222222Rn Rn emanationemanation

Sample descriptionSample description Emanation rate Emanation rate

Stainless steel foilStainless steel foil (4.6 ± 0.9) µBq/m(4.6 ± 0.9) µBq/m22

Teflon foilTeflon foil < 9 µBq/m< 9 µBq/m22

Borexino PMTBorexino PMT < 40 µBq< 40 µBq

Activated Carbon - Activated Carbon - CarboActCarboAct

(0.3 ± 0.1) (0.3 ± 0.1) mBq/kgmBq/kg

Silicon rubberSilicon rubber (196 ± 4) mBq/m(196 ± 4) mBq/m22

PolyurethanePolyurethane (< 0.3 – 40) (< 0.3 – 40) mBq/mmBq/m22

Nitrogen stripping Nitrogen stripping columncolumn

(2.3 ± 0.3) mBq(2.3 ± 0.3) mBq

PC storage tank TK4 (~30 PC storage tank TK4 (~30 mm33))

(25 ± 3) mBq(25 ± 3) mBq


Selected results – Selected results – 222222Rn Rn diffusion diffusion

RH standard salt RH [%] D [cm2/s] S

Permeability P [cm2/s]

Effective permeability Peff [cm2/s]

Mg(ClO4)2 0 (2.10.4)×10-12 4.5 0.7 (9.52.3)×10-12 (5.81.4)×10-12

H3PO4 · ½H2O 9 1 (2.30.3)×10-12 2.5 0.3 (5.81.1)×10-12 (3.70.7)×10-12

LiCl2 · H2O 12 1 (2.20.3)×10-12 2.2 0.3 (4.80.9)×10-12 (3.00.6)×10-12

CaCl2 · 6H2O 32 2 (4.30.5)×10-12 1.8 0.2 (7.71.2)×10-12 (6.01.1)×10-12

Na2Cr2O7 · 2H2O 52 2 (1.90.3)×10-11 1.4 0.2 (2.70.6)×10-11 (2.50.6)×10-11

Na2S2O3 · 5H2O 76 2 (6.50.9)×10-11 1.5 0.2 (9.81.9)×10-11 (9.61.9)×10-11

K2CrO4 88 3 (1.30.2)×10-10 1.5 0.2 (2.00.4)×10-10 (1.90.4)×10-10

Na2SO4 · 10H2O 93 3 (3.30.4)×10-10 1.0 0.1 (3.30.6)×10-10 (3.30.6)×10-10

H2O vapors 100 3 (1.30.2)×10-9 0.7 0.1 (9.12.0)×10-10 (9.12.0)×10-10

222Rn diffusion, solubility and permeability coefficients as a function of relative humidity for a 0.018-mm-thick nylon foil (Nylon 6, H[HN(CH2)5 CO]n OH)


Selected results – Selected results – 222222Rn diffusion Rn diffusion (2)(2)

0 10 20 30 40 50 60 70 80 90 1001,0x10-12

1,0x10-11

1,0x10-10

1,0x10-9

Rn

diff

usi

on

co

effic

ien

t in

nyl

on

[cm2 /s

]

Relative humidity [%]


A combination of A combination of 222222Rn diffusion Rn diffusion and emanation measurementsand emanation measurements

• Applied for investigations of Applied for investigations of 222222Ra content in Ra content in a foil used for the construction of the a foil used for the construction of the Borexino Inner VesselBorexino Inner Vessel

• Emanation from ~10 kg (~140 mEmanation from ~10 kg (~140 m22) of ) of material performed under „dry“ and „wet“ material performed under „dry“ and „wet“ conditionsconditions

• Mathematical model of Mathematical model of 222222Rn production and Rn production and emanation allowed to distinguish between emanation allowed to distinguish between the surface and bulk the surface and bulk 226226Ra contamination Ra contamination


Nylon foil in the emanation Nylon foil in the emanation chamberchamber


Obtained Obtained 226226Ra concentrations Ra concentrations (Sniamid)(Sniamid)

• Sensitivities: Sensitivities: - surface - surface 226226Ra conc. ~0.5 µBq/mRa conc. ~0.5 µBq/m22

- bulk - bulk 226226Ra conc. Ra conc. ~10 µBq/kg ~10 µBq/kg

• Measured: Measured: - surface - surface 226226Ra conc. < 0.8 µBq/mRa conc. < 0.8 µBq/m22

- bulk - bulk 226226Ra conc. Ra conc. < 21 µBq/kg< 21 µBq/kg - total - total 226226Ra content: (16 ± 4) µBq/kg Ra content: (16 ± 4) µBq/kg -> 1.3 ppt-> 1.3 ppt 238 238U-equivalentU-equivalent


OutlineOutline





• SummarySummary


SummarySummary

• Measurements of a few Measurements of a few 222222Rn atoms possible Rn atoms possible @MPIK@MPIK

• Emanation studies for sample volume up to Emanation studies for sample volume up to 80 l (?00 m80 l (?00 m22) with the sensitivity at the level ) with the sensitivity at the level of 40 – 150 µBq (< 0.5 µBq/mof 40 – 150 µBq (< 0.5 µBq/m22))

• Measurements of Measurements of 222222Rn diffusion coefficient Rn diffusion coefficient for thin membranes at the sensitivity of for thin membranes at the sensitivity of ~10~101313 cm cm22/s/s

• Several different samples are under Several different samples are under investigations for Borexino/GERDA/GeMPI‘s...investigations for Borexino/GERDA/GeMPI‘s...

Sudbury, Canada Workshop in Low Radioactivity Techniques 12-13. December 2004 Highly sensitive...

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