behaviour of rn - max-planck-institut für kernphysik · long and short exposition time ssp in n2...

1

Marcin Marcin WójcikWójcik , Nikodem , Nikodem FrodymaFrodyma , Krzysztof , Krzysztof PelczarPelczar

GERDA GERDA Collaboration MeetingCollaboration Meeting

JagellonianJagellonian UniversityUniversity, Kraków 2008, Kraków 2008

Behaviour ofBehaviour of

222222RnRnand its daughtersand its daughters

in liquid nitrogenin liquid nitrogen

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�� RnRn as aas a timetime--dependentdependent background source inbackground source in e.g.e.g. thethe

GERDAGERDA experimentexperiment

�� Rn and RnRn and Rn--daughters location in cryostat with liquid gasdaughters location in cryostat with liquid gas

�� Rn partition between liquid and gas phaseRn partition between liquid and gas phase

�� Behaviour of Rn and its daughtersBehaviour of Rn and its daughters in in LNLN22 in electric fieldin electric field

Problems and Questions Problems and Questions

Behaviour of Rn222 and its daughters in LN2, GERDA Collaboration Meeting, Kraków 2008

M. Wójcik, N. Frodyma, K. Pelczar, Jagiellonian Univers ity, Kraków

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222222RnRn and itsand its daughtersdaughters

222Rn

226Ra

218Po

214Pb

214Bi

214Po

210Pb

α

α

ββ

α α

210Bi

210Po

206Pb

α

β

T1/2 = 1622 y

E = 4.8 MeV

T1/2 = 3.8 dE = 5.5 MeV

T1/2 = 3.1 m

E = 6.0 MeV

T1/2 = 26.8 m

Em = 0.7 MeV

β T1/2 = 19.8 m

Em = 1.5 MeV

T1/2 = 164 µsE = 7.7 MeV

T1/2 = 22.3 yEm = 0.06 MeV

T1/2 = 5.0 dEm = 1.2 MeV

T1/2 = 138.4 d

E = 5.3 MeV

Stable



4Behaviour of Rn222 and its daughters in LN2, GERDA Collaboration Meeting, Kraków 2008


222222RnRn and itsand its daughtersdaughters

222Rn 218Po 214Pb 214Bi 214Po α βα β

+ +_ _ + + ?

in gas:

in liquid:

++

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GERDAGERDA –– model model of the detectorof the detector



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RnRn dissolving in LNdissolving in LN22



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„„Free evaporationFree evaporation”” of of LLNN22 with with RnRn



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9




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0

2

4

6

8

10

12

14

16

0:00:00 6:00:00 12:00:00 18:00:00 24:00:00time [hh:mm:ss]

coun

t rat

e[c

ount

s/m

in]

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0

2

4

6

8

10

12

14

16

144:00:00 150:00:00 156:00:00 162:00:00 168:00:00

time [hh:mm:ss]

coun

t rat

e[c

ount

s/m

in]

Fit parameters (y = ax +b)a = 7.6E-5 ± 2.3E-5 cpm/mb = 1.565 ± 0.025 cpm

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0,1

1

10

100

1000

303:30:00 309:30:00 315:30:00 321:30:00 327:30:00time [hh:mm:ss]

coun

t rat

e[c

ount

s/m

]

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RnRn count rate growth after LNcount rate growth after LN22 evaporationevaporation



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Measurement of the Measurement of the RnRn concentration in LNconcentration in LN22



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RnRn concentration in liquid and gaseous nitrogenconcentration in liquid and gaseous nitrogen



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Variable heating inside the DewarVariable heating inside the Dewar





Variable heating inside the DewarVariable heating inside the Dewar

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RnRn--daughters depositiondaughters deposition on on stainless steel platesstainless steel plates(SSP)(SSP) andand alfaalfa --spectrometryspectrometry

SSP placed in different posotions

and under different conditions:

� Liquid nitrogen

� Gaseous nitrogen

� High voltage applied

� Long and short exposition time

SSP in N2 gas ----------------

SSP in liquid N2 ----------------



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alfaalfa--spectrometerspectrometer





214Po

218Po

T1/2 = 186 s

T1/2 = 1188 s

alfaalfa--spectrometerspectrometer

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High voltage influenceHigh voltage influence on counts of on counts of 214214PPoo



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Counts of Counts of 214214Po and Po and 218218Po Po vsvs applied voltageapplied voltagennegativeegative voltagevoltage



LN2

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Counts of Counts of 214214Po and Po and 218218Po Po vsvs applied voltageapplied voltageppositiveositive voltagevoltage

LN2



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RnRn (and daughters) concentration(and daughters) concentrationgrowth in time (with growth in time (with ––2000V applied)2000V applied)

LN2



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Plans Plans for further measurementsfor further measurements

� Germanium plates

� Liquid argon

� Dynamics simulations



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Preliminary conclusionsPreliminary conclusions



� Large part of Rn is dissolved in LN2

� The Rn concentration in evaporated gas is lower than in liquid gas and depends on the evaporating rate (heating power)

� High voltage forces Rn to concentrate around the SSP� The polarity of HV is not meaningless� The concentration of Rn depends on time of SSP exposure

Open questionsOpen questions

� Mechanism of Rn and Rn – daughters concentration

27

Marcin Marcin WójcikWójcik , Nikodem , Nikodem FrodymaFrodyma , Krzysztof , Krzysztof PelczarPelczar

GERDA GERDA Collaboration MeetingCollaboration Meeting

Jagellonian UniversityJagellonian University, Kraków 2008, Kraków 2008

Behaviour ofBehaviour of

222222RnRnand its daughtersand its daughters

in liquid nitrogenin liquid nitrogen

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Temperature inside the Temperature inside the dewardewar(top and bottom, after N(top and bottom, after N22 evaporation)evaporation)



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Temperature difference between top and bottom Temperature difference between top and bottom wall wall of the of the dewardewar (after nitrogen evaporated)(after nitrogen evaporated)



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Rn concentrationRn concentration growthgrowth (after LN2 evaporated)(after LN2 evaporated)with constant flow ratewith constant flow rate



behaviour of rn - max-planck-institut für kernphysik · long and short exposition time ssp in n2...

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