DEVELOPMENT OF BETA SPECTROMETRY USING CRYOGENIC DETECTORS

DEVELOPMENT OF BETA SPECTROMETRY

USING CRYOGENIC DETECTORS

M. Loidl, C. Le-Bret, M. Rodrigues, X. Mougeot

CEA Saclay – LIST / LNE, Laboratoire National Henri Becquerel, France

MetroFissionWP 5: Nuclear Decay Data

METALLIC MAGNETIC CALORIMETERS:ONE TYPE OF CRYOGENIC DETECTORS

ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 2

Thermal detectors:

T = E /C

Paramagnetic thermometer

T M

SQUID magnetometer

M V

Thermal link

d = C /G

Very low temperature (10 – 20 mK) :

C T (metals at very low T)T = E /C

d = C /G

E kBT 2C

•

• thermodynamicfluctuation noise

| PAGE 3ICRM 2013 | Antwerp, Belgium | 17-21 June 2013

METALLIC MAGNETIC CALORIMETERS FOR BETA SPECTROMETRY

Source embedded inside the detector absorber

4 sr solid angleno back-scattering at the detector surfaceenergy loss of beta particles in the source: energy should be detected anyway

• • •

• Determination of the absorber dimensions by Monte Carlo simulation detection efficiency close to 100 %

• Very low T low thermodynamic fluctuation noise high energy resolution low energy threshold

MEASUREMENT OF ANALLOWED BETA SPECTRUM OF LOW MAXIMUM ENERGY:

Ni-63

Ni- 63: THEORETICAL SPECTRUM


• Allowed transition: Theoretical spectrum can be calculated with high degree of• confidence validate measurement method by comparison experiment - theory• Exchange effect (creation of beta electron into a bound orbital; simultaneous emission of a• bound electron) has been included in the code BetaShape developed at LNHB


Ni- 63: SPECTRUM MEASURED USING DRIED SOURCES

Sources made by drying a drop of NiCl2 solution

Experimental spectra differ fromone another and from theory

Agreement with theory better when including exchange effect

No clear influence of

- carrier concentration (MD8) - absorber material (MD11)

Part of energy in NiCl2 metastable states detection of energy incomplete?

•

•

•

•


Ni- 63: ELECTROPLATED SOURCES (1)

Requirements:

• metallic Ni deposit

• activity / surface ~ 100 Bq / mm2

• minimize quantity of inactive Ni

electrolyte containing a small Ni concentration

Nickel chloride concentration [mol/L] 0.01

Hypophosphite ion concentration [mol/L] 0.25

Acetic acid concentration [mol/L] 0.5

Mass activity [kBq/g] 67.5

Anode material Pt

Cathode material Au

Temperature [°C] 70

Current density [mA/mm2] 2 - 5

Deposition time [min] 2

Activity per unit surface [Bq/mm2] 274



• Energy threshold: 200 eV

• Energy resolution: 51 eV (FWHM) @ 59.5 keV

• Excellent agreement experiment - theory• when taking account of exchange effect

• Confirmation of the calculation of the• exchange effect in the code BetaShape• (developed at LNHB)

241Am 59.5 keV line



Au absorberAg absorberTheory w. exchange effect

Ag Kescape peak

241Am 59.5 keV line

Energy (keV)

Cou

nts

/ 10

0 eV

Au / Ag absorbers:

no influence of the absorber material

ICRM 2013 | Antwerp, Belgium | 17-21 June 2013| PAGE 10

MEASUREMENT OF AFORBIDDEN BETA SPECTRUM OF LOW MAXIMUM ENERGY:

Pu-241


Pu- 241: SPECTRUM MEASURED WITH A DRIED SOURCE (1)

Good agreement between experiment and theorystarting from ~ 7 keV

Discrepancy at low energies

First forbidden, non-uniquetransition;no shape factor used fortheoretical spectrum

discrepancy at lowenergies due to

insufficiency of theory or to our detector / source?

•

•

•

ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 12| PAGE 12

Case of 241Pu: very small error if calculated as an allowed transition:“ approximation” well fulfilled:2 = Z/2R > E0

Discrepancy at low energiesgreatly reduced if the exchange effect is taken into account

Remaining discrepancymost likely due to the useof a dried source

•

•

•

Pu- 241: SPECTRUM MEASURED WITH A DRIED SOURCE (2)

>

STUDY OF ABSORBERS FOR HIGHER ENERGY (1)

Higher energy beta spectra:

Correction for energy loss by escape of Bremsstrahlung photons from the detector must be considered.

Example: 36Cl

Pure beta emitter; second forbidden non-unique transition

Emax = 709 keV

Au absorber thickness for stopping 709 keV electrons: 260 µm

Monte Carlo simulation:

36Cl source = 300 µm enclosed inside aAu cylinder = 1 mm, thickness 2 x 260 µm


STUDY OF ABSORBERS FOR HIGHER ENERGY (2)

Input: theoretical spectrum of 36ClOutput: simulated detected spectrum

Calculation of a correction function


CONCLUSION AND PERSPECTIVES

Metallic magnetic calorimeters are in an excellent position for the precise measurement of the shapes of low energy beta spectra

Great influence of the type of beta source:

drop deposited sources: discrepant spectraelectroplated sources: reproducible spectra,good agreement experiment – theorypromising alternative: source implantation into absorber

Higher energy beta spectra: correction for energy loss by escape of photons from the detector must be considered

•

•

--

-

•


METALLIC MAGNETIC CALORIMETERS FOR BETA SPECTROMETRY (2)

Linearity check using (external) 55Fe, 109Cd and 241Am sources

Experimental data points Linear fit

Tabulated line energy [keV]

Exp

erim

enta

l lin

e po

sitio

ns [

chan

nels

]

Residuals < fit uncertainty (≤ 0.1 %);

No tendency

fit uncertainty

DEVELOPMENT OF BETA SPECTROMETRY USING CRYOGENIC DETECTORS

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