DEVELOPMENT OF BETA SPECTROMETRY USING CRYOGENIC DETECTORS
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Transcript of 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
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• 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
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• 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
ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 5
• 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
ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 6
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?
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ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 7
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
ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 8
Ni- 63: ELECTROPLATED SOURCES (2)
• 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
ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 9
Ni- 63: ELECTROPLATED SOURCES (3)
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
ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 11
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?
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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
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Pu- 241: SPECTRUM MEASURED WITH A DRIED SOURCE (2)
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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
ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 14
STUDY OF ABSORBERS FOR HIGHER ENERGY (2)
Input: theoretical spectrum of 36ClOutput: simulated detected spectrum
Calculation of a correction function
ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 15
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
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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