MetroFission
WP 5: Nuclear Decay Data
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
METALLIC MAGNETIC CALORIMETERS:
ONE TYPE OF CRYOGENIC DETECTORS
Thermal detectors:
DT = E /C
Paramagnetic thermometer
DT
DM
SQUID magnetometer
DM
DV
Thermal link
td = C /G
Very low temperature (10 – 20 mK) :
• C  T (metals at very low T)
• sE 
kBT 2C
DT = E /C
thermodynamic
fluctuation noise
td = C /G
ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 2
METALLIC MAGNETIC CALORIMETERS
FOR BETA SPECTROMETRY
Source embedded inside the detector absorber
• 4p sr solid angle
• no back-scattering at the detector surface
• energy 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
ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 3
MEASUREMENT OF AN
ALLOWED 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
ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 5
Ni- 63: SPECTRUM MEASURED USING DRIED SOURCES
• Sources made by drying
a drop of NiCl2 solution
• Experimental spectra differ from
one 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 b energy
incomplete?
ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 6
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 7
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 g line
ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 8
Ni- 63: ELECTROPLATED SOURCES (3)
Au / Ag absorbers:
Counts / 100 eV
no influence of the absorber material
Ag Ka escape peak
241Am
Au absorber
Ag absorber
Theory w. exchange effect
59.5 keV g line
Energy (keV)
ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 9
MEASUREMENT OF A
FORBIDDEN BETA SPECTRUM
OF LOW MAXIMUM ENERGY:
Pu-241
| |PAGE
ICRM 2013 | Antwerp, Belgium
17-2110
June 2013
Pu- 241: SPECTRUM MEASURED WITH A DRIED SOURCE (1)
• Good agreement between
experiment and theory
starting from ~ 7 keV
• Discrepancy at low energies
• First forbidden, non-unique
transition;
no shape factor used for
theoretical spectrum
discrepancy at low
energies due to
insufficiency of theory
or to
our detector / source?
ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 11
Pu- 241: SPECTRUM MEASURED WITH A DRIED SOURCE (2)
• Case of 241Pu:
very small error if calculated
as an allowed transition:
“x approximation” well fulfilled:
2x = aZ/2R >> E0
• Discrepancy at low energies
greatly reduced if the
exchange effect is taken into
account
• Remaining discrepancy
most likely due to the use
of a dried source
ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 12
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:
source f = 300 µm enclosed inside a
Au cylinder f = 1 mm, thickness 2 x 260 µm
36Cl
STUDY OF ABSORBERS FOR HIGHER ENERGY (2)
Input: theoretical spectrum of 36Cl
Output: simulated detected spectrum
Calculation of a correction function
ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 14
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 spectra
- electroplated sources: reproducible spectra,
good agreement experiment – theory
- promising alternative: source implantation into absorber
• Higher energy beta spectra: correction for energy loss by escape of
photons from the detector must be considered
ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 15
METALLIC MAGNETIC CALORIMETERS
FOR BETA SPECTROMETRY (2)
Linearity check using (external) 55Fe, 109Cd and 241Am sources
Linear fit
Residuals (channels)
Experimental line positions [channels]
Experimental data points
fit uncertainty
5
3
1
-1 0
20
40
60
80
100
-3
-5
Energy (keV)
Residuals < fit uncertainty
(≤ 0.1 %);
No tendency
Tabulated line energy [keV]
ICRM 2013 | Antwerp, Belgium | 17-21 June 2013 | PAGE 16