DEVELOPMENT OF BETA SPECTROMETRY USING CRYOGENIC DETECTORS

1. 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

2. METALLIC MAGNETIC CALORIMETERS:ONE TYPE OF CRYOGENIC DETECTORS Thermal detectors: DT = E/C Paramagneticthermometer DTDM SQUID magnetometer DMDV Thermal link td = C/G Verylowtemperature (10 – 20 mK) : C T(metalsatverylowT) DT = E/C thermodynamic fluctuation noise sE kBT 2C td = C/G ICRM 2013 | Antwerp, Belgium | 17-21 June 2013

3. METALLIC MAGNETIC CALORIMETERS FOR BETA SPECTROMETRY Pour personnaliser le pied de page et la date : « Insertion / En-tête et pied de page » Personnaliser la zone de de pied de page Cliquer sur appliquer partout 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

4. MEASUREMENT OF ANALLOWED BETA SPECTRUM OF LOW MAXIMUM ENERGY:Ni-63

5. 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

6. Ni-63: spectrummeasuredusingdried 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

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

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 keVgline ICRM 2013 | Antwerp, Belgium | 17-21 June 2013

9. Ni-63: electroplated sources (3) Au / Ag absorbers: no influence of the absorber material Counts / 100 eV Ag Ka escape peak 241Am 59.5 keVgline Au absorber Ag absorber Theory w. exchange effect Energy (keV) ICRM 2013 | Antwerp, Belgium | 17-21 June 2013

10. MEASUREMENT OF AFORBIDDEN BETA SPECTRUM OF LOW MAXIMUM ENERGY:Pu-241 ICRM 2013 | Antwerp, Belgium | 17-21 June 2013

11. 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

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

13. 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 f = 300 µm enclosed inside a Au cylinder f = 1 mm, thickness 2 x 260 µm

14. 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

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 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

16. metallicmagneticcalorimetersfor beta spectrometry (2) Linearity check using (external) 55Fe, 109Cd and 241Am sources Experimental data points Linear fit fit uncertainty Experimentalline positions [channels] Residuals< fit uncertainty (≤ 0.1 %); No tendency Tabulated line energy [keV] ICRM 2013 | Antwerp, Belgium | 17-21 June 2013