Total absorption γ -ray spectroscopy of niobium isomers

Abstract

The β intensity distributions of the decays of 100gs,100m Nb and 102gs,102m Nb have been determined using the Total Absorption γ-Ray Spectroscopy technique. The JYFLTRAP double Penning trap system was employed to disentangle the isomeric states involved, lying very close in energy, in a campaign of challenging measurements performed with the Decay Total Absorption γ-ray Spectrometer at the Ion Guide Isotope Separator On-Line facility in Jyväskylä. The low-spin isomeric state of each niobium case was populated through the decay of the zirconium parent, that was treated as a contaminant. We have applied a method to extract this contamination, and additionally we have obtained β intensity distributions for these zirconium decays. The β-strength distributions evaluated with these results were compared with calculations in quasiparticle random-phase approximation, suggesting a prolate configuration for the ground states of 100,102 Zr. The footprint of the Pandemonium effect was found when comparing our results for the analyses of the niobium isotopes with previous decay data. The β-intensities of the decay of 102m Nb were obtained for the first time. A careful evaluation of the uncertainties was carried out, and the consistency of our results was validated taking advantage of the segmentation of our spectrometer. The final results were used as input in reactor summation calculations. A large impact on antineutrino spectrum calculations was already reported and here we detail the significant impact on decay heat calculations.

Determination of β -decay ground state feeding of nuclei of importance for reactor applications

“…This is obtained from the HR spectroscopy level scheme at low excitation energies supplemented with the predictions of the Hauser-Feshbach nuclear statistical model above a given excitation energy where the levels are treated as a binned continuum [49]. The statistical model provides a realistic description of the electromagnetic cascade energy and multiplicity distribution, that in modern segmented spectrometers can be tested as well [26,27,53] and eventually modified.…”

“…In both cases the TAGS analysis is strongly affected by the uncertainty in the contamination of the parent activity (see Ref. [26] for more details). The characteristic of the 4πγ − β method of being almost insensitive to the actual β-intensity distribution obtained in the TAGS analysis can be of advantage here.…”

“…Over the past few years, many other examples have shown the potential of the TAGS technique to obtain g.s. feeding probabilities [20][21][22][23][24][25][26][27]. However, the TAGS deconvolution method has some limitations: (1) the difficulties in validating the shape of the MC simulations of the β penetration in the spectrometer (see discussion in Ref.…”

Total absorption spectroscopy of the β decay of Zr101,102 and TcDombos1, Spyrou2, Naqvi3 et al. 2021Phys. Rev. CSelf Cite10000View full textAdd to dashboardCite

“…For nuclides in this mass region, a comparison of theoretical and experimental B(GT) distributions may be used to learn about the shape (spherical, oblate, or prolate) of the ground state of the parent nucleus. This idea was proposed by Hamamoto et al for neutron-deficient nuclides in the 28 < Z < 66 region [12,13], explored further by Sarriguren et al for neutron-deficient and neutronrich nuclides [5,6,[14][15][16][17][18][19][20][21][22][23][24][25], and experimentally studied by the Valencia-Strasbourg-Madrid-Surrey and Valencia-Nantes-Surrey-Jyväskylä Collaborations [26][27][28][29][30][31][32][33]. Similar studies of deformation effects on B(GT) were performed in the rubidium isotope chain [7].…”

Mapping reactor neutrino spectra from TAO to JUNO

“…In the last decade, these approaches have been challenged by new data (or by reanalyses of old data) that do not compare well with computed spectra, even invoking nonstandard physics such as sterile neutrinos [19][20][21] (not considered herein). A primary example is the unexpected "bump" observed around 5 MeV in current SBL oscillation experiments [10][11][12]22] (and possibly in older data [23]), whose understanding is still entangled with many issues, including normalization anomalies in the total flux and its fuel components [24][25][26][27][28][29][30][31], incomplete information in nuclear databases [32][33][34][35], possible energy-scale systematics [36], suppression of β-decay spectra systematics [37] via total absorption [38][39][40][41][42][43] and other techniques [44], and, on the theory side, improved calculations of (allowed and forbidden) β decay spectra [45][46][47][48][49][50][51][52][53].…”