0000000001309319
AUTHOR
J. Hakala
Experimental study of $^{100}$Tc $\beta$ decay with total absorption $\gamma$-ray spectroscopy
International audience; The β decay of Tc100 has been studied by using the total absorption γ-ray spectroscopy technique at the Ion Guide Isotope Separator On-Line facility in Jyväskylä. In this work the new Decay Total Absorption γ-ray Spectrometer in coincidence with a cylindrical plastic β detector has been employed. The β intensity to the ground state obtained from the analysis is in good agreement with previous high-resolution measurements. However, differences in the feeding to the first-excited state as well as weak feeding to a new level at high excitation energy have been deduced from this experiment. Theoretical calculations performed in the quasiparticle random-phase approximatio…
Electron-capture branch of Tc-100 and tests of nuclear wave functions for double-beta decays
We present a measurement of the electron-capture branch of 100Tc. Our value, B(EC)=(2.6±0.4)×10−5, implies that the 100Mo neutrino absorption cross section to the ground state of 100Tc is roughly one third larger than previously thought. Compared to previous measurements, our value of B(EC) prevents a smaller disagreement with QRPA calculations relevant to double-β decay matrix elements.
Total Absorption Spectroscopy Study of $^{92}$Rb Decay: A Major Contributor to Reactor Antineutrino Spectrum Shape
The antineutrino spectra measured in recent experiments at reactors are inconsistent with calculations based on the conversion of integral beta spectra recorded at the ILL reactor. $^{92}$Rb makes the dominant contribution to the reactor spectrum in the 5-8 MeV range but its decay properties are in question. We have studied $^{92}$Rb decay with total absorption spectroscopy. Previously unobserved beta feeding was seen in the 4.5-5.5 region and the GS to GS feeding was found to be 87.5(25)%. The impact on the reactor antineutrino spectra calculated with the summation method is shown and discussed.
High-precision mass measurements for the isobaric multiplet mass equation atA= 52
Masses of $^{52}$Co, $^{52}$Co$^m$, $^{52}$Fe, $^{52}$Fe$^m$, and $^{52}$Mn have been measured with the JYFLTRAP double Penning trap mass spectrometer. Of these, $^{52}$Co and $^{52}$Co$^m$ have been experimentally determined for the first time and found to be more bound than predicted by extrapolations. The isobaric multiplet mass equation for the $T=2$ quintet at $A=52$ has been studied employing the new mass values. No significant breakdown (beyond the $3\sigma$ level) of the quadratic form of the IMME was observed ($\chi^2/n=2.4$). The cubic coefficient was 6.0(32) keV ($\chi^2/n=1.1$). The excitation energies for the isomer and the $T=2$ isobaric analogue state in $^{52}$Co have been d…
The summertime Boreal forest field measurement intensive (HUMPPA-COPEC-2010): an overview of meteorological and chemical influences
This paper describes the background, instrumentation, goals, and the regional influences on the HUMPPACOPEC intensive field measurement campaign, conducted at the Boreal forest research station SMEAR II (Station for Measuring Ecosystem-Atmosphere Relation) in Hyyti¨al¨a, Finland from 12 July–12 August 2010. The prevailing meteorological conditions during the campaign are examined and contrasted with those of the past six years. Back trajectory analyses show that meteorological conditions at the site in 2010 were characterized by a higher proportion of southerly flow than in the other years studied. As a result the summer of 2010 was anomalously warm and high in ozone making the campaign rel…
Total absorption γ-ray spectroscopy of the β decays of 96gs,mY
The β decays of the ground state (gs) and isomeric state (m) of 96Y have been studied with the total absorption γ-ray spectroscopy technique at the Ion Guide Isotope Separator On-Line facility. The separation of the 8+ isomeric state from the 0− ground state was achieved thanks to the purification capabilities of the JYFLTRAP double Penning trap system. The β-intensity distributions of both decays have been independently determined. In the analyses the deexcitation of the 1581.6 keV level in 96Zr, in which conversion electron emission competes with pair production, has been carefully considered and found to have significant impact on the β-detector efficiency, influencing the β-intensity di…
Determination of β-decay ground state feeding of nuclei of importance for reactor applications
In β-decay studies the determination of the decay probability to the ground state (g.s.) of the daughter nucleus often suffers from large systematic errors. The difficulty of the measurement is related to the absence of associated delayed γ-ray emission. In this work we revisit the 4πγ−β method proposed by Greenwood and collaborators in the 1990s, which has the potential to overcome some of the experimental difficulties. Our interest is driven by the need to determine accurately the β-intensity distributions of fission products that contribute significantly to the reactor decay heat and to the antineutrinos emitted by reactors. A number of such decays have large g.s. branches. The method is…
Precise half-life measurement of the Si-26 ground state
The beta-decay half-life of 26Si was measured with a relative precision of 1.4*10e3. The measurement yields a value of 2.2283(27) s which is in good agreement with previous measurements but has a precision that is better by a factor of 4. In the same experiment, we have also measured the non-analogue branching ratios and could determine the super-allowed one with a precision similar to the previously reported measurements. The experiment was done at the Accelerator Laboratory of the University of Jyvaskyla where we used the IGISOL technique with the JYFLTRAP facility to separate pure samples of 26Si.
Applications of the total absorption technique to improve reactor decay heat calculations: study of the beta decay of [sup 102,104,105]Tc
The decay heat of the fission products plays an important role in predicting the heat‐up of nuclear fuel after reactor shutdown. This form of energy release is calculated as the sum of the energy‐weighted activities of all fission products P(t) = ΣEiλiNi(t), where Ei is the decay energy of nuclide i (gamma and beta component), λi is the decay constant of nuclide i and Ni(t) is the number of nuclide i at cooling time t. Even though the reproduction of the measured decay heat has improved in recent years, there is still a long standing discrepancy at t∼1000 s cooling time for some fuels. A possible explanation for this disagreement can been found in the work of Yoshida et al. [1], who demonst…
Study of the $��$-decay of $^{100}$Tc with Total Absorption $��$-Ray Spectroscopy
The \b{eta}-decay of 100 Tc has been studied using the Total Absorption ��-Ray Spectroscopy technique at IGISOL. In this work the new DTAS spectrometer in coincidence with a cylindrical plastic \b{eta} detector has been employed. The \b{eta}-intensity to the ground state obtained from the analysis is in good agreement with previous high-resolution measurements. However, differences in the feeding to the first excited state as well as weak feeding to a new level at high excitation energy have been deduced from this experiment. Theoretical calculations performed in the quasiparticle random- phase approximation (QRPA) framework are also reported. Comparison of these calculations with our measu…
Results of DTAS Campaign at IGISOL : Overview
The β decays of more than twenty fission fragments were measured in the first experiments with radioactive-ion beams employing the Decay Total Absorption γ-ray Spectrometer. In this work, we summarize the main results obtained so far from this experimental campaign carried out at the Ion Guide Isotope Separator On-Line facility. The advances introduced for these studies represent the state-of-the-art of our analysis methodology for segmented spectrometers. peerReviewed
Study of the $\beta$-decay of $^{100}$Tc with Total Absorption $\gamma$-Ray Spectroscopy
The \b{eta}-decay of 100 Tc has been studied using the Total Absorption {\gamma}-Ray Spectroscopy technique at IGISOL. In this work the new DTAS spectrometer in coincidence with a cylindrical plastic \b{eta} detector has been employed. The \b{eta}-intensity to the ground state obtained from the analysis is in good agreement with previous high-resolution measurements. However, differences in the feeding to the first excited state as well as weak feeding to a new level at high excitation energy have been deduced from this experiment. Theoretical calculations performed in the quasiparticle random- phase approximation (QRPA) framework are also reported. Comparison of these calculations with our…
Penning-trap-assisted study of excitations in $^{88}$Br populated in β decay of $^{88}$Se
Excited levels of 88Br populated in the β decay of 88Se have been studied by means of βγ and γ γ spectroscopy methods. Neutron-rich parent 88Se nuclei were produced with proton-induced fission of 238U using the Ion Guide Isotope Separator On-Line (IGISOL) method and separated from contaminants using a dipole magnet and the coupled JYFLTRAP Penning trap at the Accelerator Laboratory of the University of Jyvaskyl ¨ a. The level scheme ¨ of 88Br has been constructed and log f t values of levels were determined. The ground-state spin of 88Br is now firmly determined to be 1−. Low-energy levels in 88Br were interpreted as members of the πp3/2(νd5/2) 3, πp−1 3/2(νd5/2) 3, πf −1 5/2 (νd5/2) 3, and…
Total absorption γ-ray spectroscopy of the β-delayed neutron emitters 137I and 95Rb
The decays of the β-delayed neutron emitters 137I and 95Rb have been studied with the total absorption γ-ray spectroscopy technique. The purity of the beams provided by the JYFLTRAP Penning trap at the ion guide isotope separator on-line facility in Jyväskylä allowed us to carry out a campaign of isotopically pure measurements with the decay total absorption γ-ray spectrometer, a segmented detector composed of 18 NaI(Tl) modules. The contamination coming from the interaction of neutrons with the spectrometer has been carefully studied, and we have tested the use of time differences between prompt γ rays and delayed neutron interactions to eliminate this source of contamination. Due to the s…
Enhanced Gamma-Ray Emission from Neutron Unbound States Populated in Beta Decay
International audience; Total absorption spectroscopy was used to investigate the beta-decay intensity to states above the neutron separation energy followed by gamma-ray emission in 87,88Br and 94Rb. Accurate results were obtained thanks to a careful control of systematic errors. An unexpectedly large gamma intensity was observed in all three cases extending well beyond the excitation energy region where neutron penetration is hindered by low neutron energy. The gamma branching as a function of excitation energy was compared to Hauser-Feshbach model calculations. For 87Br and 88Br the gamma branching reaches 57% and 20% respectively, and could be explained as a nuclear structure effect. So…
Mass measurements and implications for the energy of the high-spin isomer in 94Ag.
Nuclides in the vicinity of 94Ag have been studied with the Penning trap mass spectrometer JYFLTRAP at the Ion-Guide Separator On-Line. The masses of the two-proton-decay daughter 92Rh and the beta-decay daughter 94Pd of the high-spin isomer in 94Ag have been measured, and the masses of 93Pd and 94Ag have been deduced. When combined with the data from the one-proton or two-proton-decay experiments, the results lead to contradictory mass excess values for the high-spin isomer in 94Ag, -46370(170) or -44970(100) keV, corresponding to excitation energies of 6960(400) or 8360(370) keV, respectively.
Mass of astrophysically relevant 31Cl and the breakdown of the isobaric multiplet mass equation
The mass of $^{31}$Cl has been measured with the JYFLTRAP double Penning trap mass spectrometer at the Ion-Guide Isotope Separator On-Line (IGISOL) facility. The determined mass-excess value, -7034.7(34) keV, is 15 times more precise than in the Atomic Mass Evaluation 2012. The quadratic form of the isobaric multiplet mass equation for the T=3/2 quartet at A=31 fails ($\chi^2_n$=11.6) and a non-zero cubic term, d=-3.5(11) keV, is obtained when the new mass value is adopted. $^{31}$Cl has been found to be less proton-bound with a proton separation energy of $S_p$=265(4) keV. Energies for the excited states in $^{31}$Cl and the photodisintegration rate on $^{31}$Cl have been determined with s…
TAS measurements for reactor physics and nuclear structure
In this contribution we will present recent total absorption measurements of the beta decay of neutron‐rich nuclei performed at the IGISOL facility of the Univ. of Jyvaskyla. In the measurements the JYFL Penning Trap was used as a high resolution isobaric separator. The total absorption technique will be described and the impact of recent results in the fields of reactor physics (decay heat calculations) and nuclear structure will be discussed.
Electron-capture branch of 100Tc and tests of nuclear wave functions for double-beta decays
We present a measurement of the electron-capture branch of $^{100}$Tc. Our value, $B(\text{EC}) = (2.6 \pm 0.4) \times 10^{-5}$, implies that the $^{100}$Mo neutrino absorption cross section to the ground state of $^{100}$Tc is roughly one third larger than previously thought. Compared to previous measurements, our value of $B(\text{EC})$ prevents a smaller disagreement with QRPA calculations relevant to double-$\beta$ decay matrix elements.
CCDC 812274: Experimental Crystal Structure Determination
Related Article: J.Hakala, M.M.Hanninen, A.Lehtonen|2011|Inorg.Chem.Commun.|14|1362|doi:10.1016/j.inoche.2011.05.021
CCDC 867356: Experimental Crystal Structure Determination
Related Article: J.Hakala, R.Sillanpaa, A.Lehtonen|2012|Inorg.Chem.Commun.|21|21|doi:10.1016/j.inoche.2012.03.043
CCDC 183073: Experimental Crystal Structure Determination
Related Article: T.Kunnari, K.D.Klika, G.Blanco, C.Mendez, P.Mantsala, J.Hakala, R.Sillanpaa, P.Tahtinen, J.Salas, K.Ylihonko|2002|J.Chem.Soc.,Perkin Trans.1||1818|doi:10.1039/b200444p