Penning-trap mass measurements on 92, 94-98, 100Mo with JYFLTRAP

Penning-trap measurements on stable 92, 94-98, 100Mo isotopes have been performed with relative accuracy of \ensuremath1⋅10−8\ensuremath1⋅10−8 with the JYFLTRAP Penning-trap mass spectrometer by using 85Rb as a reference. The Mo isotopes have been found to be about 3keV more bound than given in the Atomic Mass Evaluation 2003 (AME03). The results confirm that the discrepancy between the ISOLTRAP and JYFLTRAP data for 101-105Cd isotopes was due to an erroneous value in the AME03 for 96Mo used as a reference at JYFLTRAP. The measured frequency ratios of Mo isotopes have been used to update mass-excess values of 30 neutron-deficient nuclides measured at JYFLTRAP. peerReviewed

Direct mass measurements of neutron-rich zirconium isotopes up toZr104

Atomic masses of radioactive zirconium isotopes from {sup 96}Zr to {sup 104}Zr have been measured with a relative accuracy of {<=}5x10{sup -7} using a Penning trap coupled to the ion guide isotope separator on-line system. The obtained two-neutron separation energies show strong local correlation in relation to the shape change and shape coexistence between N=58 and 60.

First isomeric yield ratio measurements by direct ion counting and implications for the angular momentum of the primary fission fragments

We report the first experimental determination of independent isomeric yield ratios using direct ion counting with a Penning trap, which offered such a high resolution in mass that isomeric states could be separated. The measurements were performed at the Ion Guide Isotope Separator On-Line (IGISOL) facility at the University of Jyvaskyla. The isomer production ratios of Ge-81, Y-96,Y-97 Sn-128(,1)30, and Sb-129 in the 25-MeV proton-induced fission of U-na(t) and Th-232 were studied. Three isomeric pairs (Ge-81, Y-96, and Sb-129) were measured for the first time for the U-na(t)(p, f) reaction, while all the reported yield ratios for the Th-232(p, f) reaction were determined for the first ti…

First determination of β-delayed multiple neutron emission beyond A = 100 through direct neutron measurement : The P2n value of 136Sb

Background: β-delayed multiple neutron emission has been observed for some nuclei with A≤100, being the Rb100 the heaviest β2n emitter measured to date. So far, only 25P2n values have been determined for the ≈300 nuclei that may decay in this way. Accordingly, it is of interest to measure P2n values for the other possible multiple neutron emitters throughout the chart of the nuclides. It is of particular interest to make such a measurement for nuclei with A>100 to test the predictions of theoretical models and simulation tools for the decays of heavy nuclei in the region of very neutron-rich nuclei. In addition, the decay properties of these nuclei are fundamental for the understanding of a…

Experimental study of 100Tc β decay with total absorption γ -ray spectroscopy

The β decay of 100Tc 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 approximation framework are also r…

Total absorption studies of high priority decays for reactor applications: 86Br and 91Rb

Preliminary results from beta decay studies of nuclei that are important for reactor applications are presented. The beta decays have been studied using the total absorption technique (TAS) and the pure beams provided by the JYFLTRAP system at the IGISOL facility of the University of Jyväskylä. peerReviewed

High-precision mass measurement ofS31with the double Penning trap JYFLTRAP improves the mass value forCl32

Mass Measurement on the rp-Process Waiting Point 72Kr

The mass of one of the three major waiting points in the astrophysical rp process $^{72}$Kr was measured for the first time with the Penning trap mass spectrometer ISOLTRAP. The measurement yielded a relative mass uncertainty of $\deltam/m = 1.2\times 10–7 (\deltam$ = 8 keV). $^{73,74}$Kr, also needed for astrophysical calculations, were measured with more than 1 order of magnitude improved accuracy. We use the ISOLTRAP masses of $^{72–74}$Kr to reanalyze the role of $^{72}$Kr (T$_{1/2}$ = 17.2 s) in the rp process during x-ray bursts and conclude that $^{72}$Kr is a strong waiting point delaying the burst duration with at least 80\% of its $\beta$-decay half-life.

Study of the β decay of fission products with the DTAS detector

Total Absorption Spectroscopy measurements of the β decay of 103Mo and 103Tc, important contributors to the decay heat summation calculation in reactors, are reported in this work. The analysis of the experiment, performed at IGISOL with the new DTAS detector, show new β intensity that was not detected in previous measurements with Ge detectors. peerReviewed

Penning-trap-assisted study of excitations in Br88 populated in β decay of Se88

Excited levels of $^{88}\mathrm{Br}$ populated in the $\ensuremath{\beta}$ decay of $^{88}\mathrm{Se}$ have been studied by means of $\ensuremath{\beta}\ensuremath{\gamma}$ and $\ensuremath{\gamma}\ensuremath{\gamma}$ spectroscopy methods. Neutron-rich parent $^{88}\mathrm{Se}$ nuclei were produced with proton-induced fission of $^{238}\mathrm{U}$ 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 Jyv\"askyl\"a. The level scheme of $^{88}\mathrm{Br}$ has been constructed and $logft$ values of levels were determined. The ground-state spin o…

Characterization of a neutron–beta counting system with beta-delayed neutron emitters

A new detection system for the measurement of beta-delayed neutron emission probabilities has been characterized using fission products with well known β-delayed neutron emission properties. The setup consists of BELEN-20, a 4π neutron counter with twenty 3He proportional tubes arranged inside a large polyethylene neutron moderator, a thin Si detector for β counting and a selftriggering digital data acquisition system. The use of delayed-neutron precursors with different neutron emission windows allowed the study of the effect of energy dependency on neutron, β and β-neutron rates. The observed effect is well reproduced by Monte Carlo simulations. The impact of this dependency on the accura…

Towards commissioning the new IGISOL-4 facility

Abstract The Ion Guide Isotope Separator On-Line facility at the Accelerator Laboratory of the University of Jyvaskyla is currently being re-commissioned as IGISOL-4 in a new experimental hall. Access to intense beams of protons and deuterons from a new MCC30/15 cyclotron, with continued possibility to deliver heavy-ion beams from the K = 130 MeV cyclotron, offers extensive opportunities for long periods of fundamental experimental research, developments and applications. A new layout of beam lines with a considerable increase in floor space offers new modes of operation at the facility, as well as a possibility to incorporate more complex detector setups. We present a general overview of I…

Electron capture on116In and implications for nuclear structure related to double-βdecay

The electron capture decay branch of ${}^{116}$In has been measured to be $[2.46\ifmmode\pm\else\textpm\fi{}0.44(\mathrm{stat}.)\ifmmode\pm\else\textpm\fi{}0.39(\mathrm{syst}.)]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ using Penning trap-assisted decay spectroscopy. The corresponding Gamow-Teller transition strength is shown to be compatible with the most recent value extracted from the $(p,n)$ charge-exchange reaction, providing a resolution to longstanding discrepancies. This transition can now be used as a reliable benchmark for nuclear-structure calculations of the matrix element for the neutrinoless double-$\ensuremath{\beta}$ decay of ${}^{116}$Cd and other nuclides.

High-Precision Proton-Capture Q Values for 25Al(p,γ)26Si and 30P(p,γ)31Si

The masses of astrophysically relevant nuclei, 25Al and 30P, have recently been measured with the JYFLTRAP double Penning trap at the new IGISOL-4 facility at the University of Jyväskylä. Unparalleled precisions of 63 and 64 eV were achieved for the 25Al and 30P masses, respectively. The proton-capture Q values for 25Al(p, γ)26Si and 30P(p, γ)31S were also determined, and their precisions improved by a factor of 4 and 2, respectively, in comparison with AME12. The impact of the more precise values on the resonant proton-capture rate has also been studied. peerReviewed

Developments for neutron-induced fission at IGISOL-4

At the IGISOL-4 facility, neutron-rich, medium mass nuclei have usually been produced via charged particle-induced fission of natural uranium and thorium. Neutron-induced fission is expected to have a higher production cross section of the most neutron-rich species. Development of a neutron source along with a new ion guide continues to be one of the major goals since the commissioning of IGISOL-4. Neutron intensities at di↵erent angles from a beryllium neutron source have been measured in an on-line experiment with a 30 MeV proton beam. Recently, the new ion guide coupled to the neutron source has been tested as well. Details of the neutron source and ion guide design together with prelimi…

Super-Allowed β Decay of23Mg Studied with a High-Precision Germanium Detector

Large Impact of the Decay of Niobium Isomers on the Reactor ¯νe Summation Calculations

Even mass neutron-rich niobium isotopes are among the principal contributors to the reactor antineutrino energy spectrum. They are also among the most challenging to measure due to the refractory nature of niobium, and because they exhibit isomeric states lying very close in energy. The β-intensity distributions of 100gs;100mNb and 102gs;102mNb β decays have been determined using the total absorption γ-ray spectroscopy technique. The measurements were performed at the upgraded Ion Guide Isotope Separator On-Line facility at the University of Jyväskylä. Here, the double Penning trap system JYFLTRAP was employed to disentangle the β decay of the isomeric states. The new data obtained in this …

Total absorption γ -ray spectroscopy of the β -delayed neutron emitters I137 and Rb95

The decays of the β-delayed neutron emitters I137 and Rb95 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 Jyvaskyla 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…

Measurement of the heaviest Beta-delayed 2-neutron emitter: 136Sb

The Beta-delayed neutron emission probability, Pn , of very exotic nuclei is crucial for the understanding of nuclear structure properties of many isotopes and astrophysical processes such as the rapid neutron capture process (r-process). In addition Beta-delayed neutrons are important in a nuclear power reactor operated in a prompt sub-critical, delayed critical condition, as they contribute to the decay heat inducing fission reactions after a shut down. The study of neutron-rich isotopes and the measurement of Beta-delayed one-neutron emitters (Beta1n) is possible thanks to the Rare Isotope Beam (RIB) facilities, where radioactive beams allow the production of exotic nuclei of interest, w…

On the resonant neutrinoless double-electron-capture decay of ^{136}Ce

Abstract The double-electron-capture Q value for the 136Ce decay to 136Ba has been determined at JYFLTRAP. The measured value 2378.53(27) keV excludes the energy degeneracy with the 0 + excited state of the decay daughter 136Ba at 2315.32(7) keV in a resonant 0 ν ECEC decay by 11.67 keV. The new Q value differs from the old adopted value 2419(13) keV (Atomic Mass Evaluation 2003) by 40 keV and is 50 times more precise. Our calculations show that the precise Q value renders the resonant 0 ν ECEC decay of 136Ce undetectable by the future underground detectors. We measured also the double-β decay Q value of 136Xe to be 2457.86(48) keV which agrees well with the value 2457.83(37) keV measured a…

Characterization of a cylindrical plastic β-detector with Monte Carlo simulations of optical photons

In this work we report on the Monte Carlo study performed to understand and reproduce experimental measurements of a new plastic β-detector with cylindrical geometry. Since energy deposition simulations differ from the experimental measurements for such a geometry, we show how the simulation of production and transport of optical photons does allow one to obtain the shapes of the experimental spectra. Moreover, taking into account the computational effort associated with this kind of simulation, we develop a method to convert the simulations of energy deposited into light collected, depending only on the interaction point in the detector. This method represents a useful solution when extens…

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

12 pags., 6 figs., 3 tabs.

Precise measurements of half-lives and branching ratios for the ββ mirror transitions in the decay of 23Mg and 27Si

Half-lives and branching ratios for the two mirror ββ decays of 23Mg and 27Si have been measured at the University of Jyväskylä with the IGISOL facility. The results obtained, T1/2=11.303(3)T1/2=11.303(3) s and T1/2=4.112(2)T1/2=4.112(2) s for the half-lives of 23Mg and 27Si , respectively, are 7 and 8 times more precise than the averages of previous measurements. The values obtained for the super-allowed branching ratios of 23Mg and 27Si are B.R.=92.18(8)%B.R.=92.18(8)% and B.R.=99.74(2)%B.R.=99.74(2)% , respectively. The result for 23Mg is three times more precise than the average of the previous measurements, while for 27Si the precision has not been improved, the average of the previous…

Mass measurements in the vicinity of the doubly magic waiting pointNi56

Masses of $^{56,57}\mathrm{Fe}$, $^{53}\mathrm{Co}$${}^{m}$, $^{53,56}\mathrm{Co}$, $^{55,56,57}\mathrm{Ni}$, $^{57,58}\mathrm{Cu}$, and $^{59,60}\mathrm{Zn}$ have been determined with the JYFLTRAP Penning trap mass spectrometer at the Ion-Guide Isotope Separator On-Line facility with a precision of $\ensuremath{\delta}m/m\ensuremath{\leqslant}3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$. The ${Q}_{\mathrm{EC}}$ values for $^{53}\mathrm{Co}$, $^{55}\mathrm{Ni}$, $^{56}\mathrm{Ni}$, $^{57}\mathrm{Cu}$, $^{58}\mathrm{Cu}$, and $^{59}\mathrm{Zn}$ have been measured directly with a typical precision of better than $0.7 \mathrm{keV}$ and Coulomb displacement energies have been dete…

Total absorption γ-ray spectroscopy of the β-delayed neutron emitters 87Br, 88Br, and 94Rb

We investigate the decay of 87,88Br and 94Rb using total absorption γ -ray spectroscopy. These important fission products are β-delayed neutron emitters. Our data show considerable βγ intensity, so far unobserved in high-resolution γ -ray spectroscopy, from states at high excitation energy. We also find significant differences with the β intensity that can be deduced from existing measurements of the β spectrum. We evaluate the impact of the present data on reactor decay heat using summation calculations. Although the effect is relatively small it helps to reduce the discrepancy between calculations and integral measurements of the photon component for 235U fission at cooling times in the r…

Strong γ-ray emission from neutron unbound states populated in β-decay: Impact on (n,γ) cross-section estimates

J. L. Taín et al. -- 6 pags., 7 figs., 1 tab. -- Open Access funded by Creative Commons Atribution Licence 4.0

The 1+→0+ Gamow–Teller strength of the 58Cug.s.→58Nig.s. transition

The ground-state branch in the beta decay of Cu-58 has been remeasured by using gamma-ray detection combined with ion-guide-based on-line mass separation. The measured value 80.8(7)% is three times more precise and in agreement with the earlier reported value. The deduced Gamow-Teller strength of this transition, to be used for the calibration of the charge-exchange reactions, is 0.0821(7). (C) 2001 Elsevier Science B.V. All rights reserved.

Accurate Q value for the 74Se double-electron-capture decay

Abstract The Q value of the neutrinoless double-electron-capture ( 0 ν ECEC ) decay of 74Se was measured by using the JYFLTRAP Penning trap. The determined value is 1209.169(49) keV, which practically excludes the possibility of a complete energy degeneracy with the second 2 + state (1204.205(7) keV) of 74Ge in a resonant 0 ν ECEC decay. We have also computed the associated nuclear matrix element by using a microscopic nuclear model with realistic two-nucleon interactions. The computed matrix element is found to be quite small. The failure of the resonant condition, combined with the small nuclear matrix element and needed p-wave capture, suppresses the decay rate strongly and thus excludes…

Total Absorption Spectroscopy of Fission Fragments Relevant for Reactor Antineutrino Spectra and Decay Heat Calculations

Volume: 111 Host publication title: WONDER-2015 Host publication sub-title: 4TH INTERNATIONAL WORKSHOP ON NUCLEAR DATA EVALUATION FOR REACTOR APPLICATIONS Isbn(print): 978-2-7598-1970-6 Beta decay of fission products is at the origin of decay heat and antineutrino emission in nuclear reactors. Decay heat represents about 7% of the reactor power during operation and strongly impacts reactor safety. Reactor antineutrino detection is used in several fundamental neutrino physics experiments and it can also be used for reactor monitoring and non-proliferation purposes. Rb-92,Rb-93 are two fission products of importance in reactor antineutrino spectra and decay heat, but their beta-decay properti…

Precision Mass Measurements beyond $^{132}$Sn: Anomalous behaviour of odd-even staggering of binding energies

Atomic masses of the neutron-rich isotopes $^{121-128}$Cd, $^{129,131}$In, $^{130-135}$Sn, $^{131-136}$Sb, and $^{132-140}$Te have been measured with high precision (10 ppb) using the Penning trap mass spectrometer JYFLTRAP. Among these, the masses of four r-process nuclei $^{135}$Sn, $^{136}$Sb, and $^{139,140}$Te were measured for the first time. The data reveals a strong $N$=82 shell gap at $Z$=50 but indicates the importance of correlations for $Z&gt;50$. An empirical neutron pairing gap expressed as the odd-even staggering of isotopic masses shows a strong quenching across $N$=82 for Sn, with the $Z$-dependence that is unexplainable by the current theoretical models.

Production of pure samples of 131mXe and 135Xe

Pure samples of (131m)Xe, (133m)Xe, (133)Xe and (135)Xe facilitate the calibration and testing of noble gas sampler stations and related laboratory instrumentation. We have earlier reported a Penning trap-based production method for pure (133m)Xe and (133)Xe samples. Here we complete the work by reporting the successful production of pure (131m)Xe and (135)Xe samples using the same technique. In addition, we present data on xenon release from graphite.

Simulations of the stopping efficiencies of fission ion guides

With the Ion Guide Isotope Separator On-Line (IGISOL) facility, located at the University of Jyväskylä, products of nuclear reactions are separated by mass. The high resolving power of the JYFLTRAP Penning trap, with full separation of individual nuclides, capacitates the study of nuclides far from the line of stability. For the production of neutron-rich medium-heavy nuclides, fissioning of actinides is a feasible reaction. This can be achieved with protons from an in-house accelerator or, alternatively, with neutrons through the addition of a newly developed Be(p,xn)-converter. The hereby-obtained fission products are used in nuclear data measurements, for example fission yields, nuclear …

Total absorption spectroscopy of fission fragments relevant for reactor antineutrino spectra

International audience; The accurate determination of reactor antineutrino spectra remains a very active research topic for which new methods of study have emerged in recent years. Indeed, following the long-recognized reactor anomaly (measured antineutrino deficit in short baseline reactor experiments when compared with spectral predictions), the three international reactor neutrino experiments Double Chooz, Daya Bay and Reno have recently demonstrated the existence of spectral distortions in their measurements with respect to the same predictions. These spectral predictions were obtained through the conversion of integral beta-energy spectra obtained at the ILL research reactor. Several s…

Isomeric states close to doubly magic $^{132}$Sn studied with JYFLTRAP

The double Penning trap mass spectrometer JYFLTRAP has been employed to measure masses and excitation energies for $11/2^-$ isomers in $^{121}$Cd, $^{123}$Cd, $^{125}$Cd and $^{133}$Te, for $1/2^-$ isomers in $^{129}$In and $^{131}$In, and for $7^-$ isomers in $^{130}$Sn and $^{134}$Sb. These first direct mass measurements of the Cd and In isomers reveal deviations to the excitation energies based on results from beta-decay experiments and yield new information on neutron- and proton-hole states close to $^{132}$Sn. A new excitation energy of 144(4) keV has been determined for $^{123}$Cd$^m$. A good agreement with the precisely known excitation energies of $^{121}$Cd$^m$, $^{130}$Sn$^m$, an…

High-precision mass measurements of 25Al and 30P at JYFLTRAP

The masses of the astrophysically relevant nuclei 25Al and 30P have been measured with a Penning trap for the first time. The mass-excess values for 25Al ( $\Delta = -8915.962(63)$ keV) and 30P ( $\Delta = -20200.854(64)$ keV) obtained with the JYFLTRAP double Penning trap mass spectrometer are in good agreement with the Atomic Mass Evaluation 2012 values but $ \approx$ 5-10 times more precise. A high precision is required for calculating resonant proton-capture rates of astrophysically important reactions 25Al (p, $ \gamma$ )26Si and 30P(p, $ \gamma$ )31S . In this work, $ Q_{(p,\gamma)} = 5513.99(13)$ keV and $ Q_{(p,\gamma)} = 6130.64(24)$ keV were obtained for 25Al and 30P , respectivel…

Optimizing charge breeding techniques for ISOL facilities in Europe: conclusions from the EMILIE project

ThuM07; International audience; The present paper summarizes the results obtained from the past few years in the framework ofthe Enhanced Multi-Ionization of short-Lived Isotopes for Eurisol (EMILIE) project. The EMILIEproject aims at improving the charge breeding techniques with both Electron Cyclotron ResonanceIon Sources (ECRIS) and Electron Beam Ion Sources (EBISs) for European Radioactive Ion Beam(RIB) facilities. Within EMILIE, an original technique for debunching the beam from EBIS chargebreeders is being developed, for making an optimal use of the capabilities of CW post-acceleratorsof the future facilities. Such a debunching technique should eventually resolve duty cycle andtime st…

Medium-spin structure of neutron-rich Pd and Cd isotopes

Cadmium isotopes are traditionally considered as good examples of nearly spherical, vibrational nuclei, which can be described by quadrupole vibrators in the collective model, as well as the U(5) dynamical symmetry in the interacting boson model (IBM). However, the shape coexistence of more deformed intruder states originating from proton 2p–4h excitation across the Z = 50 major shell is another interesting structural aspect, whose presence in Pd-isotopes has also been demonstrated [1,2].

Total Absorption Spectroscopy of Fission Fragments Relevant for Reactor Antineutrino Spectra and Decay Heat Calculations

Beta decay of fission products is at the origin of decay heat and antineutrino emission in nuclear reactors. Decay heat represents about 7% of the reactor power during operation and strongly impacts reactor safety. Reactor antineutrino detection is used in several fundamental neutrino physics experiments and it can also be used for reactor monitoring and non-proliferation purposes. 92,93Rb are two fission products of importance in reactor antineutrino spectra and decay heat, but their β-decay properties are not well known. New measurements of 92,93Rb β-decay properties have been performed at the IGISOL facility (Jyväskylä, Finland) using Total Absorption Spectroscopy (TAS). TAS is complemen…

Transport of ions in ion guides under flow and diffusion

Abstract A model for ion transport simulations in the ion guide stopping chamber is introduced. Computed transport time distributions are compared to the experimental data obtained in on- and off-line conditions. It is shown that millisecond transport times are feasible and that diffusion of ions is an important mechanism in transport.

Excited levels in the multishaped 117Pd nucleus studied via β decay of 117Rh

Monoisotopic samples of exotic, neutron-rich 117Rh nuclei, produced in the proton-induced fission of 238U and separated using the IGISOL mass separator coupled to the JYFLTRAP Penning trap, were used to perform β and γ coincidence spectroscopy of 117Pd. The spin parity of the ground state of 117Pd was determined to be 1/2+ and the 19.1 ms isomer at 203.2 keV was assigned a spin-parity 7/2−. The 117Rh β−-decay scheme was considerably extended, and various sequences of the levels were interpreted as resulting from the prolate, oblate, and triaxial nuclear shapes. Some of the β− decays were considered as the allowed Gamow-Teller transitions. The experimental distribution of Gamow-Teller streng…

Measurements of isomeric yield ratios of fission products from proton-induced fission on natU and 232Th via direct ion counting

Independent isomeric yield ratios (IYR) of 81Ge, 96Y, 97Y, 97Nb, 128Sn and 130Sn have been determined in the 25 MeV proton-induced fission of natU and 232Th. The measurements were performed at the Ion Guide Isotope Separator On-Line (IGISOL) facility at the University of Jyväskylä. A direct ion counting measurement of the isomeric fission yield ratios was accomplished for the first time, registering the fission products in less than a second after their production. In addition, the IYRs of natU were measured by means of γ-spectroscopy in order to verify the consistency of the recently upgraded experimental setup. From the obtained results, indications of a dependence of the production rate …

Mass Measurements for the rp Process

One of the key parameters for the reaction network calculations for the rapid proton capture (rp) process, occurring e.g., in type I X-ray bursts, are the masses of the involved nuclei. Nowadays, masses of even rather exotic nuclei can be measured very precisely employing Penning-trap mass spectrometry. With the JYFLTRAP Penning trap at the IGISOL facility, masses of around 100 neutron-deficient nuclei have been determined with a typical precision of a few keV. Most recently, 25Al, 30P, 31Cl, and 52Co have been measured. Of these, the precision of the mass-excess value of 31Cl was improved from 50 to 3.4 keV, and the mass of 52Co was experimentally determined for the first time. The mass of…

Electron capture on 116In and implications for nuclear structure related to double-\beta decay

The electron capture decay branch of 116In has been measured to be [2.46 ± 0.44(stat.) ± 0.39(syst.)] × 10−4 using Penning trap-assisted decay spectroscopy. The corresponding Gamow-Teller transition strength is shown to be compatible with the most recent value extracted from the (p, n) charge-exchange reaction, providing a resolution to longstanding discrepancies. This transition can now be used as a reliable benchmark for nuclearstructure calculations of the matrix element for the neutrinoless double-β decay of 116Cd and other nuclides. peerReviewed

Extension of Penning-trap mass measurements to very short-lived nuclides

Abstract Mass measurements on 33,34,42,43 Ar have been performed at the ISOLTRAP spectrometer. An accuracy of δm ≈4 keV has been achieved for all measured isotopes. With 33 Ar it is the first time that a nuclide with a half-life shorter than one second has been investigated using a Penning trap. This became possible due to the recently installed linear radio-frequency ion-trap system and an improved, faster measurement cycle.

Status of the ion trap project at IGISOL

The IGISOL fa ility at the Department of Physi s of the University of Jyväskylä (JYFL) is delivering radioa tive beams of short-lived exoti nu lei, in parti ular the neutron-ri h isotopes from the ssion rea tion. These nu lei are studied with the nu lear spe tros opy methods. In order to substantially in rease the quality and sensitivity of su h studies the beam should undergo beam handling: ooling, bun hing and isobari puri ation. The rst two pro esses are performed with the use of an RFQ ooler/bun her. The isobari puri ation will be made by a Penning trap pla ed after the RF- ooler element. This ontribution des ribes the urrent status of the ion trap pro je t and its future prospe ts. The…

First evidence of multiple β-delayed neutron emission for isotopes with a > 100

The β-delayed neutron emission probability, Pn, of very neutron-rich nuclei allows us to achieve a better understanding of the nuclear structure above the neutron separation energy, Sn. The emission of neutrons can become the dominant decay process in neutron-rich astrophysical phenomena such as the rapid neutron capture process (r-process). There are around 600 accessible isotopes for which β-delayed one-neutron emission (β1n) is energetically allowed, but the branching ratio has only been determined for about one third of them. β1n decays have been experimentally measured up to the mass A ∼ 150, plus a single measurement of 210Tl. Concerning two-neutron emitters (β2n), ∼ 300 isotopes are …

Penning trap for isobaric purification of radioactive ion beams at IGISOL

Precision Mass Measurements beyondSn132: Anomalous Behavior of Odd-Even Staggering of Binding Energies

Atomic masses of the neutron-rich isotopes $^{121--128}\mathrm{Cd}$, $^{129,131}\mathrm{In}$, $^{130--135}\mathrm{Sn}$, $^{131--136}\mathrm{Sb}$, and $^{132--140}\mathrm{Te}$ have been measured with high precision (10 ppb) using the Penning-trap mass spectrometer JYFLTRAP. Among these, the masses of four $r$-process nuclei $^{135}\mathrm{Sn}$, $^{136}\mathrm{Sb}$, and $^{139,140}\mathrm{Te}$ were measured for the first time. An empirical neutron pairing gap expressed as the odd-even staggering of isotopic masses shows a strong quenching across $N=82$ for Sn, with a $Z$ dependence that is unexplainable by the current theoretical models.

Total absorption γ -ray spectroscopy of the β -delayed neutron emitters Br87 , Br88 , and Rb94

We investigate the decay of 87,88Br and 94Rb using total absorption γ -ray spectroscopy. These important fission products are β-delayed neutron emitters. Our data show considerable βγ intensity, so far unobserved in high-resolution γ -ray spectroscopy, from states at high excitation energy. We also find significant differences with the β intensity that can be deduced from existing measurements of the β spectrum. We evaluate the impact of the present data on reactor decay heat using summation calculations. Although the effect is relatively small it helps to reduce the discrepancy between calculations and integral measurements of the photon component for 235U fission at cooling times in the r…

r Process (n, γ) Rate Constraints from the γ Emission of Neutron Unbound States in β decay

Total absorption gamma-ray spectroscopy is used to measure accurately the intensity of γγ emission from neutron-unbound states populated in the ββ-decay of delayed-neutron emitters. From the comparison of this intensity with the intensity of neutron emission a constraint on the (n, γγ) cross section for highly unstable neutron-rich nuclei can be deduced. A surprisingly large γγ branching was observed for a number of isotopes which might indicate the need to increase by a large factor the Hauser-Feshbach (n, γγ) cross-section estimates that impact on r process abundance calculations. peerReviewed

Total Absorption Spectroscopy Study ofRb92Decay: 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 antineutrino 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.

Recent mass measurements for the r process at JYFLTRAP

Mass Measurements for the rp Process

Status of HIGISOL a new version equipped with SPIG and electric field guidance

A new HIGISOL chamber devoted to the study of short-lived products from heavy-ion-induced fusion-evaporation reactions is proposed. It enables, via the extraction of ions by means of a SPIG (SextuPole rf Ion Guide), to improve the mass resolving power by a factor 2.5 compared to the previous system using a skimmer-ring assembly. The gas cell was also equiped with an electric field for faster transportation of recoiling ions to the nozzle where they are ejected with the gas jet. The first results obtained both with a radioactive α-source and cyclotron beam will be reported.

Excited levels in the multishaped Pd117 nucleus studied via β decay of Rh117

Monoisotopic samples of exotic, neutron-rich $^{117}\mathrm{Rh}$ nuclei, produced in the proton-induced fission of $^{238}\mathrm{U}$ and separated using the IGISOL mass separator coupled to the JYFLTRAP Penning trap, were used to perform $\ensuremath{\beta}$ and $\ensuremath{\gamma}$ coincidence spectroscopy of $^{117}\mathrm{Pd}$. The spin parity of the ground state of $^{117}\mathrm{Pd}$ was determined to be $1/{2}^{+}$ and the 19.1 ms isomer at 203.2 keV was assigned a spin-parity $7/{2}^{\ensuremath{-}}$. The $^{117}\mathrm{Rh}$ ${\ensuremath{\beta}}^{\ensuremath{-}}$-decay scheme was considerably extended, and various sequences of the levels were interpreted as resulting from the prol…

Summation Calculations for Reactor Antineutrino Spectra, Decay Heat and Delayed Neutron Fractions Involving New TAGS Data and Evaluated Databases

9 pags., 3 figs. -- Open Access funded by Creative Commons Atribution Licence 4.0

New levels in 118Pd observed in the beta-decay of very neutron-rich 118Rh isotope

We investigate the β decay of very neutron-rich 118Rh isotope using on-line mass-separated sources which are produced by applying 25 MeV proton induced symmetric fission of natural uranium at the IGISOL facility. The β–γ and γ–γ coincidence spectroscopy is employed to establish the level scheme of daughter nucleus 118Pd. Five low-lying new levels are identified for the first time with tentative spin and parity assignments based on the even-mass Pd systematics.

Coulomb displacement energies as a probe for nucleon pairing in the $f_{7/2}$ shell

Coulomb displacement energies of $T=1/2$ mirror nuclei have been studied via a series of high-precision $Q_\mathrm{EC}$-value measurements with the double Penning trap mass spectrometer JYFLTRAP. Most recently, the $Q_\mathrm{EC}$ values of the $f_{7/2}$-shell mirror nuclei $^{45}$V ($Q_\mathrm{EC}=7123.82(22)$ keV) and $^{49}$Mn ($Q_\mathrm{EC}=7712.42(24)$ keV) have been measured with an unprecedented precision. The data reveal a 16-keV ($1.6\sigma$) offset in the adopted Atomic Mass Evaluation 2012 value of $^{49}$Mn suggesting the need for further measurements to verify the breakdown of the quadratic form of the isobaric multiplet mass equation. Precisely measured $Q_\mathrm{EC}$ values…

Characterization and performance of the DTAS detector

11 pags., 16 figs., 3 tabs.

Accurate mass measurements on neutron-deficient krypton isotopes

soumis à Nuclear Physics A; The masses of $^{72-78,80,82,86}$Kr were measured directly with the ISOLTRAP Penning trap mass spectrometer at ISOLDE/CERN. For all these nuclides, the measurements yielded mass uncertainties below 10 keV. The ISOLTRAP mass values for $^{72-75}$Kr outweighed previous results obtained by means of other techniques, and thus completely determine the new values in the Atomic-Mass Evaluation. Besides the interest of these masses for nuclear astrophysics, nuclear structure studies, and Standard Model tests, these results constitute a valuable and accurate input to improve mass models. In this paper, we present the mass measurements and discuss the mass evaluation for t…

Enhancedγ-Ray Emission from Neutron Unbound States Populated inβDecay

Total absorption spectroscopy is used to investigate the β-decay intensity to states above the neutron separation energy followed by γ-ray emission in (87,88)Br and (94)Rb. Accurate results are obtained thanks to a careful control of systematic errors. An unexpectedly large γ intensity is observed in all three cases extending well beyond the excitation energy region where neutron penetration is hindered by low neutron energy. The γ branching as a function of excitation energy is compared to Hauser-Feshbach model calculations. For (87)Br and (88)Br the γ branching reaches 57% and 20%, respectively, and could be explained as a nuclear structure effect. Some of the states populated in the daug…

A neutron source for IGISOL-JYFLTRAP : Design and characterisation

A white neutron source based on the Be(p, nx) reaction for fission studies at the IGISOL-JYFLTRAP facility has been designed and tested. 30MeV protons impinge on a 5mm thick water-cooled beryllium disc. The source was designed to produce at least 1012 fast neutrons/s on a secondary fission target, in order to reach competitive production rates of fission products far from the valley of stability. The Monte Carlo codes MCNPX and FLUKA were used in the design phase to simulate the neutron energy spectra. Two experiments to characterise the neutron field were performed: the first was carried out at The Svedberg Laboratory in Uppsala (SE), using an Extended-Range Bonner Sphere Spectrometer and …

Penning trap for isobaric mass separation at IGISOL

Abstract A cylindrical Penning trap has been built at the ion guide isotope separator facility IGISOL of the University of Jyvaskyla. The main goal of the Penning trap application is to purify low-energy radioactive ion beams. The aim is to make isobarically pure beams. The technical description is presented.

QECvalues of the superallowedβemittersC10,Ar34,Ca38, andV46

The ${Q}_{\mathrm{EC}}$ values of the superallowed ${\ensuremath{\beta}}^{+}$ emitters $^{10}\mathrm{C}$, $^{34}\mathrm{Ar}$, $^{38}\mathrm{Ca}$, and $^{46}\mathrm{V}$ have been measured with the JYFLTRAP Penning-trap mass spectrometer to be 3648.12(8), 6061.83(8), 6612.12(7), and 7052.44(10) keV, respectively. All four values are substantially improved in precision over previous results. Of the well-known superallowed emitters, only $^{14}\mathrm{O}$ has yet to have had its ${Q}_{\mathrm{EC}}$ value measured with a Penning trap.

ANDES Measurements for Advanced Reactor Systems

Abstract A significant number of new measurements was undertaken by the ANDES “Measurements for advanced reactor systems” initiative. These new measurements include neutron inelastic scattering from 23 Na, Mo, Zr, and 238 U, neutron capture cross sections of 238 U, 241 Am, neutron induced fission cross sections of 240 Pu, 242 Pu, 241 Am, 243 Am and 245 Cm, and measurements that explore the limits of the surrogate technique. The latter study the feasibility of inferring neutron capture cross sections for Cm isotopes, the neutron-induced fission cross section of 238 Pu and fission yields and fission probabilities through full Z and A identification in inverse kinematics for isotopes of Pu, Am…

JYFLTRAP: a Penning trap for precision mass spectroscopy and isobaric purification

In this article a comprehensive description and performance of the double Penning-trap setup JYFLTRAP will be detailed. The setup is designed for atomic mass measurements of both radioactive and stable ions and additionally serves as a very high-resolution mass separator. The setup is coupled to the IGISOL facility at the accelerator laboratory of the University of Jyväskylä. The trap has been online since 2003 and it was shut down in the summer of 2010 for relocation to the upgraded IGISOL facility. Numerous atomic mass and decay energy measurements have been performed using the time-of-flight ion-cyclotron resonance technique. The trap has also been used in several decay spectroscopy expe…

Accurate Fission Data for Nuclear Safety

The Accurate fission data for nuclear safety (AlFONS) project aims at high precision measurements of fission yields, using the renewed IGISOL mass separator facility in combination with a new high current light ion cyclotron at the University of Jyvaskyla. The 30 MeV proton beam will be used to create fast and thermal neutron spectra for the study of neutron induced fission yields. Thanks to a series of mass separating elements, culminating with the JYFLTRAP Penning trap, it is possible to achieve a mass resolving power in the order of a few hundred thousands. In this paper we present the experimental setup and the design of a neutron converter target for IGISOL. The goal is to have a flexi…

Characterization of a cylindrical plastic {\beta}-detector with Monte Carlo simulations of optical photons

V. Guadilla et al. -- 5 pags., 8 figs., tab.

Fission yield measurements at IGISOL

The fission product yields are an important characteristic of the fission process. In fundamental physics, knowledge of the yield distributions is needed to better understand the fission process. For nuclear energy applications good knowledge of neutroninduced fission-product yields is important for the safe and efficient operation of nuclear power plants. With the Ion Guide Isotope Separator On-Line (IGISOL) technique, products of nuclear reactions are stopped in a buffer gas and then extracted and separated by mass. Thanks to the high resolving power of the JYFLTRAP Penning trap, at University of Jyväskylä, fission products can be isobarically separated, making it possible to measure rela…

Trap-assisted separation of nuclear states for gamma-ray spectroscopy: the example of100Nb

Low-lying levels in 100Mo are known to be populated by beta decay from both the ground and isomeric states in 100Nb. The small energy difference (~3 ppm) between the two parent states and the similarity of their half-lives make it difficult to distinguish experimentally between the two decay paths. A new technique for separating different states of nuclei has recently been developed in a series of experiments at the IGISOL facility, using the JYFLTRAP installation, at the University of Jyvaskyla where mass resolution ~2 ppm was achieved in mass measurements and in the production of 133mXe. This paper reports on the extension of this technique to allow the separate study of the gamma-ray dec…

JYFLTRAP: a cylindrical Penning trap for isobaric beam purification at IGISOL

Abstract A Penning trap has been installed for isobaric beam purification at the IGISOL-facility at the University of Jyvaskyla. In this paper, the technical details of this new device together with results of the first tests are presented. The mass resolving power, depending on the excitation parameters and the ion species, can be as high as 145 000 and the total transmission has been determined to be 17%. In addition, it is shown that with this experimental setup it is possible to measure atomic masses up to A=120 with accuracies of approximately 50 keV .

Ultra-high resolution mass separator—Application to detection of nuclear weapons tests

Abstract A Penning trap-based purification process having a resolution of about 1 ppm is reported. In this context, we present for the first time a production method for the most complicated and crucially important nuclear weapons test signature, 133mXe. These pure xenon samples are required by the Comprehensive Nuclear-Test-Ban Treaty Organization to standardize and calibrate the worldwide network of xenon detectors.

Large Impact of the Decay of Niobium Isomers on the Reactor ν¯e Summation Calculations

Even mass neutron-rich niobium isotopes are among the principal contributors to the reactor antineutrino energy spectrum. They are also among the most challenging to measure due to the refractory nature of niobium, and because they exhibit isomeric states lying very close in energy. The beta-intensity distributions of Nb-100gs,Nb-100m and Nb-102gs,Nb-02m beta decays have been determined using the total absorption.-ray spectroscopy technique. The measurements were performed at the upgraded Ion Guide Isotope Separator On-Line facility at the University of Jyvaskyla. Here, the double Penning trap system JYFLTRAP was employed to disentangle the beta decay of the isomeric states. The new data ob…

Penning trap at IGISOL

The IGISOL facility [1] at the Department of Physics of the University of Jyvaskyla (JYFL) is delivering radioactive beams of short-lived exotic nuclei, in particular the neutron-rich isotopes from fission reaction. These nuclei are studied with the nuclear and collinear laser spectroscopy methods. In order to obtain a meaningful increase, in comparison to a standard level, of precision and sensitivity of such studies an improvement of the radioactive beam quality is necessary. This improvement will be achieved due to a radioactive beam handling which consists of three steps: beam cooling, bunching and (isobaric) purification. The latter means a possibility of obtaining a pure monoisotopic …

TAGS measurements of $^{100}$Nb ground and isomeric states and $^{140}$Cs for neutrino physics with the new DTAS detector

V. Guadilla et al. -- 4 pags., 6 figs. -- Open Access funded by Creative Commons Atribution Licence 4.0

Prospects for advanced electron cyclotron resonance and electron beam ion source charge breeding methods for EURISOL

International audience; As the most ambitious concept of isotope separation on line (ISOL) facility, EURISOL aims at producing unprecedented intensities of post-accelerated radioactive isotopes. Charge breeding, which transforms the charge state of radioactive beams from 1+ to an n+ charge state prior to postacceleration, is a key technology which has to overcome the following challenges: high charge states for high energies, efficiency, rapidity and purity. On the roadmap to EURISOL, a dedicated R&D is being undertaken to push forward the frontiers of the present state-of-the-art techniques which use either electron cyclotron resonance or electron beam ion sources. We describe here the gui…

QEC value of the superallowed β emitter 42Sc

The QEC value of the superallowed β+ emitter Sc42 has been measured with the JYFLTRAP Penning-trap mass spectrometer at the University of Jyväskylä to be 6426.350(53) keV. This result is at least a factor of four more precise than all previous measurements, which were also inconsistent with one another. As a byproduct we determine the excitation energy of the 7+ isomeric state in Sc42 to be 616.762(46) keV, which deviates by 8σ from the previous measurement. peerReviewed

Mass Measurement on therp-Process Waiting PointKr72

With the aim of improving nucleosynthesis calculations, we performed for the first time, a direct high-precision mass measurement on the waiting point in the astrophysical rp-process 72Kr. We used the ISOLTRAP Penning trap mass spectrometer located at ISOLDE/CERN. The measurement yielded a relative mass uncertainty of δm/m = 1.2×10-7. In addition, the masses of 73Kr and 74Kr were measured directly with relative mass uncertainties of 1.0×10-7 and 3×10-8, respectively. We analyzed the role of 72Kr in the rp-process during X-ray bursts using the ISOLTRAP and previous mass values of 72-74Kr.

QEC value of the superallowed β emitter Sc42

Precise measurements of superallowed ${0}^{+}\ensuremath{\rightarrow}{0}^{+}$ $\ensuremath{\beta}$ decay presently provide the most precise value for the weak mixing amplitude ${V}_{u\phantom{\rule{0}{0ex}}d}$. As the largest element of the CKM matrix, ${V}_{u\phantom{\rule{0}{0ex}}d}$ is a critical piece of the Standard Model of the electroweak interaction. The new, precise Penning-trap mass measurement of the decay energy for the superallowed transition in ${}^{42}$Sc opens the door for a much more precise $f\phantom{\rule{0}{0ex}}t$ value determination if its half-life can be measured more precisely as well.

Total absorption spectroscopy study of the β decay of Br86 and Rb91

The beta decays of 86Br and 91Rb have been studied using the total absorption spectroscopy technique. The radioactive nuclei were produced at the IGISOL facility in Jyvaskyla and further purified using the JYFLTRAP. 86Br and 91Rb are considered high priority contributors to the decay heat in reactors. In addition 91Rb was used as a normalization point in direct measurements of mean gamma energies released in the beta decay of fission products by Rudstam et al. assuming that this decay was well known from high-resolution measurements. Our results shows that both decays were suffering from the Pandemonium effect and that the results of Rudstam et al. should be renormalized.

High-precision mass measurement of 31S with the double Penning trap JYFLTRAP improves the mass value for 32Cl

b-decay of 116Agm and the vibrational structure of 116Cd

The structure of near neutron midshell 116 Cd has been investigated via β decay of 116 Ag m by β-γ and γ-γ coincidence spectroscopy. The 116 Ag m activity was produced by symmetric fission of natural uranium induced by 25 MeV protons. The ion guide technique has been employed to produce online mass separated sources. The decay scheme of 116 Ag m has been considerably extended by adding 19 new excited states of 116 Cd . The newly identified 116 Cd state at 1869.7 keV, along with other four levels near 2 MeV, are interpreted as forming the complete three-phonon quintuplet. The vibrational structure of 116 Cd is discussed in the context of an anharmonic vibrator. peerReviewed