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Direct mass measurements of neutron-deficient nuclides around the N=50 shell closure below $^{100}$Sn were performed at the FRS Ion Catcher (FRS-IC) at GSI, Germany. The nuclei were produced by projectile fragmentation of $^{124}$Xe, separated in the fragment separator FRS and delivered to the FRS-IC. The masses of 14 ground states and two isomers were measured with relative mass uncertainties down to 1×10−7 using the multiple-reflection time-of-flight mass spectrometer of the FRS-IC, including the first direct mass measurements of $^{98}$Cd and $^{97}$Rh. A new QEC=5437±67 keV was obtained for $^{98}$Cd, resulting in a summed Gamow-Teller (GT) strength for the five observed transitions (0+⟶1+) as B(GT)=2.94−0.28+0.32. Investigation of this result in state-of-the-art shell model approaches accounting for the first time experimentally observed spectrum of GT transitions points to a perfect agreement for N=50 isotones. The excitation energy of the long-lived isomeric state in $^{94}$Rh was determined for the first time to be 293±21 keV. This, together with the shell model calculations, allows the level ordering in $^{94}$Rh to be understood.

Mass measurements of the $^{69}$As, $^{70,71}$Se and $^{71}$Br isotopes, produced via fragmentation of a $^{124}$Xe primary beam at the FRS at GSI, have been performed with the multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) of the FRS Ion Catcher with an unprecedented mass resolving power of almost 1,000,000. For the $^{69}$As isotope, this is the first direct mass measurement. A mass uncertainty of 22 keV was achieved with only 10 events. For the $^{70}$Se isotope, a mass uncertainty of 2.6 keV was obtained, corresponding to a relative accuracy of $\delta$m/m = 4.0$\times 10^{-8}$, with less than 500 events. The masses of the $^{71}$Se and $^{71}$Br isotopes were measured with an uncertainty of 23 and 16 keV, respectively. Our results for the $^{70,71}$Se and $^{71}$Br isotopes agree with the 2016 Atomic Mass Evaluation, and our result for the $^{69}$As isotope resolves the discrepancy between previous indirect measurements. We measured also the mass of $^{14}$N$^{15}$N$^{40}$Ar (A=69) with a relative accuracy of $\delta$m/m = 1.7$\times 10^{-8}$, the highest yet achieved with a MR-TOF-MS. Our results show that the measured restrengthening of the proton-neutron interaction ($\delta$V$_{pn}$) for odd-odd nuclei at the N=Z line above Z=29 (recently extended to Z=37) is hardly evident at N-Z=2, and not evident at N-Z=4. Nevertheless, detailed structure of $\delta$V$_{pn}$ along the N-Z=2 and N-Z=4 lines, confirmed by our mass measurements, may provide a hint regarding the ongoing $\approx$500 keV discrepancy in the mass value of the $^{70}$Br isotope, which prevents including it in the world average of ${Ft}$-value for superallowed 0$^+\rightarrow$ 0$^+$ $\beta$ decays. The reported work sets the stage for mass measurements with the FRS Ion Catcher of nuclei at and beyond the N=Z line in the same region of the nuclear chart, including the $^{70}$Br isotope., Comment: 11 pages, 4 figures, accepted for publication at Physical Review C

Understanding the evolution of the nuclear charge radius is one of the long-standing challenges for nuclear theory. Recently, density functional theory calculations utilizing Fayans functionals have successfully reproduced the charge radii of a variety of exotic isotopes. However, difficulties in the isotope production have hindered testing these models in the immediate region of the nuclear chart below the heaviest self-conjugate doubly-magic nucleus 100Sn, where the near-equal number of protons (Z) and neutrons (N) lead to enhanced neutron-proton pairing. Here, we present an optical excursion into this region by crossing the N = 50 magic neutron number in the silver isotopic chain with the measurement of the charge radius of 96Ag (N = 49). The results provide a challenge for nuclear theory: calculations are unable to reproduce the pronounced discontinuity in the charge radii as one moves below N = 50. The technical advancements in this work open the N = Z region below 100Sn for further optical studies, which will lead to more comprehensive input for nuclear theory development., Laser spectroscopic measurements of isotopes near the doubly-magic 100-Sn are challenging due to difficulties in their production. Here the authors measure the ground state charge radius of the proton-rich 96-Ag isotope and find a discontinuity in the nuclear size when crossing the neutron number N equal to 50.

The JYFLTRAP double Penning trap at the Ion Guide Isotope Separator On-Line (IGISOL) facility has been used to measure the atomic masses of 13 neutron-rich rare-earth isotopes. Eight of the nuclides, $^{161}$Pm, $^{163}$Sm, $^{164,165}$Eu, $^{167}$Gd, and $^{165,167,168}$Tb, were measured for the first time. The systematics of the mass surface has been studied via one- and two-neutron separation energies as well as neutron pairing-gap and shell-gap energies. The proton-neutron pairing strength has also been investigated. The impact of the new mass values on the astrophysical rapid neutron capture process has been studied. The calculated abundance distribution results in a better agreement with the solar abundance pattern near the top of the rare-earth abundance peak at around $A\approx165$., Comment: 15 pages, 17 figures

An off-line ion source station has been commissioned at the IGISOL (Ion Guide Isotope Separator On-Line) facility. It offers the infrastructure needed to produce stable ion beams from three off-line ion sources in parallel with the radioactive ion beams produced from the IGISOL target chamber. This has resulted in improved feasibility for new experiments by offering reference ions for Penning-trap mass measurements, laser spectroscopy and atom trap experiments., Comment: 3 pages, 1 figure, submitted to Nuclear Instruments and Methods

6 pags., 3 figs., 1 tab. -- 27th International Nuclear Physics Conference (INPC2019) 29 July - 2 August 2019, Glasgow, UK, In this contribution we summarize the recent study of the β decay of neutron-rich nuclei with isomeric states close in energy to the ground states. The disentanglement of each pair of β-decaying states was achieved by applying different strategies and using the purification capabilities of the JYFLTRAP double Penning trap system at the Ion Guide Isotope Separator On-Line facility in Jyväskylä. The Total Absorption γ-ray Spectroscopy technique was employed to determine the β intensity probabilities populating the excited states in the daughter nuclei. Previously undetected β intensity was found and we have already evaluated the impact of part of these results on reactor summation calculations. The possibility to populate states associated with the Pygmy Dipole Resonance in the β decay of 96gsY has also been investigated thanks to the sensitivity of our technique to high-lying strength in the daughter nuclei., This work has been supported by the CNRS challenge NEEDS and the associated NACRE project, as well as by the Spanish Ministerio de Econom´ıa y Competitividad under Grants No. FPA2011-24553, No. AIC-A-2011-0696, No. FPA2014-52823-C2-1-P, No. FPA2015-65035-P, No. FPI/BES-2014-068222, No. FPA2017-83946-C2-1-P and the program Severo Ochoa (SEV-2014-0398), by the Spanish Ministerio de Educacion under the FPU12/01527 Grant, by the European Commission under the FP7/EURATOM contract 605203 and the FP7/ENSAR contract 262010, and by the Junta para la Ampliacion de Estudios ´ Programme (CSIC JAE-Doc contract) co-financed by ESF.

The absolute mass value of $^{168}$Yb has been directly determined with the JYFLTRAP Penning trap mass spectrometer at the Ion Guide Isotope Separator On-Line (IGISOL) facility. A more precise value of the mass of $^{168}$Yb is needed to extract possible signatures of beyond standard model physics from high-precision isotope shift measurements of Yb atomic transition frequencies. The measured mass-excess value, ME($^{168}$Yb) = $-$61579.846(94) keV, is 12 times more precise and deviates from the Atomic Mass Evaluation 2016 value by 1.7$\sigma$. The impact on precision isotope shift studies of the stable Yb isotopes is discussed., Comment: 4 pages, 2 figures

For the production of exotic nuclei at the IGISOL facility, an ion guide for neutron-induced fission has been developed and tested in experiments. Fission fragments are produced inside the ion guide and collected using a helium buffer gas. Meanwhile, a GEANT4 model has been developed to simulate the transportation and stopping of the charged fission products. In a recent measurement of neutron-induced fission yields, implantation foils were located at different positions in the ion guide. The gamma spectra from these foils and the fission targets are compared to the results from the GEANT4 simulation. In order to allow fission yield measurements in the low yield regions, towards the tails and in the symmetric part of the mass distribution, the stopping and extraction efficiency of the ion guide has to be significantly improved. This objective can be achieved by increasing the size while introducing electric field guidance using a combination of static electrodes and an RF-carpet. To this end, the GEANT4 model is used to optimise the design of such an ion guide.

Isomeric states in 128In and 130In have been studied with the JYFLTRAP Penning trap at the IGISOL facility. By employing state-of-the-art ion manipulation techniques, three different beta-decaying states in 128In and 130In have been separated and their masses measured. JYFLTRAP was also used to select the ions of interest for identification at a post-trap decay spectroscopy station. A new beta-decaying high-spin isomer feeding the isomer in 128Sn has been discovered in 128In at 1797.6(20) keV. Shell-model calculations employing a CD-Bonn potential re-normalized with the perturbative G-matrix approach suggest this new isomer to be a 16⁺ spin-trap isomer. In 130In, the lowest-lying (10⁻) isomeric state at 58.6(82) keV was resolved for the first time using the phase-imaging ion cyclotron resonance technique. The energy difference between the 10⁻ and 1⁻ states in 130In, stemming from parallel/antiparallel coupling of (π0g-19/2) ⊗ (v0h-111/2), has been found to be around 200 keV lower than predicted by the shell model. Precise information on the energies of the excited states determined in this work is crucial for producing new improved effective interactions for the nuclear shell model description of nuclei near 132Sn.

12 pags., 6 figs., 3 tabs., 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 4π γ − 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 relevant for nuclear structure studies as well. Pertinent formulas are revised and extended to the special case of β-delayed neutron emitters, and the robustness of the method is demonstrated with synthetic data. We apply it to a number of measured decays that serve as test cases and discuss the features of the method. Finally, we obtain g.s. feeding intensities with reduced uncertainty for four relevant decays that will allow future improvements in antineutrino spectrum and decay heat calculations using the summation method., This work has been supported by the Spanish Ministerio de Economía y Competitividad under Grants No. FPA2011- 24553, No. AIC-A-2011-0696, No. FPA2014-52823-C2- 1-P, No. FPA2015-65035-P, No. FPI/BES-2014-068222, No. FPA2017-83946-C2-1-P, and No. RTI2018-098868-BI00 and the program Severo Ochoa (SEV-2014-0398); by the Spanish Ministerio de Educación under Grant No. FPU12/01527; by the Spanish Ministerio de Ciencia e Innovación under Grant No. PID2019-104714GB-C21; by the European Commission under CHANDA project funded under FP7-EURATOM-FISSION Grant No. 605203; the FP7/ENSAR Contract No. 262010; the SANDA project funded under H2020-EURATOM-1.1 Grant No. 847552; the Horizon 2020 research and innovation programme under Grant No. 771036 (ERC CoG MAIDEN); by the Generalitat Valenciana regional funds PROMETEO/2019/007/; and by the Junta para la Ampliacion de Estudios ´ Programme (CSIC JAE-Doc contract) co-financed by ESF. We acknowledge the support of the UK Science and Technology Facilities Council (STFC) Grant No. ST/P005314/1; of the Polish National Agency for Academic Exchange (NAWA) under Grant No. PPN/ULM/2019/1/00220; and of the National Science Center, Poland, under Contract No. 2019/35/D/ST2/02081. This work was also supported by the Academy of Finland under the Finnish Centre of Excellence Programme (Project No. 213503, Nuclear and Accelerator-Based Physics Research at JYFL). A.K. and T.E. acknowledge support from the Academy of Finland under Projects No. 275389 and No. 295207, respectively. This work has also been supported by the CNRS challenge NEEDS and the associated NACRE project, the CNRS/in2p3 PICS TAGS between Subatech and IFIC, and the CNRS/in2p3 Master projects Jyvaskyla and OPALE.

The use of multi-nucleon transfer (MNT) reactions to produce neutron-rich nuclei in the heavy region has received an increased attention in the last decade. The feasibility of employing such reactions at the FRS Ion Catcher facility at GSI and the IGISOL facility at JYFL is studied using a combination of theoretical calculations and experiment simulations. The reactions are computed within a Langevin-type model, and the Geant program is used to simulate the transport of the resulting products within the experimental setups of the above-mentioned facilities. The angular distribution of ion release, possible target choices and target-to-beam-dump distances are discussed. peerReviewed

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 sensitivity of our spectrometer, we have found a significant amount of β intensity to states above the neutron separation energy that deexcite by γ rays, comparable to the neutron emission probability. The competition between γ deexcitation and neutron emission has been compared with Hauser-Feshbach calculations, and it can be understood as a nuclear structure effect. In addition, we have studied the impact of the β-intensity distributions determined in this work on reactor decay heat and reactor antineutrino spectrum summation calculations. The robustness of our results is demonstrated by a thorough study of uncertainties and with the reproduction of the spectra of the individual modules and the module-multiplicity gated spectra. This work represents the state-of-the-art of our analysis methodology for segmented total absorption spectrometers.

Angle-integrated cross-section measurements of the $^{56}$Ni(d,n) and (d,p) stripping reactions have been performed to determine the single-particle strengths of low-lying excited states in the mirror nuclei pair $^{57}$Cu-$^{57}$Ni situated adjacent to the doubly magic nucleus $^{56}$Ni. The reactions were studied in inverse kinematics utilizing a beam of radioactive $^{56}$Ni ions in conjunction with the GRETINA $\gamma$-array. Spectroscopic factors are compared with new shell-model calculations using a full $pf$ model space with the GPFX1A Hamiltonian for the isospin-conserving strong interaction plus Coulomb and charge-dependent Hamiltonians. These results were used to set new constraints on the $^{56}$Ni(p,$\gamma$)$^{57}$Cu reaction rate for explosive burning conditions in x-ray bursts, where $^{56}$Ni represents a key waiting point in the astrophysical rp-process., Comment: Final version accepted and published. 5 pages, 2 figures

Female role models reduce the impact on women of stereotype threat, i.e. of being at risk of conforming to a negative stereotype about one’s social, gender, or racial group (Fine in Delusion of Gender. W.W. Norton & Co. NY, p. 36, 2010 [1]; Steele and Aronson in J Pers Soc Psychol 69:797–811, 1995 [2]). This can lead women scientists to underperform or to leave their scientific career because of negative stereotypes such as, not being as talented or as interested in science as men. Sadly, history rarely provides role models for women scientists; instead, it often renders these women invisible (CafeBabel Homepage [3]). In response to this situation, we present a selection of twelve outstanding women who helped to develop nuclear astrophysics., SCOPUS: cp.p, info:eu-repo/semantics/published

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 obtained in this challenging measurement have a large impact in antineutrino summation calculations. For the first time the discrepancy between the summation model and the reactor antineutrino measurements in the region of the shape distortion has been reduced.

15 pags. 17 figs., 5 tabs., The β-intensity distributions of the decays of Nb100gs,100m and Nb102gs,102m have been determined using the total absorption γ-ray spectroscopy technique. The JYFLTRAP double Penning trap system was employed 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. Different strategies were applied to disentangle the isomeric states involved, lying very close in energy. The low-spin component of each niobium case was populated through the decay of the zirconium parent, which 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 a quasiparticle random-phase approximation, suggesting a prolate configuration for the ground states of Zr100,102. 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 Nb102m, for which there were no previous data, were obtained. 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., This work has been supported by the Spanish Ministerio de Economía y Competitividad under Grants No. FPA2011- 24553, No. AIC-A-2011-0696, No. FPA2014-52823-C2-1- P, No. FPA2015-65035-P, No. FPI/BES-2014-068222, No. FPA2017-83946-C2-1-P, and the program Severo Ochoa (SEV-2014-0398), by the Spanish Ministerio de Educación under the FPU12/01527 Grant, by the European Commission under the FP7/EURATOM Contract No. 605203 and the FP7/ENSAR Contract No. 262010, and by the Junta para la Ampliación de Estudios Programme (CSIC JAE-Doc contract) co-financed by ESF. We acknowledge the support of the UK Science and Technology Facilities Council (STFC) Grant No. ST/P005314/1. This work was also supported by the Academy of Finland under the Finnish Centre of Excellence Programme (Project No. 213503, Nuclear and AcceleratorBased Physics Research at JYFL). The authors thank the IAEA for supporting and encouraging the work in this field.

The MORA (Matter's Origin from the RadioActivity of trapped and oriented ions) project aims at measuring with unprecedented precision the D correlation in the nuclear beta decay of trapped and oriented ions. The D correlation offers the possibility to search for new CP-violating interactions, complementary to searches done at the LHC and with Electric Dipole Moments. Technically, MORA uses an innovative in-trap orientation method which combines the high trapping efficiency of a transparent Paul trap with laser orientation techniques. The trapping, detection, and laser setups are under development, for first tests at the Accelerator laboratory, JYFL, in the coming years., 16 pages, 6 figures, proceedings of the TCP 2018 conference, to appear in Hyp. Int

9 pags., 3 figs. -- Open Access funded by Creative Commons Atribution Licence 4.0, Three observables of interest for present and future reactors depend on the β decay properties of the fission products: antineutrinos from reactors, the reactor decay heat and delayed neutron emission. In these proceedings, we present new results from summation calculations of the first two quantities quoted above, performed with evolved independent yields coupled with fission product decay data, from various nuclear data bases or models. New TAGS results from the latest experiment of the TAGS collaboration at the JYFL facility of Jyväskylä will be displayed as well as their impact on the antineutrino spectra and the decay heat associated to fission pulses of the main actinides.

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 preliminary results from the first neutron-induced fission experiment at IGISOL-4 are presented in this report. peerReviewed

The IGISOL-4 facility in the JYFL Accelerator Laboratory of the University of Jyvaskyla (JYFL-ACCLAB) produces low-energy radioactive ion beams, primarily for nuclear spectroscopy, utilizing an ion guide-based, ISOL-type mass separator. Recently, new ion manipulation techniques have been introduced at the IGISOL-4 including the application of the PI-ICR (Phase-Imaging Ion Cyclotron Resonance) technique at the JYFLTRAP Penning trap, as well as commissioning of a Multi-Reflection Time-Of-Flight (MR-TOF) separator/spectrometer. The successful operation of the MR-TOF also required significant improvement of the Radio-Frequency Quadrupole (RFQ) cooler and buncher device beam pulse time structure. In addition, laser ionization techniques have been developed for particular cases, for example, a hot cavity laser ion source for silver production. A new stable isotope ion source and a beam line has been introduced for tuning and calibration purposes. In addition to the installations at the IGISOL-4 facility, the extension of the vacuum-mode recoil separator MARA (Mass Analysing Recoil Apparatus), MARA-LEB (MARA Low Energy Branch) has been under development. MARA-LEB will utilize the gas-cell technique and laser ionization to convert MeV-scale radioactive beams to low-energy ones.

Background: $\beta$-delayed multiple neutron emission has been observed for some nuclei with A$\leq$100, with $^{100}$Rb being the heaviest $\beta$2n emitter measured to date. So far, only 25 P$_{2n}$ values have been determined for the $\sim$300 nuclei that may decay in this way. Accordingly, it is of interest to measure P$_{2n}$ values for the other possible multiple neutron emitters throughout the chart of the nuclides. It is of particular interest to make such 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 astrophysical nucleosynthesis processes such as the $r$-process, and safety inputs for nuclear reactors. Purpose: To determine for the first time the two neutron branching ratio, P$_{2n}$ value, for $^{136}$Sb through a direct neutron measurement, and to provide precise P$_{1n}$ values for $^{136}$Sb and $^{136}$Te. Method: Pure beams were provided by the JYFLTRAP at the IGISOL facility of the University of Jyv\"askyl\"a, Finland. The purified ions were implanted into a moving tape at the end of the beam line. The detection setup consisted of a plastic scintillator placed right behind the implantation point, and the BELEN detector, based on neutron counters embedded in a polyethylene matrix. The analysis was based on the study of the $\beta$- and neutron- growth-and-decay curves and the $\beta$-one-neutron and $\beta$-two-neutron time correlations. Results: The P$_{2n}$ value of $^{136}$Sb was found to be 0.31(5)\% and the measured P$_{1n}$ values for $^{136}$Sb and $^{136}$Te were found to be 31.9(15)\% and 1.47(6)\%, respectively. The measured P$_{2n}$ value is a factor 20 smaller than predicted by the FRDM+QRPA model used for $r$-process calculations.

11 pags., 16 figs., 3 tabs., DTAS is a segmented total absorption γ-ray spectrometer developed for the DESPEC experiment at FAIR. It is composed of up to eighteen NaI(Tl) crystals. In this work we study the performance of this detector with laboratory sources and also under real experimental conditions. We present a procedure to reconstruct offline the sum of the energy deposited in all the crystals of the spectrometer, which is complicated by the effect of NaI(Tl) light-yield non-proportionality. The use of a system to correct for time variations of the gain in individual detector modules, based on a light pulse generator, is demonstrated. We describe also an event-based method to evaluate the summing-pileup electronic distortion in segmented spectrometers. All of this allows a careful characterization of the detector with Monte Carlo simulations that is needed to calculate the response function for the analysis of total absorption γ-ray spectroscopy data. Special attention was paid to the interaction of neutrons with the spectrometer, since they are a source of contamination in studies of β-delayed neutron emitting nuclei., This work has been supported by the Spanish Ministerio de Economia y Competitividad under grants FPA2011-24553, AIC-A-2011-0696, FPA2014-52823-C2-1-P and the program Severo Ochoa (SEV-2014-0398), by the European Commission under the FP7/EURATOM contract 605203, and by the Spanish Ministerio de Educacion Cultura y Deporte under the FPU12/01527 grant. The work was also supported by the UK Science and Technology Facilities Council (STFC) grant 14 ST/P005314/1. E. Ganioglu was supported by the Istanbul University Scientic Research Project Unit under FYO-2017-24144 project.

The Phase-Imaging Ion-Cyclotron-Resonance (PI-ICR) technique has been commissioned at the JYFLTRAP double Penning trap mass spectrometer. This technique is based on projecting the ion motion in the Penning trap onto a position-sensitive multichannel-plate ion detector. Mass measurements of stable 85 Rb $ ^{+}$ and 87 Rb $ ^{+}$ ions with well-known mass values show that relative uncertainties $ \Delta m/m \leq 7\cdot 10^{-10}$ are possible to reach with the PI-ICR technique at JYFLTRAP. The significant improvement both in resolving power and in precision compared to the conventional Time-of-Flight Ion Cyclotron Resonance technique will enable measurements of close-lying isomeric states and of more exotic isotopes as well as ultra-high precision measurements required, e.g., for neutrino physics. In addition, a new phase-dependent cleaning method based on the differences in the accumulated cyclotron motion phases has been demonstrated with short-lived 127 In $ ^{+}$ and 127m In $ ^{+}$ ions.

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 prolate, oblate, and triaxial nuclear shapes. Some of the ${\ensuremath{\beta}}^{\ensuremath{-}}$ decays were considered as the allowed Gamow-Teller transitions. The experimental distribution of Gamow-Teller strength is discussed.

The rare-earth peak in the $r$-process abundance pattern depends sensitively on both the astrophysical conditions and subtle changes in nuclear structure in the region. This work takes an important step elucidating the nuclear structure and reducing the uncertainties in $r$-process calculations via precise atomic mass measurements at the JYFLTRAP double Penning trap. $^{158}$Nd, $^{160}$Pm, $^{162}$Sm, and $^{164-166}$Gd have been measured for the first time and the precisions for $^{156}$Nd, $^{158}$Pm, $^{162,163}$Eu, $^{163}$Gd, and $^{164}$Tb have been improved considerably. Nuclear structure has been probed via two-neutron separation energies $S_{2n}$ and neutron pairing energy metrics $D_n$. The data do not support the existence of a subshell closure at $N=100$. Neutron pairing has been found to be weaker than predicted by theoretical mass models. The impact on the calculated $r$-process abundances has been studied. Substantial changes resulting in a smoother abundance distribution and a better agreement with the solar $r$-process abundances are observed., 8 pages, 4 figures, accepted for publication in Physical Review Letters

Isomeric yield ratios for the odd-$A$ isotopes of $^{119-127}$Cd and $^{119-127}$In from 25-MeV proton-induced fission on natural uranium have been measured at the JYFLTRAP double Penning trap, by employing the Phase-Imaging Ion-Cyclotron-Resonance technique. With the significantly improved mass resolution of this novel method isomeric states separated by 140 keV from the ground state, and with half-lives of the order of 500 ms, could be resolved. This opens the door for obtaining new information on low-lying isomers, of importance for nuclear structure, fission and astrophysics. In the present work the experimental isomeric yield ratios are used for the estimation of the root-mean-square angular momentum ($J_\mathrm{rms}$) of the primary fragments. The results show a dependency on the number of unpaired protons and neutrons, where the odd-$Z$ In isotopes carry larger angular momenta. The deduced values of $J_\mathrm{rms}$ display a linear relationship when compared with the electric quadrupole moments of the fission products., Comment: 10 pages, 4 captioned figures

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 time. The comparison of the experimentally determined isomeric yield ratios with data available in the literature shows a reasonable agreement, except for the case of Sn-130 for unspecified reasons. The obtained results were also compared with the GEF model, where good agreement can be noticed in most cases for both reactions. Serious discrepancies can only be observed for the cases of Y-96(,)97 for both reactions. Moreover, based on the isomeric yield ratios, the root-mean-square angular momenta (J(r)(ms)) of the fission fragments after scission were estimated using the TALYS code. The experimentally determined isomeric yield ratios, and consequently the deduced J(rms), for Sn-130 are significantly lower compared to Sn-128 for both fissioning systems. This can be attributed to the more spherical shape of the fragments that contribute to the formation of Sn-130, due to their proximity to the N = 82 shell closure. The values of J(rms) for Sb-129 are higher than Sn-128 for both reactions, despite the same neutron number of both nuclides (N = 78), indicating the odd-Z effect where fission fragments with odd-Z number tend to bear larger angular momentum than even-Z fragments. The isomer production ratio for the isotopes of Sn is more enhanced in the U-na(t)(p, f) reaction than in Th-232(p, f). The opposite is observed for Y-96 and Y-97. These discrepancies might be associated to different scission shapes of the fragments for the two fission reactions, indicating the impact that the different fission modes can have on the isomeric yield ratios.

V. Guadilla et al. -- 5 pags., 8 figs., tab., 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 extensive simulations have to be done, as in the case of the calculation of the response function of the spectrometer in a total absorption γ-ray spectroscopy analysis., This work has been supported by the Spanish Ministerio de Economía y Competitividad under grants FPA2011-24553, AIC-A-2011-0696, FPA2014-52823-C2-1-P and the program Severo Ochoa (SEV-2014-0398), by the European Commission under the FP7/EURATOM contract 605203, and by the Spanish Ministerio de Educación under the FPU12/01527 grant.

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

Electron capture on $^{20}$Ne is thought to play a crucial role in the final evolution of electron-degenerate ONe stellar cores. Recent calculations suggest that the capture process is dominated by the second-forbidden transition between the ground states of $^{20}$Ne and $^{20}$F, making an experimental determination of this transition strength highly desirable. To accomplish this task we are refurbishing an intermediate-image magnetic spectrometer capable of focusing 7 MeV electrons, and designing a scintillator detector surrounded by an active cosmic-ray veto shield, which will serve as an energy-dispersive device at the focal plane., 4 pages, 1 figure, NIC-XIV

J. L. Taín et al. -- 6 pags., 7 figs., 1 tab. -- Open Access funded by Creative Commons Atribution Licence 4.0, Total absorption gamma-ray spectroscopy is used to measure accurately the intensity of ¿ emission from neutron-unbound states populated in the ß-decay of delayed-neutron emitters. From the comparison of this intensity with the intensity of neutron emission one can deduce information on the (n,¿) cross section for unstable neutron-rich nuclei of interest in r process abundance calculations. A surprisingly large ¿ branching was observed for a number of isotopes. The results are compared with Hauser-Feshbach calculations and discussed., This work was supported by Spanish Ministerio de Economía y Competitividad under grants FPA2008-06419, FPA2010- 17142, FPA2011-24553, FPA2014-52823-C2-1-P, CPAN CSD- 2007-00042 (Ingenio2010) and the program Severo Ochoa (SEV-2014-0398). WG would like to thank the University of Valencia for support. This work was supported by the Academy of Finland under the Finnish Centre of Excellence Programme 2012-2017 (Project No. 21350). Work supported by EPSRC(UK) and STFC(UK) and the UK National Measurement Office. Work supported by the European Commission under the FP7/EURATOM contract 605203. FGK acknowledges support from the U.S. Department of Energy, under contract number DEAC02- 06CH11357.

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

A new accurate determination of beta-delayed neutron emission probabilities from nuclei in the low mass region of the light fission group has been performed. The measurements were carried out using the BELEN 4π neutron counter at the IGISOL-JYFL mass separator in combination with a Penning trap. The new results significantly improve the uncertainties of neutron emission probabilities for {sup 91}Br, {sup 86}As, {sup 85}As, and {sup 85}Ge nuclei.

A new method for determining independent fission products is used in an experiment at the Accelerator Laboratory of the University of Jyvaskyla. The method combines the chemical universality of the ion guide technique and the unique properties of the Penning trap. A beam of charged particles is formed by stopping fission products in gaseous helium. The Penning trap is employed as a highly accurate filter to identify particles by their mass. The yields of fission products are determined by the ion count downstream of the trap. The setup’s mass resolving power is on the order of 105 with a radio frequency excitation time of 400 ms. Such high mass resolution occasionally allows us not only to separate nuclides but to separate the isomeric and ground states of nuclei as well. Independent yields of fission products are measured in the fission reaction of the 232Th isotope by protons with an energy of 25 MeV. A short description of the method ae nd soexperimental data are supplememnted by the results fro theoretical calculations.

The mass of $^{31}\mathrm{Cl}$ 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, $\ensuremath{-}7034.7(34)$ 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 $({\ensuremath{\chi}}_{n}^{2}=11.6)$ and a nonzero cubic term, $d=\ensuremath{-}3.5(11)$ keV, is obtained when the new mass value is adopted. $^{31}\mathrm{Cl}$ has been found to be less proton-bound, with a proton separation energy of ${S}_{p}=264.6(34)$ keV. Energies for the excited states in $^{31}\mathrm{Cl}$ and the photodisintegration rate on $^{31}\mathrm{Cl}$ have been determined with significantly improved precision by using the new ${S}_{p}$ value. The improved photodisintegration rate helps to constrain astrophysical conditions where $^{30}\mathrm{S}$ can act as a waiting point in the rapid proton capture process in type-I x-ray bursts.

Independent isotopic yields for elements from Zn to La in the 25 MeV proton-induced fission of ${}^{nat}U$ were determined with the JYFLTRAP facility. In addition, isotopic yields for Zn, Ga, Rb, Sr, Zr, Pd and Xe in the 50 MeV proton-induced fission of ${}^{nat}U$ were measured. The deduced isotopic yield distributions are compared with a Rubchenya model, the GEF model with universal parameters and the semi-empirical Wahl model. Of these, the Rubchenya model gives the best overall agreement with the obtained data. Combining the isotopic yield data with mass yield data to obtain the absolute independent yields was attempted. The result depends on the mass yield distribution.

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 self-triggering 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 accuracy of neutron emission probabilities is discussed. A new accurate value of the neutron emission probability for the important delayed-neutron precursor 137I was obtained, P n = 7.76 ( 14 ) %.

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 , respectively. The effect of the more precise values on the resonant proton-capture rates has been studied. In addition to nuclear astrophysics, the measured QEC value of 25Al , 4276.805(45) keV, is relevant for studies of T = 1/2 mirror beta decays which have a potential to be used to test the Conserved Vector Current hypothesis.

The decay heat of fission products plays an important role in predictions of the heat released by nuclear fuel in reactors. In this contribution we present results of the analysis of the measurement of the beta decay of some refractory isotopes that were considered possible important contributors to the decay heat in reactors. The measurements presented here were performed at the IGISOL facility of the University of Jyvaeskylae, Finland. In our measurements we have combined for the first time a Penning trap (JYFLTRAP), which was used as a high resolution isobaric separator, with a total absorption spectrometer. The results of the measurements as well as their consequences for decay heat summation calculations are discussed.

Over 90 neutron-deficient nuclides between 10C and 111I have been measured at the JYFLTRAP mass spectrometer with a precision of better than 10 keV. Masses of these nuclides are important for modeling astrophysical rp and νp processes and nucleosynthesis occurring in novae. Here, a review of the mass measurement programme of the neutron-deficient nuclides performed at JYFLTRAP for nuclear astrophysics studies is given.

A novel method to determine independent yields in particle-induced fission employing the ion guide technique and ion counting after a Penning trap has been developed. The method takes advantage of the fact that a Penning trap can be used as a precision mass filter, which allows an unambiguous identification of the fission fragments. The method was tested with 25MeV and 50MeV proton-induced fission of 238U . The data is internally reproducible with an accuracy of a few per cent. A satisfactory agreement was obtained with older ion guide yield measurements in 25MeV proton-induced fission. The results for Rb and Cs yields in 50MeV proton-induced fission agree with previous measurements performed at an isotope separator equipped with a chemically selective ion source.

The Penning trap mass spectrometer JYFLTRAP, coupled to the Ion Guide Isotope Separator On-Line (IGISOL) facility at Jyvaskyla, was employed to measure the atomic masses of neutron-rich 70-73Ni and 73, 75Cu isotopes with a typical accuracy less than 5keV. The mass of 73Ni was measured for the first time. Comparisons with the previous data are discussed. Two-neutron separation energies show a weak subshell closure at 68 28Ni40 . A well established proton shell gap is observed at Z = 28 .

The production of neutron-deficient krypton isotopes having astrophysical importance has been studied at the ISOLDE PBS facility at CERN. To investigate several effects on the yield a Monte Carlo code has been extensively applied.

The beta-decay of 232Fr to excited states in 232Ra has been studied using gamma-gamma coincidence detection combined with the isotope separator on-line technique at the ISOLDE PSB facility at CERN. Earlier findings are confirmed and three new gamma lines are reported. In addition to the beta-decay characteristics of 232Fr, the K = 0 ground-state band in 232Ra is identified. A yield survey of neutron-rich Fr isotopes, important also for the EURISOL project, is incorporated.

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 determined to be 374(13) keV and 2922(13) keV, respectively. The $Q$ value for the proton decay from the $19/2^-$ isomer in $^{53}$Co has been determined with an unprecedented precision, $Q_{p} = 1558.8(17)$ keV. The proton separation energies of $^{52}$Co and $^{53}$Ni relevant for the astrophysical rapid proton capture process have been experimentally determined for the first time. \end{abstract}, Comment: 12 pages, 13 figures, submitted to Phys. Rev. C (26.9.2016)

To study the β-decay properties of some well known delayed neutron emitters an experiment was performed in 2009 at the IGISOL facility (University of Jyvaskyla in Finland) using Total Absorption -ray Spectroscopy (TAGS) technique. The aim of these measurements is to obtain the full β-strength distribution below the neutron separation energy (Sn) and the γ/neutron competition above. This information is a key parameter in nuclear technology applications as well as in nuclear astrophysics and nuclear structure. Preliminary results of the analysis show a significant γ-branching ratio above Sn. © Owned by the authors, published by EDP Sciences, 2014.

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 confirm that the pairing effect in the Coulomb energies is quenched when entering the $f_{7/2}$ shell and reaches a minimum in the midshell., Comment: 5 pages, 5 figures, submitted to Phys. Rev. C

The JYFLTRAP double Penning-trap system was moved to a new location along with the Ion Guide Isotope Separator On-line (IGISOL) facility at the Accelerator Laboratory of the University of Jyvaskyla. The move made it possible to upgrade various parts of the facility. For example, separate beam lines for JYFLTRAP and the collinear laser spectroscopy station were constructed after the radio-frequency quadrupole cooler and buncher. In this contribution we give an overview of the new JYFLTRAP facility and results from the first stable ion-beam tests.

In a nuclear reactor, the decay of fission fragments is at the origin of decay heat and antineutrino flux. These quantities are not well known while they are very important for reactor safety and for our understanding of neutrino physics. One reason for the discrepancies observed in the estimation of the decay heat and antineutrinos flux coming from reactors could be linked with the Pandemonium effect. New measurements have been performed at the JYFL facility of Jyvaskyla with a Total Absorption Spectrometer (TAS) in order to circumvent this effect. An overview of the TAS technique and first results from the 2009 measurement campaign will be presented. © Owned by the authors, published by EDP Sciences, 2013.

Understanding the β-decay properties of fission products is very important for nuclear reactor monitoring & safety. Indeed, the β-decay of fission products is a source of power during nuclear reactor operation and after, this activity is the main contributor to the decay-heat representing ∼7–8% of a reactor nominal power. β-decay is also at the origin of the antineutrinos coming from nuclear reactor. The study of antineutrinos is mandatory for nuclear safeguard policies based on antineutrino detection. But there are still some discrepancies in the calculation of the decay-heat and antineutrino spectra. One reason of the distortions observed seems to be linked to the Pandemonium effect. In order to improve the accuracy in the prediction of these quantities, new measurements of fission products β-decay properties, not sensitive to this effect, have been performed with a Total Absorption spectrometer (TAS). An overview of the TAS technique and first results from the latest experiment will be presented.