Impact of Ir modification on the durability of FeNC catalysts under start-up and shutdown cycle conditions

A common problem associated with FeNC catalysts is their poor stability dominated by the carbon oxidation reaction (COR). In this work, the feasibility of stabilizing FeNC catalysts with small quantities of Ir was explored. With iridium being present, instead of COR the oxygen evolution reaction should be favored. The impact on structure and morphology was investigated by 57Fe Mössbauer spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy. The catalytic activity and durability for the oxygen reduction reaction was evaluated by rotating ring disc electrode experiments and accelerated stress tests mimicking the start-up and shutdown cycle (SS…

Copper-catalyzed click reactions: quantification of retained copper using 64Cu-spiked Cu(I), exemplified for CuAAC reactions on liposomes

Abstract The Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) is a powerful, highly reliable and selective reaction which allows for a rapid synthesis in high yields and under mild conditions (pH, temperature). However, the cytotoxicity of copper requires its complete removal prior to an application in vivo. This is an issue especially when it comes to CuAAC reactions on macromolecular structures or drug delivery systems, as copper might be retained by these systems. Thus, a quantification of the final copper content of these systems is inevitable, which we exemplified for a CuAAC reaction on liposomes using 64Cu-spiked Cu(I). In this respect, a Cu(II) nitrate solution was irradiated at t…

Chemical studies of Fl (element 114): Heaviest chemically studied element

The performance of thin layers produced by molecular plating as α-particle sources

Abstract Sources for α-spectroscopy studies were prepared. Constant current density molecular plating was used to produce layers containing the α-particle emitter 147 Sm. Different parameters of the molecular plating process were varied, namely the plating solvent (an isopropanol/isobutanol mixture, pyridine, and N , N -dimethylformamide), the applied deposition time (90, 180, and 360 min), and the surface roughness of the deposition substrate (ca. 10, 20, and 300 nm). Using different analytical techniques, Sm deposition yields, chemical composition of the produced surfaces, surface homogeneity, roughness and morphology were investigated. Alpha spectra were recorded with a Si solid-state de…

Actinide and lanthanide thin-layer developments using a drop-on-demand printing system

Actinide and lanthanide thin layers with specific requirements regarding thickness, homogeneity, chemical purity, mechanical stability, and backing properties are applied in a multitude of physics and chemistry experiments. A novel target preparation method, the so-called “Drop-on-Demand” (DoD) technique, based on a commercial nanoliter (nL) dispenser is applied since a few years in the Nuclear Chemistry unit at Johannes Gutenberg University Mainz. The wetting behaviour of the nL droplets on the substrate’s surface is a key parameter determining the spatial distribution of the deposited material after evaporation. By switching from aqueous to organic solvents as well as by substrate surface…

Direct detection of the 229Th nuclear clock transition

Today’s most precise time and frequency measurements are performed with optical atomic clocks. However, it has been proposed that they could potentially be outperformed by a nuclear clock, which employs a nuclear transition instead of an atomic shell transition. There is only one known nuclear state that could serve as a nuclear clock using currently available technology, namely, the isomeric first excited state of 229Th (denoted 229mTh). Here we report the direct detection of this nuclear state, which is further confirmation of the existence of the isomer and lays the foundation for precise studies of its decay parameters. On the basis of this direct detection, the isomeric energy is const…

Development and characterization of a Drop-on-Demand inkjet printing system for nuclear target fabrication

Abstract A novel target preparation method based on Drop-on-Demand (DoD) inkjet printing has been developed. Conventional preparation methods like the electrochemical method “Molecular Plating” or the “Polymer-Assisted Deposition Method” are often limited, e.g., concerning the dimensions and geometries of depositions or by the requirement for electrically conducting substrates. Here, we report on the development of a new technique, which overcomes such limits by using a commercially available DoD dispenser. A variety of solutions with volumes down to 5 nL can be dispensed onto every manageable substrate. The dispensed volumes were determined with a radioactive tracer and the deposits of eva…

TASISpec—A highly efficient multi-coincidence spectrometer for nuclear structure investigations of the heaviest nuclei

TASISpec (TASCA in Small Image mode Spectroscopy) combines composite Ge- and Si-detectors for a new detector setup aimed towards multi-coincidence gamma -ray, X-ray, conversion electron, fission fragment, and a-particle spectroscopy of the heaviest nuclei. It exploits the TASCA separator's unique small image focal mode, i.e. the fact that evaporation residues produced in fusion-evaporation reactions can be focused into an area of less than 3 cm in diameter. This provides the possibility to pack detectors in very close geometry, resulting in an unprecedented detection efficiency of radioactive decays in prompt and delayed coincidence with implanted nuclei. Crown Copyright (C) 2010 Publis…

The research reactor TRIGA Mainz – a strong and versatile neutron source for science and education

Abstract The TRIGA Mark II-reactor at the Johannes Gutenberg University Mainz (JGU) is one of three research reactors in Germany. The TRIGA Mainz became first critical on August 3rd, 1965. It can be operated in the steady state mode with a maximum power of 100 kWth and in the pulse mode with a peak power of 250 MWth and a pulse length of 30 ms. The TRIGA Mainz is equipped with a central thimble, a rotary specimen rack, three pneumatic transfer systems, four beam tubes, and a graphite thermal column. The TRIGA Mainz is intensively used both for basic and applied research in nuclear chemistry and nuclear physics. Two sources for ultra-cold neutrons (UCN) are operational at two beam ports. At …

The recoil transfer chamber—An interface to connect the physical preseparator TASCA with chemistry and counting setups

Performing experiments with transactinide elements demands highly sensitive detection methods due to the extremely low production rates (one-atom-at-a-time conditions). Preseparation with a physical recoil separator is a powerful method to significantly reduce the background in experiments with sufficiently long-lived isotopes (t1/2≥0.5 s). In the last years, the new gas-filled TransActinide Separator and Chemistry Apparatus (TASCA) was installed and successfully commissioned at GSI. Here, we report on the design and performance of a Recoil Transfer Chamber (RTC) for TASCA—an interface to connect various chemistry and counting setups with the separator. Nuclear reaction products recoiling o…

A compact apparatus for mass selective resonance ionization spectroscopy in a buffer gas cell

Abstract An ultra-sensitive laser spectroscopic method for the investigation of transuranium nuclides has been developed based on resonance ionization in an argon buffer gas cell. This method has been combined with ion-guide extraction and mass selective direct detection of the resonantly ionized atoms. Using argon as a buffer gas, recoils of fusion reactions can be thermalized even at low pressure. The differential pumping system consists of only one roots pump and two turbo molecular pumps. The set-up has been tested with 243 Am evaporated from a filament located inside the optical gas cell. Resonance ionization is performed using a two-step excitation with an excimer-dye-laser combinatio…

Alpha-Photon Coincidence Spectroscopy Along Element 115 Decay Chains

Produced in the reaction 48Ca+243Am, thirty correlated α-decay chains were observed in an experiment conducted at the GSI Helmholzzentrum fur Schwerionenforschung, Darmstadt, Germany. The decay chains are basically consistent with previous findings and are considered to originate from isotopes of element 115 with mass numbers 287, 288, and 289. A set-up aiming specifically for high-resolution charged particle and photon coincidence spectroscopy was placed behind the gas-filled separator TASCA. For the first time, γ rays as well as X-ray candidates were observed in prompt coincidence with the α-decay chains of element 115.

Implementation of an aerodynamic lens for TRIGA-SPEC

Abstract We report on the optimization of the gas-jet system employed to couple the TRIGA-SPEC experiment to the research reactor TRIGA Mainz. CdI2 aerosol particles suspended in N2 as carrier gas are used for an effective transport of fission products from neutron induced 235 U fission from the target chamber to a surface ion source. Operating conditions of the gas-jet were modified to enable the implementation of an aerodynamic lens, fitting into the limited space available in front of the ion source. The lens boosts the gas-jet efficiency by a factor of 4–10. The characterization of the gas-jet system as well as the design of the aerodynamic lens and efficiency studies are presented and …

New measurement of the 242Pu(n,γ) cross section at n-TOF-EAR1 for MOX fuels: Preliminary results in the RRR

The spent fuel of current nuclear reactors contains fissile plutonium isotopes that can be combined with 238U to make mixed oxide (MOX) fuel. In this way the Pu from spent fuel is used in a new reactor cycle, contributing to the long-term sustainability of nuclear energy. The use of MOX fuels in thermal and fast reactors requires accurate capture and fission cross sections. For the particular case of 242Pu, the previous neutron capture cross section measurements were made in the 70’s, providing an uncertainty of about 35% in the keV region. In this context, the Nuclear Energy Agency recommends in its “High Priority Request List” and its report WPEC-26 that the capture cross section of 242Pu…

Recoil-α-fission and recoil-α–α-fission events observed in the reaction 48Ca + 243Am

Products of the fusion-evaporation reaction 48Ca + 243Am were studied with the TASISpec set-up at the gas-filled separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany. Amongst the detected thirty correlated α-decay chains associated with the production of element Z=115, two recoil-α-fission and five recoil-α-α-fission events were observed. The latter five chains are similar to four such events reported from experiments performed at the Dubna gas-filled separator, and three such events reported from an experiment at the Berkeley gas-filled separator. The four chains observed at the Dubna gas-filled separator were assigned to start from the 2n-evaporation ch…

First ionization potential of the heaviest actinide lawrencium, element 103

The first ionization potential (IP1 ) of element 103, lawrencium (Lr), has been successfully determined for the first time by using a newly developed method based on a surface ionization process. The measured IP 1 value is 4.9630.08 0.07 eV. This value is the smallest among those of actinide elements and is in excellent agreement with the value of 4.963(15) eV predicted by state-of-the-art relativistic calculations also performed in this work. Our results strongly support that the Lr atom has an electronic configuration of [Rn]7s 2 5f 14 7p 1 1/2 , which is influenced by strong relativistic effects. The present work provides a reliable benchmark for theoretical calculations and also opens t…

Qvalue and half-life of double-electron capture in184Os

The observation of neutrinoless double-beta transitionswould reveal physics beyond the Standard Model, asit would establish neutrinos to be Majorana particles,which implies a violation of the lepton number conserva-tion. Experiments searching for these transitions have fo-cused on the detection of neutrinoless double-beta decay(0 ) rather than neutrinoless double-electron capture(0). One reason among others is in general the sig-ni cantly shorter half-life of the 0 process. However,in the case of neutrinoless double-electron capture, thetransition is expected to be resonantly enhanced if theinitial and the nal state of the transition are degeneratein energy [1{3].In this work, we inves…

Production, isolation and characterization of radiochemically pure 163Ho samples for the ECHo-project

Abstract Several experiments on the study of the electron neutrino mass are based on high-statistics measurements of the energy spectrum following electron capture of the radionuclide 163Ho. They rely on the availability of large, radiochemically pure samples of 163Ho. Here, we describe the production, separation, characterization, and sample production within the Electron Capture in Holmium-163 (ECHo) project. 163Ho has been produced by thermal neutron activation of enriched, prepurified 162Er targets in the high flux reactor of the Institut Laue-Langevin, Grenoble, France, in irradiations lasting up to 54 days. Irradiated targets were chemically processed by means of extraction chromatogr…

Cross section limits for theCm248(Mg25,4n−5n)Hs268,269reactions

We report on an attempt to produce and detect $^{268}\mathrm{Hs}$ and $^{269}\mathrm{Hs}$ in the nuclear fusion reaction $^{25}\mathrm{Mg}+^{248}\mathrm{Cm}$ using the gas phase chemistry apparatus COMPACT. No decay chains attributable to the decay of hassium isotopes were observed during the course of this experiment. From the nonobservation of $^{269}\mathrm{Hs}$ we derive a cross section limit of 0.4 pb (63% confidence limit) for the reaction $^{248}\mathrm{Cm}(^{25}\mathrm{Mg},4n)^{269}\mathrm{Hs}$ at a center-of-target beam energy of 140 MeV. The evaluated cross section limit for the $^{248}\mathrm{Cm}(^{25}\mathrm{Mg},5n)^{268}\mathrm{Hs}$ reaction depends on the assumed half-life of …

Production and Decay of Element 114: High Cross Sections and the New NucleusHs277

The fusion-evaporation reaction Pu-244(Ca-48, 3-4n)(288,289)114 was studied at the new gas-filled recoil separator TASCA. Thirteen correlated decay chains were observed and assigned to the production and decay of (288, 289)114. At a compound nucleus excitation energy of E* = 39.8-43.9 MeV, the 4n evaporation channel cross section was 9.8(-3.1)(+3.9) pb. At E* = 36.1-39.5 MeV, that of the 3n evaporation channel was 8.0-(+7.4)(4.5) pb. In one of the 3n evaporation channel decay chains, a previously unobserved alpha branch in (281)Ds was observed ( probability to be of random origin from background: 0.1%). This alpha decay populated the new nucleus (277)Hs, which decayed by spontaneous fission…

First Observation of Atomic Levels for the Element Fermium (Z=100)

The atomic level structure of the element fermium was investigated for the first time using a sample of $2.7\ifmmode\times\else\texttimes\fi{}{10}^{10}$ atoms of the isotope $^{255}\mathrm{F}\mathrm{m}$ with a half-life of 20.1 h. The atoms were evaporated from a filament and stored in the argon buffer gas of an optical cell. Atomic levels were sought by the method of resonance ionization spectroscopy using an excimer-dye-laser combination. Two atomic levels were found at wave numbers $(25\text{ }099.8\ifmmode\pm\else\textpm\fi{}0.2)$ and $(25\text{ }111.8\ifmmode\pm\else\textpm\fi{}0.2)\text{ }\text{ }{\mathrm{c}\mathrm{m}}^{\ensuremath{-}1}$. Partial transition rates to the $5{f}^{12}7{s}…

Systematic evidence for quasifission in Be9−, C12−, and O16 -induced reactions forming No258,260

Radiative neutron capture on 242Pu in the resonance region at the CERN n_TOF-EAR1 facility

The spent fuel of current nuclear reactors contains fissile plutonium isotopes that can be combined with uranium to make mixed oxide (MOX) fuel. In this way the Pu from spent fuel is used in a new reactor cycle, contributing to the long-term sustainability of nuclear energy. However, an extensive use of MOX fuels, in particular in fast reactors, requires more accurate capture and fission cross sections for some Pu isotopes. In the case of 242Pu there are sizable discrepancies among the existing capture cross-section measurements included in the evaluations (all from the 1970s) resulting in an uncertainty as high as 35% in the fast energy region. Moreover, postirradiation experiments evaluat…

Direct mass measurements of cadmium and palladium isotopes and their double-βtransitionQvalues

The Q-value of the double-electron capture in Cd-108 has been determined to be (272.04 +/- 0.55) keV in a direct measurement with the double-Penning trap mass spectrometer TRIGA-TRAP. Based on this result a resonant enhancement of the decay rate of Cd-108 is excluded. We have confirmed the double-beta transition Q-values of Cd-106 and Pd-110 recently measured with the Penning-trap mass spectrometers SHIPTRAP and ISOLTRAP, respectively. Furthermore, the atomic masses of the involved nuclides Cd-106, Cd-108, Cd-110, Pd-106, Pd-108 and Pd-110 have been directly linked to the atomic mass standard.

Low-lying states in Ra219 and Rn215 : Sampling microsecond α -decaying nuclei

Short-lived α-decaying nuclei "northeast" of 208Pb in the chart of nuclides were studied using the reaction 48Ca+243Am with the decay station TASISpec at TASCA, GSI Darmstadt. Decay energies and times from pile-up events were extracted with a tailor-made pulse-shape analysis routine and specific α-decay chains were identified in a correlation analysis. Decay chains starting with the even-even 220Ra and its odd-A neighbors, 219Fr, and 219,221Ra, with a focus on the 219Ra→215Rn decay, were studied by means of α-γ spectroscopy. A revised α-decay scheme of 219Ra is proposed, including a new decay branch from a previously not considered isomeric state at 17 keV excitation energy. Conclusions on …

Determination of the Bi209(n,γ)Bi210g cross section using the NICE detector

The capture cross section of $^{209}\mathrm{Bi}(n,\ensuremath{\gamma})^{210g}\mathrm{Bi}$ was measured at different astrophysically relevant energies including thermal capture cross section (25 meV), resonance integral, and the Maxwellian averaged cross section at a thermal energy of $kT=30$ keV. The partial capture cross section $({\ensuremath{\sigma}}_{g})$ was determined using the activation technique and by measuring the $^{210}\mathrm{Po}$ activity. The newly developed and tested NICE detector setup was used to measure the $\ensuremath{\alpha}$ activity of the $^{210}\mathrm{Po}$. Using this setup the thermal and resonance integral cross sections were determined to be $16.2\phantom{\ru…

First Determination of the Ionization Potential of Actinium and First Observation of Optical Transitions in Ferminm

For the determination of the first ionization potential of actinium, 227Ac was electrodeposited on a Ta backing and covered with ~1 μm Zr. From this filament, Ac atoms were evaporated at ≥ 1250 °C. By resonant excitation with UV light of 388.67 nm and subsequent excitation with light of ca. 568 nm, Ac was ionized in an external electrical field. By determining the ionization thresholds as a function of the electrical field strength and by extrapolation to zero field strength, the first ionization potential of 43398(3) cm−1 = 5.3807(3) eV was measured.About 1 ng of 255Fm, half life 20.1 h, was prepared at ORNL by milking from 255Es produced in the High Flux Isotope Reactor and shipped to Mai…

Backings and targets for chemical and nuclear studies of transactinides with TASCA

Abstract At GSI the gas-filled separator TASCA (TransActinide Separator and Chemistry Apparatus) was set up to investigate the chemical and physical properties of the heaviest elements making use of the highest beam intensities available [ www.gsi.de/tasca ; M. Schadel, D. Ackermann, A. Semchenkov, A. Turler, GSI Scientific Report 2005, GSI Report 2006-1, p. 262]. Appropriate backings and targets have to be developed. Conceivable backing materials are aluminium, titanium, and carbon. Aluminium backings and titanium backings in different thickness and from different companies are produced by cold rolling. Deposition by resistance heating is applied for carbon backings. For experiments in a c…

Resonance ionization spectroscopy of fermium (Z=100)

Laser spectroscopy has been applied for the first time to measure resonant transition frequencies of fermium (Zs 100). A number of 2.7=10 atoms was electrodeposited on a Ta filament and covered with a 1 mm Ti layer. Fm 10

Superheavy element flerovium (element 114) is a volatile metal.

The electron shell structure of superheavy elements, i.e., elements with atomic number Z ≥ 104, is influenced by strong relativistic effects caused by the high Z. Early atomic calculations on element 112 (copernicium, Cn) and element 114 (flerovium, Fl) having closed and quasi-closed electron shell configurations of 6d(10)7s(2) and 6d(10)7s(2)7p1/2(2), respectively, predicted them to be noble-gas-like due to very strong relativistic effects on the 7s and 7p1/2 valence orbitals. Recent fully relativistic calculations studying Cn and Fl in different environments suggest them to be less reactive compared to their lighter homologues in the groups, but still exhibiting a metallic character. Expe…

Preparation of targets for the gas-filled recoil separator TASCA by electrochemical deposition and design of the TASCA target wheel assembly

Abstract The Transactinide Separator and Chemistry Apparatus (TASCA) is a recoil separator with maximized transmission designed for performing advanced chemical studies as well as nuclear reaction and structure investigations of the transactinide elements ( Z >103) on a one-atom-at-a-time basis. TASCA will provide a very clean transactinide fraction with negligible contamination of lighter elements from nuclear side reactions in the target. For TASCA a new target chamber was designed and built at GSI including the rotating target wheel assembly ARTESIA for beam intensities up to 2 μA (particle). For the production of longer-lived isotopes of neutron-rich heavier actinide and transactinide e…

Digital liquid-scintillation counting and effective pulse-shape discrimination with artificial neural networks

Abstract A typical problem in low-level liquid scintillation (LS) counting is the identification of α particles in the presence of a high background of β and γ particles. Especially the occurrence of β-β and β-γ pile-ups may prevent the unambiguous identification of an α signal by commonly used analog electronics. In this case, pulse-shape discrimination (PSD) and pile-up rejection (PUR) units show an insufficient performance. This problem was also observed in own earlier experiments on the chemical behaviour of transactinide elements using the liquid-liquid extraction system SISAK in combination with LS counting. α-particle signals from the decay of the transactinides could not be unambigu…

Level lifetimes in neutron-rich Ru isotopes

The neutron-rich Ru isotopes are situated between the strongly deformed Sr-Zr region with axial deformation of f l _ 0.40 [1] and the spherical Cd-Sn region. Evidence for triaxiality of even-even Ru isotopes has been presented in [2-5], and lifetimes of some of their 2 + states have been measured in fission studies [6-9]. It seems, however, that in these experiments the nearly identical energies of the 2 + ---* 0 + transitions in l~ and 11~ could not be separated. Therefore, high-resolution measurements are required in order to perceive the evolution of deformation with increasing neutron number. So far only few measurements by the delayed-coincidence method [10] have been performed on chem…

Erste Messung der Ionisationsenergie von Americium und Curium

Zeptosecond contact times for element Z=120 synthesis

The synthesis of new superheavy elements beyond oganesson (Z=118) requires fusion reactions with projectile nuclei with proton numbers larger than that of $^{48}$Ca (Z=20), which has been successfully employed for the synthesis of elements with Z=112-118. In such reactions, fusion is drastically hindered by fast non-equilibrated dynamical processes. Attempts to produce nuclei with Z=120 using the $^{64}$Ni+$^{238}$U, $^{58}$Fe+$^{244}$Pu, $^{54}$Cr+$^{248}$Cm, and $^{50}$Ti+$^{249}$Cf reactions have been made, which all result in larger Coulomb forces than for $^{48}$Ca-induced reactions, but no discovery has been confirmed to date. In this work, mass and angle distributions of fission frag…

Application of fast solvent extraction processes to studies of exotic nuclides

Fast solvent extraction is a chemical separation method, which can be applied to study exotic nuclides. Since about 1970 the SISAK technique, which is an on-line method based on multi-stage solvent extraction separations, has been successfully used to investigate the nuclear properties of β-decaying nuclides with half-lives down to about one second. During the last decade it has become possible to produce transactinide elements in high enough yields to investigate their chemical properties on a one-atom-at-a-time scale. For this purpose it was necessary to improve and change the detection part of the SISAK system in order to be capable to detect spontaneously fissioning and α-decaying nucli…

Studies on Flat Sandwich-type Self-Powered Detectors for Flux Measurements in ITER Test Blanket Modules

Neutron and gamma flux measurements in designated positions in the test blanket modules (TBM) of ITER will be important tasks during ITER’s campaigns. As part of the ongoing task on development of nuclear instrumentation for application in European ITER TBMs, experimental investigations on self-powered detectors (SPD) are undertaken. This paper reports the findings of neutron and photon irradiation tests performed with a test SPD in flat sandwich-like geometry. Whereas both neutrons and gammas can be detected with appropriate optimization of geometries, materials and sizes of the components, the present sandwich-like design is more sensitive to gammas than 14 MeV neutrons. Range of SPD curr…

Ca48+Bk249Fusion Reaction Leading to ElementZ=117: Long-Livedα-DecayingDb270and Discovery ofLr266

The superheavy element with atomic number Z=117 was produced as an evaporation residue in the 48Ca+249Bk fusion reaction at the gas-filled recoil separator TASCA at GSI Darmstadt, Germany. The radioactive decay of evaporation residues and their α-decay products was studied using a detection setup that allowed measuring decays of single atomic nuclei with half-lives between sub-μs and a few days. Two decay chains comprising seven α decays and a spontaneous fission each were identified and are assigned to the isotope 294-117 and its decay products. A hitherto unknown α-decay branch in 270Db (Z=105) was observed, which populated the new isotope 266Lr (Z=103). The identification of the long-liv…

TRIGA-SPEC: A setup for mass spectrometry and laser spectroscopy at the research reactor TRIGA Mainz

The research reactor TRIGA Mainz is an ideal facility to provide neutron-rich nuclides with production rates sufficiently large for mass spectrometric and laser spectroscopic studies. Within the TRIGA-SPEC project, a Penning trap as well as a beam line for collinear laser spectroscopy are being installed. Several new developments will ensure high sensitivity of the trap setup enabling mass measurements even on a single ion. Besides neutron-rich fission products produced in the reactor, also heavy nuclides such as 235-U or 252-Cf can be investigated for the first time with an off-line ion source. The data provided by the mass measurements will be of interest for astrophysical calculations on…

TRIGA-SPEC: the prototype of MATS and LaSpec

Investigation of short-lived nuclei is a challenging task that MATS and LaSpec will handle at the low energy branch of Super-FRS at FAIR. The groundwork for those experiments is laid-out already today at the TRIGA-SPEC facility as a powerful development platform located at the research reactor TRIGA Mainz. The latest status, new developments and first results of commissioning runs are presented here.

Experimental Assessment of a Flat Sandwich-Like Self-Powered Detector for Nuclear Measurements in ITER Test Blanket Modules

Neutron and gamma flux measurements in designated positions in the test blanket modules (TBMs) of ITER will be important tasks during its campaigns. Investigations on self-powered detectors (SPDs), a class of reactor flux monitors are undertaken in the framework of an ongoing project on development of nuclear instrumentation for European ITER TBMs. This paper reports the findings of experiments performed with an SPD in flat sandwich-like geometry. A detector with vanadium emitter is chosen for preliminary studies. Its irradiation in a thermal neutron field gives a proof of the principle of flat SPDs. It is further irradiated in the mixed neutron-gamma field of a 14-MeV neutron generator and…

Sodium chloride is an ionic checkpoint for human TH2 cells and shapes the atopic skin microenvironment.

The incidence of allergic diseases has increased over the past 50 years, likely due to environmental factors. However, the nature of these factors and the mode of action by which they induce the type 2 immune deviation characteristic of atopic diseases remain unclear. It has previously been reported that dietary sodium chloride promotes the polarization of T helper 17 (T(H)17) cells with implications for autoimmune diseases such as multiple sclerosis. Here, we demonstrate that sodium chloride also potently promotes T(H)2 cell responses on multiple regulatory levels. Sodium chloride enhanced interleukin-4 (IL-4) and IL-13 production while suppressing interferon-gamma (IFN-gamma) production i…

Chemical investigation of hassium (element 108).

The periodic table provides a classification of the chemical properties of the elements. But for the heaviest elements, the transactinides, this role of the periodic table reaches its limits because increasingly strong relativistic effects on the valence electron shells can induce deviations from known trends in chemical properties. In the case of the first two transactinides, elements 104 and 105, relativistic effects do indeed influence their chemical properties, whereas elements 106 and 107 both behave as expected from their position within the periodic table. Here we report the chemical separation and characterization of only seven detected atoms of element 108 (hassium, Hs), which were…

Production and characterization of a custom-made 228Th source with reduced neutron source strength for the Borexino experiment

A custom-made 228Th source of several MBq activity was produced for the Borexino experiment for studying the external background of the detector. The aim was to reduce the unwanted neutron emission produced via (alpha,n) reactions in ceramics used typically for commercial 228Th sources. For this purpose a ThCl4 solution was converted chemically into ThO2 and embedded into a gold foil. The paper describes the production and the characterization of the custom-made source by means of gamma-activity, dose rate and neutron source strength measurements. From gamma-spectroscopic measurements it was deduced that the activity transfer from the initial solution to the final source was >91% (at 68%…

Shape coexistence near the double-midshell nucleus 111Rh

The decay of 111Ru obtained from fast on-line chemical and mass separation has been investigated by β-γ-t and γ-γ coincidence techniques. Earlier spin and parity assignments of 111Rh levels based on extrapolations of level systematics are confirmed. In particular, the K=1/2 intruder band is supported by the hindrance of E2 transitions between deformed and spherical states and enhancement of intraband E2 transitions. The excitation energies of intruder band members in Rh isotopes show a minimum at 109Rh64, with two neutrons less than 111Rh at the N=66 midshell. This trend, which differs from the one in the higher-Z neighbouring elements Ag and Cd with minima at N=66, follows the evolution of…

Thermal (n, γ) cross section and resonance integral of 171Tm

Background: About 50% of the heavy elements are produced in stars during the slow neutron capture process. The analysis of branching points allows us to set constraints on the temperature and the neutron density in the interior of stars. Purpose: The temperature dependence of the branch point 171Tm is weak. Hence, the 171Tm neutron capture cross section can be used to constrain the neutron density during the main component of the s process in thermally pulsing asymptotic giant branch (TP-AGB) stars. Methods: A 171Tm sample produced at the ILL was activated with thermal and epithermal neutrons at the TRIGA research reactor at the Johannes Gutenberg-Universität Mainz. Results: The thermal neu…

Smooth crack-free targets for nuclear applications produced by molecular plating

The production process of smooth and crack-free targets by means of constant current electrolysis in organic media, commonly known as molecular plating, was optimized. Using a Nd salt, i.e., [Nd(NO3)(3)center dot 6H(2)O], as model electrolyte several constant current density electrolysis experiments were carried out to investigate the effects of different parameters, namely the plating solvent (isopropanol and isobutanol mixed together, pyridine, and N,N-dimethylformamide), the electrolyte concentration (0.11, 0.22, 0.44 mM), the applied current density (0.17, 0.3, 0.7, and 1.3 mA/cm(2)), and the surface roughness of the deposition substrates (12 and 24 nm). Different environments (air and …

Measurement of the first ionization potential of lawrencium (element 103)

Lawrencium, with atomic number 103, has an isotope with a half-life of 27 seconds; even so, its first ionization potential has now been measured on an atom-at-a-time scale and agrees well with state-of-the-art theoretical calculations that include relativistic effects. The most dramatic modern revision of Mendeleev's periodic table of elements came in 1944 when Glenn T. Seaborg placed a new series of elements, the actinides (atomic numbers 89–103), below the lanthanides. In this issue of Nature, Yuichiro Nagame and colleagues report the first measurement of one of the basic atomic properties of element 103 (lawrencium), namely its first ionization potential. Lawrencium is only accessible vi…

Measurement of the Pu-242(n,gamma) cross section from thermal to 500 keV at the Budapest research reactor and CERN n_TOF-EAR1 facilities

The design and operation of innovative nuclear systems requires a better knowledge of the capture and fission cross sections of the Pu isotopes. For the case of capture on 242Pu, a reduction of the uncertainty in the fast region down to 8-12% is required. Moreover, aiming at improving the evaluation of the fast energy range in terms of average parameters, the OECD NEA High Priority Request List (HPRL) requests high-resolution capture measurements with improved accuracy below 2 keV. The current uncertainties also affect the thermal point, where previous experiments deviate from each other by 20%. A fruitful collaboration betwen JGU Mainz and HZ Dresden-Rossendorf within the EC CHANDA project…

First superheavy element experiments at the GSI recoil separator TASCA: The production and decay of element 114 in thePu244(Ca48,3-4n) reaction

Experiments with the new recoil separator, Transactinide Separator and Chemistry Apparatus (TASCA), at the GSI were performed by using beams of Ca-48 to irradiate targets of Pb206-208, which led to the production of No252-254 isotopes. These studies allowed for evaluation of the performance of TASCA when coupled to a new detector and electronics system. By following these studies, the isotopes of element 114 ((288-291)114) were produced in irradiations of Pu-244 targets with Ca-48 beams at compound nucleus excitation energies around 41.7 and 37.5 MeV, demonstrating TASCA's ability to perform experiments with picobarn-level cross sections. A total of 15 decay chains were observed and were as…

Quantitative molecular plating of large-area 242Pu targets with improved layer properties

Abstract For measurements of the neutron-induced fission cross section of 242Pu, large-area (42 cm2) 242Pu targets were prepared on Ti-coated Si wafers by means of constant current density molecular plating. Radiochemical separations were performed prior to the platings. Quantitative deposition yields (>95%) were determined for all targets by means of alpha-particle spectroscopy. Layer densities in the range of 100–150 μg/cm2 were obtained. The homogeneity of the targets was studied by radiographic imaging. A comparative study between the quality of the layers produced on the Ti-coated Si wafers and the quality of layers grown on normal Ti foils was carried out by applying scanning electron…

Attempts to chemically investigate element 112

Summary Two experiments aiming at the chemical investigation of element 112 produced in the heavy ion induced nuclear fusion reaction of 48Ca with 238U were performed at the Gesellschaft für Schwerionenforschung (GSI), Darmstadt, Germany. Both experiments were designed to determine the adsorption enthalpy of element 112 on a gold surface using a thermochromatography setup. The temperature range covered in the thermochromatography experiments allowed the adsorption of Hg at about 35 °C and of Rn at about -180 °C. Reports from the Flerov Laboratory for Nuclear Reactions (FLNR), Dubna, Russia claim production of a 5-min spontaneous fission (SF) activity assigned to 283112 for the 238U(48Ca,3n)…

Review of the SISAK system in transactinide research

Abstract The performance of the SISAK 1 liquid–liquid extraction system applied in transactinide experiments has been improved with respect to the equipment itself and the way it is operated. The improvements were checked in on-line experiments, under conditions similar to those during transactinide experiments. As a result, the yield of the separation system was increased by a factor >5. Furthermore, a cleaner organic scintillation phase was obtained due to a better phase separation. This reduced the β-background, which disturbs the α-measurements. The sensitivity of the SISAK apparatus, including the gasjet and the detection system has been improved by more than one order of magnitude.

On the use of stacks of fission-like targets for neutron capture experiments

The measurement of neutron induced reactions on unstable isotopes is of interest in many fields, from nuclear energy to astrophysics or applications; in particular transuranic isotopes are essential for the development of innovative nuclear reactors and for the management of the radioactive waste. In such measurements, the quality of the associated radioactive target is crucial for the success of the experiment, but in many cases the geometry, amount of mass and encapsulation of the target are not optimal, leading to limited results. In this work we propose to produce high quality radioactive targets for capture as a stack of thin targets using the techniques usually employed for fission me…

Isotope Shift Measurements for Superdeformed Fission Isomeric States

Optical isotope shift measurements have been performed for the ${}^{240,242}{\mathrm{Am}}^{f}$ fission isomers with low target production rates of $10{\mathrm{s}}^{\ensuremath{-}1}$ employing resonance ionization spectroscopy in a buffer gas cell. Isotope shift ratios ${\mathrm{IS}}^{240f,241}/{\mathrm{IS}}^{243,241}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}39.2(8)$ and ${\mathrm{IS}}^{242f,241}/{\mathrm{IS}}^{243,241}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}41.4(8)$ have been measured at the 500.02 nm transition. A difference in the nuclear mean charge radii $\ensuremath{\delta}〈{r}^{2}{〉}_{\mathrm{opt}}^{242f,241}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}5.34(2…

Determination of the first ionization potential of actinide elements by resonance ionization mass spectroscopy

Abstract Resonance ionization mass spectroscopy (RIMS) in the presence of an external static electric field has been used for the determination of photoionization thresholds. Extrapolation of the thresholds obtained with different electric field strengths to zero field strength directly leads to the first ionization potential (IP). The ionization potentials of the transplutonium elements americium, curium, berkelium and californium could be measured for the first time. Due to the high sensitivity of RIMS, samples of only 1012 atoms have been used. The results are: IPAm = 5.9738(2)eV, IPCm = 5.9915(2)eV, IPBk = 6.1979(2)eV and IPCf = 6.2817(2)eV. The same technique was applied to thorium, ne…

Search for elements 119 and 120

A search for production of the superheavy elements with atomic numbers 119 and 120 was performed in the 50Ti+249Bk and 50Ti+249Cf fusion-evaporation reactions, respectively, at the gas-filled recoil separator TASCA at GSI Darmstadt, Germany. Over four months of irradiation, the 249Bk target partially decayed into 249Cf, which allowed for a simultaneous search for both elements. Neither was detected at cross-section sensitivity levels of 65 and 200 fb for the 50Ti+249Bk and 50Ti+249Cf reactions, respectively, at a midtarget beam energy of Elab=281.5 MeV. The nonobservation of elements 119 and 120 is discussed within the concept of fusion-evaporation reactions including various theoretical pr…

Liquid-scintillation detection of preseparated 257Rf with the SISAK-system

Abstract The fast liquid–liquid extraction system SISAK with continuous liquid scintillation detection was coupled to the Berkeley Gas-filled Separator to enable studies of the chemical properties of α -decaying transactinide elements. The preseparated transactinide 257Rf (4.7 s), was transported via a He/KCl-jet directly into the scintillation solution. This permitted the first unambiguous detection of transactinide atoms by the means of the α -liquid scintillation detectors of the SISAK-system. During the experiment, 89 257Rf atoms were observed. The type of events observed correspond well with the expectations based on half-lives, decay branches and transport- and hold-up times. The succ…

Comparison of ultracold neutron sources for fundamental physics measurements

Ultracold neutrons (UCNs) are key for precision studies of fundamental parameters of the neutron and in searches for new CP violating processes or exotic interactions beyond the Standard Model of particle physics. The most prominent example is the search for a permanent electric dipole moment of the neutron (nEDM). We have performed an experimental comparison of the leading UCN sources currently operating. We have used a 'standard' UCN storage bottle with a volume of 32 liters, comparable in size to nEDM experiments, which allows us to compare the UCN density available at a given beam port.

Radiative neutron capture on Pu242 in the resonance region at the CERN n_TOF-EAR1 facility

The spent fuel of current nuclear reactors contains fissile plutonium isotopes that can be combined with uranium to make mixed oxide (MOX) fuel. In this way the Pu from spent fuel is used in a new reactor cycle, contributing to the long-term sustainability of nuclear energy. However, an extensive use of MOX fuels, in particular in fast reactors, requires more accurate capture and fission cross sections for some Pu isotopes. In the case of Pu242 there are sizable discrepancies among the existing capture cross-section measurements included in the evaluations (all from the 1970s) resulting in an uncertainty as high as 35% in the fast energy region. Moreover, postirradiation experiments evaluat…

First online operation of TRIGA-TRAP

Abstract We report on the successful coupling of the Penning-trap mass spectrometry setup TRIGA-TRAP to the research reactor TRIGA Mainz. This offers the possibility to perform direct high-precision mass measurements of short-lived nuclei produced in neutron-induced fission of a 235 U target located near the reactor core. An aerosol-based gas-jet system is used for efficient transport of short-lived neutron-rich nuclei from the target chamber to a surface ion source. In conjunction with new ion optics and extended beam monitoring capabilities, the experimental setup has been fully commissioned. The design of the surface ion source, efficiency studies and first results are presented.

High-resolution laser resonance ionization spectroscopy of $^{143-147}$Pm

The European physical journal / A 56(2), 69 (2020). doi:10.1140/epja/s10050-020-00061-8

Sodium chloride is an ionic checkpoint for human Th2 cell responses and shapes the atopic skin microenvironment

One sentence summarySodium is an ionic checkpoint for the induction and amplification of human Th2 cell responses and shapes the atopic skin microenvironment, where it could serve as a novel therapeutic target for Th2 mediated diseases.AbstractThere has been a strong increase in the incidence of allergic diseases over the last 50 years. Environmental factors most likely account for this phenomenon. However, the nature of these factors and the mode of action by which they induce the type 2 immune deviation, which is characteristic of atopic diseases, remains unclear. It has previously been reported that dietary sodium chloride promotes the polarization of Th17 cells with implications for aut…

Preparation of targets by electrodeposition for heavy element studies

Abstract For heavy element studies at GSI, lanthanide and actinide targets have been prepared by molecular plating. The deposition occurs from an isopropanolic solution at 1000–1200 V with current densities of a few mA/cm 2 . Several lanthanide targets have been prepared for test experiments. With nat Gd deposited on a 10 μm thick Be backing foil a target density of 1100 μg/cm 2 could be achieved. Gd-targets were used for the production of α-emitting isotopes of Os, the homologue of hassium (Hs; Z =108), in order to develop a chemical separation procedure for Hs. 248 Cm targets with densities up to 730 μg/cm 2 have been produced for recent experiments to investigate the chemical behaviour o…

Mass measurements on stable nuclides in the rare-earth region with the Penning-trap mass spectrometer RIGA-TRAP

The masses of 15 stable nuclides in the rare-earth region have been measured with the Penning-trap mass spectrometer TRIGA-TRAP. This is the first series of absolute mass measurements linking these nuclides to the atomic-mass standard $^{12}\mathrm{C}$. Previously, nuclear reaction studies almost exclusively determined the literature values of these masses in the Atomic-Mass Evaluation. The TRIGA-TRAP results show deviations on the order of 3--4 standard deviations from the latest published values of the Atomic-Mass Evaluation 2003 for some cases. However, the binding-energy differences that are important for nuclear structure studies have been confirmed and improved. The new masses are dis…

Resonance ionization of holmium for ion implantation in microcalorimeters

Abstract The determination of the electron neutrino mass by calorimetric measurement of the 163 Ho electron capture spectrum requires ultra-pure samples. Several collaborations, like ECHo or HOLMES, intend to employ microcalorimeters into which 163 Ho is implanted as an ion beam. This makes a selective and additionally very efficient ion source for holmium mandatory. For this purpose, laser resonance ionization of stable holmium 165 Ho was studied, using a three step excitation scheme driven by pulsed Ti:sapphire lasers. Five measurements with sample sizes of 10 14 and 10 15 atoms were performed for the efficiency investigation. In average, an excellent ionization efficiency of 32(5) % coul…

Doubly Magic NucleusHs162108270

Theoretical calculations predict $^{270}\mathrm{Hs}$ ($Z=108$, $N=162$) to be a doubly magic deformed nucleus, decaying mainly by $\ensuremath{\alpha}$-particle emission. In this work, based on a rapid chemical isolation of Hs isotopes produced in the $^{26}\mathrm{Mg}+^{248}\mathrm{Cm}$ reaction, we observed 15 genetically linked nuclear decay chains. Four chains were attributed to the new nuclide $^{270}\mathrm{Hs}$, which decays by $\ensuremath{\alpha}$-particle emission with ${Q}_{\ensuremath{\alpha}}=9.02\ifmmode\pm\else\textpm\fi{}0.03\text{ }\text{ }\mathrm{MeV}$ to $^{266}\mathrm{Sg}$ which undergoes spontaneous fission with a half-life of ${444}_{\ensuremath{-}148}^{+444}\text{ }\t…

First Determination of the Ionization Potential of Americium and Curium

New measurement of the 242Pu(n,γ) cross section at n_TOF

WONDER-2015 – 4th International Workshop On Nuclear Data Evaluation for Reactor applications The use of MOX fuel (mixed-oxide fuel made of UO2 and PuO2) in nuclear reactors allows substituting a large fraction of the enriched Uranium by Plutonium reprocessed from spent fuel. With the use of such new fuel composition rich in Pu, a better knowledge of the capture and fission cross sections of the Pu isotopes becomes very important. In particular, a new series of cross section evaluations have been recently carried out jointly by the European (JEFF) and United States (ENDF) nuclear data agencies. For the case of 242Pu, the two only neutron capture time-of-flight measurements available, from 19…

MicroSISAK: continuous liquid–liquid extractions of radionuclides at 0.2 mL/min

Abstract Continuous liquid–liquid extraction of short-lived radionuclides has traditionally been performed with the SISAK system consisting of static mixers and H-centrifuges for phase separation. SISAK operates at flow rates of typically 1 mL/s. Thus, it produces large volumes of radioactive liquid waste that is difficult to dispose of. Therefore, it has been aimed to develop and use a further miniaturised extraction unit based on microtechnology and precision engineering to reduce the flow rate by at least two orders of magnitude. The accordingly developed MicroSISAK device is a micro membrane extractor in which a micromixer element with 2 × 16 feed channels of 30 µm width followed by a 6…

Toward large-area targets for “TRAKULA”

Abstract TRAKULA ( Tra nsmutationsrelevante k ernphysikalische U ntersuchungen l anglebiger A ktinide, i.e., nuclear physical investigations of long-lived actinides with relevance to transmutation) is a joint research project of the German Federal Ministry of Science and Education (BMBF) on nuclear physics investigations with modern scientific, technological and numerical methods. Experiments concerning the transmutation of radioactive waste are a central topic of the project. For this, large-area samples (≥40 cm 2 ) of 235,238 U and 239,242 Pu compounds are required for the calibration of fission chambers and for fission yield measurements. Another topic within the project requires large-a…

Gas phase synthesis of 4d transition metal carbonyl complexes with thermalized fission fragments in single-atom reactions

Abstract The formation of carbonyl complexes using atom-at-a-time quantities of short-lived transition metals from fusion and fission reactions was reported in 2012. Numerous studies focussing on this chemical system, which is also applicable for the superheavy elements followed. We report on a novel two-chamber approach for the synthesis of such complexes that allows spatial decoupling of thermalization and gas-phase carbonyl complex synthesis. Neutron induced fission on 235U and spontaneous fission of 248Cm were employed for the production of the fission products. These were stopped inside a gas volume behind the target and flushed with an inert-gas flow into a second chamber. This was fl…

Targets on superhydrophobic surfaces for laser ablation ion sources

Target preparation techniques for a laser ablation ion source at the Penning-trap mass spectrometer TRIGA-TRAP have been investigated with regard to future experiments with actinides. To be able to perform mass measurements on these nuclides considering their limited availability, an efficient target preparation technique is mandatory. Here, we report on a new approach for target production using backings, which are pretreated in a way that a superhydrophobic surface is formed. This resulted in improved targets with a more homogeneous distribution of the target material compared to standard techniques with unmodified backings. It was demonstrated that the use of these new targets in a laser…

Observation of the3nEvaporation Channel in the Complete Hot-Fusion ReactionMg26+Cm248Leading to the New Superheavy NuclideHs271

The analysis of a large body of heavy ion fusion reaction data with medium-heavy projectiles ($6\ensuremath{\le}Z\ensuremath{\le}18$) and actinide targets suggests a disappearance of the $3n$ exit channel with increasing atomic number of the projectile. Here, we report a measurement of the excitation function of the reaction $^{248}\mathrm{Cm}(^{26}\mathrm{Mg},xn)^{274\mathrm{\text{\ensuremath{-}}}x}\mathrm{Hs}$ and the observation of the new nuclide $^{271}\mathrm{Hs}$ produced in the $3n$ evaporation channel at a beam energy well below the Bass fusion barrier with a cross section comparable to the maxima of the $4n$ and $5n$ channels. This indicates the possible discovery of new neutron-r…

Fusion reaction Ca48+Bk249 leading to formation of the element Ts ( Z=117 )

The heaviest currently known nuclei, which have up to 118 protons, have been produced in 48Ca induced reactions with actinide targets. Among them, the element tennessine (Ts), which has 117 protons, has been synthesized by fusing 48Ca with the radioactive target 249Bk, which has a half-life of 327 d. The experiment was performed at the gas-filled recoil separator TASCA. Two long and two short α decay chains were observed. The long chains were attributed to the decay of 294Ts. The possible origin of the short-decay chains is discussed in comparison with the known experimental data. They are found to fit with the decay chain patterns attributed to 293Ts. The present experimental results confi…

Determination of the first ionization potential of einsteinium by resonance ionization mass spectroscopy (RIMS)

Abstract The first ionization potential of einsteinium (IP Es ) was determined by resonance ionization mass spectroscopy (RIMS) using samples with ≤10 12 atoms of 254 Es ( T 1/2 =276 days). This method is based on the measurement of photoionization thresholds as a function of applied electric field strength, followed by extrapolation to zero field strength to yield IP Es . An atomic beam of Es was created by heating a filament on which einsteinium was electrodeposited from an aqueous solution onto a tantalum backing and covered with titanium metal. Es atoms were ionized via a three-step excitation scheme, and the ions mass-selectively detected in a time-of-flight (TOF) mass spectrometer. Th…

The application of neutron activation analysis, scanning electron microscope, and radiographic imaging for the characterization of electrochemically deposited layers of lanthanide and actinide elements

Lanthanide and actinide targets are prepared at the University of Mainz by molecular plating, an electrochemical deposition from an organic solvent, for heavy-ion reaction studies at GSI. To acquire information about deposition yield, target thickness, and target homogeneity, the following analysis methods are applied. With neutron activation analysis (NAA) the deposition yield and the average thickness of the deposited material is determined. We report on the analytical procedure of NAA performed subsequent to the molecular plating process. Scanning electron microscope (SEM) is used to determine the morphology of the target surfaces. In combination with energy dispersive X-ray spectrometer…

Study of non-fusion products in the Ti50+Cf249 reaction

The isotopic distribution of nuclei produced in the 50Ti + 249Cf reaction has been studied at the gas-filled recoil separator TASCA at GSI Darmstadt, which separates ions according to differences in magnetic rigidity. The bombardment was performed at an energy around the Bass barrier and with the TASCA magnetic fields set for collecting fusion-evaporation reaction products. Fifty-three isotopes located “north-east” of 208Pb were identified as recoiling products formed in non-fusion channels of the reaction. These recoils were implanted with energies in two distinct ranges; besides one with higher energy, a significant low-energy contribution was identified. The latter observation was not ex…

A White Paper on keV sterile neutrino Dark Matter

We present a comprehensive review of keV-scale sterile neutrino Dark Matter, collecting views and insights from all disciplines involved - cosmology, astrophysics, nuclear, and particle physics - in each case viewed from both theoretical and experimental/observational perspectives. After reviewing the role of active neutrinos in particle physics, astrophysics, and cosmology, we focus on sterile neutrinos in the context of the Dark Matter puzzle. Here, we first review the physics motivation for sterile neutrino Dark Matter, based on challenges and tensions in purely cold Dark Matter scenarios. We then round out the discussion by critically summarizing all known constraints on sterile neutrin…

New measurement of the 242Pu(n,γ) cross section at n_TOF

The use of MOX fuel (mixed-oxide fuel made of UO2 and PuO2 ) in nuclear reactors allows substituting a large fraction of the enriched Uranium by Plutonium reprocessed from spent fuel. With the use of such new fuel composition rich in Pu, a better knowledge of the capture and fission cross sections of the Pu isotopes becomes very important. In particular, a new series of cross section evaluations have been recently carried out jointly by the European (JEFF) and United States (ENDF) nuclear data agencies. For the case of 242 Pu, the two only neutron capture time-of-flight measurements available, from 1973 and 1976, are not consistent with each other, which calls for a new time-of flight captu…

Direct high-precision mass measurements onAm241,243,Pu244, andCf249

The absolute masses of four long-lived transuranium nuclides, $^{241,243}\mathrm{Am}$, $^{244}\mathrm{Pu}$, $^{244}\mathrm{Pu}$, and $^{249}\mathrm{Cf}$, in the vicinity of the deformed $N=152$ neutron shell closure have been measured directly with the Penning-trap mass spectrometer TRIGA-TRAP. Our measurements confirm the AME2012 mass values of $^{241,243}\mathrm{Am}$ and $^{244}\mathrm{Pu}$ within one standard deviation, which were indirectly determined, by decay spectroscopy studies. In the case of the $^{249}\mathrm{Cf}$ mass, a discrepancy of more than three standard deviations has been observed, affecting absolute masses even in the superheavy element region. The implementation of the…

To identify the atomic number of superheavy nuclei produced in Ca-48-induced fusion-evaporation reactions, an experiment aiming at measuring characteristic X-rays is being prepared at GSI, Darmstadt, Germany. The gas-filled separator TASCA will be employed, sending the residues towards the multi-coincidence detector setup TASISpec. Two ion-optical modes relying on differing magnetic polarities of the quadrupole magnets can be used at TASCA. New simulations and experimental tests of transmission and background suppression for these two focusing modes into TASISpec are presented.

TASCAを用いたCn, Nh, Fl化学実験のためのHg, Tl, PbのSiO2及びAu表面に対するオンライン化学吸着研究

Online gas-solid adsorption studies with single atom quantities of Hg, Tl, and Pb on SiO$_{2}$ and Au surfaces were carried out using short-lived radioisotopes with half-lives in the range of 4-49 s. This is a model study to measure adsorption enthalpies of superheavy elements Cn, Nh, and Fl. The short-lived isotopes were produced and separated by the gas-filled recoil separator TASCA at GSI. The products were stopped in He gas, and flushed into gas chromatography columns made of Si detectors whose surfaces were covered by SiO$_{2}$ or Au. The short-lived Tl and Pb were successfully measured by the Si detectors with the SiO$_{2}$ surface at room temperature. On the other hand, the Hg did no…

Fast-neutron-induced fission cross section of Pu242 measured at the neutron time-of-flight facility nELBE

The fast-neutron-induced fission cross section of $^{242}\mathrm{Pu}$ was measured at the neutron time-of-flight facility $n$ELBE. A parallel-plate fission ionization chamber with novel, homogeneous, large-area $^{242}\mathrm{Pu}$ deposits on Si-wafer backings was used to determine this quantity relative to the IAEA neutron cross-section standard $^{235}\mathrm{U}(n,f)$ in the energy range of 0.5 to 10 MeV. The number of target nuclei was determined from the measured spontaneous fission rate of $^{242}\mathrm{Pu}$. This helps to reduce the influence of the fission fragment detection efficiency on the cross section. Neutron transport simulations performed with geant4, mcnp6, and fluka2011 ar…

Elucidation of constant current density molecular plating

Abstract The production of thin layers by means of constant current or constant voltage electrolysis in organic media is commonly known as molecular plating. Despite the fact that this method has been applied for decades and is known to be among the most efficient ones for obtaining quantitative deposition, a full elucidation of the molecular plating is still lacking. In order to get a general understanding of the process and hence set the basis for further improvements of the method, constant current density electrolysis experiments were carried out in a mixture of isopropanol and isobutanol containing millimolar amounts of HNO 3 together with [Nd(NO 3 ) 3 ·6H 2 O] used as a model electrol…

Determination of the first ionization potential of nine actinide elements by resonance ionization mass spectroscopy (RIMS)

The high sensitivity of RIMS enables the precise determination of the first ionization potential of actinide elements with a sample size of ≤1012 atoms. By multiple resonant laser excitation, the actinide atoms under investigation are ionized in the presence of an electric field, and the ions are mass-selectively detected in a time-of-flight spectrometer. The first ionization potential is obtained by scanning the wavelength of the laser used for the last excitation step across the ionization threshold Wth—indicated by a sudden increase of the ion count rate—at various electric field strengths. Extrapolation of Wth to electric field strength zero leads directly to the first ionization potent…

Study of the average charge states of 188Pb and 252,254No ions at the gas-filled separator TASCA

The average charge states of Pb-188 and No-252,No-254 ions in dilute helium gas were measured at the gas-filled recoil separator TASCA. Hydrogen gas was also used as a filling gas for measurements of the average charge state of No-254. Helium and hydrogen gases at pressures from 0.2 mbar to 2.0 mbar were used. A strong dependence of the average charge state on the pressure of the filling gases was observed for both, helium and hydrogen. The influence of this dependence, classically attributed to the so-called "density effect", on the performance of TASCA was investigated. The average charge states of No-254 ions were also measured in mixtures of helium and hydrogen gases at low ga…

Additional results from the first dedicated search for neutron–mirror neutron oscillations

International audience; The existence of a mirror world holding a copy of our ordinary particle spectrum could lead to oscillations between the neutron (n) and its mirror partner (n′). Such oscillations could manifest themselves in storage experiments with ultracold neutrons whose storage lifetime would depend on the applied magnetic field. Here, extended details and measurements from the first dedicated experimental search for nn′ oscillations published in [G. Ban, K. Bodek, M. Daum, R. Henneck, S. Heule, M. Kasprzak, N. Khomutov, K. Kirch, S. Kistryn, A. Knecht, P. Knowles, M. Kuźniak, T. Lefort, A. Mtchedlishvili, O. Naviliat-Cuncic, C. Plonka, G. Quéméner, M. Rebetez, D. Rebreyend, S. R…

Thermal neutron capture cross section of the radioactive isotopeFe60

Background: Fifty percent of the heavy element abundances are produced via slow neutron capture reactions in different stellar scenarios. The underlying nucleosynthesis models need the input of neutron capture cross sections.Purpose: One of the fundamental signatures for active nucleosynthesis in our galaxy is the observation of long-lived radioactive isotopes, such as $^{60}\mathrm{Fe}$ with a half-life of $2.60\ifmmode\times\else\texttimes\fi{}{10}^{6}$ yr. To reproduce this $\ensuremath{\gamma}$ activity in the universe, the nucleosynthesis of $^{60}\mathrm{Fe}$ has to be understood reliably.Methods: An $^{60}\mathrm{Fe}$ sample produced at the Paul Scherrer Institut (Villigen, Switzerla…

Thermal (n,γ) cross section and resonance integral ofTm171

Multi-color resonance ionization of laser ablated gadolinium at high laser power

Abstract Spectroscopic and analytical properties of a trace analytical method using multi-step resonance ionization at high laser intensities (>kW/cm 2 ) have been investigated with gadolinium as a test element. Strongly saturated transitions are observed, which have been used for a temperature determination of the atoms in the laser ablated plume. Regimes of multi-step resonance ionization and multiphoton ionization could be distinguished. Analytical performances due to resonance enhancement and resulting discrimination against non-resonant background, precision in isotope ratio determination and overall detection efficiency are discussed.

A laser desorption/resonance enhanced photoionisation TOF-system for the spatially resolved trace analysis of elements

Abstract A novel method for direct and spatially resolved elemental trace analysis with high sensitivity and elemental selectivity is presented. The concept is based on the combination of a commercial MALDI-TOF mass spectrometer with a pulsed laser system for resonant postionisation of neutrals. While the MALDI method is usually applied for investigations of large organic compounds and biomolecules, the technique discussed here concerns the low mass range around 1 ⩽ A ⩽ 300. The analytical performances of the setup with respect to mass analysis, spatial resolution and overall detection efficiency are discussed.