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A dense plasma focus (DPF) nuclear fusion device is an attractive pulsed neutron source in many applications, due to its relatively large neutron yield, produced in a short time duration. To design a DPF that generates neutrons within a specified time profile, or that generates a neutron energy spectrum with specific properties, it is necessary to characterize and model the results of the fusion process releasing the neutrons. The time–energy spectrum of fusion neutrons is an ideal quantity used in validating multiphysics codes that simulate the pinch and fusion processes, because it is a quantity that requires physics of each of the stages leading up to and ending in the fusion reaction to be simulated correctly. In particular, since DPF fusion neutrons are not monoenergetic—and there can often be several fusion pinches creating neutrons—a computer simulation matching high quality neutron spectrum measurements provides confidence in the fidelity of the simulation. In order to make such a comparison, it is first necessary to have quality measurements from which to infer the spectrum. In this work, we project neutron spectroscopy as the classical tomographic inverse problem from neutron time-of-flight data at multiple distances, but enhanced by using an additional measurement of the time profile of the fusion pinch near its source and by using detector pairs set up in a geometry that allows for scatter background subtraction. The detector pairs enhance the quality of the time-of-flight measurements, and the additional constraint posed by the measured time profile allows for reconstructions discretized as finely as the time measurements and in energy as finely as 100 keV, without the problem being underdetermined. We present results from a deuterium-fueled DPF at the U.S. Department of Energy’s Nevada National Security Site and show that we can infer the time–energy spectrum from our measurements for both single and multi-pinch fusion reactions with equal fidelity.

International audience; A great many experimental studies devoted to exploring in detail the properties of radioactive decay of the isotopes of transfermium elements by means of alpha, beta, and gamma spectroscopy have been performed over the past fifteen years at the Flerov Laboratory of Nuclear Reactions (Joint Institute for Nuclear Research, Dubna). High-intensity accelerated heavy-ion beams of ${}^{22}$Ne, ${}^{48}$Ca, ${}^{50}$Ti, and ${}^{54}$Cr from the U-400 cyclotron were used in experiments with the SHELS kinematic separator. An upgrade of the separator and detector system is planned in the future with the aim of improving the transportation efficiency for the nuclei under study and the detection efficiency for gamma rays.

Isomeric states in $^{256}\mathrm{No}$ were investigated using internal conversion electron and $\ensuremath{\gamma}$-ray spectroscopy with the GABRIELA detection system at the focal plane of the SHELS recoil separator, at the Flerov Laboratory for Nuclear Research (FLNR, JINR, Dubna). The nuclei of interest were produced using the highly asymmetric fusion-evaporation reaction $^{238}\mathrm{U}(^{22}\mathrm{Ne},4n)^{256}\mathrm{No}$. The emission of internal conversion electrons and $\ensuremath{\gamma}$ rays occurring between a $^{256}\mathrm{No}$ implantation and a subsequent $\ensuremath{\alpha}$-decay event were studied, resulting in the observation of high-$K$ isomerism in this nobelium isotope. The nature of the isomeric states is discussed in terms of possible two- and four-quasiparticle structures.

Background Research contributions by registered dietitian nutritionists (RDNs) are important for enhancing the use of nutrition-related evidence-based guidelines in dietetics practice. Involvement of RDNs in research activities has been studied previously, but little is known about the drivers (motivators) of sustaining research involvement by RDNs who work in clinical practice. Objective To identify key characteristics of established RDN clinician researchers and drivers that contributed to their sustained research involvement. Design We used a convergent parallel mixed methods study design utilizing the clinician career research trajectory as a framework. Research involvement was examined using the Practice-Based Dietitian Research Involvement Survey (PBDRIS). Workplace support was assessed using the Research Capacity and Culture (RCC) survey. Semistructured interviews were used to investigate key themes in established RDN clinician researchers. Participants/setting We identified 450 RDNs involved with research activities in the United States through hand-searching clinically relevant nutrition journals and contacted them to participate in an online survey. A total of 29 RDNs met criteria and completed (6.4%) the quantitative survey, then a subsample (n=10) participated in semistructured interviews to explore drivers for continued research involvement. Results Research involvement scores (n=29) from the PBDRIS ranged from 60.0% to 97.5%, indicating involvement in higher-level research-related tasks by our sample participants. RCC results revealed the importance of workplace support and mentorship. Interviews with established RDN clinician researchers identified exposure, curiosity, and dedication as three overarching themes with eight subthemes driving continued research involvement. Conclusion Based on the experiences of select RDN clinician researchers who have demonstrated success in sustaining their research involvement, we found that having an available mentor, support from their workplace environment, and personal drive were integral to their success.

International audience; In the reaction of complete fusion of $^{48}$Ca-ions with a $^{204}$Pb target, a new α line, related to the decay of a new, previously unknown isotope ($^{249}$No), has been detected in an experiment carried out at the SHELS separator. The α decay energy (E$_{α}$ = 9129 keV) and the half-life (T$_{1/2}$ = 38.1 ± 2.5 ms) are measured using the GABRIELA detector array. The SF branching ratio was estimated (b$_{SF}$ ≤ 0.2%).

International audience; GABRIELA (Gamma Alpha Beta Recoil Investigations with the Electromagnetic Analyzer) is a detection system installed at the focal plane of the SHELS (Separator for Heavy Elements Spectroscopy) recoil separator for gamma and internal conversion electron spectroscopy of heavy and superheavy nuclei. GABRIELA has recently been upgraded. The characteristics of the new setup are presented using the Geant4 Monte Carlo simulation toolkit and validated against experimental results. The impact of summing on the gamma-ray and electron detection efficiencies is discussed.

International audience; The mass, energy and angular distributions of binary fragments formed in the reactions $^{64}$Ni + $^{238}$U, $^{58}$Fe + $^{244}$Pu, $^{52}$Cr + $^{248}$Cm, $^{54}$Cr + $^{248}$Cm at energies near the Coulomb barrier have been measured. The analysis of energy distributions of the symmetric fragments with mass numbers ${{{{A}_{{{\text{CN}}}}}} \mathord{\left/ {\vphantom {{{{A}_{{{\text{CN}}}}}} 2}} \right. \kern-0em} 2} \pm 20$ formed in these reactions have been applied to separate compound nucleus fission and quasi-fission. The estimated fusion probability for the reactions Cr, Fe, and Ni ions with actinide targets shows an exponential dependence on the mean fissility parameter of the system and shows also that reaction with Cr ions is more favorable for production of the super heavy element with Z = 120.

SIRIUS (Spectroscopy & Identification of Rare Isotopes Using S3) is a detection system designed for the focal plane of S3 (the Super Separator Spectrometer), which is part of the SPIRAL2 (Systeme de Production d’Ions RAdioactifs en Ligne de 2e generation) facility at GANIL (France). This study presents the characterization of the Side silicon detector of SIRIUS. This new “Strippy-pad” detector design benefits from an ultra-high resistivity and the windowless technique from Micron Semiconductor Ltd. These detectors were tested at the IPHC Strasbourg on a dedicated test bench with custom fast preamplifiers coupled to digital electronics cards. Combining all these elements, we obtained resolutions as good as 13.6 keV for certain pixels of this detector for 8.8 MeV alpha particles , with an average resolution measured at 14.7 keV over the whole detector.

International audience; The neutron yield from the spontaneous fission of the short-lived neutron-deficient$^{254}$Rf nucleus produced in the complete fusion reaction with the beam of multiply charged ions from the U400 accelerator at the Flerov Laboratory of Nuclear Reactions (FLNR), Joint Institute for Nuclear Research (JINR), is measured using the combined detection system of the SHELS velocity filter. The half-life and the branching ratio of$^{254}$Rf are also measured. The data on the multiplicity of prompt neutrons from spontaneous fission of$^{256}$Rf ($\bar {\nu }$ = 3.87 ± 0.34) are presented for the first time.

The Super Separator Spectrometer (S3S3) facility is developed in the framework of the SPIRAL2 project [1]. S3S3 has been designed to extend the capability of the facility to perform experiments with extremely low cross sections, taking advantage of the very high intensity stable beams of the superconducting linear accelerator of SPIRAL2. It will mainly use fusion-evaporation reactions to reach extreme regions of the nuclear chart: new opportunities will be opened for super-heavy element studies and spectroscopy at and beyond the driplines. In addition to our previous article (Dechery et al. [2]) introducing the optical layout of the spectrometer and the expected performances, this article will present the current status of the main elements of the facility: the target station, the superconducting multipole, and the magnetic and electric dipoles, with a special emphasis on the status of the detection system SIRIUS and on the low-energy branch which includes the REGLIS3 system. S3S3 will also be a source of low energy radioactive isotopes for delivery to the DESIR facility.

A crystal of lithium niobate was configured for use as a longitudinal-mode piezoelectric transformer (PT). An electron gun was coupled to the transformer to allow for controlled release of charge to the high-voltage terminal of the PT. An electron tube extracted a beam from a thermionic emission source, and cylindrical optics focused the beam to a 2-mm spot at the PT output. Two diagnostic methods were used to measure the operation of the PT: bremsstrahlung X-ray spectroscopy and laser-optical interrogation. Both diagnostics showed that the PT is able to process up to 1.5 $\mu \text{A}$ of current at 20-kV output in a continuous mode. The laser-optical method was also used to compare the mechanical stress, electric field, and developed voltage between the fundamental and secondary harmonic resonance modes.

International audience; In the last years we carried out several experiments aimed to investigate properties of short-lived SF isotopes. The neutron-deficient isotopes of nobelium were produced in fusion-evaporation reactions using 206,208Pb targets and an intense 48Ca-beam. Fusionevaporation residues were separated by the SHELS separator and implanted into a largearea double-sided 48×48 strip silicon detector surrounded by 3He-based neutron counters. Half-lives and decay branching ratios for 252,254No isotopes were measured. The average number of neutrons per spontaneous fission of 254No determined for the first time.

The GABRIELA [1] set-up is used at the FLNR to perform detailed nuclear structure studies of transfermium nuclei. Following the modernization of the VASSILISSA separator (SHELS) [2] the GABRIELA detection system has also been upgraded. The characteristics of the upgraded detection system will be presented along with results from some recent electronics tests., Comment: 6 pages, 3 figure, 1 table uncorrected pre-print of EXON 2018 conference proceedings

Recent experiments on the Mercury pulsed power accelerator were performed with a large-area bremsstrahlung diode operated at 5 MV. Extensive measurements of the x-ray dose distribution were made using TLDs, both in the near field and far field of the x-ray beam. In order to understand the operation of the diode and the properties of the x-ray beam, numerical simulations of the diode and beam were performed. Particle-in-cell simulations of the diode were driven using the measured currents from the experiment in order to simulate the electron beam produced by the accelerator. These beam electrons were then used as a source in Monte Carlo simulations of the bremsstrahlung converter to compute the generated x-ray beam. The photons from this simulation were then transported to the near- and far-field TLD locations and doses were computed. The dose predictions were compared to measurements, showing reasonably good agreement.

The reliable detection of special nuclear materials continues to be a primary goal of national security programs conducted by Defense Nuclear Nonproliferation agencies. While these programs are diverse, many share a core need for a small, robust pulsed neutron generator. This project addresses this need by building a portable dense plasma focus (DPF) neutron source. DPF technology offers many benefits that are infeasible using conventional neutron sources: it can generate intense neutron pulses, operate at relatively low voltage, and be scaled to a lightweight form factor. Large-scale DPF sources produce prolific neutron radiation but require heavy machinery for transport and are therefore not ideal for mobile applications. Alternatively, compact DPF systems can be fabricated that are easily transported by human operators and generate sufficient neutron output to accomplish mobile active interrogation missions. Recently, researchers at Mission Support and Test Services (MSTS) have constructed a bench-top DPF system to produce neutron radiation. The system comprises commercially available high voltage power supplies, capacitors, and cold-cathode thyratron switches and weighs approximately 25 kg. The system draws approximately 750 Wand can be powered using lithium-ion battery packs. A custom plasma process chamber was designed using hybrid PIC-MHD modeling software and constructed using off-the-shelf components. A control system was implemented on a microcontroller platform to discharge the DPF source with a repetition rate up to 0.2 Hz. A suite of neutron yield and time-of- flight diagnostics was used to measure the radiation output of the portable DPF source.

The structure of low-lying excited states in $^{251}\mathrm{Fm}$, populated by the $\ensuremath{\alpha}$ decay of $^{255}\mathrm{No}$, has been investigated by means of combined $\ensuremath{\gamma}$ and internal conversion electron spectroscopy. The values for the internal conversion coefficients for the $1/{2}^{+}\ensuremath{\rightarrow}5/{2}^{+}$ and $5/{2}^{+}\ensuremath{\rightarrow}9/{2}^{\ensuremath{-}}$ transitions have been measured. The determined $M2/E3$ mixing ratio and lifetime for the $5/{2}^{+}$ decay to the ground state allowed to determine the corresponding reduced transitions strengths of $B(E3)=18(6)$ W.u. and $B(M2)=3.0(6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ W.u. These results, as well as the results of previous studies in $N=151$ isotopes, are compared to theoretical calculations beyond the mean-field approach, including the first QRPA calculations using the Gogny D1M parametrization for such heavy odd-$N$ nuclei. The comparison points to the importance of accounting for the octupole vibrations for a proper understanding of the low-lying nuclear structure of some of the heaviest elements.

In order to study the nucleus–nucleus interactions for syntheses of superheavy nuclei, we measured excitation functions for the quasielastic scattering of 48Ca+208Pb, 50Ti+208Pb, and 48Ca+248Cm using the gas-filled-type recoil ion separator GARIS. The quasielastic scattering events were clearly separated from deep-inelastic events by using GARIS and its focal plan detectors, except for high-incident-energy points. The quasielastic barrier distributions were successfully extracted for these systems, and compared with coupled-channels calculations. The results of the calculations indicate that vibrational and rotational excitations of the colliding nuclei, as well as neutron transfers before contact, strongly affect the structure of the barrier distribution. For the reactions of 48Ca+208Pb and 50Ti+208Pb, a local maximum of the barrier distribution occurred at the same energy as the peak of the 2n evaporation cross section of the system. On the other hand, for the hot fusion reaction of 48Ca+248Cm, the 4n e...

series of experiments performed in 2014–2015 using the SHELS separator and a beam of multicharged ions from the U-400 accelerator at the Flerov Laboratory of Nuclear Reactions (Joint Institute for Nuclear Research) in Dubna is described. In preparation for a large program of experiments with a beam of highly charged ions of 50Ti, an experiment is performed to study the spontaneous fissioning (SF) of short-lived neutron-deficient isotope 256Rf formed in complete fusion reaction50Ti + 208Pb = 256Rf + 2n. The half-life of 256Rf is measured along with the probability of its SF decay. The average number of neutrons per one event of 256Rf SF ( $$\bar v$$ = 4.47 ± 0.09) is obtained for the first time. The results from experiments to study the SF of short-lived neutron-deficient isotopes synthesized in complete fusion reaction 48Ca + 204Pb → 252No* are presented as well. Two short-lived activities attributed to the SF of the ground and isomeric states of 250No are revealed. The half-life, total kinetic energies of fission fragments, and neutron multiplicities are measured for the obtained short-lived nuclei. The average numbers of neutrons per one SF event are $$\bar v$$ = 4.38 ± 0.13 and $$\bar v$$ = 3.90 ± 0.20, respectively, for SF activity with t1/2 = 5.1 ± 0.3 and t1/2 = 36 ± 3 μs.

This study describes an experiment on investigating the properties of spontaneous fission of shortlived neutron-deficient nuclei synthesized in the reaction of complete fusion 48Ca + 204Pb = 252No*. The experiment is performed using the SHELS separator and the beam of multicharged ions at U-400 accelerator (LNR, JINR). Two activities undergoing spontaneous fission, which can be related to the ground and isomeric states of 250No nucleus, are registered. The half-lives, total kinetic energies of fission fragments, and neutron multiplicities are measured for the short-lived nuclei. The average number of neutrons per fission for the activity with t 1/2 = 5.1 ± 0.3 μs is = 4.38 ± 0.13 μs, and for nuclei with the half-life t 1/2 = 36 ± 3 μs it is xxxxx.

Explanation of the so-called Oklo phenomenon can only be found by associating neutron physics and geological observations. The framework of Reactor Zone #9 (RZ9) from the Oklo uranium deposit in Gabon is discussed. A realistic model of RZ9 is proposed and studied with present-day numerical tools. Anchor points for this model are set by means of a selection of relevant parameters acting on geological conditions and neutron-transport physics, including ore homogeneity, initial reactor thickness, reflector effect and initial neutron poison content. Based on Monte Carlo simulations, the present modeling enables discussion of start-up conditions of the RZ9 reactor at optimal overlap of two opposing long-term processes: geochemical enrichment of the uranium content of the ore and its progressive impoverishment in 235U. On the basis of the present work, the inception and operation of Oklo natural reactors can be discussed from the largest to smallest initial core size, whereas before, only the largest ones had found some explanation.

The piezoelectric effect is analyzed as a means to produce X-rays. A mass of crystalline piezoelectric material is used to convert a low-voltage input electrical signal into a high-voltage output signal by storing energy in a longitudinally vibrating mechanical wave. Output energy is extracted in the form of a high-voltage electron beam using a field-emission diode mounted on the surface of the crystal. The electron beam produces X-rays via bremsstrahlung interactions with a metallic surface.

One hundred years after the discovery of the atomic nucleus by Ernest Rutherford, the nuclear chart has been extended far from stability, providing more and more stringent tests for nuclear models. Nuclei at the extremes of the chart are produced with extremely low production cross-sections and one has to ingeniously upgrade the best experimental devices in order to reduce the observational limits.

SIRIUS is a state-of-the-art detector system for nuclear decay spectroscopy that will be mounted at the focal plane of S3 (Super Separator Spectrometer), which is part of the new SPIRAL2 facility at GANIL, Caen in France. Such a system requires high performance as it is dedicated to the study of very exotic nuclei. It is the result of collaboration between GANIL CSNSM, IRFU, and IPHC It is composed of a succession of detectors (Trackers, Silicon detector DSSD and Tunnel plus an array of five clover Germanium detectors). This set-up is mounted in a compact geometry. The energy measurement varies from 50 keV to over 500 MeV with high precision (2 × 10−3) at low energies and 1 % for the detection of heavy ions. A major challenge has been the development of new electronics with a very large dynamic range maintaining an adequate energy resolution for the measured particles (with energies from a few hundred keV up to 500 MeV).

International audience; In the last years we carried out several experiments aimed to investigate properties of short-lived SF isotopes. The neutron-deficient isotope 256Rf were produced in fusion-evaporation reactions using an 208Pb target and an intense 50Ti beam. Fusion-evaporation residues were separated by the SHELS separator (FLNR, Dubna) and implanted into a large-area double-sided silicon 48×48 strip detector surrounded by 3He-based neutron counters. The half-life and decay branching ratio of 256Rf is measured. The average number of neutrons per spontaneous fission of 256Rf is determined for the first time. Next we carried out an experiment aimed at investigating the properties of spontaneous fission of neutron deficient isotope 250No produced in the reaction with 48Cabeam and 204Pb-target. Earlier two spontaneous fission half-lives (t1/2 = 5.1±0.3 μs and t1/2 = 36±3 μs) originate from 250No were registered. The obtained excitation functions after the evaporation of 2 neutrons from the compound 252No nuclei have been compared with similar data obtained earlier. From the experimental data for the first time the average number of neutrons per spontaneous fission and TKE-spectra of fission fragments of both 250No activities was determined.

International audience; Spontaneous fission properties of the short-lived neutron-deficient 256Rf nucleus produced in thecomplete fusion reaction with a beam of multiply charged heavy 50Ti ions from the U-400 cyclotron (FLNR,JINR) are experimentally investigated. Its half-life and decay branching ratio are measured. The averagenumber of neutrons per spontaneous fission of 256Rf ( = 4.47 ± 0.09) is determined for the first time.

International audience; Superheavy nuclei exist solely due to quantum shell effects,which create a pocket in the potential-energy surface of the nucleus, thusproviding a barrier against spontaneous fission. Determining the height ofthe fission barrier and its angular-momentum dependence is important toquantify the role that microscopic shell corrections play in enhancing andextending the limits of nuclear stability. In this talk, the first measurement ofa fission barrier in the very heavy nucleus 254No will be presented.

The occurrence of more than 15 natural nuclear Reactor Zones (RZ) in a geological environment remains a mystery even 40 years after their discovery. The present work gives for the first time an explanation of the chemical and physical processes that caused the start-up of the fission reactions with two opposite processes, uranium enrichments and progressive impoverishment in 235 U. Based on Monte-Carlo neutronics simulations, a solution space was defined taking into account realistic combinations of relevant parameters acting on geological conditions and neutron transport physics. This study explains criticality occurrence, operation, expansion and end of life conditions of Oklo natural nuclear reactors, from the smallest to the biggest ones.

6 pages; International audience; Isomeric states in 253No have been investigated by conversion-electron and gamma-ray spectroscopy with the GABRIELA detection system. The 31 micro second isomer reported more than 30 years ago is found to decay to the ground state of 253No by the emission of a 167 keV M2 transition. The spin and parity of this low-lying isomeric state are established to be 5/2+. The presence of another longer-lived isomeric state is also discussed.

The Super Separator Spectrometer S 3 is a major experimental system developed for SPIRAL2. It has been designed for physics experiments with very low cross sections by taking full advantage of the very high intensity stable beams to be produced by LINAG, the superconducting linear accelerator at GANIL. These intensities will open new opportunities in several physics domains using fusion evaporation reactions, principally: super-heavy and very heavy element properties, spectroscopy at and beyond the dripline, and isomer and ground-state properties. The common feature of these experiments is the requirement to separate very rare events from intense backgrounds. S 3 accomplishes this with a large acceptance, a high background rejection efficiency, and a physical mass separation. This article will present the technical specifications and optical constraints needed to achieve these physical goals. The optical layout of the spectrometer will be presented, focusing on technical elements of the target system, the superconducting multipole magnets used to correct high-order optical aberrations, the electric and magnetic dipoles, and the open multipole triplet used for primary beam rejection. The expected system performance will be presented for three experimental cases using 3 specific optical modes of the spectrometer.

WOS: 000240847400007, The observation of the new nuclide Re-159(75)84 provides important insights into the evolution of single-particle structure and the mass surface in heavy nuclei beyond the proton drip line. This nuclide, 26 neutrons away from the nearest stable rhenium isotope, was synthesised in the reaction Cd-106(Ni-58, p4n) and identified via its proton radioactivity using the RITU gas-filled separator and the GREAT focal-plane spectrometer. Comparisons of the measured proton energy (E-p = 1805 +/- 20 keV) and decay half-life (t(1/2) = 21 +/- 4 mu s) with values calculated using the WKB method indicate that the proton is emitted from an h(11/2) state. The implications of these results for future experimental investigations into even more proton unbound nuclei using in-flight separation techniques are considered. (c) 2006 Elsevier B.V. All rights reserved., Science and Technology Facilities Council [EP/C543157/1, EP/C015371/1, EP/C015266/1, ST/G008671/1]

Evaluation and dissemination of the outcomes of school-based health center (SBHC) services is essential for the continual growth and funding of SBHCs in the United States. Since their inception, SBHCs have been practice sites for nurse practitioners and have used interdisciplinary teams to provide care for underserved school-aged children. Early research and evaluation focused on describing the types of services and the quality of care provided. Supporters of SBHCs were anxious to demonstrate that the care provided was "as good as" care delivered in traditional primary care practices. Documentation of program impacts, such as changes in population health indicators or improved academic achievement, has been more elusive. Current evaluation priorities outlined by the National Assembly on School-Based Health Care include evaluation of mental health services using a new online tool; assessing productivity of SBHC staff; measuring quality; and attempts to link SBHC care with improved academic outcomes.