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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; 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.

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

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.

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.

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.

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]

Guilds consist of groups of species that use mutual resources or collections of overlapping resources. Guilds are often comprised of members of the same family or genus, but they can span larger taxonomic categories. Predacious arthropods, such as carabid beetles, centipedes and spiders, and small carnivorous vertebrates, such as woodland salamanders, overlap extensively in microhabitat and prey types. These taxa, though unrelated, may form important guilds of forest floor predators. We examined the behavioral interactions between a carabid ground beetle (Platynus tenuicollis) and a small woodland salamander (the red-backed salamander, Plethodon cinereus) in laboratory encounters. These species occur syntopically and feed on similar prey. Individuals of P. cinereus are territorial and defend cover objects against conspecific and congeneric intruders. Because both species require moist conditions, it seems probable that they would compete for resources, such as cover objects and prey, as the fores...

The first fully kinetic, collisional, and electromagnetic simulations of the breakdown phase of a MA-scale dense plasma focus are described and shown to agree with measured electrical characteristics, including breakdown time. In the model, avalanche ionization is driven by cathode electron emission, and this results in incomplete gas breakdown along the insulator. This reinforces the importance of the conditioning process that creates a metallic layer on the insulator surface. The simulations, nonetheless, help explain the relationship between the gas pressure, the insulator length, and the coaxial gap width. Previously, researchers noted three breakdown patterns related to pressure. Simulation and analytical results show that at low pressures, long ionization path lengths lead to volumetric breakdown, while high pressures lead to breakdown across the relatively small coaxial electrode gap. In an intermediate pressure regime, ionization path lengths are comparable to the insulator length which promotes i...

International audience; Investigations of complete fusion reactions leading to the synthesis of heavy and superheavy nuclei have been an important part of the experimental program at the Flerov Laboratory of Nuclear Reactions (JINR, Dubna). For synthesis and decay studies of heavy nuclei, a project of modernization of the existing experimental set up VASSILISSA is now underway. The results of the first experimental tests with the modernized VASSILISSA separator are presented, in particular the experimentally measured transmission coefficients for recoil nuclei synthesized in asymmetric reactions with a Ne-22 beam. These results completely confirm the ion optical calculations performed during the design stage of the modernization.

We report on the first measurement of the fission barrier height in a heavy shell-stabilized nucleus. The fission barrier height of 254No is measured to be Bf=6.0±0.5 MeV at spin 15ℏ and, by extrapolation, Bf=6.6±0.9 MeV at spin 0ℏ. This information is deduced from the measured distribution of entry points in the excitation energy versus spin plane. The same measurement is performed for 220Th and only a lower limit of the fission barrier height can be determined: Bf(I)8 MeV. Comparisons with theoretical fission barriers test theories that predict properties of superheavy elements.

The gamma-ray multiplicity and total energy emitted by the heavy nucleus 254No have been measured at 2 different beam energies. From these measurements, the initial distributions of spin I and excitation energy E * of 254No were constructed. The distributions display a saturation in excitation energy, which allows a direct determination of the fission barrier. 254No is the heaviest shell-stabilized nucleus with a measured fission barrier. © Owned by the authors, published by EDP Sciences, 2014.

Piezoelectric transformers can be useful as compact, high-voltage supplies. At the University of Missouri, the effect of adding output circuits to bipolar piezoelectric transformers is being studied. These piezoelectric transformers produce output voltages in excess of 25 kV from medium-voltage, radio frequency inputs. However, the high output voltage and low output current of these devices can make it difficult to acquire an accurate electrical measurement of the output voltage without affecting the transformer ratio or resonance of the device. This paper will analyze capacitive voltage dividers as a means of diagnostic measurement and Cockcroft-Walton type circuits to increase the voltage multiplication beyond that of the piezoelectric transformer alone.

Laser‐plasma accelerated ion and electron beam sources are an emerging field with vast prospects, and promise many superior applications in a variety of fields such as hadron cancer therapy, compact radioisotope generation, table‐top nuclear physics, laboratory astrophysics, nuclear forensics, waste transmutation, Special Nuclear Material (SNM) detection, and inertial fusion energy. LANL is engaged in several projects seeking to develop compact high‐current and high‐energy ion and electron sources. We are especially interested in two specific applications: ion fast ignition/capsule perturbation and radiation oncology. Laser‐to‐beam conversion efficiencies of over 10% are needed for practical applications, and we have already shown inherent efficiencies of >5% from flat foils, on Trident using only a 5th of the intensity [1] and energy of the Nova Petawatt laser [2]. With clever target designs, like structured curved cone targets, we have also been able to achieve major ion energy gains, leading to the highest energy laser‐accelerated proton beams in the world [3]. These new target designs promise to help usher in the next generation of particle sources realizing the potential of laser‐accelerated beams.

A detailed study of known and new SD bands in Tb isotopes has been performed with the use of the EUROBALL IV gamma-ray array. The high-statistics data set has allowed for the extension of known SD bands at low and high spins by new gamma-ray transitions. These transitions, as it turns out, correspond to the rotational frequencies where the principal superdeformed gaps (Z=66,N=86) close giving rise to up- or down-bending mechanisms. This enables to attribute the underlying theoretical configurations with much higher confidence as compared to the previous identifications. Five new SD bands have been discovered, three of them assigned to the Tb-152 and the two others to the Tb-151 nuclei. Nuclear mean-field calculations have been used to interpret the structure of known SD bands as well as of the new ones in terms of nucleonic configurations.

To assess the attitude of obstetrics and gynecology nurses towards their own health and their health-related behaviors.Two hundred and ninety community obstetrics and gynecology nurses in Israel were asked to complete a questionnaire on attitude to self-health, way of life, smoking habits, and regular breast, blood and PAP smear examinations.The average body mass index of the responders was 25.2 kg/m2. However, more than half the nurses (163/287, 56.8%) considered themselves as being above-average in weight, and only 41.1% as being appropriate in weight; 55% were on weight-loss diets. Smoking was reported by 44.8%. Blood tests, PAP smears and breast evaluations were regularly done by 72.5%, 83.0% and 55.7%, respectively.Obstetrics and Gynecology nurses in Israel are aware of the importance of their own health and have good health habits, except for cigarette smoking, which remains a problem among this group.

Using state-of-the-art γ-ray spectroscopic techniques, the first rotational band of a superheavy element, extending up to a spin of 20 , was discovered in the nucleus 256Rf. To perform such an experiment at the limits of the present instrumentation, several developments were needed. The most important of these developments was of an intense isotopically enriched 50Ti beam using the MIVOC method. The experimental set-up and subsequent analysis allowed the 256Rf ground-state band to be revealed. The rotational properties of the band are discussed and compared with neighboring transfermium nuclei through the study of their moments of inertia. These data suggest that there is no evidence of a significant deformed shell gap at Z = 104.

Selected surfactant systems containing a series of ethoxylated nonionic surfactants in combination with an anionic surfactant system have been studied to evaluate phase behavior as well as oil recovery potential. These experiments were conducted to evaluate possible improved phase behavior and overall oil recovery potential of mixed surfactant systems over a broad range of conditions. Both polyacrylamide polymers and Xanthan biopolymers were evaluated. Studies were initiated to use a chemical flooding simulation program, UTCHEM, to simulate oil recovery for laboratory and field applications and evaluate its use to simulate oil saturation distributions obtained in CT-monitoring of oil recovery experiments. The phase behavior studies focused on evaluating the effect of anionic-nonionic surfactant proportion on overall phase behavior. Two distinct transition behaviors were observed, depending on the dominant surfactant in the overall system. The first type of transition corresponded to more conventional behavior attributed to nonionic-dominant surfactant systems. This behavior is manifested by an oil-water-surfactant system that inverts from a water-external (highly conducting) microemulsion to an oil-external (nonconducting) one, as a function of temperature. The latter type which inverts in an opposite manner can be attributed to the separation of the anionic-nonionic mixtures into water- and oil-soluble surfactants. Both types of transition behavior can still be used to identify relative proximity to optimal areas. Determining these transition ranges provided more insight on how the behavior of these surfactant mixtures was affected by altering component proportions. Efforts to optimize the chemical system for oil displacement experiments were also undertaken. Phase behavior studies with systems formulated with biopolymer in solution were conducted.

Recent experiments in the Trident laser facility (Los Alamos National Laboratory) have shown that hollow conical targets with a flat top at the tip can enhance the maximum energy of proton beams created during the interaction of an ultra-intense short laser pulse with the target (Gaillard S A et al 2011 Phys. Plasmas 18 056710). The proton energies that have been seen in these experiments are the highest energies observed so far in laser-driven proton acceleration. This is attributed to a new acceleration mechanism, direct light pressure acceleration of electrons (DLLPA), which increases the number and energy of hot electrons that drive the proton acceleration. This acceleration process of protons due to a two-temperature sheath formed at the flat-top rear side is very robust and produces a large number of protons per shot, similar to what is regularly observed in target normal sheath acceleration (Hatchett S P et al 2000 Phys. Plasmas 7 2076, Maksimchuk A et al 2000 Phys. Rev. Lett. 84 4108, Snavely R A et al 2000 Phys. Rev. Lett. 85 2945) with flat foils. In this paper, we investigate the electron kinetics during DLLPA, showing that they are governed by two mechanisms, both of which lead to continuous electron acceleration along the inner cone wall. Based on our model, we predict the scaling of the hot electron temperature and ion maximum energy with both laser and target geometrical parameters. The scaling of T_e^{DLLPA}=m_e c_0 \frac {a_0^2} {4} with the laser strength parameter a0 leads to an ion energy scaling that surpasses that of some recently proposed acceleration mechanisms such as radiation pressure acceleration (RPA), while in addition the maximum electron energy is found to scale linearly with the length of the cone neck. We find that when optimizing parameters, high proton energies suitable for applications can be reached using compact short-pulse laser systems with pulse durations of only a few tens to hundreds of laser periods.

We present experimental results showing a laser-accelerated proton beam maximum energy cutoff of 67.5 MeV, with more than 5 × 106 protons per MeV at that energy, using flat-top hollow microcone targets. This result was obtained with a modest laser energy of ∼80 J, on the high-contrast Trident laser at Los Alamos National Laboratory. From 2D particle-in-cell simulations, we attribute the source of these enhanced proton energies to direct laser-light-pressure acceleration of electrons along the inner cone wall surface, where the laser light wave accelerates electrons just outside the surface critical density, in a potential well created by a shift of the electrostatic field maximum with respect to that of the magnetic field maximum. Simulations show that for an increasing acceleration length, the continuous loading of electrons into the accelerating phase of the laser field yields an increase in high-energy electrons.

WOS: 000286708700015, A new high-spin isomeric state (t(1/2) = 2.8 +/- 0.1 mu s) in Re-160 has been identified. This high-spin isomer is unique in that it only decays by gamma-decay and not by proton or alpha-particle emission as is the case in every other proton emitter between Z = 64 and 80. Shell model calculations indicate how the convergence of the h(9/2) and f(7/2) neutron levels in this region could open up a gamma-decay path from the high-spin isomer to the low-spin ground state of 160Re. providing a natural explanation for this anomalous absence of charged-particle emission. The consequences of these observations for future searches for proton emission from even more exotic nuclei and in-beam spectroscopic studies are considered. (C) 2010 Elsevier B.V. All rights reserved., UK Science and Technology Facilities Council; Swedish Natural Science Research Council; Academy of Finland [44875, 209430, 111965]; European Union [RII3-CT-2004-506065, HPMT-CT-2001-00250]; Science and Technology Facilities Council [ST/G008671/1, ST/J000108/1, EP/C015371/1, ST/J000094/1, EP/C015266/1, ST/G008620/1, ST/F012039/1], The authors thank the technical staff at the University of Jyvaskyla for their excellent support, Paul Morrall for making the targets and Witek Nazarewicz for stimulating discussions. This work was supported by the UK Science and Technology Facilities Council; the Swedish Natural Science Research Council; the Academy of Finland through the Finnish Centre of Excellence Programme (project 44875 Nuclear and Condensed Matter Physics Programme at JYFL) and support for C.S. (contract 209430) and P.T.G. (contract 111965); the European Union Sixth Framework contract EURONS (RII3-CT-2004-506065) and the European Union Marie Curie Programme (contract HPMT-CT-2001-00250).

Young reptiles have higher relative energy demands than adults, but the proposed ontogenetic changes in diet to fulfil these demands were not found in the algae-eating Galapagos marine iguanas on Santa Fe. Feeding and digestion rates were investigated to analyse how young achieve higher energy intake. Daily food intake of free ranging marine iguana hatchlings (6–11 months old) was about one third that of adults, but relative intake (g dry mass · g−1 wet mass · day−1) was four times higher in the hatchlings. During feeding experiments, relative daily food intake of hatchling marine iguanas was approximately three times higher than that of adults (0.042 vs 0.013 g dry mass · g−0.8 wet mass · day−1), and mean gut passage time was two times shorter (5 vs 10 days). The hatchlings also maintained high body temperatures (36.7° C) even under relatively cool day-time air temperatures of 32° C. Apparent digestibility of algal food measured both during feeding trials and by Mn2+ AAS (atomic absorption spectrometry) for free-ranging iguanas was 70%, independent of body size and temperature. The red algae prevailing in the diet were high in protein (30% dry mass) and energy (12.1 kJ/g dry mass). Diving iguanas had higher rates of energy intake than intertidal foragers, but daily intake was less. Maintenance of high body temperature enabled hatchlings to achieve high digestion rates and, combined with high relative intake, thus achieve sufficient energy intake for rapid growth despite higher mass specific metabolic rates. Estimates of biomass of marine iguanas and their algal food are given for a section of coastline on Santa Fe.