A novel laboratory platform has been designed and built for the irradiation of a plasma crystal (PC) with an electron beam (e-beam) having an energy around 10 keV and a current of tens of ...milliamperes. The pulsed e-beam collimated to a few millimeter-size spot is aimed at a crystal made of dust particles levitated in a radio-frequency (RF) plasma. The platform consists of three vacuum chambers connected in-line, each with different utility: one for generating free electrons in a pulsed hollow-anode Penning discharge, another for the extraction and acceleration of electrons at Formula: see text kV and for focusing the e-beam in the magnetic field of a pair of circular coils, and the last one for producing PCs above a RF-driven electrode. The main challenge is to obtain both a stable e-beam and PC by insuring appropriate gas pressures, given that the e-beam is formed in high vacuum (Formula: see text Torr), while the PC is produced at much higher pressures (Formula: see text Torr). The main diagnostics include a high speed camera, a Faraday cup and a Langmuir probe. Two applications concerned with the creation of a pair of dust flow vortices and the rotation of a PC by the drag force of the e-beam acting on the strongly coupled dust particles are presented. The dust flow can become turbulent as demonstrated by the energy spectrum, featuring vortices at different space scales.
This Letter presents the first experimental observation of the attractive strong interaction between a proton and a multistrange baryon (hyperon) Ξ−. The result is extracted from two-particle ...correlations of combined p−Ξ−⊕p¯−Ξ¯+ pairs measured in p−Pb collisions at sNN=5.02 TeV at the LHC with ALICE. The measured correlation function is compared with the prediction obtained assuming only an attractive Coulomb interaction and a standard deviation in the range 3.6, 5.3 is found. Since the measured p−Ξ−⊕p¯−Ξ¯+ correlation is significantly enhanced with respect to the Coulomb prediction, the presence of an additional, strong, attractive interaction is evident. The data are compatible with recent lattice calculations by the HAL-QCD Collaboration, with a standard deviation in the range 1.8, 3.7. The lattice potential predicts a shallow repulsive Ξ− interaction within pure neutron matter and this implies stiffer equations of state for neutron-rich matter including hyperons. Implications of the strong interaction for the modeling of neutron stars are discussed.
Small multilayered laminated samples consisting of stacks of W (or K-doped W) foils without an interlayer or with interlayers from Cu, V, and Ti were exposed to a pulsed electron beam with an energy ...of 6 MeV in several irradiation sessions. All samples maintained their macroscopic integrity, suggesting that the W-metal laminate concept is compatible with high heat flux applications. The surface of the samples was analyzed using a scanning electron microscope (SEM) before and after each irradiation session. The experimental results indicate that electron beam irradiation induces obvious modifications on the surface of the samples. Morphological changes such as the appearance of nanodroplets, nanostructures, and melting and cracking, depending on the sample type and the electron beam fluence, are observed. The irradiation is carried out in a vacuum at a pressure of 2 to 4 × 10
torr, without active cooling for the samples. The structures observed on the surface of the samples are likely due to electron beam heating and vaporization followed by vapor condensation in the volume adjacent to the surface.
The N=52Ga83β decay was studied at ALTO. The radioactive 83Ga beam was produced through the ISOL photofission technique and collected on a movable tape for the measurement of γ-ray emission following ...β decay. While β-delayed neutron emission has been measured to be 56–85% of the decay path, in this experiment an unexpected high-energy 5–9 MeV γ-ray yield of 16(4)% was observed, coming from states several MeVs above the neutron separation threshold. This result is compared with cutting-edge QRPA calculations, which show that when neutrons deeply bound in the core of the nucleus decay into protons via a Gamow–Teller transition, they give rise to a dipolar oscillation of nuclear matter in the nucleus. This leads to large electromagnetic transition probabilities which can compete with neutron emission, thus affecting the β-decay path. This process is enhanced by an excess of neutrons on the nuclear surface and may thus be a common feature for very neutron-rich isotopes, challenging the present understanding of decay properties of exotic nuclei.
The low-spin structure of the semimagic 64Ni nucleus has been considerably expanded: combining four experiments, several 0+ and 2+ excited states were identified below 4.5 MeV, and their properties ...established. The Monte Carlo shell model accounts for the results and unveils an unexpectedly complex landscape of coexisting shapes: a prolate 0+ excitation is located at a surprisingly high energy (3463 keV), with a collective 2+ state 286 keV above it, the first such observation in Ni isotopes. The evolution in excitation energy of the prolate minimum across the neutron N=40 subshell gap highlights the impact of the monopole interaction and its variation in strength with N.
Due to their highly tunable properties, layered double hydroxides (LDHs) are an emerging class of the favorably layered crystals used for the preparation of multifunctional polymer/layered crystal ...nanocomposites. In contrast to cationic clay materials with negatively charge layers, LDHs are the only host lattices with positively charged layers (brucite-like), with interlayer exchangeable anions and intercalated water.
In this work, the deposition of thin films of Mg and Al based LDH/polymers nanocomposites by laser techniques is reported. Matrix assisted pulsed laser evaporation was the method used for thin films deposition. The Mg–Al LDHs capability to act as a host for polymers and to produce hybrid LDH/polymer films has been investigated. Polyethylene glycol with different molecular mass compositions and ethylene glycol were used as polymers. The structure and surface morphology of the deposited LDH/polymers films were examined by X-ray diffraction, Fourier transform infra-red spectroscopy, atomic force microscopy and scanning electron microscopy.
•Hybrid composites deposited by matrix assisted pulsed laser evaporation (MAPLE).•Mg–Al layered double hydroxides (LDH) and polyethylene glycol (PEG) are used.•Mixtures of PEG1450 and LDH were deposited by MAPLE.•Deposited thin films preserve the properties of the starting material.•The film wettability can be controlled by the amount of PEG.
The study of the strength and behavior of the antikaon-nucleon (Kover ¯N) interaction constitutes one of the key focuses of the strangeness sector in low-energy quantum chromodynamics (QCD). In this ...Letter a unique high-precision measurement of the strong interaction between kaons and protons, close and above the kinematic threshold, is presented. The femtoscopic measurements of the correlation function at low pair-frame relative momentum of (K^{+}p⊕K^{-}pover ¯) and (K^{-}p⊕K^{+}pover ¯) pairs measured in pp collisions at sqrts=5, 7, and 13 TeV are reported. A structure observed around a relative momentum of 58 MeV/c in the measured correlation function of (K^{-}p⊕K^{+}pover ¯) with a significance of 4.4σ constitutes the first experimental evidence for the opening of the (Kover ¯^{0}n⊕K^{0}nover ¯) isospin breaking channel due to the mass difference between charged and neutral kaons. The measured correlation functions have been compared to Jülich and Kyoto models in addition to the Coulomb potential. The high-precision data at low relative momenta presented in this work prove femtoscopy to be a powerful complementary tool to scattering experiments and provide new constraints above the Kover ¯N threshold for low-energy QCD chiral models.
The pT-differential production cross sections of the prompt charmed mesons D0, D+, D*+, and D+s and their charge conjugate in the rapidity interval –0.96 < ycms < 0.04 were measured in p–Pb ...collisions at a center-of-mass energy √sNN = 5.02 TeV with the ALICE detector at the LHC. The nuclear modification factor RpPb, quantifying the D-meson yield in p–Pb collisions relative to the yield in pp collisions scaled by the number of binary nucleon-nucleon collisions, is compatible within the 15%–20% uncertainties with unity in the transverse momentum interval 1 < pT < 24 GeV/c. No significant difference among the RpPb of the four D-meson species is observed. The results are described within uncertainties by theoretical calculations that include initial-state effects. In conclusion, the measurement adds experimental evidence that the modification of the momentum spectrum of D mesons observed in Pb-Pb collisions with respect to pp collisions is due to strong final-state effects induced by hot partonic matter.
The differential charged jet cross sections, jet fragmentation distributions, and jet shapes are measured in minimum bias proton-proton collisions at center-of-mass energy radicals = 7 TeV using the ...ALICE detector at the LHC. Jets are reconstructed from charged particle momenta in the midrapidity region using the sequential recombination k sub(T) and anti-k sub(T) as well as the SISCone jet finding algorithms with several resolution parameters in the range R = 0.2-0.6. Differential jet production cross sections measured with the three jet finders are in agreement in the transverse momentum (p sub(T)) interval 20 < (ProQuest: Formulae and/or non-USASCII text omitted) < 100 GeV /c They are also consistent with prior measurements carried out at the LHC by the ATLAS Collaboration. The jet charged particle multiplicity rises monotonically with increasing jet p sub(T), in qualitative agreement with prior observations at lower energies. The transverse profiles of leading jets are investigated using radial momentum density distributions as well as distributions of the average radius containing 80% (<"R sub(80)>") of the reconstructed jet p sub(T). The fragmentation of leading jets with R = 0.4 using scaled p sub(T) spectra of the jet constituents is studied. The measurements are compared to model calculations from event generators (PYTHIA, PHOJET, HERWIG). The measured radial density distributions and <"R sub(80)> " distributions are well described by the PYTHIA model (tune Perugia-2011). The fragmentation distributions are better described by HERWIG.
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