54686029
Dynamic polarization effects in ion channeling through single-wall carbon nanotubes
Ion channeling through a single-wall carbon nanotube is simulated by solving Newton’s equations for ion motion at intermediate energies, under the action of both the surface-atom repulsive forces and the polarization forces due to the dynamic perturbation of the nanotube electrons. The atomic repulsion is described by a continuum potential based on the Thomas-Fermi-Moliere model, whereas the dynamic polarization of the nanotube electrons is described by a two-dimensional hydrodynamic model, giving rise to the transverse dynamic image force and the longitudinal stopping force. In the absence of centrifugal forces, a balance between the image force and the atomic repulsion is found to give rise to ion trajectories which oscillate over peripheral radial regions in the nanotube, provided the ion impact position is not too close to the nanotube wall, the impact angle is sufficiently small, and the incident speed is not too high. Otherwise, the ion is found to oscillate between the nanotube walls, passing over a local maximum of the potential in the center of the nanotube, which results from the image interaction. The full statistical analysis of 10 3 ion trajectories has been made to further demonstrate the actual effect of dynamic polarization on the ion channeling.
119981129
Interactions of fast ions with carbon nanotubes: Self-energy and stopping power
The interactions of charged particles with carbon nanotubes are studied by means of the linearized hydrodynamic theory for electronic excitations on the nanotube surface. General expressions are derived for the induced potential, the self-energy, and the stopping power for a charged particle moving paraxially in a nanotube. Numerical results are obtained showing the influence of the damping factor, the nanotube radius, and the particle position on its self-energy and the stopping power. Results for stopping power in the linearized hydrodynamic model are compared with those obtained by means of the dielectric formalism in random-phase approximation, showing a close agreement between the two approaches for high speeds of charged particles.
206022542
Kinetic Study on Channelling of Protons in Metallic Carbon Nanotubes
Based on the kinetic model and the dielectric response theory, a theoretical model is put forward to describe the transport of protons along nanotube axes. With the introduction of electron band structure for different nanotubes like zigzag and armchair nanotubes of metallic properties, the collective excitation of electrons on the cylinders induced by the incident ions is studied, showing several distinct peaks in the curves of the energy loss function. Furthermore, the stopping power and the self-energy are calculated as functions of ion velocities, especially taking into account the influence of damping coefficients. It is conceivable from the results that, in the kinetic formulation, plasmon excitation plays a major role in the stopping. And as the damping increases, the peaks of the stopping power shift to the lower velocities, with the broadening of the plasmon resonance.
98624315
Dynamic interactions of fast ions with multiwalled carbon nanotubes
Abstract We use a two-fluid hydrodynamic model to describe the dielectric response of the σ and π electron systems on a multiwalled carbon nanotube consisting of up to several tens of concentric cylindrical shells. In particular, we evaluate the stopping power and the dynamical image potential for ions moving parallel to the nanotube axis. It is found that both quantities are profoundly affected by the increasing number of nanotube shells, as a consequence of the rich plasmon spectra developed due to the inter- and intra-shell electrostatic interactions between the electron systems.
219179959
COMMISSIONING OF IMP 14.5GHZ ECR ION SOURCE
A 14.5 GHz.~ew. ECR ion source has been designed and constructed for the upgraded injection beam line of HIRF1.. SFC(Heavy Ion ~esearch FaCility m Lanzhou, Sector Focus Cyclotron) so that eventually two ECR ion sources could be available on the line. The new ECR Ion source has a compact struClUre with a high magnetic mirror ratio and a long chamber. The maximum axial magnetic field on the axis is around 1.5Tesla and the bexapole field on the chamber wall is I.OTesla. The ion source is being tested on the test bench. The preliminary results are typically 100 eJ1A of 0 7+, 160 eJ1A of Arll+ and 50 eJ1A of Xe26+. The design points, characteristics and commissioning are presented .
64774799
Preliminary results of the Moon shadow using ARGO-YBJ detector
ARGO-YBJ is a “full coverage” air shower detector consisting of Resistive Plate Chambers(RPCs) at the Yangbajing High Altitude Cosmic Ray Laboratory (Tibet, China) at 4300 m a.s.l. (lat=30.11° N, long=90.53° E). Using the data collected with a carpet of RPCs (1900 m 2 , about 1/3 of the whole ARGO-YBJ detector), the cosmic ray shadowing effect due to the Moon was studied. The 50% angular resolution is found to be ∼1.2° with the Chess-board method and the Moon shadow with a significance of 4.9 σ is found displaced by 0.7° westward and 0.5° northward with respect to the expected position by the equi-zenith angle Method.
123855855
Search for neutrino oscillations at the Palo Verde Nuclear reactors
We report on the results from a measurement of the anti-neutrino flux and spectrum at a distance of about 800 m from the three reactors of the Palo Verde Nuclear Generating Station using a segmented gadolinium-loaded scintillation detector. We find that the anti-neutrino flux agrees with that predicted in the absence of oscillations, excluding at 90% CL νe − νx oscillations with Δm2 > 1.12 × 10−3 eV2 for maximal mixing and sin2 2θ > 0.21 for large Δm2. Our results support the conclusion that the atmospheric neutrino oscillations observed by Super-Kamiokande do not involve νe.
197530660
First observation of the M1 transition $\psi(3686)\to \gamma\eta_c(2S)$
Using a sample of 106 million \psi(3686) events collected with the BESIII detector at the BEPCII storage ring, we have made the first measurement of the M1 transition between the radially excited charmonium S-wave spin-triplet and the radially excited S-wave spin-singlet states: \psi(3686)\to\gamma\eta_c(2S). Analyses of the processes \psi(2S)\to \gamma\eta_c(2S) with \eta_c(2S)\to \K_S^0 K\pi and K^+K^-\pi^0 gave an \eta_c(2S) signal with a statistical significance of greater than 10 standard deviations under a wide range of assumptions about the signal and background properties. The data are used to obtain measurements of the \eta_c(2S) mass (M(\eta_c(2S))=3637.6\pm 2.9_\mathrm{stat}\pm 1.6_\mathrm{sys} MeV/c^2), width (\Gamma(\eta_c(2S))=16.9\pm 6.4_\mathrm{stat}\pm 4.8_\mathrm{sys} MeV), and the product branching fraction (\BR(\psi(3686)\to \gamma\eta_c(2S))\times \BR(\eta_c(2S)\to K\bar K\pi) = (1.30\pm 0.20_\mathrm{stat}\pm 0.30_\mathrm{sys})\times 10^{-5}). Combining our result with a BaBar measurement of \BR(\eta_c(2S)\to K\bar K \pi), we find the branching fraction of the M1 transition to be \BR(\psi(3686)\to\gamma\eta_c(2S)) = (6.8\pm 1.1_\mathrm{stat}\pm 4.5_\mathrm{sys})\times 10^{-4}.
16196883
Typicality, freak observers and the anthropic principle of existence
We propose an alternative anthropic probability for calculating the probabilities in eternal inflation. This anthropic probability follows naturally from the weak anthropic principle, and does not suffer the freak observer or the typicality problems. The problem that our observed cosmological constant is not at the peak of the usual anthropic probability distribution is also solved using this proposal.