磁聚焦法测量电子荷质比实验中励磁电流测量方法的研究

根据电荷在电场、磁场中的运动特点,分析了磁聚焦法测量电子荷质比的原理;利用磁场叠加原理,从理论角度探讨了测量磁聚焦时励磁电流的方法,并对各种方法进行了比较;从实验角度对实验数据分析处理,指出了误差产生的主要原因之一,得出了测量磁聚焦时励磁电流值的新方法.     

磁荷对中子星质量半径比的约束

讨论了荷电(磁)质点的量子力学波方程及其解. 由磁场中解的奇异性讨论了磁单极的存在; 由Rubakov-Callan模型推知中子星可能含有大量磁单极. 然后采用中子星的结构方程, 讨论了磁荷对中子星质量半径比的约束, 分别得到了磁荷对中子星质量半径比上限的影响 和磁荷对中子星质量半径比下限的影响的数学表达式. 关键词： 磁单极 中子星 质量半径比     

Electron-phonon interaction and charge carrier mass enhancement in SrTiO3

We report a comprehensive THz, infrared and optical study of Nb-doped SrTiO3 as well as dc conductivity and Hall effect measurements. Our THz spectra at 7 K show the presence of an unusually narrow (<2 meV) Drude peak. For all carrier concentrations the Drude spectral weight shows a factor of three mass enhancement relative to the effective mass in the local density approximation, whereas the spectral weight contained in the incoherent midinfrared response indicates that the mass enhancement is at least a factor two. We find no evidence of a particularly large electron-phonon coupling that would result in small polaron formation.     

Towards a new measurement of the neutron electric dipole moment

Precision measurements of particle electric dipole moments (EDMs) provide extremely sensitive means to search for non-standard mechanisms of T (or CP) violation. For the neutron EDM, the upper limit has been reduced by eight orders of magnitude in 50 years thereby excluding several CP violation scenarios. We report here on a new effort aiming at improving the neutron EDM limit by two orders of magnitude, down to a level of 3 × 10⁻²⁸ e·cm. The two central elements of the approach are the use of the higher densities which will be available at the new dedicated spallation UCN source at the Paul Scherrer Institute, and the optimization of the in-vacuum Ramsey resonance technique, with storage chambers at room temperature, to reach new limits of sensitivity.     

Quark momentum-space charge distribution in deuteron and neutron/proton structure functions ratio

The electromagnetic polarizabilities of the nucleon are shown to be essentially composed of the nonresonant α _p(E ₀₊) = + 3.2, α _n(E ₀₊) = + 4.1, the t-channel α ^t _{p, n} = - β ^t _{p, n} = + 7.6 and the resonant β _{p, n}(P ₃₃(1232)) = + 8.3 contributions (in units of 10^-4fm^3). The remaining deviations from the experimental data Δα _p = 1.2±0.6, Δβ _p = 1.2±0.6, Δα _n = 0.8±1.7 and Δβ _n = 2.0±1.8 are contributed by a larger number of resonant and nonresonant processes with cancellations between the contributions. This result confirms that dominant contributions to the electric and magnetic polarizabilities may be represented in terms of two-photon coupling to the σ-meson having the predicted mass m _σ = 666MeV and two-photon width Γ _γγ = 2.6keV.     

Three-dimensional numerical studies on the effect of the particle charge to mass ratio distribution in the electrostatic coating process

Charge to mass ratio is a crucial parameter that governs the behavior of particle trajectories in a charged cloud of particles. The complex nature of the charging process limits our ability to accurately determine the charging level when particles of varying size are present. Using a numerical approach, it is possible, however, to take into account predefined values for this parameter. In this paper, the average charge to mass ratio and the distribution of the charge to mass ratio in the coating of a flat target were systematically varied to demonstrate their effect on the motion of the charged particles. The results show that the transfer efficiency increases as the average charge to mass ratio increases. It was found that the transfer efficiency is a weak function of the average particle size in the range tested and that it increases as the width of the size distribution increases.     

The effect of electric charge on the mechanical properties of graphene

The effect of electric charge on the mechanical properties of graphene under tensile loading is investigated by using molecular dynamics method.A modified atomistic moment method based on the classical electrostatics theory is proposed to obtain the distribution of extra charges induced by an external electric field and net electric charges stored in graphene.The electrostatic interactions between charged atoms are calculated using the coulomb law.The results show that the Young’s modulus and the critical fracture stress under uniaxial tension decrease with the increase of electric potential and net charges on graphene.The failure of graphene induced by electric charges is found to be controlled by charge level.The results indicate that the carbon-carbon bonds at the edge of graphene will break first.     

Diquark clustering and the neutron charge radius

We show that a quark-diquark model previously introduced to explainSU(6) violations in quasi-two-body reactions is also able to accomodate a (quantitative) interpretation of the negative charge radius of the neutron, provided one uses appropriate hypotheses for the confinements (c.q. sizes) of the quarks and diquarks involved. They effectively imply the existence of a nucleon core (i.e. a massive two-quark state of substantial spatial clustering) with zero spin and zero isospin.     

Electron beam modeling and analyses of the electric field distribution and space charge effect

In electron beam technology, one of the critical focuses of research and development efforts is on improving the measurement of electron beam parameters. The parameters are closely related to the generation, emission, operation environment, and role of the electron beam and the corresponding medium. In this study, a field calculation method is proposed, and the electric field intensity distribution on the electron beam's cross-section is analyzed. The characteristics of beam diffusion caused by the space charge effect are investigated in simulation, and the obtained data are compared with the experiment. The simulation demonstrated that the cross-sectional electric field distribution is primarily affected by the electron beam current, current density distribution, and electron beam propagation speed.     

Color oscillations and measuring the quark charge

Color oscillations analogous to neutrino oscillations but with very high frequency are shown to be present in hadron states below color threshold. Experiments to distinguish between fractionally charged and integrally charged quark models both below and above color threshold are discussed. The instantaneous quark charge is shown to be measurable only in very fast processes determined by the high-energy behavior of transition amplitudes well above color threshold. Results from the naive parton model for deep inelastic processes which indicate that real charges of quarks and gluons can be measured are shown to be in error because of neglect of color oscillations and inteference terms.     

Relativistic finite baryon size effect and the mass limit for neutron stars

We revise our previous calculation of the finite baryon size effect on the mass limit for neutron stars by making the formulation be relativistic. The result is still consistent with the observational data.Communicated by: A. Schäfer     

A new mass formula and new neutron and proton magic numbers in light nuclei

This mass formula explains gross features of the binding energy curves for all the elements from Li to Bi. It has no shell effects incorporated. Comparisons of separation energies computed from this formula and measured masses show extra-stability at N=6 (Z=3?8), Z=6 (N=6?9), N=14 (Z=7?10), Z=14 (N=14?19), N=16 (Z=7?8), Z=16 (N=24?26), loss of magicity at N=8 (Z=4), N=20 (Z=12?15) and quenching of N=50, 82, 126, Z=50 near driplines. Z=82 magicity rises at N=104 after strong quenching near N=107.     

Ultracold neutron detector for the spectrometer of a neutron lifetime measuring

The gas-discharge detector is designed for the neutron lifetime spectrometer. The detector is intended for ultracold neutron flux monitoring in measurement cycles at the specrtometer (ILL, Grenoble, France). The detector has been successively tested with a Pu–Be neutron source under laboratory conditions and as a part of the spectrometer.     

Ratios of magnetic charge to charge and of magnetic mass to mass

It is shown that, unlike the case of (vacuum) solutions describing isolated bodies, conformal Killing fields are not excluded by the structure of vacuum gravitational magnetic monopoles at null infinity. The resulting dilation must be constant. This brings support to the viewpoint that such solutions might have a role to play in the understanding of gravitational entropy and time's arrow. If, in addition, a Maxwellian magnetic monopole (Dirac string singularity) is available, the ratio of the total magnetic charge (magnetic mass) over the total electric charge (mass) can be identified. This common feature between the gravitational and the electromagnetic interaction finds its origin in the space-time topology.