Transverse Temperatures Research Articles

Newtonian gravitational constant measurement. All atomic variables become extreme when using a source mass consisting of three or more parts

Atomic interferometry methods used to measure the Newtonian gravitational constant. To improve the accuracy, one should measure the phase of an atomic interferometer at extreme values of atomic vertical velocities and coordinates. Owing to symmetry, the horizontal components of atomic velocities and coordinates are also extreme. We propose using a source mass consisting of three or more parts, since only in this case one can find such an arrangement of parts that all atomic variables become extreme. Nonlinear dependences of the phase on the uncertainties of atomic positions and velocities near those extreme values required us to modify the expression for the phase relative standard deviation. Moreover, taking into account nonlinear terms in the phase dependence on the atomic coordinates and velocities leads to a phase shift. In the last experiment to measure the Newtonian gravitational constant by atomic interferometry, this shift was not included. We took the shift into account, got a value of 199 ppm for it, and this leads to a decrease in the value of the Newton constant by 0.02%. In addition, we showed that at equal sizes of the atomic cloud in the vertical and horizontal directions, as well as at equal atomic vertical and transverse temperatures, systematic errors due to the finite size and temperature of the cloud disappear. The calculation also showed that when using the 13-ton source mass proposed recently, the measurement accuracy can reach 17 ppm for a source mass consisting of four quarters. We assumed that the source mass consisting of a set of cylinders is used for measurements. We have obtained a new analytical expression for the gravitational field of a homogeneous cylinder.

Monte Carlo simulation of mercury ion drift characteristics in an inert gas

The Monte Carlo method calculated and tabulated the diffusion-drift characteristics of mercury ions in three inert gases (He, Ar, Xe) depending on the reduced electric field strength - the average energy of the ions, their longitudinal and transverse temperatures, diffusion coefficients along and across the direction of the field. The velocity distribution function of the ions and the angular dependence of the ions bombarding the surface are investigated

Analysis of Deformation and Temperature Characteristics of High-Speed Railway Roadbed in Seasonal Frozen Regions

We have systematically studied the spatial and temporal variation characteristics of deformation and ground temperature based on measuring the values of corresponding data in the Harbin-Dalian high-speed railway roadbed. The regularity and non-uniformity of roadbed deformation distribution were analyzed based on the relationships between its values and structure type, development of freezing depth, roadbed filling, and transverse position. We also compared the difference of freezing conditions at different locations and heat absorption of the roadbed; then we analyzed the differences of freezing depth in four selected roadbed sections and the characteristics of average ground temperature along the vertical direction in the coldest and hottest months. Based on the above analyses, the source of the spatial and temporal characteristics of roadbed deformation, influencing factors, and the potential hazards of transverse thermal difference to roadbed stability have been discussed. The results showed that the distribution of roadbed deformation in seasonal frozen regions had certain regularity, non-uniformity, and randomness. Roadbed freezing processes of roadbed at different transverse locations in different regions were similar. The differences of transverse thermal regime were widespread, and the influence of external temperature on the west shoulder was most obvious. The coldest and warmest month temperatures at a certain depth followed a spindle-shaped trend. Both the increase of latitude and height of roadbed may affect the difference of transverse ground temperatures.

Drift Characteristics of Metal Ions in Helium in an External Electric Field

The results of Monte Carlo calculations of the drift characteristics of metal ions (Li, Be, Al, Fe, Cu, W, Hg, and Au) in a constant uniform electric field 1 < E/N < 1000 Td in helium are presented. The dependences of the mobility, longitudinal and transverse diffusion coefficients, and mean kinetic energy of ions, as well as their longitudinal and transverse temperatures, on the electric field strength are given.

Temperature Dependence of the Vibrational Mode of Pb1 –xSnxTe Films Grown by MBE on the GaAs/CdTe Hybrid Substrate

Reflectance spectra of thin Pb1 –xSnxTe films (~60 nm) with x = 0.25, 0.53, and 0.59, grown by MBE on hybrid GaAs/CdTe substrates, are measured in the frequency range of 20–5500 cm–1 and the temperature range of 5–300 K. The temperature dependence of transverse optical phonon frequencies and structural phase transition temperatures are determined based on a dispersion analysis. An increase in the plasma frequency with decreasing temperature in the range 300‒77 K in all films is detected.

Shaped nozzles for cryogenic buffer-gas beam sources

Cryogenic buffer gas beams are important sources of cold molecules. In this work we explore the use of a converging-diverging nozzle with a buffer-gas beam. We find that, under appropriate circumstances, the use of a nozzle can produce a beam with improved collimation, lower transverse temperatures, and higher fluxes per solid angle.

On the Ion Drift in Cold Gas

The problem of ion drift in such a strong electric field that the ion drift velocity significantly exceeds the thermal velocity of atoms is considered. In the case where the ion mass is identical to the gas particle mass, scattering is isotropic in the center-of-mass system and the ion scattering cross section is independent of the collision velocity (hard sphere model). The ion velocity distribution function is calculated by the Monte Carlo method, its characteristics and diffusion coefficient are determined. A comparison with known numerical and analytical solutions is performed. It is found that average characteristics (drift velocity, longitudinal and transverse temperatures) are in very good agreement with the values obtained from integral relations for the two-temperature Maxwellian distribution; however, the ion velocity distribution itself differs significantly from the shifted two-temperature Maxwellian distribution.

Experimental investigation on effects of water-based ultrasonic vibrations, transverse magnetic field and water temperatures on percussion laser drilling performance

A novel magnetic-ultrasonic assisted laser drilling technology, which integrates and couples water-based ultrasonic vibrations with an external transverse magnetic field for assisting the process of percussion laser drilling, is reported to carry out laser drilling experiments for improving hole drilling performance. The influence of water temperature on drilling performance for water-based magnetic-ultrasonic assisted percussion laser drilling technology is first reported. The influential mechanisms and roles of magnetic assistance and/or water-based ultrasonic assistance on the process and performance of percussion laser drilling were analysed, including both blind hole and through hole drilling. The effects of water-based ultrasonic vibrations and/or magnetic assistance on laser drilling performance were systematically studied via corresponding comparisons. It was demonstrated that the couple magnetic-ultrasonic assistance effectively increased laser drilling performance, by increasing laser energy absorption efficiency inside a drilling hole, enhancing material removal, increasing drilled depth, reducing recast layer formation and hole taper, improving microstructure and micro hardness performance, and relieving residual stress. Besides, it was reported that the uniform mechanical vibrations induced by water-based ultrasonic assistance effectively relieved residual stress (65.8% reduction) for the drilled specimen. The addition of an external transverse magnetic field could further relieve residual stress with a reduction percentage of 89.1%, resulting from the coupled magnetic-ultrasonic assistance. In addition, the water medium with a relatively high temperature was helpful for decreasing residual stress on the drilled sample. The alteration of water temperature (from 33.9 °C to 64.2 °C) not only greatly changed the value but also changed the direction of the residual stress (hole entrance: changing from −163 MPa to +32 MPa; hole exit: changing from −284 MPa to +64 MPa). However, the water temperature showed small effects on microstructure, micro hardness, recast layer thickness, hole cross-section, hole circularity deviation, and hole taper angle.

Calculation of the debye temperatures of hexagonal crystals from elastic constants

Hexagonal crystals are less symmetric than cubic crystals, but the integrations to calculate debye temperatures from single crystal elastic constants are simpler and easier for hexagonal crystals. Houston's method actually works for hexagonal crystals in contrast to cubic crystals where it fails. The literature on these calculations for hexagonal crystals is reviewed and checked against modern computer calculations, and errors both small and substantial have been found in the use of Houston's method for hexagonal crystals in published papers. Examples of correct calculations of transverse, longitudinal, and overall debye temperatures are given for eleven different hexagonal crystals of interest, and for a number of arbitrary sets of elastic constants in the Wolcott tables. Mixing of longitudinal and transverse modes is a major problem for some cubic crystals, but appears to be less for known hexagonal crystals. The mixing of modes was examined for a particular case of C44 greater than C11 for one set of values covering hexagonal, tetragonal, and cubic symmetries. The one integration for any hexagonal crystal that can be performed analytically is also reviewed.

Theoretical Estimation and Multiparticle Simulation on Evolution of Longitudinal and Transverse Temperatures During Pulse Compression in Compact Simulator for Heavy Ion Inertial Fusion

Kinetic energy exchange in the longitudinal and transverse directions of a charged particle beam during longitudinal pulse compression is discussed through a compact beam simulator for heavy ion inertial fusion. With the goal of understanding the beam behavior in a compact beam simulator experiment, the evolution of the transverse and longitudinal thermal spreads is evaluated using theoretical estimation and numerical simulation. The multiparticle simulation results show the longitudinal and transverse coupling motions via the space charge effect during the longitudinal pulse compression. The ratio of effective temperatures in the longitudinal and transverse directions derived from numerical results is higher than that evaluated from theoretical estimation. It is implied that the discrepancy is caused by the nonlinear space charge effect during the longitudinal bunch compression.

Analysis of inhomogeneous-excitation frequency shifts of ytterbium optical lattice clocks

We have investigated the frequency shifts caused by inhomogeneous excitation in a 171Yb optical lattice clock. The dependences of the inhomogeneity on the temperature of the cold ytterbium atoms and the misaligning angle between the lattice laser and the clock laser are analyzed by numerical calculations. The dependence of the fractional collisional frequency shift on the ground state fraction under different cold atom temperatures, atom numbers, lattice trap depths and unequal transverse and longitudinal temperatures are also shown. The results show that the uncertainty of the ytterbium clocks, contributed by the inhomogeneous excitation, can be reduced to be 10−19 or even lower with certain conditions.

Evolution of transverse flow and effective temperatures in the parton phase from a multiphase transport model

I study the space-time evolution of transverse flow and effective temperatures in the dense parton phase with the string melting version of a multi-phase transport model. Parameters of the model are first constrained to reproduce the bulk data on the rapidity density, $p_{\rm T}$ spectrum and elliptic flow at low $p_{\rm T}$ for central and mid-central Au+Au collisions at $200A$ GeV and Pb+Pb collisions at $2760A$ GeV. I then calculate the transverse flow and effective temperatures in volume cells within mid-spacetime-rapidity $|\eta|<1/2$. I find that the effective temperatures extracted from different variables, which are all evaluated in the rest frame of a volume cell, can be very different; this indicates that the parton system in the model is not in full chemical or thermal equilibrium locally, even after averaging over many events. In particular, the effective temperatures extracted from the parton energy density or number density are often quite different than those extracted from the parton mean $p_{\rm T}$ or mean energy. For these collisions in general, effective temperatures extracted from the parton energy density or number density are higher than those extracted from the parton mean $p_{\rm T}$ in the inner part of the overlap volume, while the opposite occurs in the outer part of the overlap volume. I argue that this indicates that the dense parton matter in the inner part of the overlap volume is over-populated; I also find that all cells with energy density above 1 GeV/fm$^3$ are over-populated after a couple of fm/$c$.

Estimation of the electron density and radiative energy losses in a calcium plasma source based on an electron cyclotron resonance discharge

The parameters of a calcium plasma source based on an electron cyclotron resonance (ECR) discharge were calculated. The analysis was performed as applied to an ion cyclotron resonance system designed for separation of calcium isotopes. The plasma electrons in the source were heated by gyrotron microwave radiation in the zone of the inhomogeneous magnetic field. It was assumed that, in such a combined trap, the energy of the extraordinary microwave propagating from the high-field side was initially transferred to a small group of resonance electrons. As a result, two electron components with different transverse temperatures—the hot resonance component and the cold nonresonance component—were created in the plasma. The longitudinal temperatures of both components were assumed to be equal. The entire discharge space was divided into a narrow ECR zone, where resonance electrons acquired transverse energy, and the region of the discharge itself, where the gas was ionized. The transverse energy of resonance electrons was calculated by solving the equations for electron motion in an inhomogeneous magnetic field. Using the law of energy conservation and the balance condition for the number of hot electrons entering the discharge zone and cooled due to ionization and elastic collisions, the density of hot electrons was estimated and the dependence of the longitudinal temperature T e∥ of the main (cold) electron component on the energy fraction β lost for radiation was obtained.

Waves in Warm Constant-Density Cylindrical Electron Beams

A dispersion equation is derived for waves in a warm constant-density cylindrical electron beam where electrons exhibit 3-D orbits in a uniform magnetic field and where the rigid-rotor beam model has transverse temperatures confined to the beam interior to provide a cold sharp beam edge suitable for matching RF fields. The equation solutions for surface waves in a warm beam emitted from a magnetically shielded gun can be obtained immediately from solutions for surface waves in a cold beam. Validation of such warm-beam solutions was made using TWT hot-test data and particle-in-cell-code simulations. Standard transcendental-equation solutions are found for surface waves in warm small-vorticity beams and space-charge waves in warm large-vorticity beams. Reduced plasma frequencies are increased for surface waves and decreased for space-charge waves by increasing the transverse-temperature thermal parameter. Beam temperatures were included in a Pierce-theory determinantal equation in the small-transverse-wavenumber limit.

Laser guiding of cold molecules in a hollow optical fiber and continuous-wave cold molecular beam generation

A novel scheme for guiding arbitrary buffer-gas cooled neutral molecules in a hollow optical fiber (HOF) using a red-detuned HE11 mode is proposed and analysed theoretically. We give the electromagnetic field distribution of the HE11 mode in the HOF and calculate the optical potential of an I2 molecule, and study the molecule guiding mechanism using a classical Monte Carlo simulation. Using a 6 kW input laser, an S-shape HOF with a 2 cm curvature radius for both bends, and an input molecular beam with a transverse temperature of 0.5 K and longitudinal temperature of 5 K, we obtain a guiding efficiency of ∼0.126% for the scheme, and the transverse and longitudinal temperatures of the guided molecular beam are 1.9 mK and 0.5 K, respectively.

Generation of a continuous-wave cold molecular beam by using an optical velocity filter

We propose a novel scheme to generate a cw cold molecular beam by optically guided buffer-gas-cooled molecules around an S-shaped integrated fiber bundle. First we calculate the two-color evanescent field around the fiber bundle and its optical potential for I2 molecules. Then we estimate the guiding efficiency of the output molecular beam and its transverse and longitudinal temperatures based on a classical model. Finally, we study the dynamic process of the molecular guiding by using a classical Monte Carlo simulation, by which we obtain some simulated results consistent with the theoretically calculated results. Our study shows that when the power of the input CO2 laser is 10 W and the curvature radius of the fiber bundle is 0.2 cm, a cw cold molecular beam with a longitudinal and transverse temperature of 57 mK and 0.29 mK can be generated by our scheme. It is clear that such a cold molecular beam has some important applications in molecular optics and other fields.

Theoretical investigation of nonequilibrium processes in shock wave in bubbly liquid

The effects related to a translational nonequilibrium at the shock wave front in a bubbly liquid flow with volume gas contents within 0.3 ≤ φ ≤ 0.98 have been theoretically studied. Analytical expressions for the longitudinal and transverse pressures, longitudinal and transverse temperatures, viscous stresses, and heat flux are obtained and the corresponding values are calculated for various Mach numbers and gas contents in the bubbly flow. The influence of the translational nonequilibrium at the shock wave front on the bubble fragmentation process is considered.

A bright, slow cryogenic molecular beam source for free radicals

We demonstrate and characterize a cryogenic buffer gas-cooled molecular beam source capable of producing bright beams of free radicals and refractory species. Details of the beam properties (brightness, forward velocity distribution, transverse velocity spread, rotational and vibrational temperatures) are measured under varying conditions for the molecular species SrF. Under typical conditions we produce a beam of brightness 1.2 × 10(11) molecules/sr/pulse in the X(2)Σ(+)(v = 0, N(rot) = 0) state, with 140(m/s) forward velocity and a rotational temperature of ≈ 1 K. This source compares favorably to other methods for producing beams of free radicals and refractory species for many types of experiments. We provide details of construction that may be helpful for others attempting to use this method.

Anomalous effective dimensionality of quantum gas adsorption near nanopores

Three problems involving quasi-one-dimensional (1D) ideal gases are discussed. Thesimplest problem involves quantum particles localized within the ‘groove’, a quasi-1Dregion created by two adjacent, identical and parallel nanotubes. At low temperature (T), the transverse motion of the adsorbed gas, in the planeperpendicular to the axes of the tubes, is frozen out. Then, the lowT heatcapacity C(T) of N particles is that of a 1D classical gas: . The dimensionless heat capacityC* increaseswhen T ≥ 0.1Tx, y (transverse excitation temperatures), asymptoting atC* = 2.5. The second problem involves a gas localized between two nearlyparallel, co-planar nanotubes, with small divergence half-angleγ. In this case, too, the transverse motion does not contribute toC(T) atlow T, leaving a problem of a gas of particles in a 1D harmonic potential (along thez axis, midway betweenthe tubes). Setting ωz as the angular frequency of this motion, for , the behavior approaches that of a 2D classical gas,C* = 1; one might haveexpected instead C* = 1/2, as in the groove problem, since the limit is 1D. For , the thermal behavior is exponentially activated,C* ∼ (τz/T)2e − τz/T. Athigher T (), motion is excited in the y direction, perpendicular to the plane of nanotubes, resulting in thermal behavior (C* = 7/4) corresponding to agas in 7/2 dimensions,while at very high T (), the behavior becomes that of aD = 11/2 system. The third problem is that of a gas of particles, e.g. 4He, confined in the interstitial region between four square parallel pores. The lowT behavior found in this case is again surprising—that of a 5D gas.

Well-posed two-temperature constitutive equations for stable dense fluid shock waves using molecular dynamics and generalizations of Navier-Stokes-Fourier continuum mechanics

Guided by molecular dynamics simulations, we generalize the Navier-Stokes-Fourier constitutive equations and the continuum motion equations to include both transverse and longitudinal temperatures. To do so we partition the contributions of the heat transfer, the work done, and the heat flux vector between the longitudinal and transverse temperatures. With shockwave boundary conditions time-dependent solutions of these equations converge to give stationary shockwave profiles. The profiles include anisotropic temperature and can be fitted to molecular dynamics results, demonstrating the utility and simplicity of a two-temperature description of far-from-equilibrium states.