Superimposition of a magnetic field around an ion guide for electron ionization time-of-flight mass spectrometry

A new electron ionization source was developed for orthogonal acceleration time-of-flight mass spectrometry (TOFMS) based on the superimposition of a magnetic field around a radio frequency-only (rf-only) ion guide. The cylindrically symmetric magnetic field compresses the electron beam from the electron source into a long narrow volume along the ion guide axis. The magnetic field also helps to maintain a narrow energy distribution of electrons that penetrate the full length of the ion guide despite the influence of the radial rf field. Ionization occurs inside the ion guide with improved efficiency resulting from efficient use of electrons, prolonged interaction time, and nontraditionally large ionization volume. At the same time, the rf field effectively focuses ions radially and confines them to the axis of the ion guide by collisional focusing, leading to high ion transmission efficiency. Furthermore, the source can also be operated in a trap-and-pulse mode to improve the ion sampling duty cycle of orthogonal acceleration TOFMS. To validate the design concept of this new ion source, a simple prototype using a single set of cylindrical rods was constructed and retrofitted to an orthogonal acceleration TOFMS. A significant increase in ion signal intensity was observed by operating the source in a pulsed ion extraction mode. Low detection limits (for example, 12 fg for toluene) were determined at 12.5 spectra s(-1) in the full spectrum mode.     

Hydromagnetic stability of helical flows permeated by a magnetic field with a radial component

In this paper, we have studied the linear stability of the nondissipative helical flow of an incompressible perfectly conducting fluid between two concentric cylinders permeated by a non-zero radial magnetic field. It is found that a rigidly rotating column of a perfectly conducting fluid permeated by a magnetic field [($\text{A/r}$), ($\text{C/r}$), $\text{B}{}_0$], where $\text{A, C, B}{}_0$ are constants, is stable for all infinitesimal disturbances.     

Effect of the characteristic magnetic field of a high-current electron beam on energy release in targets

The character of the energy released by a high-current electron beam in metal targets is studied taking into account the self-action of the beam.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 52, No. 6, pp. 977–980, June, 1987.     

Effects of the radial magnetic field on the DC magnetizing effect in the toroidal core

Curves of circumferential magnetic induction of a supermalloy tape wound core obtained by the de magnetizing effect are presented, They exhibit, for high radial applied fields, negative susceptibilities, and show the impossibility of saturating the sample. These features are interpreted as secondary effects of the radial field employed to magnetize the sample.     

Investigation of the effect of a magnetic field on the thermophysical characteristics of ferromagnetic suspensions

The effect of a constant magnetic field on the heat-transfer process in ferromagnetic suspensions has been experimentally investigated. The effective thermal conductivity of ferromagnetic suspensions is shown to be anisotropic in character.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 32, No. 5, pp. 835–839, May, 1977.     

Effects of an external magnetic field on thermo-acoustical waves in a linear isotropic thermo-elastic dielectric material

Summary Thermo-mechanico-electromagnetic coupled waves propagating in a linear isotropic thermo-elastic dielectric material are theoretically investigated, in case an external magnetic field is applied to the material. Here the constitutive equations derived from the Clausius-Duhem inequality and Vernotte's heat conduction law are adopted. There are three types of coupled waves: the predominantly electromagnetic wave, the predominantly mechanical transverse wave and the predominantly thermo-mechanical longitudinal wave. The first and second waves have no thermal coupling. The third wave has thermal coupling and its propagation velocity and attenuation constant are perturbed by the external magnetic field.     

The effect of an alternating electric field on the liquid dielectric convection in a horizontal capacitor

The electroconvective instability in a low conducting nonuniformly heated liquid occurring in an alternating electric field between plates of a horizontal plane capacitor was studied in terms of the equations of electrohydrodynamics for arbitrary field modulation frequencies and various shapes (harmonic and triangular). In the gravitational field, the instability is determined by the interplay of dielectrophoretic and thermogravitational mechanisms. The layer heated from above can feature the parametric instability. In the low-frequency range, a numerical solution to the problem obtained by the Floquet method well agrees with the asymptotic results.     

Electrical and optical characteristics of nanosecond discharge confined between dielectric walls in a diode with a slit cathode

The electrical and optical characteristics of a transverse nanosecond pulsed electric discharge confined between dielectric walls in a helium-filled diode with a hollow (slit) cathode has been experimentally studied in the range of gas pressures of 1–100 Torr. It is shown that the cathode current density in the anomalous glow discharge regime is several orders of magnitude greater than the anode current density. A relationship is established between the characteristic radiation relaxation time and the fast diffusion cooling of electron gas after the jump in the near-wall potential.     

Electron source and acceleration regime of a picosecond electron beam in a gas-filled diode with inhomogeneous field

It is experimentally demonstrated that, upon the application of a subnanosecond high-voltage pulse to the gap of a diode filled with air at atmospheric pressure, a bunch of runaway electrons is formed in a sharply inhomogeneous electric field near the cathode. The bunch duration does not exceed 50 ps, which is shorter than the electron flight time through the interelectrode gap in the continuous acceleration regime. This duration remained unchanged when the gap width was varied between 6 and 26 mm. The electron energy in the picosecond electron beam, as determined from the time-of-flight measurements in the drift channel behind the anode foil of the diode, agree with the results of numerical calculations of the electron acceleration dynamics in the vacuum diode approximation.     

The effect of a magnetic field on the resistance between electrodes in a current-conducting channel with an anisotropic medium

An electrical network is used to model the function of the resistance between electrodes of various shapes in a current-conducting channel with an anisotropic medium.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 15, No. 5, pp. 918–921, November, 1968.     

On the mechanism of the external magnetic field action on the electron temperature and ion charge state distribution in a vacuum arc plasma

When an external axial magnetic field is applied to a vacuum arc, the radial expansion of plasma from cathode spots transforms into a plasma flow along the magnetic field, provided that the electron-ion collision frequency is smaller than the Larmor frequency. As the magnetic field strength increases, the diameter of the resulting cylindrical channel decreases. This leads to an increase in the electron temperature and the ion charge due to enhanced Joule heating of the plasma. Unlike the intrinsic azimuthal magnetic field, the external axial field only restricts expansion of the plasma, rather than compressing the plasma jet.     

The effect of a space charge of electrons multiply backscattered from the anode on the current in a planar diode

The effect of a space charge of electrons multiply backscattered from the anode on the current in a planar diode was theoretically studied. Spectral distributions of the energy of electrons moving along the electric field were calculated by the Monte Carlo code. It was found that the maximum decrease in the current of diodes with high-Z anodes does not exceed 20%.     

The effect of heat-treatment in a magnetic field or under an applied stress on the magnetic properties of silicon-iron

The effects of heat-treatment in a magnetic field or under an applied stress have been studied in this investigation. Magnetic properties (magnetostriction and power loss in particular), measured along the rolling direction in grain-oriented silicon-iron were unaffected by magnetic annealing, but their stress-sensitivities were improved by annealing under tension.Magnetic annealing was found to be effective in non-oriented silicon-iron and also in grain-oriented material if it was annealed with the field applied along directions other than the rolling direction.The magnetic annealing results can be explained largely on the basis of the Néel-Taniguchi theory of directional ordering of atom pairs. The changes obtained by annealing under stress showed that directional order only plays a minor part. The magnetic changes could be explained by assuming that during heat-treatment under stress a process of magnetostriction strain relief occurs, forming a residual internal stress.Other alloys similar to silicon-iron showed no more response to magnetic annealing or annealing under stress than silicon-iron.     

磁流体太阳能集热器的温度和热流量特性的实验研究

由于磁流体有很好的吸热和传热特性，将其用作磁流体太阳能集热器的介质是很有应用前景的。设计了一个磁流体太阳能集热器用于温度和热流量特性试验，对2种磁流体进行了试验，结果显示：在磁流体静止不动的时候，磁流体太阳能集热器的磁流体温度可达60℃以上，最高的可达97℃；然而，当磁流体以5m的流速流动时，出口的最高温度仍可达65℃，热流量超过600W／m^2。另外，随着磁流体流速的加大，出口温度将会下降，而热流量则会增加，这对于太阳能集热器工作条件的选择（如温度和热流量的选择）有十分重要的意义。     

Development and applications of an analytical electron microscope with a field emission electron gun

An analytical electron microscope with a field emission electron gun has been developed in order to improve the function of material identification, in order to obtain higher resolution of images, sharper electron diffraction patterns, and purer x-ray spectra with no effects of contamination from smaller areas than in the conventional instruments so far utilized. The performance capabilities of this newly developed analytical electron microscope, the Model H-600FE, have been examined and found to be very useful for the material characterization of nanometer-size areas. Various attributes of the microscope became apparent with reference to the results of different studies. These include better convergence of the electron beam (demonstrated by examination of an MoS₂ thin film), high-resolution transmission electron microscopy (using a gold film), high-resolution scanning electron microscopy (with a carbon film containing nanometer-size holes), high-angle resolution electron diffraction (of an iron carbide film), and precision x-ray analysis of nanometer-size areas (using a pyroxene crystal and a Cu---Zn---Al shape memory alloy).     

Modeling of the scattering of electromagnetic waves by a thin dielectric coating on a cylinder

Double-sided boundary conditions containing only tangential components of a diffracted field are used to model the interaction of electromagnetic waves with a cylinder of arbitrary cross section covered with a thin dielectric layer. The obtained boundary-value problem is reduced to a system of two singular integral equations of the second kind with kernels whose structure is similar to the kernels of integral equations of the first kind for a perfectly conducting scatterer. The numerical solution of the integral equations of the problem is obtained by the method of mechanical quadratures. The scattering properties of an elliptic cylinder with different dielectric coatings are studied in the superhigh-frequency band. It is shown that the coating strongly affects the diffraction properties of the cylinder. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 1, pp. 96–104, January–February, 2006.     

Field ion microscope examination of the action of an intense ion flux from a laser plasma on tungsten

Results are presented of field ion microscope examinations of the structure of tungsten samples exposed to the action of a high-intensity ion flux (∼10²² ions/cm²·s) from a lead laser plasma. It was observed that the surface layer becomes amorphized and the defect spectrum was established. The limiting mechanical properties of irradiated tips were determined. Promising directions for further research are indicated. Pis’ma Zh. Tekh. Fiz. 24, 52–57 (November 26, 1998)     

Ion detection by Fourier transform ion cyclotron resonance: the effect of initial radial velocity on the coherent ion packet

Ion detection by Fourier transform ion cyclotron resonance (FT-ICR) is accomplished by observing a coherent ion packet produced from an initially random ensemble of ions. The coherent packet is formed by excitation with a resonant oscillating electric field. Ions that are out of phase with the applied radio frequency (rf) electric field experience a continuous misalignment of the electric field vector. The misalignment creates a net force of the electric field perpendicular to ion motion. The perpendicular component of the rf electric field creates a frequency shift resulting in phase synchronization of the ion ensemble. The phase coherence of the ion packet affects both the sensitivity and the resolution of FT-ICR.     

Method of determining the magnetic field of a recording head by using tapes of various coating thicknesses

In magnetic recording, the field configuration of the writing head is of major importance, but it is difficult to measure its actual strength. This paper describes a method of determining both the field geometry of a head and the field strength by using tapes of various coating thicknesses. By differentiating the magnetic flux with respect to the thickness, remanence curves are obtained. These curves may be compared to the remanence which was measured statically. This way, the oersteds of the head field can be determined in a much closer vicinity to the head gap than by previously described methods.