Note on the Determination of Electrode Shapes for a Pierce‐Type Electron Gun

1957 ◽  
Vol 28 (5) ◽  
pp. 634-634 ◽  
Author(s):  
George R. Brewer
Keyword(s):  
Electron Gun

Three-Dimensional Electron-Beam Deflection and Missed Joint in Welding Dissimilar Metals

1997 ◽  
Vol 119 (4) ◽  
pp. 832-839 ◽  
Author(s):  
P. S. Wei ◽  
F. K. Chung
Keyword(s):  
Electron Beam ◽  
Electrical Contact ◽  
Three Dimensional ◽  
Electron Gun ◽  
Beam Deflection ◽  
Beam Power ◽  
Dissimilar Metals ◽  
Electrical Contact Resistance ◽  
Paraboloid Of Revolution

Three-dimensional deflection of the electron beam resulting in a missed joint due to thermoelectric magnetism generated while welding dissimilar metals is systematically investigated. The incident energy rate distribution is assumed to be Gaussian and the deep and narrow welding cavity induced is idealized as a paraboloid of revolution. With a three-dimensional analytical solution for the temperature and by solving Maxwell’s electromagnetic equations, thermoelectric currents, magnetic flux densities, and deflections of the beam are found. The predictions agree with available experimental data. The results find that missed joints can be reduced by increasing the dimensionless accelerating voltage-to-Seebeck e.m.f. parameter, Peclet number, and effective electrical contact resistance parameter, and decreasing dimensionless beam power, magnetic permeabilities, and electrical conductivity ratio between metals 1 and 2. Tilting workpieces and shifting the electron gun from the joint line are also feasible. A three-dimensional analysis is required for a successful determination of beam deflection.

Ein Näherungsverfahren zur Berechnung rotationssymmetrischer elektrostatischer Felder mit beliebigen Randbedingungen und seine Anwendung auf einen Elektronenstrahlerzeuger mit Spitzenkathode

1971 ◽  
Vol 26 (10) ◽  
pp. 1667-1675 ◽  
Author(s):  
Hermann Rauh
Keyword(s):  
Boundary Conditions ◽  
Ray Tracing ◽  
Analytical Solutions ◽  
Surface Charge Density ◽  
Rotational Symmetry ◽  
Electron Gun ◽  
Arbitrary Boundary ◽  
Electron Trajectories ◽  
Electrostatic Fields

Abstract An approximate method is described for calculating electrostatic fields of rotational symmetry with arbitrary boundary conditions. The method is based on the computation of the surface charge density on the field forming electrodes. Successfully tested by well-known analytical solutions, the method is applied to the determination of electron trajectories in an electron gun with a point cathode. The ray tracing is done by the Runge-Kutta-Nyström procedure.

Optimization of III-N Based Devices Grown by RF Atomic Nitrogen Plasma Using In-Situ Cathodoluminescence

1997 ◽  
Vol 468 ◽  
Author(s):  
J. M. Van Hove ◽  
P. P. Chow ◽  
J. J. Klaassen ◽  
R. Hickman ◽  
A. M. Wowchak ◽  
...  
Keyword(s):  
Growth Conditions ◽  
Nitrogen Plasma ◽  
Electron Gun ◽  
Material Composition ◽  
Band Edge ◽  
Rf Plasma ◽  
Band Edge Emission ◽  
Rejection Ratio

ABSTRACTIn-situ cathodoluminescence (CL) is presented as a technique to optimize GaN, and AlGaN films deposited by MBE using an RF plasma as a source of reactive nitrogen. Excitation of the MBE grown nitride films is conveniently achieved in the preparation chamber using an Auger electron gun. The photoemission is monitored through a side port and dispersed with a 1/8 m monochromator with a typical resolution of 3 nm. The in-situ CL spectra of AlGaN and GaN films provides quick determination of both material composition, doping, and quality from the position and width of the band edge emission. The use of CL for the assessment of material composition in the growth of nitride materials is extremely beneficial since the complementary technique of RHEED oscillations is not routinely observed for these systems. The determination of material quality using CL has been used to optimize growth conditions for GaN PIN junction photovoltaic detectors on (0001) sapphire. Detectors having peak responsivity of 0.175 AAV at the GaN band edge of 365 nm and a UV to visible rejection ratio of greater than 105 have been fabricated. The high rejection ratio is accredited to the reduction of the yellow defect levels in the MBE grown material. Material optimization using in-situ CL for growth of AlGaN MODFETs having drain currents of 425 ma/mm and gm of 66 mS/mm is discussed.

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

Distance to SN 1987A and the LMC

1999 ◽  
Vol 190 ◽  
pp. 549-554
Author(s):  
Nino Panagia
Keyword(s):  
Angular Size ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Light Curves ◽  
Distance Modulus ◽  
Absolute Size ◽  
Sn 1987A

Using the new reductions of the IUE light curves by Sonneborn et al. (1997) and an extensive set of HST images of SN 1987A we have repeated and improved Panagia et al. (1991) analysis to obtain a better determination of the distance to the supernova. In this way we have derived an absolute size of the ringRabs= (6.23 ± 0.08) x 1017cm and an angular sizeR″ = 808 ± 17 mas, which give a distance to the supernovad(SN1987A) = 51.4 ± 1.2 kpc and a distance modulusm–M(SN1987A) = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to bed(LMC) = 52.0±1.3 kpc, which corresponds to a distance modulus ofm–M(LMC) = 18.58±0.05.

International determination of the total motion of the pole

1961 ◽  
Vol 13 ◽  
pp. 29-41
Author(s):  
Wm. Markowitz
Keyword(s):  
Secular Motion ◽  
The Future

A symposium on the future of the International Latitude Service (I. L. S.) is to be held in Helsinki in July 1960. My report for the symposium consists of two parts. Part I, denoded (Mk I) was published [1] earlier in 1960 under the title “Latitude and Longitude, and the Secular Motion of the Pole”. Part II is the present paper, denoded (Mk II).

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