Small Deflection Angles Research Articles

Feasibility of lorentz readout of a high-density fast magnetic memory

A random-access magnetic-film memory with a desired bit density ρ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</inf> of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> /cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is postulated with writing and reading each to be performed with a deflectable electron beam within 1 μs. Curie point writing is suggested, while detection of the deflection of electrons due to the Lorentz force is proposed for readout. The transmission, reflection, mirror, and impact scanning methods of Lorentz microscopy are each explored as readout methods. Because of the absence of a heat-absorbing substrate, the transmission method is completely impractical, while the desired value of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\rhoL</tex> is unattainable for the mirror and impact scanning methods because of the fields from other bits (ρ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</inf> must be reduced to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4 \times 10^{6}</tex> /cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> for these methods). Moreover, the small attainable Lorentz deflection angles and the low brightness of conventional electron emitters necessitate further reduction of the bit density to values much less than ρ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</inf> for the reflection and mirror methods, unless a field-emission source is used. Excessive power dissipation forces a reduction of density below ρ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</inf> for the impact scanning method. The reflection method may be feasible if a sufficiently high fraction of elastically scattered electrons can be demonstrated, if a reliable field emission source can be employed, and if the sophisticated electron optics involved can be built and installed in ultrahigh vacuum.

Two-dimensional small-angle deflection theory

The aberrations resulting from the deflection of an electron beam by two similar, mutually perpendicular magnetic fields have been evaluated. The beam is assumed to be composed of noninteracting, nonrelativistic particles converging, when undeflected, to a single point in the center of the target. If dynamic focusing is used, the field shapes can be adjusted to eliminate astigmatism and minimize coma. Field optimization procedures are presented with a numerical example. The correct densities and boundaries are recorded by a computer-controlled plotter.

Comparison and Appraisal of Approximation Formulas for Total Elastic Molecular Scattering Cross Sections

The Massey—Mohr (MM), Schiff (S), and Landau—Lifshitz (LL) approximations for the total elastic cross section (Q) are intercompared. All can be shown to follow from the same assumption, (i.e., the classical small-angle deflection function, thence the Jeffreys—Born phases via the semiclassical equivalence relationship), sufficing to determine the velocity dependence of Q. Thus, for V=±C(s)/rs, Q(s)=p(s)[C(s)/hv ]2/(s—1) The coefficient p(s) is the same for the S and LL approximations; the ratio pSLL(s)/pMM(s)≥1, (&amp;lt;1.075); it is 1.0709 and 1.0458 for s=6 and 12, respectively. A numerical calculation for a repulsive (s=12) interaction shows that the SLL formula reproduces the partial-wave calculated Q to within ½%. A graphical presentation suggests the generality of this result; it also indicates the source of bias in the MM approximation. For a ``realistic'' intermolecular potential, (restricting consideration to collisions in the ``thermal'' energy range), the influence of the repulsion is only to produce undulations in Q(v); the correct value of C(6) may be obtained by velocity averaging the ``apparent'' CSLL(6).

About scan magnification of TV picture tubes

In a television receiver the horizontal deflection is of critical importance because of the high deflection power. Recently various proposals have been published, according to which the electron beam is to be deflected over a small angle only, in order to diminish the deflection power. Subsequently this small deflection angle is to be increased by an electrostatic or magnetic lens. In the present paper, it is shown with the aid of general laws of electron optics that such a scan magnification by an electrostatic or magnetic lens necessarily causes a decrease of the resolution, and thereby, of the quality of the television picture, unless known possibilities of increasing the resolution are employed simultaneously. The calculation also affirms that with magnetic deflection, unlike electrostatic deflection, post-acceleration does not lead to a significant reduction in deflection power with unchanged resolution.

Deflection Distortions Contributed by the Principal Field of a Ring Deflection Yoke

To achieve a more detailed understanding of the factors contributing to deflective distortions, an analysis was made of a simple ring deflection yoke. This type of yoke was selected because its magnetic field can be described by an infinite series whose first term is of principal significance. A practical ring yoke can be wound (with a simple sinusoidal winding distribution) which will establish a magnetic field described completely by this first term. Additional windings can also be added which produce fields corresponding to any of the subsequent terms of the series. This permits a detailed study of the effects of the winding distribution function upon the deflection distortions. Fortunately, these higher order fields are all zero on the yoke axis and are always negligible in the study of small angle deflections.

Relaxation of a System of Particles with Coulomb Interactions

The relaxation to a Maxwellian distribution of a system of particles interacting through inverse-square-law forces is investigated in the approximation of two-particle interactions resulting in small-angle deflections of particle trajectories. The time required for the relaxation of the distribution in the neighborhood of the average energy is found to agree with the self-collision time defined by Spitzer. The time required for the distribution to become Maxwellian throughout the range from zero energy to several times the average energy is found to be nearly ten times the self-collision time. Filling of the high-energy portion of the Maxwell distribution is also discussed.

"Improvement in color kinescopes through optical analogy"

The relationship between phosphor dots on the screen and the holes in the shadow mask has been determined by light beams emanating from small light sources located at the red, green and blue color centers. This is acceptable for tubes with small deflection angles, but becomes less acceptable for tubes with large deflection angles. This is due to the fact that in an operating tube the electrons do not appear to originate from points in a fixed deflection plane, but rather from points in a deflection plane which moves closer to the shadow mask as the deflection angle is increased. This causes a color impurity for the larger deflection angles. The color impurity has been eliminated by determining the relationship between phosphor dots on the screen and the holes in the shadow mask with an exact light analogy for the electron trajectories.

The use of shorter wavelengths in X-ray diffraction in relation to scintillation counting

After referring to the advantages of scint i l lat ion count ing discussed in earlier papers, in par t icular to the high yield i t offers in the Mo K range, the conditions are discussed which a crystal -counter powder goniometer mus t sat isfy in order to be adap ted to the small deflection angles encountered wi th short wavelengths and to be free of aberrat ions which depend on the individual powder specimen and set t ing and which therefore cannot be allowed for on general terms. Two ar rangements complying wi th these conditions are described.