摘要:

The work‐function distribution of commercial pressed matrix cathodes has been investigated from room temperature to 1300°K. The measurements were obtained by probing the surface with a beam of electrons in the retarding field region. The beam, which was of the order of 2 &mgr; in diameter, sampled the work function of 30 000 regions of the surface during the 3 sec. required for one scan. The results show that the emitter exhibits a very patchy behavior at low temperatures, while a relatively uniform temperature insensitive region exists from ∼900° to 1400°K. Above this temperature, activation and poisoning effects are dominant. Patch field distribution measurements show that surface fields as high as 1500 V/cm exist in the patchy state, whereas a well activated pressed matrix cathode would have surface fields only of the order of 100 V/cm. The measurement of thermionically emitted electrons is in good agreement with results obtained by the incident electron beam. These data as well as work‐function and conductivity measurements from various microregions are discussed in terms of a thin semiconductor surface layer.

ISSN:0021-8979    

DOI:10.1063/1.1709049

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Mo¨ssbauer spectra were taken at room temperature on rolled Vicalloy samples in (i) a state obtained by quenching the sample from 950°C; (ii) a state obtained by annealing for optimum permanent magnet properties. Annealing results in a narrowing of the absorption peaks, an increase in hyperfine field, and the appearance of an additional absorption peak indicative of a paramagnetic phase. These results are interpreted in terms of the known phase diagram of Fe&sngbnd;Co&sngbnd;V, and lend support to the description of Vicalloy magnets as fine‐particle magnets.

ISSN:0021-8979    

DOI:10.1063/1.1709050

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The internal quantum efficiencies of red (∼7000 Å) emitting diodes have been evaluated from measurements of external efficiencies by the method of indices of refraction matching. The internal efficiencies of the diodes are on the average about a factor of five larger than the external efficiencies. The highest internal quantum efficiency was 3.85×10−2. Free carriers account for the absorption losses of the emitted radiation, but nonradiative recombination processes are responsible for the low values of the internal efficiency.

ISSN:0021-8979    

DOI:10.1063/1.1709051

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The explosion of ovoid conductors (noncylindrical exploding wires) is observed with pulsed x‐rays and is shown to occur only after the original ovoid shape is severely distorted, toward cylindrical symmetry.

ISSN:0021-8979    

DOI:10.1063/1.1709052

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The sampling theorem is used to obtain expressions for the diffracted amplitudeG(y, z) at any point in space, once the distribution along the axisG(y, 0) is known at the sampling points. In the case of a circular symmetrical pupil,G(y, 0) is simply the Fourier transform of the pupil function. The real or imaginary parts ofG(y, z) may be obtained either from the real or from the imaginary part ofG(y, 0). By suitable oversampling, the real part ofG(y, z) may be found from its imaginary part, and vice versa. A technique for the synthesis of antenna patterns is suggested.

ISSN:0021-8979    

DOI:10.1063/1.1709053

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The aberration of coma, occurring in a magnetically deflected electron beam, has been studied. Shapes of the deflected spot and equal‐density contours within it have been calculated for the cases where the density distribution across the beam before deflection is assumed to be either uniform or Gaussian. When coma is close to its minimum, the shape of the spot assumes a fan shape.

ISSN:0021-8979    

DOI:10.1063/1.1709054

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The concepts of the dynamical theory of x‐ray diffraction are applied to optical holography. Aplane‐grating hologram is the assumed diffraction element and its behavior is shown to be consistent with that of its x‐ray counterpart, namely a thin, one‐dimensionally periodic structure. Evidence is cited which corroborates the theory. In particular, an anomalous transmission of light through the plane‐grating structure, at the Bragg angle, is reported‐referred to as the Borrmann effect in the x‐ray‐crystal situation‐which in x‐ray optics is taken asprima facieevidence for the dynamical theory. The usually observed subsidiary maxima about the Bragg peak and their reported asymmetry are explainable in terms of the dynamical theory as effects due to a finite lattice. The minimum angle of deviation found in holograms, so familiar to prisms and line gratings, is described as a finite‐lattice effect.It is concluded that the dynamical approach in holography is a useful one for the thick emulsion, whereas the simple kinematic theory is more adequate for thin emulsions. However, attention is drawn to the use of the dynamical theory even for the case of thin emulsions to help provide some physical insight into the diffraction of light by holograms.

ISSN:0021-8979    

DOI:10.1063/1.1709055

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

It is shown that a tracer plate will diffuse into a specimen which is being plastically deformed by a process called mechanical diffusion. The magnitude of the penetration via mechanical diffusion is about equal to the offset of the individual glide packets; this offset, in turn, is caused by the nonhomogeneous character of the deformation. It is shown that several examples of enhanced diffusion previously attributed to either vacancy supersaturation or pipe diffusion may in large part be accounted for by mechanical diffusion. In general, mechanical‐diffusion effects are probably considerably larger than enhanced‐diffusion effects due to these other processes.

ISSN:0021-8979    

DOI:10.1063/1.1709056

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Ferromagnetic resonance measurements at 9.5 Gc/sec were made on a number of films of pure iron, pure nickel, and alloys of iron and nickel (Permalloy) before and after 2‐MeV3He‐particle irradiation. The3He particle flux was about 3×1017/cm2and, during irradiation, the film temperature did not exceed 81°C, as determined by thin‐film thermocouples. The resonance field as a function of angle in the film plane,H0(&thgr;), and the half‐width, &Dgr;H, were measured at room temperature. In general,H0decreased (by about 2, 35, and 15 Oe for the iron, Permalloy, and nickel films, respectively) as a result of the irradiation, except for the composition range between 26% and 37% Ni whereH0increased. Also, the half‐width generally decreased with irradiation and the half‐width change was smallest for compositions around 76% Ni. The changes inH0were different for films of a given set evaporated onto various substrates (soft glass, fused quartz, single‐crystal quartz). Irradiating films in a saturating magnetic field, in the remanent state, and in the demagnetized state gaveHk's which were larger, the larger the magnetic induction of the film during irradiation. Irradiating a film (or reirradiating a previously irradiated film) in a magnetic field also rotated the easy axis of the film into the direction of the field applied during irradiation. The rotation of the easy axis was observed over the entire composition range from pure iron to pure nickel. The variation with composition of the values ofHkafter irradiation agrees qualitatively with the values obtained by others using static techniques.

ISSN:0021-8979    

DOI:10.1063/1.1709057

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

This paper presents the results of measurements of the velocities of ⟨12¯10⟩ (0001) edge dislocations in zinc as a function of applied shear stress. All tests were conducted at room temperature on 99.999% pure zinc monocrystals. Dislocations were revealed by means of the Berg‐Barrett x‐ray technique. Stress pulses of microsecond duration were applied to the test specimens by means of a torsion testing machine. Applied resolved shear stresses ranged from 0 to 17.2×106dyn/cm2and measured dislocation velocities ranged from 40–700 cm/sec.The results of this study indicate that the velocity of edge dislocations in the basal slip system of zinc is linearly proportional to the applied resolved shear stress. These results are analyzed in terms of the phonondrag theory. Agreement between this theory and the results reported here is quite good.

ISSN:0021-8979    

DOI:10.1063/1.1709058

出版商:AIP    

年代:1967

数据来源: AIP