摘要:

Theory is presented concerning the attenuation of the original beam waves, the fast, the slow, and two synchronous waves, and the generation of noise waves if part of the beam is intercepted.To obtain compact equations matrix notation is used throughout. The matrix notation offers the additional advantage that both the behavior of the waves and their mutual correlation can be studied simultaneously. This renders the theory, which accounts both for pure interception and for partial scattering of the beam, much more general in nature. The electron beam diameter is finite.In addition to attenuation of the original and generation of noise waves it is found that two new synchronous waves related to the original fast and slow waves are generated.Experiments at 550 Mc with an Adler‐Wade tube containing a movable vane show good agreement with the theory presented, provided the forward scattering is taken into account. The experiment indicates that the theory is probably correct at least insofar as the fast wave, the slow wave, and the correlated components of the synchronous waves are concerned.

ISSN:0021-8979    

DOI:10.1063/1.1728981

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The paper is concerned with the transverse velocity and position noise on electron beams. The equivalence between the actual noisy beam and a modulated filamentary beam is pointed out, and the frequency components of the equivalent filamentary beam modulation is calculated. It is shown that the transverse position noise is reduced by a factor &Ggr;2, which is identical to the space‐charge reduction factor for the longitudinal shot noise. The noise excitation is also expressed in terms of self‐power and cross‐power densities of the four normal modes on a rectilinear filamentary beam in a longitudinal magnetic field.

ISSN:0021-8979    

DOI:10.1063/1.1728982

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The amphoteric behavior of germanium in gallium arsenide has been studied quantitatively for small variations in melt composition around the maximum melting point.

ISSN:0021-8979    

DOI:10.1063/1.1728983

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

This paper provides additional experimental evidence for the Taylor theory of dislocations and the Taylor theory of the polycrystalline aggregate. For annealed copper (as had been found by Bell for annealed aluminum) the governing stress‐strain curve for plastic wave propagation is a parabola, as predicted by the Taylor theory of dislocations. Using the Taylor theory of the polycrystalline aggregate, the parabolic stress‐strain law for annealed copper, as had been shown earlier for annealed aluminum, is determinable from compression stress‐strain curves for single crystals.These experimental data in annealed copper are obtained from the free‐flight constant‐velocity impact of identical specimens using the diffraction‐grating technique for the measurement of strain and surface angle.From the results given in this paper, together with those obtained earlier by Bell for annealed aluminum and the recent results of Sperrazza for pure lead, it may be concluded that strain rate does not play a significant role in the dynamic plasticity of these annealed face‐centered‐cubic metals. As in annealed aluminum and pure lead, plastic strain propagation velocities, maximum strain amplitude, surface angle behavior, time of contact, and the coefficient of restitution for annealed polycrystalline copper are found to be given by the strain‐rate independent theory of plastic wave propagation.

ISSN:0021-8979    

DOI:10.1063/1.1728984

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Some properties of a plasma formed by an ionizing electron beam have been investigated. The electron beam and the plasma were confined by an axial magnetic field. The experiments, which were performed in argon in the pressure range 5·10−5−1·10−3mm Hg, showed that densities of the order 1012–1013ion pairs/cm3could easily be achieved. Some types of oscillations that occurred are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1728985

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A cylindrical plasma column was produced in hydrogen by a microwave electric field crossed with a static magnetic field. Under certain conditions of gas pressure, magnetic field, and strength of the microwave field, the plasma did not entirely fill the volume available to it but appeared as a narrow, perfectly stable, cylindrical column with a diameter as small as one‐fourth of the diameter of the discharge tube. The experimentally observed properties of this ``constricted'' discharge are described. It is shown that they can be explained by treating the plasma as a compressible dielectric medium.

ISSN:0021-8979    

DOI:10.1063/1.1728986

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

In this tutorial note, we show that the normal mode amplitudes of Pierce's coupled mode theory correspond to the creation and annihilation operators of quantum field theory. We show that the classical equations of motion in terms of Pierce's mode amplitudes are identical to the Heisenberg equations of motion for the creation and annihilation operators, and correspond to the quantized treatment of the classical problem.

ISSN:0021-8979    

DOI:10.1063/1.1728987

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

An rf magnetic field of sufficient amplitude gives rise to a nonlinear absorption caused by the unstable growth of certain spin waves. We have calculated the threshold for the case in which an rf field of frequency &ohgr;0is applied orthogonally to the dc field and another rf field at frequency 2&ohgr;0is simultaneously applied parallel to the dc field.We find that under these conditions the wave number of the spin waves with the lowest instability threshold varies discontinuously with the ratio of the two rf magnetic fields. If the orthogonal rf field is relatively small, the unstable spin waves have wavelength comparable with the sample dimensions. In this region the critical parallel field decreases linearly with the square of the orthogonal field.

ISSN:0021-8979    

DOI:10.1063/1.1728988

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The order‐disorder transition in a polycrystalline specimen of Cu‐32.2 at.% Au has been investigated by means of a high‐temperature x‐ray diffraction method. The experiment confirms the existence of an equilibrium Cu3Au II‐type phase in a temperature interval from 313±3°C to 328±3°C. Diffraction data from this phase are not in conflict with a previously described structure at 31.6 at.% Au based upon an ordered Cu3Au I‐type superlattice in which strictly periodic antiphase domain boundaries occur parallel to any one of the three possible cube faces. Antiphase periods ranging from 18 to 16 are found for the Cu3Au II‐type phase. There is an indication that this period may change as a function of temperature and that periods which are not integral multiples of cubic subcell edges may exist. A two‐phase field between the Cu3Au II‐type and disordered single‐phase regions has been located on the basis of fundamental reflection broadening. Unambiguous evidence for a similar field was not found between the Cu3Au I and Cu3Au II‐type single‐phase fields.

ISSN:0021-8979    

DOI:10.1063/1.1728989

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Heavy plastic deformation producing nonbasal slip in Bi2Te3changes the material fromptype tontype and decreases its resistivity. From Hall coefficient measurements, it appears that an excess of about 2×1020negative carriers can be generated in the lattice. Annealing the deformed samples at different temperatures and in different environments causes large changes in this excess carrier concentration. A simple theoretical model based on point defect generation by the plastic deformation accounts for the results. From this model, it appears that tellurium vacancies are the predominant electrically active point defects. These Te vacancies are annihilated by dislocation climb and array formation during annealing. The effect of dissolved oxygen in Bi2Te3is to add donor states to the system.

ISSN:0021-8979    

DOI:10.1063/1.1728990

出版商:AIP    

年代:1962

数据来源: AIP