Volume 33, Issue 8, 01 August 1962
Index of content:
33(1962); http://dx.doi.org/10.1063/1.1728981View Description Hide Description
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.
33(1962); http://dx.doi.org/10.1063/1.1728982View Description Hide Description
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 Γ2, 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.
Applicability of the Taylor Theory of the Polycrystalline Aggregate to Finite Amplitude Wave Propagation in Annealed Copper33(1962); http://dx.doi.org/10.1063/1.1728984View Description Hide Description
This paper provides additional experimental evidence for the Taylor theory of dislocations and the Taylor theory of the polycrystalline aggregate. For annealedcopper (as had been found by Bell for annealedaluminum) 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 annealedcopper, as had been shown earlier for annealedaluminum, is determinable from compression stress‐strain curves for single crystals.
These experimental data in annealedcopper 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 annealedaluminum 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 annealedaluminum and pure lead, plastic strain propagation velocities, maximum strain amplitude, surface angle behavior, time of contact, and the coefficient of restitution for annealedpolycrystallinecopper are found to be given by the strain‐rate independent theory of plastic wave propagation.
33(1962); http://dx.doi.org/10.1063/1.1728985View Description Hide Description
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 5·10−5−1·10−3 mm Hg, showed that densities of the order 1012–1013 ion pairs/cm3 could easily be achieved. Some types of oscillations that occurred are discussed.
33(1962); http://dx.doi.org/10.1063/1.1728986View Description Hide Description
A cylindrical plasma column was produced in hydrogen by a microwaveelectric 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.
33(1962); http://dx.doi.org/10.1063/1.1728987View Description Hide Description
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.
33(1962); http://dx.doi.org/10.1063/1.1728988View Description Hide Description
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 ω0 is applied orthogonally to the dc field and another rf field at frequency 2ω0 is 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.
High‐Temperature X‐Ray Diffraction Study of the Order‐Disorder Transition in a Cu‐32.2 Atomic Percent Gold Alloy33(1962); http://dx.doi.org/10.1063/1.1728989View Description Hide Description
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.
33(1962); http://dx.doi.org/10.1063/1.1728990View Description Hide Description
Heavy plastic deformation producing nonbasal slip in Bi2Te3 changes the material from p type to n type and decreases its resistivity. From Hall coefficient measurements, it appears that an excess of about 2×1020 negative 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 defectgeneration 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 Bi2Te3 is to add donor states to the system.
33(1962); http://dx.doi.org/10.1063/1.1728991View Description Hide Description
Crystals of Ba2TiP2O9 were grown from the melt by the Bridgman technique. Two types of twinning occur, namely: growth twins and mechanical twins. The growth twins form with the (100) plane as the twin plane and mechanical twins form with the (001) plane as the twin plane. In twinned crystals, growth proceeds most rapidly in the  direction. Rapid growth in this direction is believed to result from efficient nucleation at the re‐entrant corners formed by the 〈310〉 faces of the twin components. The mechanical twins form according to pseudo‐merohedral symmetry by reflection across the (001) twin plane. The angle of obliquity is 4° and the twinning shear is 0.140.
33(1962); http://dx.doi.org/10.1063/1.1728992View Description Hide Description
Internal frictionmeasurements were made as a function of hydrostaticpressures up to 3 kb by use of a piezoelectric torsional oscillator inside the pressure vessel, as well as with a Marx composite oscillator both before and after pressure treatment. Specimens were prepared by cold‐working 99.99% aluminumpolycrystals to a 50% reduction in width, followed by an anneal at 300°C. Measurements outside the pressure vessel showed that the strain amplitude dependence was irreversibly increased by amounts up to 1500% of the initial values as a result of the application of 3 kb for 15 min at 25°C. The original amplitude dependence was restored by annealing 15 min at 300°C. A subsequent compression again increased the amplitude dependence but to a lesser extent. After several such annealing‐compression cycles there was no irreversible effect within 4% of background. Additional cold‐work followed by annealing again produced the effect. The effect increased with increasing pressure. An increase in amplitude dependence of up to 600% also occurred in samples which had not been previously cold‐worked. The internal friction at constant strain amplitude increased faster than linearly with increasing pressure and decreased linearly with decreasing pressure. Successive pressure cycles gave the same effect but with decreasing magnitude. After about 3 cycles, both increasing and decreasing pressure gave the same linear dependence of the damping, corresponding to within 8% of the background damping. It is suggested that irreversible dislocation effects might occur as the result of shear stresses produced near voids by the hydrostatic stress.
33(1962); http://dx.doi.org/10.1063/1.1728993View Description Hide Description
Attempts have been made to grow single‐crystal HgS using a vapor phase growth technique. The lack of success led to the discovery of a phase transformation which occurs between the temperature of deposition and room temperature. The crystals were deposited in the cubic meta‐cinnabar form and transformed to the hexagonal cinnabar form upon cooling, with a resultant destruction of the deposited crystals. There is a large supercooling effect which seems to depend upon particle size. Upon heating cinnabar in an atmosphere of air the transformation to meta‐cinnabar occurs at 335°±10°C. Possibilities for the use of other techniques in the growth of single‐crystal HgS are considered.
Influence of the Kα1 α2 Doublet on the Determination of the Twin Fault Probability from X‐Ray Diffraction Profiles33(1962); http://dx.doi.org/10.1063/1.1728994View Description Hide Description
The contribution of the Kα1α2 asymmetry to the total observed asymmetry is calculated for x‐ray diffraction profiles from fcc specimens containing twin faults. The profiles are approximated by exp(−k 2 x 2), (1+k 2 x 2)−2, or (1+k 2 x 2)−1. Calculations, using data from filed and annealedPermalloy, show that the α1α2 asymmetry introduces no serious error in determining the twin fault probability as long as the observations are made at values of the abscissa which correspond to at least half the distance from the profile maximum to the profile zero point. For asymmetries measured closer to the profile maximum, the α1α2 asymmetry can become important. A method to correct for the α1α2 asymmetry is given.
33(1962); http://dx.doi.org/10.1063/1.1728995View Description Hide Description
The carrier concentration homogeneity in a semiconductor can be quantitatively measured from the position of the plasma edge. This has been demonstrated for an InAs sample for which changes of homogeneity of about 0.5% have been measured. This plasma edge method for measuringcarrier concentration inhomogeneities is at least an order of magnitude more sentitive than other methods reported to date and can be applied for any semiconductor that has a well‐defined plasma edge.
33(1962); http://dx.doi.org/10.1063/1.1728996View Description Hide Description
Propagation of waves in a transmission system consisting of a plasma column and a coaxial helix is investigated. The propagating characteristics of the structure are analyzed by a straightforward field analysis. It is demonstrated that the field solution can be reduced to a simple circuit equation describing two coupled tuned circuits. This analytical result shows that the propagation of waves in the plasma‐helix structure can be described by a purely capacitive coupling of modes between the space‐charge modes of plasma column and the helix mode. The result of this study is compared with the earlier Russian work by Bulgakov et al. The limitation of the perturbation techniques is discussed and the condition for the validity of the small perturbation assumption is given. The experimental method of separating and measuring the two coupled modes of propagation by means of mode‐selecting techniques is described.
33(1962); http://dx.doi.org/10.1063/1.1728997View Description Hide Description
Using a simple model, the motion of an ensemble of small conducting spheres located between two parallel electrodes is investigated theoretically in the case where the flow is space‐charge‐limited. A more realistic but more complicated model is proposed. The experimental apparatus used to check the theoretical predictions is described; agreement between theory and experiment is fair. Possible applications of such diodes are mentioned.
33(1962); http://dx.doi.org/10.1063/1.1728998View Description Hide Description
Anisotropicelastic stress was applied to semiconductor surfaces parallel to the plane of shallow p‐njunctions. The resistance of diffused and alloyed junctions was found to be highly stress‐sensitive under both forward and reverse bias. Reversible resistance decreases under stress by factors of more than 103 were observed.
33(1962); http://dx.doi.org/10.1063/1.1728999View Description Hide Description
A strong external electric field in a plasma produces electrons with a temperature considerably higher than the temperature of the neutral gas in a plasma. We investigate here the currents produced by such electrons in a strong ac field. We discuss several cases of interest. Case 1 deals with the effect of a strong ac field on the plasma. It is found that the current has a component of frequency ω and a weaker component of frequency 3ω. The results are valid if ν0>ω>δν0. Here ν0 is the collision frequency of the electrons and δ is the fraction of energy transferred to the neutrals in a single collision. Case 2 deals with the effect of a strong steady electric field on which a weak ac field of frequency ω is superimposed. Here the current has a steady component plus an additional ac component of frequency ω which leads the ac field by a phase given by Eq. (33). Case 3 is similar to case 2 except that electron‐ion collisions have been considered. The measurement of the current and phases should lead to a determination of the collision frequency.
33(1962); http://dx.doi.org/10.1063/1.1729000View Description Hide Description