摘要:

Sputtering ratios for copper have been determined in the energy ranges 5–40 kev for bombardment by Ar+, He+, and D+. Argon values range from 6.48 at 5 kev to 9.25 at 27.5 kev, deuterium from 0.048 at 10 kev to 0.023 at 44 kev, and helium from 0.23 at 15 kev to 0.75 at 40 kev.Preliminary data are included for 30‐kev sputtering of copper by H+(0.011), D+(0.03), He+(0.13), N+(5.28), Ne+(3.61), Ar+(9.02), CU+(9.60), Kr+(15.15), and U+(20.9). Also included are sputtering ratios at 30 kev for Ar+on Ta(2.7), Mo(3.31), and Al(2.38). Most of these data are the result of a single measurement, and require further verification.A definite pressure dependence of the sputtering ratio for Ar+on Cu was found in the range of 0.04 to 0.08 &mgr;.

ISSN:0021-8979    

DOI:10.1063/1.1735605

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The measurements of electrical charges on dust clouds of crushed KCl monocrystals previously irradiated with &bgr; rays shows that the value of the mean charge depends on irradiation time. In the case of KCl irradiated with &bgr; rays, a photoelectric effect is not observed, despite the presence ofFcenters.

ISSN:0021-8979    

DOI:10.1063/1.1735606

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

Macroscopic equations for conservation of charge, momentum, and energy, as derived from the Boltzmann equation, are applied to an electron stream having a velocity spread. For small velocity spreads, these equations are simple to treat. The noise parameters,Sand &Pgr;, which determine the minimum noise figure of a beam‐type microwave tube, lose their invariance in the presence of velocity spread; they become functions of position. The changes ofSand &Pgr; are such as to lower the minimum noise figure. These results are in agreement with a detailed numerical solution of the Boltzmann equation as previously reported by others.

ISSN:0021-8979    

DOI:10.1063/1.1735607

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The problem of forming molecular beams for use in ammonia masers is examined. It is shown theoretically and experimentally that through the use of a new type of parabolic focuser with a ``point source'' effuser, the molecular flow may either be reduced by a factor of 8, for the same power output, or the power output may be increased by a factor of 2 for the same molecular flow. A theory of beam formation in a multitube effuser is described. This shows that the most intense molecular beam is formed by an effuser of small overall diameter. Design considerations are discussed for parabolic, upper‐state focusers, and for coaxial, lower‐state focusers. The operation of a system is described, using a lower‐state focuser and an ionization detector, in which lower‐state molecules produced by maser oscillation may be detected.

ISSN:0021-8979    

DOI:10.1063/1.1735608

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The characteristics of molecular beams formed by sources consisting of long tube arrays are measured for several sources. The peak beam intensity and the beam width are calculated when collisions in the source are taken into account under the assumption that a limited region of Knudsen type flow occurs near the low‐pressure end of the source. The peak beam intensity and the beam width are calculated to vary as the square root of the total flow rate for source pressures giving useful directivity, in good agreement with the observations. Considerations in the design of sources are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1735609

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The impact of aluminum projectiles on steel plates for impact velocities of 2500 m/sec to 3000 m/sec and about 1100 m/sec was studied. Crater volume and penetration were measured. Shock wave velocity from the free surface was determined and the particle velocity calculated. For annealed 4130 steel plates impacted at 2750 m/sec average velocity, the average free surface particle velocity was 0.205 mm/&mgr;sec. Existing theory on cratering and penetration gave excellent agreement with the observed values.

ISSN:0021-8979    

DOI:10.1063/1.1735610

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

By using the optical grid method the diffraction of water waves from circular and elliptic cylinders were measured and compared with theory. The scattered wave intensitySand the total energy scattered per sec per unit intensityQwere measured and the results bear out the well‐known fact that for angles less than 30 deg or in the vicinity of 180 deg, one cannot separate out the scattered wave and the incident plane wave.The optical grid method is described in detail and the advantage of its being able to measure the instantaneous field emphasized.

ISSN:0021-8979    

DOI:10.1063/1.1735611

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

A pump signal propagating along a dispersionless transmission line with a distributed nonlinear capacitance is subject to deformation, since different parts of the signal move with different velocities. This process of deformation will eventually result in the formation of an electromagnetic shock wave. The deformation will affect the parametric amplification process. If a small signal consisting of a positive pulse, short compared to the pump cycle, is added to the pump signal at the input end, then it is shown that the small signal at the output must be non‐negative. All other small signals, including in particular those with sinusoidal time variation, can be regarded as superpositions of these short pulses. As a consequence it is shown that, in general, a sinusoidal signal will not be increased in its fundamental frequency component, by traveling down the line together with the pump signal. There are certain exceptional frequencies, multiples of one half the pump frequency, where a suitably phased small signal may be increased at its fundamental frequency, but not by a sufficient amount to be of practical interest.

ISSN:0021-8979    

DOI:10.1063/1.1735612

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The ``steady‐state'' creep of Al2O3single crystals was investigated. The experimental data are analyzed according to three mechanisms: the dislocation climb mechanism, the micro‐creep mechanism, and the Peierls stress mechanism. It is shown that the dislocation climb mechanism fits experimental data best. The expectation that Peierls stress mechanism is rate controlling in the ``steady‐state'' creep of Al2O3is ungrounded.

ISSN:0021-8979    

DOI:10.1063/1.1735614

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

Direct observations of interfacial growth and the approach of centers between spheres of sodium chloride were made in an argon atmosphere and over a temperature range of 700 to 800°C. The rate law governing the increase of the contact area between spheres, the effect of changing size scale on this rate and the absence of a change in the center‐to‐center distance during sintering all indicate that the rate‐determining mechanism of material transport in this sintering process is evaporation‐condensation. A model is presented which considers Stefan flow to occur within a thin boundary layer in the gaseous phase adjacent to the condensing surface, the sintering rate being predominantly governed by the rate at which sodium chloride vapor diffuses through this boundary layer. The marked pressure‐dependence of the empirical relationship between contact area and sintering time for fixed temperature and sphere size is consistent with the proposed model.

ISSN:0021-8979    

DOI:10.1063/1.1735615

出版商:AIP    

年代:1960

数据来源: AIP