摘要:

Highly bunched electron beams in the 1 to 3 million electron volt range, having a sharply peaked velocity spectrum, represent a powerful attack on the submillimeter wave (100 to 3000 kmc/sec) generation problem. In this paper the theory of a rebatron for producing a high‐energy beam, wherein both the current wave form and the velocity distribution function approach delta functions, is presented. Computations indicate that the emergent 1.5‐Mev beam has an appreciable harmonic content up to harmonics as high as the 1000th and has a velocity spread of 0.07% for the electrons of interest. Pulsed beam powers of the order of 100 000 w should be possible using a 3 kmc/sec rebatron.

ISSN:0021-8979    

DOI:10.1063/1.1722916

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A practical design of anS‐band rebatron for producing a high power, bunched, megavolt electron beam, theoretically possessing harmonic current frequencies in the submillimeter range is presented. An indirect experimental method of evaluating the beam obtained from the rebatron, based on measuring momenta spectra, gives very satisfactory agreement with theory. The validity of this indirect method of beam analysis is strengthened by a measurement of the ratio of the 26th beam harmonic current amplitudes under two different sets of conditions determined experimentally by momenta spectra measurements. No highly critical tolerance conditions are encountered in the investigation.

ISSN:0021-8979    

DOI:10.1063/1.1722917

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A new method for the coherent generation of relatively high powers at submillimeter wavelengths through the electronic excitation at a single frequency of a selected higher orderTM0mnmode in a cylindrical cavity which is large compared to the wavelength is investigated. The theoretical relationship between the generated power,P, the harmonic current component,Is, and the wavelength, &lgr;, is typically of the order ofP(watts)≃3000[Is(amp)]2[&lgr;(mm)]12for a 1‐Mev electron beam. Experimental measurements at a wavelength of 8.310 mm which successfully demonstrate the method are described.

ISSN:0021-8979    

DOI:10.1063/1.1722918

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Values of the photoelectric quantum efficiency of glass for different wavelengths have been determined and data have been obtained on the status of electrons placed on glass surfaces. One of the borosilicate glasses commonly used in discharge tube manufacture and soda glass were studied in vacuum with 2537 A photons from a quartz Heraeus mercury arc and with light from a glow discharge operating in pure A and Ne from 10−1to 10 mm pressure. Clean borosilicate glass in vacuum at 22°C with fields of some 1000 v/cm across it yields photoelectric current densities of the order of 10−12amp/cm2for the full light of a 110 volt arc focussed on 10 cm2area through quartz optics. This current comes from the 3–4% Na impurity atoms on the surface. Soda glass yields currents in proportion to the density of Na atoms. The normal conductivity of the glass comes from Na+ions of some 0.5 volt activation energy normally present. It is enhanced 10‐fold by Na+ions liberated at the surface by light. Na+ions next the cathode cannot leave the glass, but electrons enter the glass from the metal cathode backing of lower work function to neutralize the ion space charge as it builds up near the cathode. Electrons sprayed onto the glass surface have a mobility of ∼5×10−5cm2/volt sec in the glass in contrast to the value of ∼1×10−7cm2/volt sec for the Na+ions reported by Kraus. Photons above 3300 A do not contribute to the conductivity in any fashion. The photoelectric yield for 2537 A was obtained directly in absolute magnitude by use of a vacuum bolometer. For the light from glow discharges ≪1200 A, the efficiency was obtained indirectly by comparison with values for Pt and Au. The values obtained are tabulated below.Wave−Borosili−Sodalength Acate glassglassAuPt    Remarks2537 A10−46×10−410−2…Vacuum≫2300 A10−4……10−3Glow discharge≪1250 A10−3…10−110−10.1 to 10 mm Hg

ISSN:0021-8979    

DOI:10.1063/1.1722919

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

High frictional temperatures during the dry or imperfectly lubricated rubbing of steel produce gross structural changes and intense hardening of the surface layers. In consequence of these changes the wear time curve shows a marked inflexion, the wear rate of soft steel on soft steel diminishing by more than an order of magnitude as the hardened skin develops. The protective layer establishes itself more readily as the carbon content of the steel increases, a feature explained by the ease with which eutectoid pearlite transforms to austenite, and thence to martensite, during the rapid temperature cycle. By simulating the hot spots during wear by the thermal action of electric sparks, the hardness change is shown to be intensified by nitrogen or carbon absorbed from the atmosphere or lubricant.

ISSN:0021-8979    

DOI:10.1063/1.1722920

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Using perturbation theory, expressions are derived for the frequency shift of a circularly polarized resonant microwave cavity upon insertion of a ferrite sample small compared with the wavelength. Retardation effects are considered in deriving the rf fieldh2internal to the sample. By integratingh1·h2dv(whereh1is the applied rf field) over the sample volume, a closed‐form expression is obtained for the cavity frequency shift. The theory is applied to the magnetic resonance in ferrites. The calculated magnetic resonance line shape is found to remain symmetrical as the sample size is increased. Retardation effect, thus, does not explain the asymmetry of the resonance lines which have been observed for polycrystalline ferrite. Results of the theory are also compared with measurements on a single crystal of ferrite having the rather large maximum permeability loss term of 100. Theoretical and measured values are in close agreement.The theory is also compared with the somewhat different results of other recent theoretical treatments, in which an approximate expression for an effective magnetic dipole moment for the sample was computed, rather than integrating the internal rf fields over the volume of the sample.

ISSN:0021-8979    

DOI:10.1063/1.1722921

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Electron mirror microscopy is a rather novel research instrument. It has recently been demonstrated that it can provide micrographs not only of the relief structure of a specimen but also of such purely electrical properties as contact potentials, conductivities, surface charges, and even space charges. This paper deals with the feasibility of electron mirror microscopy for pictorial representation of magnetic properties in general, and of magnetic domain patterns in particular. It is shown that electron mirror microscopy is actually a feasible and independent method for electronically depicting magnetic patterns. The section of the paper dealing with experimental work begins with magnetic specimens of artificial nature, e.g., a recorder head, containing one or more linear magnetic dipole stray fields which are controllable. After establishing the basic facts of magnetic contrast formation with this type specimen, the paper reports on experiments conducted with specimens of barium ferrite and nickel ferrite containing actual magnetic domain patterns. Samples of electron mirror micrographs of domain patterns of these materials are shown and compared with domain patterns of the same specimen areas obtained by the conventional powder technique. The identical nature of the configurations on both micrographs provided final proof of the feasibility of electron mirror microscopy in depicting magnetic patterns. Criteria required to distinguish magnetic patterns from those of electrical or relief origin are derived from the experimental findings and are verified by elementary theoretical considerations about magnetic contrast formation in electron mirror microscopy.

ISSN:0021-8979    

DOI:10.1063/1.1722922

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Two identical linear circuits are excited by generators furnishing equal and opposite voltages. Homologous portions of the two circuits are interchanged at random times with, on the average,rinterchanges per unit time. Because of these interchanges, the currents in the remaining portions are irregular. A theorem is derived that permits one to calculate the statistical averages of these currents. It states that one may disregard the interchanging; instead, one merely replaces the complex frequencysbys+2rin the circuit functions [e.g., the impedancesZ(s)] of the portions that were being interchanged. On the basis of this theorem one may design counting rate meters with nonlinear (e.g., logarithmic) scale, useful in reactor instrumentation, and function generators for functions of practical importance, such as the logarithmic and exponential functions, and powers with arbitrary exponent. The nature of the function depends only on linear passive circuit elements, such as resistors and capacitors.

ISSN:0021-8979    

DOI:10.1063/1.1722923

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

The condensation zone of a condensing vapor flowing in a channel is idealized as an interface separating vapor and liquid phases of the fluid with a concentrated friction, heat removal, and cold liquid injector mechanism at the interface. Rankine‐Hugoniot relations are obtained including effects of the mass, momentum, and energy sources at the interface. For a stationary interface, an explicit approximate solution is obtained giving the final liquid state in terms of the other parameters. In addition, a rapidly converging iterative procedure is presented with this solution as a first approximation and utilizing directly thermodynamic tables of the vapor and liquid. Examples corresponding to steam flow in a pipe and to an underwater steam jet are considered and their Hugoniot curves are computed and compared to similar curves obtained in detonation theory. The thermodynamic requirements of the existence of a steam‐water interface limit these curves in extent and result in upper and lower bounds on the values of the cooling parameters.

ISSN:0021-8979    

DOI:10.1063/1.1722924

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A dynamical theory is developed for the explosive production of multiple shocks in metals which undergo a phase transition. In addition to the formation of two compressive shocks, it is found that a rarefaction shock is also produced which will overtake one of the compressive shocks.

ISSN:0021-8979    

DOI:10.1063/1.1722925

出版商:AIP    

年代:1957

数据来源: AIP