摘要:

In electron beam devices the thermal velocities of the electrons leaving the cathode limit the current density which can be attained with given cathode current density, cathode temperature, potential, and angular spread of arriving electrons. By using Liouville's theorem, limiting expressions are obtained which are valid for any point focus or line focus concentrating system using steady electric and magnetic fields. Current densities in perfectly focused beams are also evaluated. Curves are presented which relate the nearness of approach to the maximum attainable current density with the fraction of cathode current necessarily lost in the concentrating system. Use of the expressions obtained is illustrated by applying them to cathode ray tubes and electron multipliers.

ISSN:0021-8979    

DOI:10.1063/1.1707256

出版商:AIP    

年代:1939

数据来源: AIP

摘要:

An investigation of the electrolytic polishing of copper by the Jacquet method has thrown new light on the mechanism responsible for the polishing action. From a study of the voltage‐current curves it is concluded that when conditions are right for polishing the concentration of dissolved copper at the anode is the highest possible. Accordingly the concentration gradient which exists at the anode limits the rate at which copper can dissolve,i.e., diffuse into the bulk of the electrolyte (orthophosphoric acid). Since there is greater diffusion from raised areas of the anode because of steeper concentration gradients near them, the surface will become progressively more nearly level. The surface does not etch for the concentration gradient alone controls the rate of solution. Details are given for the electrolytic polishing of iron with an orthophosphoric acid electrolyte. A convenient form of cell for electrolytic polishing is described.

ISSN:0021-8979    

DOI:10.1063/1.1707257

出版商:AIP    

年代:1939

数据来源: AIP

摘要:

From measured values of arc gradientE(v cm−1) and current densityI(amp. cm−2) the arc temperature is calculated for nitrogen in the pressure range 1–30 atmospheres and current range 1–10 amperes, and in hydrogen at one atmosphere pressure for the current range 1–10 amperes.

ISSN:0021-8979    

DOI:10.1063/1.1707258

出版商:AIP    

年代:1939

数据来源: AIP

摘要:

From oscillographic records of arc diameterD, gradientE, currenti, and comparative brightness data, the lumen efficiency and current densities are determined for the positive column of arcs in A, N2, He and H2in the pressure range between 1 and 100 atmospheres.

ISSN:0021-8979    

DOI:10.1063/1.1707259

出版商:AIP    

年代:1939

数据来源: AIP