摘要:

Cold electron sources have been studied with particular emphasis on mass spectrometric application. In these sources a relatively weak current from a primary emitter was amplified by an electron multiplier to provide sufficient electron current to ionize neutral gas molecules. The final designs of the cold sources use tantalum photocathodes powered by simulated sunlight as primary electron sources. The sources are highly efficient, consume negligible power, have minimal outgassing and gettering effects, and exhibit considerably less short‐term emission fluctuations than a temperature‐limited thermionic emitter. These devices would be well suited to calibration work and space flight instrumentation.

ISSN:0021-8979    

DOI:10.1063/1.1714611

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The electron opacity of anodic films formed on aluminum—copper alloys in an alkaline electrolyte under well controlled conditions is a function of the copper content of the alloys. This relation permits the development of a quantitative electron optical replica for application in revealing solute distribution and for measuring solute concentration. These replicas are extremely sensitive to small variations in copper concentrations in solid solution on a finer scale than can be defined by existing electron optical methods. Application of this replica technique to a study of aged aluminum—copper alloys has revealed some new aspects of the decomposition process.

ISSN:0021-8979    

DOI:10.1063/1.1714612

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Composite magnetic thin films consisting of layers of different magnetic materials in close molecular contact with one another are studied. Because of ferromagnetic exchange coupling between spins, the magnetization in the neighborhood of the interface of the layers is expected to rotate continuously as in Bloch walls. The experimental magnetization curve of an extremely soft magnetic layer on an extremely hard magnetic layer agrees well with the theoretical curve based on such rotation models. Drastic deformations in critical switching curves from the asteroid of conventional uniaxial films, improvement in nondestructive reading characteristics, and existence of a new switching mode which is dependent upon the sequence of external magnetic fields are also expected from a theory based on a lumped‐constant approximation to the continuous rotation model. All of these theoretical predictions have been confirmed by experiments using electroplated composite films.

ISSN:0021-8979    

DOI:10.1063/1.1714613

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

In undoped crystals of MgO, x irradiation converts a large fraction of Cr3+in octahedral symmetry to Cr2+. Heating such crystals until a blue thermoluminescence has been observed causes further reduction. Usually 95% or more of the Cr3+is converted by the combined treatments. However, in Cr‐doped MgO one is able to reduce only a small fraction of the octahedral chromium to Cr2+. The Cr2+is reconverted to Cr3+by heating. ESR measurements show that in the same temperature interval nearly all of the Fe1+formed on x irradiation has disappeared. The source of electrons acquired by Cr3+thus appears to be the Fe1+ions. The thermoluminescence is ascribed to the Cr3+‐electron interaction, as suggested by Hansler and Segelken.

ISSN:0021-8979    

DOI:10.1063/1.1714614

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Instabilities can be induced in parallel‐plane (diode) configurations when a very high current is passed through the diode, even if this current is neutralized by ions. This work extends Pierce's original calculation of the critical current for instability to find the growth rate for a wide input—current range, and then goes on to include collisions of the injected stream with background neutrals and allow for mobile neutralizing particles. Collisions damp the instability, increasing the value of input current at which onset of instability will occur; if the collision frequency &ngr; is such that &ohgr;p2L/&ngr;v0<4&pgr;, approximately, then there is no time growth. Allowing the background ions to be mobile also eliminates this type of instability. The results without collisions compare favorably with some experiments involving essentially collisionless diodes; those with collisions included do not agree with some experiments involving collision‐dominated triode lasers.

ISSN:0021-8979    

DOI:10.1063/1.1714615

出版商:AIP    

年代:1965

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1714616

出版商:AIP    

年代:1965

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1714617

出版商:AIP    

年代:1965

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1714619

出版商:AIP    

年代:1965

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1714620

出版商:AIP    

年代:1965

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1714622

出版商:AIP    

年代:1965

数据来源: AIP