摘要:

Thin‐film electron emitters are described, which operate below 200°K and below a limiting critical applied voltage (&ngr;c) in a stable temperature‐independent regime. Current‐voltage characteristics and normal electron energy distributions are presented. Fabrication and operation criteria are outlined. Comparison with temperature‐dependent emitters is made, and possible conduction mechanisms discussed briefly.

ISSN:0021-8979    

DOI:10.1063/1.1662945

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A form of spark discharge preceded by a train of streamers of increasingly large current which occurs in air at atmospheric pressure at voltages as low as 5 kV per cm of gap length is investigated. A mechanism involving the development of a heated channel of air in the gap is proposed to explain the increase of streamer size in the discharge. This mechanism is verified by means of a scanning interferometer which measures the phase shift caused by the altered index of refraction of the heated air. The dimensions and temperature of the heated channel are such that the peak phase shift produced is about one‐tenth of one wavelength. Analysis of the phase shift data permits the growth of the heated channel to be observed as a function of time and space. Further experimentation involving time‐resolved photography of the streamers is used to demonstrate a correlation of the streamers paths with the development of the heated channel. An appendix is included describing a numerical method for solving the Abel integral equation which was used to analyze the inteferometer data.

ISSN:0021-8979    

DOI:10.1063/1.1662946

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The behavior of bismuth under shock loading was studied by means of a shock‐detection technique based on the electrical response of bimetallic junctions and on the polarization effect of thin dielectric sheets under shock. The experiments were performed in the pressure range 50–180 kbar. A new shock‐induced phase transformation was found to take place at about 70 kbar. A rough estimate of the temperature increase associated with shock loading, and comparison with data of static compression experiments suggest that this new shock‐induced phase change in bismuth corresponds to the Bi III‐V transformation, previously observed only under static pressure loading.

ISSN:0021-8979    

DOI:10.1063/1.1662947

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

In shock‐wave compression experiments in which the interface temperature between two different materials is important, it is necessary to take account of more than the usual ideal shock impedance matching conditions. Several examples are discussed by means of hydrodynamic analysis of the interaction of strong shock waves with nonideal interfaces. It is demonstrated that significant residual thermal inhomogeneities exist near the interface which may be of use in understanding and measuring thermal properties of shock‐compressed materials.

ISSN:0021-8979    

DOI:10.1063/1.1662948

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Thermal conduction processes at material interfaces representative of those produced by shock compression are studied in order to understand the temperature history at the interface. The transient effects due to small gaps and thin layers are calculated, as well as the modifications due to a melting transition in one of the materials.

ISSN:0021-8979    

DOI:10.1063/1.1662949

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A study has been made of the structure and the dc electrical properties of a metal‐glass thick‐film system. The metal part is formed by thermal decomposition of an organometallic solution and consists of Au and Rh. The glass component is a lead boroaluminosilicate. The influence of the firing treatment, of the composition of the metal part, and of the metal‐to‐glass ratio on the structure and the electrical properties of the film has been investigated. Some glasses, derived from the original glass component, have been used. In this system it is possible to have very small temperature coefficients of resistance in a wide temperature range. Sheet resistances can vary by several orders of magnitude. Under certain conditions the conduction behaves anomalously below 186 K. The different types of conduction in this thick‐film system are correlated with the different structures.

ISSN:0021-8979    

DOI:10.1063/1.1662950

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The principal features in the Auger electron spectrum from a SiO2surface are presented. The primary electron beam bombarding the SiO2surface has a profound influence on its composition, in that it dissociates the surface leaving it enriched in elemental silicon. The main parameters affecting the dissociation are found to be the electron‐beam current density, the beam energy, the presence of impurities on the surface, and the residual gas pressure of oxygen. The effects of these parameters on the dissociation have been studied and some suggestions to minimize the dissociation are made. The results of the present study do not agree with the mechanism proposed by Lineweaver for oxygen release from electron‐irradiated glass.

ISSN:0021-8979    

DOI:10.1063/1.1662951

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Ion‐bombardment‐induced compaction of fused silica is measured using a cantilever plate technique for H, He, O, Ne, and A ions with a variety of ion energies. A phenomenological theory is developed which is based on the superposition of two independent compaction mechanisms, one proportional to the density of energy deposited into atomic collisions and the other dependent on the density of energy deposited into electronic excitations. All the present experimental data can be fit to within experimental error with the model using only three adjustable parameters and ion‐energy partitioning calculations. Further substantiation of the present energy partitioning calculations and model are provided by showing the proportionality between the density of energy deposited into atomic collisions and other workers' published results for ion‐bombardment‐induced index‐of‐refraction changes in quartz and fused silica. It is concluded that the atomic‐collision‐induced‐compaction and index‐of‐refraction changes are ion independent. Finally, a dose‐rate dependence of the ionization‐induced compaction is noted for the first time.

ISSN:0021-8979    

DOI:10.1063/1.1662952

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The photoinjection of electrons and holes from a sensitizing layer of amorphous selenium into films of the poly(N‐vinyl carbazole) : trinitrofluorenone, PVK : TNF, charge‐transfer complex has been studied by means of xerographic discharge techniques. The observed discharges are interpreted as being space‐charge limited and thus allow a determination of the carrier mobilities as a function of TNF loading. The mobilities determined in this way are consistent with measurements reported which used the time‐of‐flight technique. The asymmetries of discharge observed depending on whether electrons or holes are injected from the selenium are thus associated with mobility limitations and not to significant energy barriers between the transport states in amorphous selenium and PVK : TNF. An upper limit can therefore be inferred for the separation between the transport states for electrons and holes in this charge‐transfer complex.

ISSN:0021-8979    

DOI:10.1063/1.1662954

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The thermal diffusivity of mercury has been measured from 120 to 370 K, using the heat pulse method. The results are analyzed by computed solutions of the three‐layer thermal diffusivity problem, and compared with recommended values published by the Thermophysical Properties Research Center. Agreement is obtained to within 5% in the liquid phase and 10% in the solid phase.

ISSN:0021-8979    

DOI:10.1063/1.1662955

出版商:AIP    

年代:1974

数据来源: AIP