摘要:

A high‐temperature Hall‐effect apparatus is described which allows measurements up to temperatures greater than 1200 K using the van der Pauw method. The apparatus was designed for measurements on refractory materials having high charge carrier concentrations and generally low mobilities. Pressure contacts are applied to the samples. Consequently, special contacting methods, peculiar to a specific sample material, are not required. The apparatus has been semiautomated to facilitate measurements. Results are presented onn‐ andp‐type silicon.

ISSN:0034-6748    

DOI:10.1063/1.1137581

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A simple device has been designed to measure continuously and reproducibly the amount of the shape recovery related to the two‐way shape memory effect in specimens undergoing thermal cycling. Using this device, it is possible to follow the dimensional changes of the specimens, to record the exact temperatures where shape changes occur, and to evaluate the amount of hysteresis involved with the shape recovery phenomenon.

ISSN:0034-6748    

DOI:10.1063/1.1137582

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A low‐cost digital system based on an 8‐bit Apple II microcomputer has been designed to provide on‐line control, data acquisition, and evaluation of sound absorption measurements in gases. The measurements are conducted in a resonant tube, in which an acoustical standing wave is excited, the excitation removed, and the sound absorption evaluated from the free decay envelope. The free decay is initiated from the computer keyboard after the standing wave is established, and the microphone response signal is the source of the analog signal for the A/D converter. The acquisition software is written inassemblylanguage and the evaluation software inbasic. This paper describes the acoustical measurement, hardware, software, and system performance and presents measurements of sound absorption in air as an example.

ISSN:0034-6748    

DOI:10.1063/1.1137583

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A device for automatic control of pressure in an ion‐atom scattering experiment has been constructed. The system was modeled to achieve the minimum time for transition from one pressure to another. The pressure controller ‘‘learns’’ the system response and iterates the parameters used in ‘‘profiling’’ the valve voltage to reduce the transition time. The device has been used with two different scattering chambers and has worked well with both.

ISSN:0034-6748    

DOI:10.1063/1.1137584

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A new type of ion source with axial extraction, based on hollow‐cathode magnetron discharge, has been developed. Constant hydrogen ion currents in excess of 1 mA with an exit source aperture of 1 mm in diameter and accelerating voltages up to 3 kV, have been extracted axially from the cylindrical hollow cathode. Similar results have been obtained with helium, argon, and nitrogen plasmas.

ISSN:0034-6748    

DOI:10.1063/1.1137585

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The diffuse reflectance of a 60GeO2–2OZnO–2OK2O glass plate was measured to be 0.13% at 10.6 &mgr;m, which is ideally small for use in power meters to compare with other absorbers such as gold black. The specular reflectance was also measured to be less than 0.01%.

ISSN:0034-6748    

DOI:10.1063/1.1137569

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A design for an unclamped high‐pressure window made from polycrystalline sodium chloride is presented. The window was used to pass an 80‐W cw CO2laser beam into a pressure chamber operating at pressures from 0.1 to 14 MPa.

ISSN:0034-6748    

DOI:10.1063/1.1137570

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A matched, slow wave transmission line is used as a current probe. It provides a linear response, fast rise time (&tgr;r<2 ns) and high‐voltage gain (&bartil;1 V/A) for current pulses up to microsecond duration.

ISSN:0034-6748    

DOI:10.1063/1.1137571

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A device for direct transfer of filtered liquids to volumetric flasks has been modified to improve time savings and simplify operational procedures.

ISSN:0034-6748    

DOI:10.1063/1.1137572

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Optical cells which maintain both constant diameter and constant internal mass during pressurization also maintain constant molar cross section (moles/cm2). In the recent article of le Noble and Schlott, ‘‘All quartz optical cell of constant diameter for use in high pressure studies,’’ the authors erroneously assume that the diameter of their constant internal mass, syringe‐type cell is constant during pressurization [W. J. le Noble and R. Schlott, Rev. Sci. Instrum.47, 770–771 (1976)]. In contrast to the authors’ principal conclusion, cell corrections are required in using the cell of their design. The corrections required to compensate for pressure‐induced variations of molar cross section allow accurate employment of le Noble and Schlotts’ useful cell design.

ISSN:0034-6748    

DOI:10.1063/1.1137574

出版商:AIP    

年代:1984

数据来源: AIP