摘要:

A two‐stage apparatus for ultrahigh pressures has been developed. It consists of a pair of Bridgman anvils in a Bundy‐type high compression belt. A normal working pressure for this arrangement is 160 kilobars in the outside belt, which gives around 700 kilobars between both Bridgman anvils or only 500 kilobars if we consider Drickamer's new calibration values. A new calibration point is proposed: ZnS maximum of resistance at 640 or 480 kilobars. The apparatus is capable of reaching pressures far above the last known calibration point of ZnS at 550 or 415 kilobars in a new scale. Attempts to convert graphite to metallic carbon without heating have not been successful.

ISSN:0034-6748    

DOI:10.1063/1.1686033

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The chevron‐shaped channel electron multiplier is a device which combines the high‐gain pulse‐counting operation of single channel electron multipliers with the imaging capabilities of microchannel arrays. It produces charge pulses averaging more than 107electrons and these gain magnitudes fall into a quasi‐Gaussian distribution with a full width at half‐maximum FWHM of approximately 130%. Suppression of ion feedback makes possible both imaging and low noise counting applications over large areas. Dark count rates are typically 1 count/sec cm2, and the dynamic range of operation covers 5–6 decades. Active areas over 45 mm diam have been fabricated, with uniform characteristics. Limiting resolution has been measured at 5 line pairs per millimeter. Because of the short length of each channel electron multiplier, the rise time and width of the output charge pulses are extremely short; large signal pulses have been detected with rise times as short as 400 psec.

ISSN:0034-6748    

DOI:10.1063/1.1686034

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A reasonably uniform cylindrical plasma, 15–20 cm diam, and collisionless for many wave experiments, is generated in fields up to 500 G by applying 200 V of rf at 80 Mc to a fine wire grid stretched across a diameter. Axial containment is provided by opposing sets of &mgr;‐metal strips that gather lines of force and create multimirror fields. Drift waves are inhibited by a short range peripheral alternating shear field, produced by an azimuthal ring of bar magnets. Densities are 108−109ions/cm3in argon with electron temperatures up to 12 eV, with a noise level, &dgr;n / n≈ 3 × 10−3, over the ion acoustic frequency range.

ISSN:0034-6748    

DOI:10.1063/1.1686035

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The application of a superconducting dc ratio transformer to precise resistance ratio measurement at temperatures below 2.2 K is described. Resistors of Si&sngbnd;Cu alloy have been tested for stability under thermal cycling and their load coefficient has been measured. The load coefficient measurements lead to a determination of the combined thermal conductance of the wire insulation and Kapitza thermal boundary conductance.

ISSN:0034-6748    

DOI:10.1063/1.1686036

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A technique is described for time resolving, to nanosecond precision, the velocity distribution of a periodically varying electron beam and for generating a direct plot of the entire phase plane distribution function. Calculations are presented to indicate the maximum time rate‐of‐change of the distribution function which may be accurately observed with this technique. The high‐frequency response obtainable with this technique makes it a powerful diagnostic tool for use in studying the interaction of an electron beam with plasmas and, in particular, the trapping phenomenon in beam‐plasma interactions.

ISSN:0034-6748    

DOI:10.1063/1.1686037

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Response and geometrical factor of a charged particle energy spectrometer are presented. Both a theoretical and an experimental approach are used. A set of two annular curved deflection plates constitutes the energy analyzer of the spectrometer. The analyzer has the features of large geometrical factor, high angular and energy resolution, and small size, which makes it specially well suited for space flight applications.

ISSN:0034-6748    

DOI:10.1063/1.1686038

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A new capacitance method is described for the measurement of local, time‐varying or steady‐state film thickness in two‐phase flow studies. The method is suitable for use in simple and complex geometries, and works for either electrically nonconducting or slightly conducting fluids. Test data were obtained on bubbles of different lengths rising in a circular tube filled with water. Results for film thicknesses and bubble residence times showed good self‐consistency and agreement with other available data.

ISSN:0034-6748    

DOI:10.1063/1.1686039

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A differential photometric ratio system for turbidity measurements is described. The high sensitivity of this instrument permits the measurement of very low densities of bacterial populations suspended in liquid media. The sensitivity is in the range between 104and 106cells/ml in natural aquatic environments.

ISSN:0034-6748    

DOI:10.1063/1.1686040

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A rather simple double beam adapter which makes possible the use of a McPherson model 225 vacuum uv monochromator as a double beam spectrophotometer is described. The principal features of the instrument are a photon counting arrangement resulting in a digital ratio measurement and an analog trace end result.

ISSN:0034-6748    

DOI:10.1063/1.1686041

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A flow system capable of circulating polarized3He gas between a target chamber and an optical pumping volume has been constructed. The two vessels hold the gas at pressures of approximately 760 and 1 Torr, respectively. The circulation unit consists of a reliable Toepler pump and a gas retrieval device made from a heated length of glass capillary tubing with a copper wire insert. Under the conditions of our experiment, the3He gas circulation rate may be varied between 0.50 and 0.15 cc STP min−1.

ISSN:0034-6748    

DOI:10.1063/1.1686042

出版商:AIP    

年代:1973

数据来源: AIP