摘要:

Development work on charging and acceleration of microparticles gives promise of a micrometeoroid simulator capable of producing velocities well into the meteoric range. Velocities up to 7 km/sec have been attained with highly charged micron‐size diamond particles with a 70‐kV accelerating voltage. Single particles electrodynamically contained in a high vacuum are charged positively by an ion current to give charge‐to‐mass ratios approaching 400 C/kg. Once charged, the particle is extracted from the containing field and accelerated by a high potential. Preliminary work on charging microparticles of other materials demonstrates the possibility of producing high charge‐to‐mass ratios on many substances by this technique.

ISSN:0034-6748    

DOI:10.1063/1.1718171

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The temperature vs time curve of a cooling or heating incandescent material is displayed either on a cathode ray oscilloscope or a strip chart recorder. Temperatures at which phase transitions occur are seen as discontinuities in the curves. The temperature‐sensing device is a photomultiplier tube. The sample is heated in an eddy current concentrator by induced radio‐frequency currents. Light from the sample is divided by a beam splitter between the phototube and an optical pyrometer which is used for temperature calibration. The temperature range displayed for a fixed starting temperature may be reduced by opposing the phototube's output voltage with an adjustable fixed voltage. Typical cooling curves are included.

ISSN:0034-6748    

DOI:10.1063/1.1718172

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A previous paper by the authors [Rev. Sci. Instr.33, 1429 (1962)] described an instrument which relates magnetization vector position in a thin film to rf mixing behavior under a crossed‐wire probe. The instrument permits nondestructive observation of small areas of the film and affords high angular resolution. This paper describes provisions for automatically indicating and recording the magnetization angle as the film is traversed by the probe. These provisions extend considerably the usefulness of the instrument in studies of film behavior and uniformity.

ISSN:0034-6748    

DOI:10.1063/1.1718173

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Anomalously high residual collector current is observed with a Bayard‐Alpert ionization gauge after the gauge has been exposed to a relatively high pressure gas which will chemisorb on the grid of the gauge. The evidence indicates that the principal portion of the anomalous residual current results from the subsequent release of the adsorbed species as high velocity ions. A small fraction of the fast ions collide with the collector resulting in a positive charge flow from the grid to the collector which is pressure independent. The more strongly chemisorbed gases are found to replace those which have been previously adsorbed. Oxygen results in the largest and most persistent anomalous residual current.

ISSN:0034-6748    

DOI:10.1063/1.1718174

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A technique is developed for obtaining the phase space density distribution within the acceptance of a synchrotron if the distribution of the emittance is known. It is shown that the matching of an injector emittance to a synchrotron acceptance depends not only on the phase space boundary but also on the phase space density distribution. The problem of maximizing the charge accepted by a synchrotron with respect to the initial accelerating voltage is considered. Two cases are treated analytically which, while highly idealized, illustrate the general method and give upper and lower bounds on the voltage. A numerical computation is carried out to obtain the optimum synchrotron voltage at injection for a practical synchrotron injection system.

ISSN:0034-6748    

DOI:10.1063/1.1718175

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A resistance‐heated furnace is described in which samples, 3½ in. long by 2½ in. in diameter, can be heated to 2800°C in an atmosphere of purified inert gas or in a vacuum of 3×10−5mm Hg at temperature. Furnace heating elements are four flat sheets of tungsten or tantalum and are easily fabricated. Replacement of these elements and full restoration of vacuum (1×10−7mm Hg for cold furnace) can be accomplished in 1 h.

ISSN:0034-6748    

DOI:10.1063/1.1718176

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Formulas are derived for correcting observed x‐ray line profiles for distortion caused by low specimen absorption coefficient in both the asymmetrical Bragg and Laue cases. In the symmetrical Bragg case (incident and reflected x‐ray beams make equal angles with the specimen surface) the present results reduce to those obtained by Keating and Warren. By making suitable approximations, all of the usual intensity formulas for the Bragg and Laue cases are obtained. It is shown that the absorption corrections for the integrated intensity can be obtained directly from measurements of the background radiation.

ISSN:0034-6748    

DOI:10.1063/1.1718177

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The design of a scanning, single‐crystal, multichannel x‐ray spectrometer for spectrochemical analysis is discussed. This design makes use of two or more sets of reflecting planes in the same crystal, and an individual detector is used for each set of planes. Such an instrument permits the choice of optimum resolution and detection conditions for different spectral regions, without compromising source design and without the introduction of mechanical complexity. It is possible also to scan different portions of the spectrum simultaneously. The features of such an instrument are contrasted with other types of spectrochemical analysis instruments, and some results obtained using such an instrument are described.

ISSN:0034-6748    

DOI:10.1063/1.1718178

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A study of contamination rates in a Hitachi HU‐11 electron microscope under various conditions was made. A decontamination device is described which lowers the contamination rate by more than a factor of two. The construction of this apparatus is such that accessories like a multiaxis tilting stage and specimen tensile straining device can be used concurrently.

ISSN:0034-6748    

DOI:10.1063/1.1718179

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

An inductively heated graphite furnace having a ⅜‐in.‐diam source of blackbody radiation for pyrometer calibration is described. The furnace is fabricated from simple, easily demountable parts and may be operated at 1800°K for 6 h with only infrequent attention; temperatures to 3000°K may be obtained for shorter periods. Source temperatures are stable and are rapidly attained. The time constant is approximately 2½ min. Special atmospheres are not required for furnace operation since graphite oxidation is minimized through furnace design.

ISSN:0034-6748    

DOI:10.1063/1.1718180

出版商:AIP    

年代:1963

数据来源: AIP