摘要:

A bubble chamber designed to operate with 500 visible liters of liquid hydrogen has been tested for performance with liquid nitrogen at Argonne National Laboratory. It features unique systems for controlling chamber overpressure and minimizing thermal gradients within the working liquid. Refrigeration requirements were determined for the full range of operating conditions from static to expansion‐pulsing at a rate of 3/sec at intervals ranging from 333 msec down to 125 msec.

ISSN:0034-6748    

DOI:10.1063/1.1683959

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A special purpose analog computer is described for calculating the second moment of the NMR absorption spectrum drawn out by a wide‐line spectrometer with an integrating phase‐sensitive detector (PSD). An experimental check on NH4Cl yielded a mean second moment within 1% of a previous value, and a standard error over 50 observations of 2%. The integrating PSD enabled these spectra to be recorded over 100‐sec sweeps with a signal‐to‐noise ratio comparable to that obtained using conventional techniques with sweep times at least an order of magnitude longer.

ISSN:0034-6748    

DOI:10.1063/1.1683960

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A research type, inert atmosphere vacuum glove box of stainless steel construction is described. The apparatus is suitable for a wide range of chemical and metallurgical applications as well as for physical property measurements on reactive samples. The design features a gas purification and recirculation system, automatic moisture monitoring system, and automatic pressure control system. A stereomicroscope with a long working distance to facilitate examination and experimentation on samples within the chamber is mounted over the chamber window. The vacuum glove box was designed to give a routine working environment of less than 1 ppm water and oxygen in argon. Mass spectrometric analysis on random samples of gas from the chamber has confirmed the operational efficiency of the apparatus.

ISSN:0034-6748    

DOI:10.1063/1.1683961

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

An apparatus and a technique for measuring electrical resistivities on reactive samples are described. Measurements were made in an inert atmosphere vacuum glove box containing a high purity helium environment. A precision micromanipulator was used to position a four point probe while observation was made through a microscope to guide the positioning of the probe. A cold stage permitted measurements to be made from room to liquid nitrogen temperature. This method was used to measure the electrical resistivities of cerium hydride single crystals.

ISSN:0034-6748    

DOI:10.1063/1.1683962

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

An apparatus has been developed for the study of the influence of applied electric fields and currents on solid state diffusion of impurities in semiconductors. Special features of the apparatus are simple procedures, versatility, and allowance for determination of impurity profiles.

ISSN:0034-6748    

DOI:10.1063/1.1683963

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A scanning electron diffraction attachment providing for energy analysis of the scattered electrons has been constructed for use in conjunction with a J.E.M. 6AS electron microscope. This attachment permits the direct recording of diffracted electron intensities as a function of angle with an accuracy of ±0.1%. The attachment can be operated to exclude all but the elastically diffracted electrons, or, alternatively, to detect electrons with a measurable amount of energy loss. The electrostatic energy analyzer has an energy cutoff of better than 1.1 eV out of 100 keV. The angular resolution of the instrument is presently 2.2×10−4rad, with minimum detectable electron intensity of 10−14A. The instrument performance is demonstrated by studying the effect of inelastic scattering in the diffraction pattern of aluminum, and by recording the plasma loss spectrum of aluminum. The filtered profiles have narrower peaks than the unfiltered ones and better peak resolution, and the contrast between peaks and background is enhanced. At low values of the scattering vector where the inelastic background is very intense, its removal reveals diffraction effects which otherwise would have been invisible. The attachment does not interfere with the conventional plate microscopy and diffraction, and provides, thereby, a method of energy analyzing the direct microscope image as well.

ISSN:0034-6748    

DOI:10.1063/1.1683964

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A high‐pressure high‐temperature x‐ray powder diffraction apparatus has been developed based on a modification of the belt apparatus, which is an internally heated compressible gasket device. The unique feature of this device is that the die‐support ring assembly is fabricated in two parts which mate along a plane normal to the piston axis. The split‐die design permits entry of the x‐ray beam into the high‐pressure volume and egress of both the diffracted rays and the undeviated beam through suitable grooves and fan‐shaped slots ground in the mating surfaces. The high‐pressure x‐ray windows are either a beryllium ring with a wedge‐shaped cross section or epoxy resin stops at the bore of the die. The high‐pressure medium is ``amorphous'' boron, and the sample is in the form of a thin cylinder which is coaxial with the pistons and normal to the x‐ray beam. The compressible gaskets between the pistons and the die are made of pyrophyllite, as they are in conventional devices, inasmuch as they are not part of the x‐ray path. High sample temperatures are attained by resistance heating of carbon rods adjacent to the sample. Present limitations on pressure and temperature are 100 kilobars and 1000°C. High‐intensity Mo K&agr;radiation is employed. The apparatus is portable and may be positioned on a conventional x‐ray source.

ISSN:0034-6748    

DOI:10.1063/1.1683965

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A method for determining the speed distribution and density of a molecular beam from time‐domain measurements of propagated beam perturbations is examined. Algebraic relations between the moments of the measured time‐of‐flight signal, of the speed‐distribution function, of the modulator gate function, and of the dynamic function of the detector and its electronics are derived. By extracting a sufficient number of moments, one can characterize any speed‐distribution function to any desired accuracy. For use in applications, moments and recursion relations of a general class of speed‐distribution functions and moments of some typical gate functions are developed. Sufficient conditions for approximating a rectangular gate function by an impulsive gate function are presented. An application to time‐of‐flight measurements in an arc‐heated supersonic molecular beam illustrates the use of the general method and emphasizes the need to consider the characteristic time of the gate function and the dynamic response functions of the detector and its electronics when interpreting time‐of‐flight signals.

ISSN:0034-6748    

DOI:10.1063/1.1683966

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Various combinations of noble gases are experimentally investigated to help improve the triggering stability of pulsed ion lasers. The results of these tests show that a 1:1 ratio of Ne&sngbnd;Ar stabilizes the triggering, but gas separation limits the repetition rate. Tests on He&sngbnd;Ar show that 15 &mgr; of Ar combined with 15 to 100 &mgr; of He produced triggering stability with no obvious detrimental effects at pulse rates up to 1000 Hz. Both mixtures displayed 25% power loss with respect to the optimum pure argon laser output.

ISSN:0034-6748    

DOI:10.1063/1.1683967

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A gauge for the measurement of the density variation in a shock wave is described. It is based on the absorption of low energy beta radiation from an169Er source. The gauge was used to study the density variation through the contact zone between the expansion chamber gas and the driver gas of a valve driven shock tube. Comparisons are made between the measured density and that calculated from pressure measurements in terms of the initial condition of the test and the driver gases. There are significant differences between these densities due to mixing of the two gases in the contact zone.

ISSN:0034-6748    

DOI:10.1063/1.1683968

出版商:AIP    

年代:1969

数据来源: AIP