摘要:

A high‐speed rotation instrument to produce centrifugal fields greater than 100 million times gravity has been constructed. Small, solid, spherical high‐carbon chromium steel rotors are suspended magnetically in high vacuum and spun by a rotating magnetic field. It is found that the spinning rotor explodes when the calculated average value of stress in the meridian plane reaches about 1.2 times the tensile strength of the material. The maximum speed of rotation so far achieved for more than a few days without bursting was obtained with a rotor of 1.50 mm diameter. The speed of 2.11×105rev/s corresponded to a centrifugal field of 1.34×108times gravity. Our instrument will find application in the study of nuclear atomic phenomena.

ISSN:0034-6748    

DOI:10.1063/1.1135955

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A practical, easily constructed design for a laboratory hydrogen/deuterium halide chemical TEA laser is presented. Typical output energies in excess of 50 mJ/pulse broadband and 5 mJ/pulse on single lines are easily obtained. Isotopically specific oscillation on thev=1→0 band of single isotopes of H35Cl–H37Cl, D35Cl–D37Cl, H79Br–H81Br, and D79Br–D81Br is demonstrated. The ease of conversion from one laser species to the next and the flexible design provide a highly versatile device for laboratory problems in chemical and physical dynamics. Major advances in the development of laboratory HCl and HBr chemical TEA lasers are also reviewed.

ISSN:0034-6748    

DOI:10.1063/1.1135956

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A new instrument is described for measuring concentrations of submicrometer particulates with diameters ranging from 0.005 to 1.0 &mgr;m and concentrations as low as 750 particles per cm3at small diameters and 25 particles per cm3at the larger diameters. Developed by the Bureau of Mines, the instrument is capable of obtaining size distributions of the sampled particulates using an electrical mobility classification which requires voltages of less than 1000 V over the entire size range. The instrument is normally operated by 115 V ac, but it contains an internal rechargeable battery pack for up to 25 h of continuous dc operation. It has been designed primarily as an incipient fire detector, but can be used as a suspended particulate monitor and size analyzer or as a laboratory instrument for studying combustion aerosols. Representative data are presented, indicating potential uses of the instrument.

ISSN:0034-6748    

DOI:10.1063/1.1135957

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The design and operation of a helium‐gas‐driven gun capable of operation to Mach one is described in this report. The gun utilizes a unique tapered‐tube decelerator that captures the sabot and prevents gas discharge from the muzzle. This feature makes it possible to operate the gun in a normal laboratory environment without excessive safety precautions.

ISSN:0034-6748    

DOI:10.1063/1.1135958

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The practical limitation on sensitivity in broad‐line NMR is frequently spurious effects on the baseline rather than the masking of the signal by thermal noise. I discuss some of the causes of spurious baseline effects and describe a simple circuit used to reduce them by a factor of 300.

ISSN:0034-6748    

DOI:10.1063/1.1135959

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

An improved portable optical counter, using a He–Ne laser with 8 mW output, measures particles ranging in size from 0.06 to 10 &mgr;m in diameterinsitu.

ISSN:0034-6748    

DOI:10.1063/1.1135960

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Both the area thermal expansion and the dielectric constant of a solid insulator are determined by a capacitance technique in which the change in area of a capacitor is first caused by the variation with temperature of the dimensions of the dielectric, and then by the variation over the same temperature range of the dimensions of copper electrodes, the same sample being used in both cases. This method is particularly convenient for small, flat crystals under hydrostatic pressure and for anisotropic crystals. It is believed that a similar method could be used to measure the compressibility. The apparatus and calculations are described, and the results of a test run on the thermal expansion of NaCl are compared with previous data. Between 77 and 250 K, the measured linear thermal expansionL(T)/L(300) of NaCl agrees with the results of a Fabry–Perot etalon experiment to within 0.03%, giving differences in the coefficient of linear expansion of 10% in the worst case.

ISSN:0034-6748    

DOI:10.1063/1.1135961

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A cw Mach Zehnder multichannel interferometer has been developed to measure time‐dependent fractional fringe shifts with an accuracy of one‐fortieth fringe. The design is quasi‐quadrature in that known phase shifts, introduced in the reference beam, are time multiplexed with the normal reference beam. This technique requires only one detector per interferometer channel as compared to two detectors for most quadrature designs. The quadrature information makes the sense of density changes unambiguous, it automatically calibrates the instrument during the plasma event, and it makes fringe shift measurements virtually independent of fringe contrast fluctuations caused by plasma refractive and/or absorptive effects. The interferometer optical design is novel in that the electro‐optic crystal used to introduce the 90° phase shifts is located in the common 2‐mm‐diam HeNe entrance beam to the interferometer, by exploiting polarization techniques, rather than in the expanded 1–2‐cm reference beam itself. This arrangement greatly reduces the size, cost, and high‐voltage requirements for the phase modulating crystal.

ISSN:0034-6748    

DOI:10.1063/1.1135935

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

An apparatus is described for investigating theinsitucreep behavior of materials during irradiation with neutrons having a spectrum similar to that of a fusion power reactor. Techniques are discussed for remote, high‐vacuum creep testing during irradiation with high‐energy neutrons from a planar Be(d,n) source used on the 1.93‐m Isochronous Cyclotron at the University of California at Davis. Significant effects of radiation damage on the creep of niobium at a flux of 2×1016n⋅m−2 s−1are reported.

ISSN:0034-6748    

DOI:10.1063/1.1135936

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

We have constructed a torsional resonance apparatus for contact‐free measurements of the electrical conductivity of solids. Owing to its use of modulation spectroscopy, the technique achieves considerable enhancement of sensitivity compared to previous contactless methods. Conductivities in the range 10−5mho/cm to 10−6mho/cm can now be measured by the contactless technique. Measurements of magnetic susceptibility as low as 10−12can be made. This sensitivity allows for investigation of magnetic impurities as dilute as 1 part in 107. In samples which display both phenomena of electrical conductivity and magnetic susceptibility, the two effects can be sorted out via analysis of frequency and/or temperature dependence. The present apparatus has potential for considerable improvement.

ISSN:0034-6748    

DOI:10.1063/1.1135937

出版商:AIP    

年代:1979

数据来源: AIP