摘要:

A near‐infrared, double‐beam, light detection system is described for use with a microspectrophotometer in polarized absorption spectroscopic studies of single crystals. The appartus employs a modulated light source and exhibits high sensitivity with good stability. Its application to a variety of spectroscopic problems has provided accurate spectral recordings with a wide range of linearity in response.

ISSN:0034-6748    

DOI:10.1063/1.1138311

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A magnet configuration has been devised, consisting of two nested coaxial coils with the current in the inner coil circulating in an opposite sense from that in the outer coil. The magnetic field generated by such an opposed pair exhibits a small region of homogeneity outside of the magnet itself, creating the possibility of constructing a unilateral nuclear‐magnetic‐resonance device capable of examining an object from only one side. Calculations on one special case, the inside‐out Helmholtz configuration, indicate a volume of 10 cm3with homogeneity of ±1% for a coil of outer radius 10 cm, and 0.1 cm3with 100‐ppm homogeneity. A second special case, consisting of two sets of opposed solenoids arranged in a quasi‐Helmholtz manner, offers homogeneity comparable to a conventional Helmholtz pair of similar diameter but with an increase in separation of as much as a factor of 2.

ISSN:0034-6748    

DOI:10.1063/1.1138312

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A simple microvibrating sample magnetometer (MVSM), particularly inexpensive, sensitive, and versatile has been developed. An alternating magnetic field superposed to a steady uniform magnetic field is applied to the sample. The sample undergoes a periodic motion around an equilibrium position, causing a pressure fluctuation within a closed gas cell which is detected as an acoustic signal by a microphone.

ISSN:0034-6748    

DOI:10.1063/1.1138313

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

An experiment is described which demonstrates a force between static charges on a metal foil and a large steady electric current in a wire. The observed force vectors cannot be readily explained in terms of diamagnetism, paramagnetism, eddy currents, thermal convection currents, or the Poynting electric field associated with a dc current outside the path of the current.

ISSN:0034-6748    

DOI:10.1063/1.1138314

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A new type of heating specimen holder which allows reflection electron microscopy (REM) imaging with incident and azimuthal angle control is described. A REM image is presented, from a bulk specimen whose surface was preparedinsitu, and shows strong contrasts due to atomic steps.

ISSN:0034-6748    

DOI:10.1063/1.1138315

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A portable thermocouple probe is designed with physical and geometric properties such that its principal performance characteristics can be predicted from relatively uncomplicated mathematical models. Theory and experiment show that usual thermocouple errors and surface‐temperature perturbations can be kept unimportant in a variety of practical applications. Techniques are described for using the probe to measure temperature of stationary and moving materials, including thermal insulating materials and thin sheets where temperature is normally severely perturbed during contact measurements. It is convenient to use the device in combination with a battery‐operated digital readout device, permitting temperatures within a few hundred degrees of ambient to be measured with an accuracy of ±2° and a response speed of about 2 s. The probe is found well suited for use in the heat‐transfer laboratory, in the factory, and in energy‐conservaton field work.

ISSN:0034-6748    

DOI:10.1063/1.1138316

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

We describe here a stable and sensitive temperature controller to be used with resistance thermometers. The temperature resolution provided by this instrument was &Dgr;T&bartil;20 &mgr;K at room temperature and &Dgr;T&bartil;1 &mgr;K at liquid4He temperature.

ISSN:0034-6748    

DOI:10.1063/1.1138317

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A high‐temperature (> 1500 K) containerless calorimeter is described and its usefulness demonstrated. The calorimeter uses the technique of omnidirectional electron bombardment of pendant drops to achieve an isothermal test environment. The small heat input into the sample (i.e., 15–50 W) can be controlled and measured. The apparatus can be used to determine the total hemispherical emissivity, specific heat, heat of fusion, surface tension, and equilibrium melting temperature of small molten drops in the temperature range of 1500 to 3500 K. The total hemispherical emissivity &egr;Tand specific heatCpof pure niobium and two alloys of niobium–germanium have been measured in the temperature range of 1700 to 2400 K. As reported in the literature, &egr;Tvaried as a function of temperature. However,Cpvalues for both the pure metal and alloys seem to be independent of temperature.Cpfor the liquid alloy phase was also measured and compared to the solid phase.

ISSN:0034-6748    

DOI:10.1063/1.1138318

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The construction and performance of a single stage nuclear demagnetization apparatus utilizing 0.267 mole of praseodymium nickel material is described. An optimization procedure to minimize entropy production during the demagnetization of the hyperfine enhanced material has been developed which enabled the cryostat to cool a liquid‐3He sample to a temperature of 350 &mgr;K. The effects of measured heat leaks and inferred eddy‐current heating are accounted for satisfactorily in a model of this procedure.

ISSN:0034-6748    

DOI:10.1063/1.1138319

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A robust plastic third sound resonator has been developed which permits a wide range of experiments to be carried out on superfluid helium films. At room temperature the cell can be filled by diffusion with a wide range of gases including He, Ne, Ar, N2, and CO2to form both substrate and experiment. The highly flexible walls allowinsitupressure measurements with a resolution of 10−6Torr. Third sound can also be detected with capacitor plates within this cell.

ISSN:0034-6748    

DOI:10.1063/1.1138320

出版商:AIP    

年代:1985

数据来源: AIP