摘要:

Instrumentation has been developed to conduct Brillouin scattering measurements on small (0.15 mm) transparent single crystals at hydrostatic pressures up to 35 kilobars in a gasketed diamond anvil cell. Phonon velocities obtained this way can be used to calculate elastic moduli as a function of pressure. Results of measurements made on NaCl yield zero‐pressure values ofc11=4.82×1011dyn cm−2,c12=1.28×1011dyn cm−2, andc44=1.27×1011dyn cm−2. The plots of the elastic moduli versus pressure are fitted with straight lines with the following slopes: ∂c11/∂P=11.62, ∂c12/∂P=3.05, and ∂c44/∂P=0.759.

ISSN:0034-6748    

DOI:10.1063/1.1134778

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

An apparatus for determining the specific volume of solid and liquid polymers as a function of pressure (to 2200 kg/cm2) and temperature (30–350 °C) has been constructed. It is based on Bridgman’s bellows method and makes use of a linear variable differential transformer (LVDT) mounted outside the pressure vessel to measure the length changes of the bellows. The off‐null output of the LVDT drives a digital indicator, displaying length changes with an accuracy of 0.01 mm, corresponding to a volume change of 10−3cm3. Typical samples weigh about 2 g. Volume changes of the sample are calculated from the bellows displacement using the pvT properties of the confining mercury, and by using a calibration function determined in a separate experiment. This apparatus is capable of measuring specific volume changes of polymers with an accuracy of 0.001–0.002 cm3/g. Results for a commercial polystyrene in the glassy and liquid states are given.

ISSN:0034-6748    

DOI:10.1063/1.1134779

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

An NMR technique capable of yielding measurements of polarization of highly oriented3He gas without appreciably disturbing the state of nuclear orientation is described. The nuclear polarization is determined through a measurement of dispersiveshiftsin the frequency of the NMR oscillator as the magnetic field is swept through resonance, rather than from the magnitude of NMR signals.

ISSN:0034-6748    

DOI:10.1063/1.1134780

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

An electric instrument for testing the piezoelectric properties of crystalline powders is described. The instrument consists of a rf oscillator, frequency modulated at the rate of 150 Hz with deviation of about 2 kHz. The sample is contained in a capacitor of the oscillator tuning circuit. The oscillator frequency is slowly and continuously shifted in a wide range of frequencies. When one of the resonant frequencies of the microcrystal powder belongs to the range of frequencies swept by the oscillator, the sudden fall of the impedance of the tank circuit appears as an amplitude modulation of the rf carrier. This modulation signal detects the piezoelectricity of the sample.

ISSN:0034-6748    

DOI:10.1063/1.1134781

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Filament sources of all alkali metal and thallium ions have been made using 90% Pt–10% Rh gauze coated with natural or synthetic aluminosilicate materials. Details of the material preparation and emitter fabrication techniques are discussed. The various ion emitters are examined as to total emission, impurity emission, and lifetime. A composite emitter capable of simultaneously producing the several ions is presented.

ISSN:0034-6748    

DOI:10.1063/1.1134782

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A stainless steel cell with external heaters, a Cu gasket seal, vacuum brazed Be windows, and a path length of 80 mm allowsinsitucollection of Mo¨ssbauer spectra for absorber wafers at temperatures up to 800 K and reacting or adsorbing gas pressures up to 1.4×105Pa (1.4 atm).

ISSN:0034-6748    

DOI:10.1063/1.1134783

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Ion currents extracted from hot cathode sources may be stabilized by a simple modification of the filament power supply to regulate the emission current. Simultaneous regulation of both current and voltage in an arc discharge is provided.

ISSN:0034-6748    

DOI:10.1063/1.1134784

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Measurements with a novel solid state sensor show the ability to detect surface charge densities smaller than 0.1 nC/cm2with an inherent spatial resolution of less than 50 &mgr;. Surface contact is not required, and the sensing process is nondestructive. These devices may be constructed in arrays using present day semiconductor processing technology.

ISSN:0034-6748    

DOI:10.1063/1.1134785

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

This note describes improvements in the commonly used Gordon coupler used in reflection‐type EPR spectrometers. The improvements permit stable, low noise operation in liquid helium at very low modulation frequencies. At microwave powers as high as 10−2W, the superheterodyne spectrometer noise at 2 Hz is only 2 or 3 times worse than at 100 kHz.

ISSN:0034-6748    

DOI:10.1063/1.1134786

出版商:AIP    

年代:1976

数据来源: AIP