摘要:

The piezoelectric and mechanical behavior at 79°K of uniaxially strained X‐cut quartz has been experimentally investigated by an impact technique for stresses ranging between 6 and 21 kbar. Knowledge of this behavior is necessary to extend to liquid nitrogen temperature the use of large diameter‐to‐thickness ratio X‐cut quartz disks as submicrosecond gauges for observing stress‐time profiles induced in materials by plane wave shock loading. For stresses up to at least 21 kbar, elastic behavior is observed. The elastic wave velocity and mechanical impedance have constant values of 5.72 mm/&mgr;sec and 152 kbar/mm/(mm/&mgr;sec), respectively, which are within ±1% of 298°K values. From a least squares fit to the data, the piezoelectric factor at 79°K relating current and stress in uniaxial strain depends on stress &sgr;xand is given by (2.11×10−8+5.5×10−11&sgr;x)C/(cm2‐kbar), as compared to (2.01×10−8+1.1×10−10&sgr;x) at 298°K. These expressions are based on 298°K values of the electrode area and thickness of the quartz disk. In the limit of zero stress, there is reasonable agreement between thee11/c11piezoelectric coefficient determined from the 79°K expression and that obtained from low signal resonance measurements. A small apparent increase in the dielectric permittivity with stress is observed at 79°K.

ISSN:0034-6748    

DOI:10.1063/1.1771368

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A slotted disk type velocity selector which transmits a velocity selected beam when rotating in either a clockwise (``forward'') or counterclockwise (``reverse'') sense has been constructed and tested. The selector has two ranges: high velocity (1880 m/sec at 30 000 rpm) with low resolution (19.2%), and low velocity (940 m/sec at 30 000 rpm) with high resolution (7.2%). The calibration of the selector is performed without reference to any of the properties of the molecular beam used in the calibration procedure.

ISSN:0034-6748    

DOI:10.1063/1.1771369

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A description is given of simple modifications of a standard laboratory research microscope which provide it with built‐in parallel, monochromatic plane polarized specimen illumination. The converted microscope has been used, along with a Faraday glass technique, to obtain improved resolution in studies of the intermediate state of superconductors.

ISSN:0034-6748    

DOI:10.1063/1.1771370

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Resistivity of electronic conductors, from metals to semi‐insulators, is determined from the change in grid current of a high frequency oscillator owing to the loading resulting from eddy currents in the sample. The signal appears as a pulse when the sample is dropped through the oscillator tank coil; greater amplification can be used than in previous eddy current methods where the sample was stationary during measurement; thus, higher resistivities can be measured. The samples can be sealed in ampoules and measured at high temperatures and pressures, limited only by the ampoule material. A typical calibration curve, made at 14 Mc and covering the range 10−6&OHgr;‐cm to 108&OHgr;‐cm is given; application to the estimation of sample homogeneity is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1771371

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An instrument designed to measure the degree of anisotropy of the cosmic radiation in the energy range 7.5–90 MeV/nucleon with an accuracy of better than one part in 104is described. The instrument has been flown on the interplanetary spacecraft Pioneer VI and VII, and the in‐flight performance and, in particular, the in‐flight calibration procedures are briefly reviewed.

ISSN:0034-6748    

DOI:10.1063/1.1771372

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1771373

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1771374

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1771375

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1771376

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1771378

出版商:AIP    

年代:1967

数据来源: AIP