摘要:

This paper describes experiments performed to measure the noise characteristics of a helium‐neon laser as a function of discharge characteristics. The discharge properties were varied by changing the pressure and current over a wide range of values. The effect of cold vs hot cathodes on the noise characteristics was also measured. Optimum regions are obtained where the laser has low noise characteristics. A large amount of data is included on noise bandwidth, laser power output as a function of pressure and current, discharge impedance characteristics, etc.

ISSN:0034-6748    

DOI:10.1063/1.1683772

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Measurements of the transverse (sample currentInormal to magnetic fieldH) and longitudinal (I∥H) magnetoresistance of110, ⅛, and ¼ W Allen‐Bradley carbon resistors were performed at various temperatures between 1.8 and 18 K in static magnetic fields up to 150 kG. Eleven different resistors having nominal values at room temperature of 47, 100, and 220 &OHgr; were investigated. A description is given of a new technique which was devised to perform these measurements. The magnetoresistance of Allen‐Bradley resistors is small, reproducible, and can be estimated from measurements on other resistors of the same nominal value. These resistors are useful, therefore, as thermometers in intense magnetic fields at low temperatures. A comparison is made between different empirical equations which have been used in attempts to fit the data. In addition, different methods are described for determining the temperatureTand sensitivityR−1(∂R/∂T)Hfrom the magnetoresistance data.

ISSN:0034-6748    

DOI:10.1063/1.1683773

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Accurate identification of atomic species in the atom probe FIM requires a highly shielded tip assembly, as well as a revision of the equation formerly used to compute them/nratios. Voltage reflections on the unterminated pulse transmission line cause the actual evaporation pulse at the tip to be greater than the applied pulse by a ``pulse factor'' &agr;. In addition, the recorded flight time of the ion under investigation differs from the actual flight time by a constant electronic time delay &dgr;. Using either of two single isotope calibration techniques, both &agr; and &dgr; can be determined. For a shielded tip assembly either technique gives a value of &agr;=2.00±0.05 and a value of &dgr;=0.06±0.02 &mgr;sec. Typical absolute mass determination using these values of &agr; and &dgr; is within ±0.6 amu atm/n=20, and ±1.6 amu atm/n=100. When masses near a known species, like hydrogen‐ or helium‐metal molecular ions, are to be detected, the practical resolution reaches ±0.2 amu at the middle of the mass range.

ISSN:0034-6748    

DOI:10.1063/1.1683774

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A new apparatus for the continuous measurement of creep at high temperatures up to 1200°C is described. The apparatus is designed specifically for testing fine wire and thin tubular samples with small cross sectional areas. A unique application of the apparatus is for the creep testing of dispersion strengthened alloys where void formation and spheroidization may be monitored. The actual test procedure is presented.

ISSN:0034-6748    

DOI:10.1063/1.1683775

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Beam intensities of 1014particles·cm−2·sec−1are measured by a torsion balance with an accuracy of 3%. The sensitivity of the balance is 21.1 rad/dyne. In a dynamic mode the sensitivity can be increased by a factor of about 50. Accommodation coefficients need not be known.

ISSN:0034-6748    

DOI:10.1063/1.1683776

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A data collection system has been developed to improve the accuracy of ir reflectivity measurements. A programmed sequence controller is used with an integrating digital voltmeter to sample the detector output of a spectrometer and to control the rotation of a sample holder. The digitized output is recorded on punched cards for computer analysis. The use of this system reduces the time required for the collection and reduction of data.

ISSN:0034-6748    

DOI:10.1063/1.1683777

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A cosmic dust sensor comprising a unique array of sensors, sensor controls, and in‐flight calibrations was placed in a heliocentric orbit (0.99 to 1.088 a.u.) on 13 December 1967 on board the Pioneer 8 satellite. The ionization and momentum imparted by the impact of a cosmic dust particle upon a surface are measured by the sensor and used to determine the particle's direction, speed, and mass. Prelaunch calibration studies using the Goddard Space Flight Center electrostatic accelerator have shown that the sensors can measure kinetic energies of impacting particles as low as 0.6 ergs and momenta as low as 2×10−5dynes·sec.

ISSN:0034-6748    

DOI:10.1063/1.1683778

出版商:AIP    

年代:1969

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1683779

出版商:AIP    

年代:1969

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1683780

出版商:AIP    

年代:1969

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1683781

出版商:AIP    

年代:1969

数据来源: AIP