摘要:

Automatic data acquisition is by means of a slightly modified version of a hard‐wired system described previously (Martin and Snowdon, 1970) combined with an on‐line minicomputer which controls the calorimeter heating rate and computes temperature and specific heat. The new cryostat, calorimeter assembly, and adiabatic shield control are briefly described. Experiments to verify the accuracy of germanium thermometry with the automatic ac bridge are detailed. Operation of the system is illustrated by results on pure copper which show a standard deviation of 0.3% (mostly due to temperature scale defects rather than inherent lack of precision) and agree well with the Copper Reference Equation below 20 K but above this temperature agree more closely with the results of Cetas, Tilford, and Swenson[Phys. Rev. 174, 835 (1968)].

ISSN:0034-6748    

DOI:10.1063/1.1686220

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A rocket instrument has been designed for the determination of nighttime atmospheric densities by means of resonant scattering. By illuminating the atmosphere with an intense parallel beam of light at the resonant wavelength of an atmospheric gas and observing the back scattering, it is possible to determine either relative or absolute atmospheric densities. In particular, the measurement of atomic hydrogen densities from 70 to 110 km will be considered.

ISSN:0034-6748    

DOI:10.1063/1.1686221

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

In this paper a tester is described which can be used to determine the linearity and fatigue in photomultipliers. Using this device, we have shown how to find the optimum arrangement of voltages to be applied to the dynodes of the photomultipliers to give linearity over the greatest possible range. When perfect linearity cannot be achieved, we have described a method which may be used to correct measured results for the lack of linearity. Detailed results are given for the 1P28 photomultiplier, but most of the ideas can similarly be applied to the other types.

ISSN:0034-6748    

DOI:10.1063/1.1686222

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The introduction of a precision, inductive, decade ratio transformer to serve as a voltage divider together with voltage followers permits one to construct a 4‐terminal ac bridge with an accuracy of better than 0.001%. Such a bridge is particularly suitable for accurate (0.003%) low‐temperature Ge resistance thermometry. This bridge also makes possible the direct intercomparison of different Ge resistance thermometers, thus allowing a direct and therefore more accurate determination of temperature gradients.

ISSN:0034-6748    

DOI:10.1063/1.1686223

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Apparatus is described that permits measurement of the electrical transport properties of semiconductors with resistance values over 1012&OHgr;. The system utilizes a guarded approach to the van der Pauw method which simplifies sample geometry and contacting and permits evaluation of thin layers. The equipment is easy to operate, reliable, and constructed of readily available commercially purchased components.

ISSN:0034-6748    

DOI:10.1063/1.1686224

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The pulsed electron gun described in this paper is of simple construction and is intended for use in studies of ionization and excitation in high pressure gases. It employs a high‐voltage discharge in helium gas and emits a 50 mm diam beam of 100 keV electrons through a titanium foil window, the transmitted pulse having an energy of approximately 1 J. The use of a coaxial discharge circuit results in a pulse duration of the order of 100 nsec. Graphs are presented showing the performance as a function of the voltage applied to the gun and of the gas pressure in the discharge region. It was found that adjustment of this pressure over the range 1–40 Pa varied the pulse duration from 300–30 nsec.

ISSN:0034-6748    

DOI:10.1063/1.1686225

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An electronic servo system has been developed to perform theI0&Dgr;R /I0Rdivision in modulation spectroscopy measurements, which is operable under variable extraneous incident light intensity. Response faster than that of the mechanical servo system is easily achieved in the electronic servo system.

ISSN:0034-6748    

DOI:10.1063/1.1686226

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A rugged silver‐silver chloride electrode has been developed and used successfully in a variety of field applications. The electrode housing is made of 2.54 cm o.d. clear acrylic plastic rod. The filling solution is 2.7Mpotassium chloride saturated with silver chloride, and contact with the external medium is made through a porous ceramic rod. Results of laboratory and field tests measuring the response of the electrode to chemical, thermal, mechanical, and electrical disturbances are presented.

ISSN:0034-6748    

DOI:10.1063/1.1686227

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

In this paper is described a circuit that has been developed for recording fast single electronic events. The single event signal is sampled with a time resolution of 2 nsec and stored in a memory bank after all the samples have been digitized.

ISSN:0034-6748    

DOI:10.1063/1.1686228

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Use of the time‐of‐flight (TOF) technique in molecular beam applications is reviewed. If the peak signal height and the hydrodynamic flow time are used as the normalization quantities, then a convenient dimensionless TOF signal is obtained in a double‐convolutional integral form which involves threedimensionless functions: the molecular beam speed distribution function, the chopper gate function, and thedynamic function of the detector and its electronics. The latter two functions are characterized,respectively, by the dimensionless characteristic timesT˜and &tgr;˜e. Numerical examples demonstratedistortions of TOF signals caused by these characteristic times and errors made in analyzing TOF signalswhen not taking into account the effects ofT˜and &tgr;˜e. The orders of magnitudes ofT˜and &tgr;˜eare notnegligible; therefore, their effects should be treated in TOF signal data reductions.

ISSN:0034-6748    

DOI:10.1063/1.1686229

出版商:AIP    

年代:1973

数据来源: AIP