摘要:

An apparatus has been designed and constructed which is capable of measuring the adiabatic Joule‐Thomson coefficient &mgr; and the isothermal Joule‐Thomson coefficient &phgr; for gases at low temperatures and high pressures. The apparatus was calibrated with nitrogen gas using pressures as high as 73.82 atm, and temperatures as low as 155.5 K. Furthermore, measurements on three methane‐ethane mixtures were carried out for a temperature range from 206.35 to 274.86 K and a pressure range from 3.37 to 42.24 atm for the adiabatic mode; and a temperature range from 222.22 to 274.70 K, and a pressure range from 3.77 to 62.93 atm for the isothermal mode.

ISSN:0034-6748    

DOI:10.1063/1.1686000

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A device is described that enables rapid measurements of the specific resistivity of powdered semiconductors and metals. The apparatus is especially useful for the screening of a large number of materials as the only sample preparation involved is the pressing of a pellet of the material. The 4‐probe van der Pauw method with pressure contacts is used. Circuits for both ac and dc measurements are given and their relative merits discussed. The cell can be used between 77 and 400 K. A controlled atmosphere can be maintained around the sample.

ISSN:0034-6748    

DOI:10.1063/1.1686001

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The helium cooled mass spectrometer ion source was modified to avoid the formation of a shock in front of it during a supersonic rocket flight. Thus the undisturbed measurement of major and minor atmospheric constituents including reactive species becomes possible in the denser parts of the atmosphere. Two instruments of this kind were extensively tested and calibrated in the laboratory. Mass spectra were obtained from them during two successful rocket flights at altitudes above 83 km.

ISSN:0034-6748    

DOI:10.1063/1.1686002

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A modified helium cooled ion source was operated in supersonic gas flows simulating some conditions of a rocket flight through the upper mesosphere and lower thermosphere. It is shown that the shock in front of this ion source is removed due to the low temperature of the ion source front part and that the mass spectrometer measures the composition of the undisturbed gas flow. Stability and angular dependence of the ion source signal are analyzed. The light emission from the cold ion source in an arc heated supersonic flow is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1686003

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A compact photoionization mass spectrometer utilizing a supersonic molecular beam sampling system is described. Beam intensities of the order of 3 × 1018molecules/sr sec are obtained for CO2. The use of this apparatus with synchrotron radiation is discussed. Results are presented for C2H2and CO2which indicate the usefulness of the nozzle beam with its attendant thermal relaxation for photoionization mass spectrometry studies.

ISSN:0034-6748    

DOI:10.1063/1.1686004

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A data acquisition system consisting of time‐of‐flight scintillation counters, associated electronics, and a PDP‐9 computer was developed and installed for use with the SLAC 40 in. hydrogen bubble chamber (HBC). The system was designed for optimum timing resolution subject to the limitations imposed by the HBC design and was used primarily to determine the momentum of a neutral beam of KL0and neutrons, by measuring time‐of‐flight from a production target to the chamber. The system was also used to trigger the HBC flash only when a low momentum beam particle was recorded. This paper gives the details of the design and operation of the hardware and of the procedures necessary to incorporate the time‐of‐flight information into the more conventional bubble chamber picture analysis.

ISSN:0034-6748    

DOI:10.1063/1.1686005

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A double crystal spectrometer control has been built to precisely measure semiautomatically both the small angles (20″) of refraction suffered by a thermal neutron beam in passing through a prism and, by substitution of a compatible second goniometer element, the large angles due to Bragg reflection of the monochromatic neutron beam. The construction, calibration, and sensitivity are described. With it a value of 4.147(2) fm was found for the neutron scattering amplitude of the silicon nuclear potential.

ISSN:0034-6748    

DOI:10.1063/1.1686006

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Circuitry for a simple and accurate ultrasonic attenuation recording system, for use with the pulse echo technique is described. Direct processing of low level signals and the use of generally available laboratory equipment reduce cost. Sensitivity is enhanced by the use of sufficient zero offset.

ISSN:0034-6748    

DOI:10.1063/1.1686007

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An instrument is described which was designed for precision studies of isothermal diffusion in liquids by optical methods using interference fringes. This optical diffusiometer is described in some detail because it has been found to function exceptionally well for such studies and also because its main components and general design allow it to be adapted to a wide variety of optical measurements and other studies. It is basically a large precision optical bench. An 884 cm long steel beam serves as the rigid base on which are bolted stainless steel dovetail ways which extend along the full length of the beam; the contact surfaces of these ways are straight and flat to about 0.005 cm over their entire length. Riders which support the optical components may be clamped at any position along the 884 cm length of the ways. The riders are designed so that components mounted on them may be centered on and made perpendicular to the optic axis of the instrument. A special measuring rider is used in conjunction with measuring notches cut every 30.48 cm (12 in.) in one edge of the ways in order to determine the position along the ways of any other rider with an accuracy of about 0.002 cm. The entire instrument was designed with special emphasis on versatility, rigidity, precision, ease of adjustment, and freedom from vibration. This instrument permits diffusion coefficients to be measured with a greater precision than has been possible with previous models.

ISSN:0034-6748    

DOI:10.1063/1.1686008

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A light scattering technique to determine the lifetime of longitudinal phonons in the GHz range is described. The method allows one to measure phonon lifetimes between 5 and 1000 nsec and is applicable to transparent media, in which stimulated Brillouin scattering can be generated.

ISSN:0034-6748    

DOI:10.1063/1.1686009

出版商:AIP    

年代:1973

数据来源: AIP