摘要:

A new method for the measurement of gas adsorption at high pressure is described in detail. The method is based on dielectric virial coefficients and it takes advantage of the dielectric technique for the accurate measurement of the compressibility factor of gases at high pressure. The method is simple, self‐sufficient, easy to use, and permits precise measurement of the density of nonideal gases. Adsorption measurements of methane on BPL‐activated carbon as a function of pressure at 25 °C are reported.

ISSN:0034-6748    

DOI:10.1063/1.1139336

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We describe a new ultrahigh‐vacuum facility which is being used for studies of solid surfaces. The target chamber is attached via a differentially pumped beamline to a 2‐MV Van de Graaff accelerator, and includes: (1) instrumentation for high‐energy ion backscattering and channeling studies and nuclear reaction analysis, (2) a 100‐mm radius hemispherical analyzer for photoemission studies, and (3) low‐energy electron diffraction (LEED) optics.

ISSN:0034-6748    

DOI:10.1063/1.1139337

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We have designed and constructed a vacuum heat treatment facility, with hot zone dimensions of 12×19×19 cm, at a cost substantially below that of a commercial unit. The design incorporates efficient water cooling and a resistive heating element. A vacuum pressure of 1.5×10−8Torr at room temperature has been obtained after baking. The temperature limit is approximately 1900 °C. This limit results from our choice of niobium as the hot zone material.

ISSN:0034-6748    

DOI:10.1063/1.1139338

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A high‐pressure cell and manipulator mounted inside an UHV surface analysis chamber has been built which can reach 1800 psi. With this apparatus, catalytic reactions on small surface area (∼1 cm2) single crystals and polycrystalline surfaces are monitored, and the effect of reactant pressure, surface composition, and surface structure are correlated with catalytic activity. This article describes in detail the apparatus and typical experimental procedure.

ISSN:0034-6748    

DOI:10.1063/1.1139339

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A closed‐cycle refrigerator/cryostat system for use in ultrasonic studies of electron irradiation damaged bulk specimens is described. The closed‐cycle refrigerator provides a convenient means for long‐term (several days) sample irradiation at low temperatures. A neon filled ‘‘thermal diode’’ is employed to permit efficient cooling, via liquid helium, of the sample below the base temperature of the refrigerator.

ISSN:0034-6748    

DOI:10.1063/1.1139340

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We describe a photon‐counting readout system for microchannel‐plate spectrometers that uses a delay line and timing circuit for the wavelength coordinate and a wedge–wedge charge division system for the orthogonal spatial coordinate. A novel zigzag layout allows these two anode patterns to coexist on a common planar substrate and share the charge from each photoevent, thereby simultaneously localizing the photon in each of its two dimensions. Unlike wedge‐and‐strip or resistive anode encoders, the delay line offers a spatial resolution that is relatively independent of the format length. Unlike discrete anode systems, the delay line readout system’s complexity is also independent of the field of view size. These facts make the delay line readout system advantageous in large format detectors. We have assembled a testbed detector having a delay line propagation speed of 2.2 mm/ns and a time resolution of 33 ps FWHM. Ultraviolet testing shows a Gaussian event distribution having a 70 &mgr;m FWHM width; the readout system blur contribution is less than 50 &mgr;m FWHM.

ISSN:0034-6748    

DOI:10.1063/1.1139341

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

An improved design of the vertically oscillating buoy viscometer with real‐time computer control, evaluation, and plotting is presented. In this method, the optically observed phase lag of the buoy relative to a sinusoidal driving force is a direct and absolute measure of viscosity. Construction features of the new version improve reassembly precision and give three‐axis positioning of the sphere, as well as an 80‐fold improvement in the signal‐to‐noise ratio for small amplitudes of the buoy motion. Design of the ‘‘crossed coil’’ system is discussed and the magnetic and mechanical faults which lead to various kinds of motional instability are considered. Boundary layer corrections are now computer corrected as are temperature variations. The evaluation of ‘‘intrinsic viscosity’’ as a measure of molecular ellipticity is discussed and one measurement set is presented.

ISSN:0034-6748    

DOI:10.1063/1.1139342

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Generally, surfactants contain trace impurities that will falsify their adsorption properties enormously. To carry out reliable experiments with surfactant solutions necessitates removing those trace impurities beforehand. A programmed apparatus for removing surface‐active trace impurities from surfactant solutions has been constructed and tested. It takes advantage of the contaminants’ stronger surface activity and considerably lower content in comparison with the main surfactant component. Surface‐active material of the solution to be purified is allowed to adsorb at its surface. After considerable reduction of the solution surface area, the adsorbed material is sucked off from the surface in a definite manner by using a fine capillary. The single operating steps are repeated periodically and automatically until the solution reaches the state of ‘‘surface chemical purity.’’ The apparatus can be utilized for a wide range of different conditions given by the individual surfactant properties simply by changing the operating parameters. The instrument favorably and effectively provides that peculiar grade of surfactant purity necessary for all kinds of fundamental surfactant research and characterization.

ISSN:0034-6748    

DOI:10.1063/1.1139343

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The two‐dimensional electrostatic modeling capability of the ANSYS finite element program is used in the design of the coax‐to‐parallel plate microwave transformer. Its two‐dimensional axisymmetric capability is used in the design of a laser‐triggered coaxial Blumlein spark gap. Finally, its three‐dimensional magnetic modeling ability is used to model a large dipole magnet (the Chicago cyclotron magnet). The results of the calculations compare well with measurements for two of the above cases.

ISSN:0034-6748    

DOI:10.1063/1.1139344

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

This article describes the development of an automated microprocessor‐based data‐acquisition system and, in particular, the use of an inexpensive microcomputer to automate an acoustic experiment. Specifically, it explains the use of a Motorola MC6801 in the single‐chip mode to control a rather complex experimental process. The system is configured to provide for automated, two‐dimensional data acquisition of ultrasonic transmissibility through a specimen surface. Results to evaluate the accuracy and the performance of the system with known analytical predictions will be presented.

ISSN:0034-6748    

DOI:10.1063/1.1139345

出版商:AIP    

年代:1987

数据来源: AIP