摘要:

Determination of the spectral density of plasma waves from the cross‐power density spectrum is shown to be simpler than the alternative determination from the cross‐correlation function. A device for measuring the cross‐power spectral density is described in detail. A model with a bandwidth of 30 MHz has been constructed using integrated circuits, and applied to the study of ion acoustic wave propagation on a plasma positive column. Since it is an analog device, it should be possible to extend the bandwidth for operation into the gigahertz range. Only a fixed delay is required to measure the quadrature component of the cross‐power spectral density. These features are in contrast to other correlators and cross‐power spectrum analyzers described to date, which are either limited to the low megahertz range, or require a variable delay line.

ISSN:0034-6748    

DOI:10.1063/1.1686491

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A phase‐sensitive pulse counting method, which shows considerable promise as a signal processing technique for modulated beam mass spectrometry, is presented. This method allows near‐simultaneous monitoring of mass peaks of interest by fast mass spectrometer scanning, while retaining the advantages of phase‐sensitive detection. The electronic system and the molecular beam apparatus are described, and mass spectrometric results for supersonic water vapor beams, obtained with the system, are presented and discussed.

ISSN:0034-6748    

DOI:10.1063/1.1686492

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

This paper describes a volumetric adsorption system and measurement procedure which takes advantage of current vacuum technology and computational techniques, to determine adsorption isotherms and adsorption thermodynamics under ultraclean conditions with high accuracy, over a wide range of temperatures and pressures.

ISSN:0034-6748    

DOI:10.1063/1.1686493

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A contour plotter has been designed to display the sensitivity uniformity of photocathodes in quantized format on the Z axis of an oscilloscope. An optical scanner, synchronously driven by the oscilloscope X‐Y deflection signals is used to raster scan the photocathode with a focused light beam. Sensitivity, resolution, and scanning time are sufficient to use the plotter to monitor sequential processing steps for photocathodes in demountable, ultrahigh vacuum systems. A general description of the contour plotter system and a detailed circuit description are given. An example relating to cesium uniformity on a III‐V photocathode is presented to illustrate the use of the contour plotter.

ISSN:0034-6748    

DOI:10.1063/1.1686494

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A new instrument for the determination of fine temperature profiles in hot, corrosive, electrically conductive, unsteady two‐phase fluid systems under vacuum or pressure is described. It features simultaneous measurement of temperatures at close locations, by a column of miniature (0.25 mm diam) thermistors mounted at the tips of supporting hypodermic tubes, and streamlined design that minimizes hydrodynamic and thermal disturbances at the measured locations. Some of the techniques used in the construction, such as the welding, insulation, and handling of fine wires (0.025 mm diam), are of interest in many other applications. The instrument has been used to measure temperature distributions with an accuracy of ±0.02°C in a model of a flash‐evaporator stage used for the desalination of saline water, and thus provided new and quantitatively significant data about the process.

ISSN:0034-6748    

DOI:10.1063/1.1686495

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Improvement of irradiance profile uniformity by choosing only a limited, central region of a laser beam is frequently used. The associated transmitted power loss is computed in dimensionless form for general utility. For example, a factor of 3 improvement in uniformity at the outer beam radius can be achieved with only about 35% power loss.

ISSN:0034-6748    

DOI:10.1063/1.1686496

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The positron detection efficiency of a Spiraltron is determined using a conventional two‐gamma coincidence detection system as a reference. Under the experimental conditions described in this note, the efficiency of the Spiraltron is found to be nearly 90%, as compared to an ∼2% efficiency of the two‐gamma system employed in our laboratory.

ISSN:0034-6748    

DOI:10.1063/1.1686497

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Details are given of a Littrow‐mounted grating spectrometer which uses a cooled linear array of silicon diodes as a detector (0.4–1.1 &mgr;) and an Erfle eyepiece as collimator/camera. The slit is illuminated by a standard 35 mm camera lens. Analog diode output signals are multiplexed, digitized, and either recorded on magnetic tape for later processing or signal‐averaged by a small on‐line computer, then recorded on magnetic tape, and displayed on an oscilloscope. Test data are presented. The device has no moving parts, is competitive with existing devices based on photomultipliers and television cameras, and can be readily modified to increase the number of channels and improve wavelength and spatial resolution and throughput.

ISSN:0034-6748    

DOI:10.1063/1.1686498

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

An economical technique for maintaining pressures up to 100 kilobar in a volume of 10 mm3at temperatures of 4.2 K and lower is discussed together with its application in resistivity measurements and Mo¨ssbauer spectroscopy. Modifications for the use in optical spectroscopy and for studies including external magnetic fields are indicated.

ISSN:0034-6748    

DOI:10.1063/1.1686499

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Double beam spectrophotometers are commonly used in chemical analysis and transmittance measurements. With some modifications, the function of such instruments can be enlarged to measure the optical surface roughness and surface slopes of any roughened material. Results obtained using a modified Perkin‐Elmer 621 double beam spectrophotometer are presented for stainless steel 304.

ISSN:0034-6748    

DOI:10.1063/1.1686500

出版商:AIP    

年代:1974

数据来源: AIP