摘要:

We present a review of the recently developed microminiature, Joule–Thomson cryogenic refrigerators. These extremely small devices are finding wide scale use in instrumentation and as coolers for the study of materials. They have recently become available through the development of a novel, low‐cost photolithographic fabrication process. We present the essentials of heat exchanger design, upon which the refrigerators are critically dependent, discuss the fabrication process, and review some of the present applications and limitations of the refrigerators, together with possible future application for cooling SQUID devices.

ISSN:0034-6748    

DOI:10.1063/1.1137820

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

H−ions produced by volume processes have been extracted from a multicusp source operated with a magnetic filter and accelerated to form a high‐quality beam. It was found that the H−beam current increased almost linearly with the discharge current. An H−ion current density of 38 mA/cm2was obtained with a discharge current of approximately 350 A. The accelerated beam was mass analyzed and the emittance of the H−component was measured. The electron component and the percentage of ion impurity in the extracted beam were also determined.

ISSN:0034-6748    

DOI:10.1063/1.1137821

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

This paper describes some details and results of an active neutral beam diagnostic mounted on the WEGA Tokamak and used in conjunction with a single‐channel neutral particle energy analyzer. The beam diagnostic permits temporal resolution over a 40‐ms interval of the Tokamak discharge during which lower hybrid heating is applied. The central ion temperature was measured to be 270 eV before heating and 340 eV during 178 kW of heating. In addition, the central neutral atom density was deduced from experimental results to be (1.5±1)×1014m−3using this active measurement technique. The relative efficiency of the charge‐exchange analyzer measured using the active beam is in good agreement with independent calibration.

ISSN:0034-6748    

DOI:10.1063/1.1137822

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Two electron‐spectrometer systems designed for electron–electron coincidence spectroscopy are described. One, based on two hemispherical analyzers and x‐ray excitation, is especially suited for Auger‐photoelectron coincidence spectroscopy (APECS) of solids and surfaces. The other, using a cylindrical mirror analyzer, a hemispherical analyzer, and electron‐beam excitation is designed for near‐dipole (e, 2e) spectroscopy of gaseous samples. Typical results obtained with these instruments are presented.

ISSN:0034-6748    

DOI:10.1063/1.1137823

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A simple spectrometer is described for directly measuring both a high electric field (0.1–100 kV/cm) and wavelength over a broadband (0.1–10 cm). The combination of interference and gas breakdown are utilized in measuring the electric field and wavelength. Electron diffusion and the characteristic breakdown relation limit resolution of submillimeter wavelengths by requiring very high electric field (>100 kV/cm).

ISSN:0034-6748    

DOI:10.1063/1.1137824

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Surface fluctuation spectroscopy is a dynamic light scattering technique which involves the detection of thermal fluctuations (capillary waves) that cover every liquid interface. The advantages of this technique over conventional mechanical methods are discussed. The signal resolution and precision are improved by using a grating heterodyne technique coupled with a digital correlator. Detailed calculations showed that, for the measured power spectrum (the Fourier transform of the correlation function) to take the Lorentzian shape, it is necessary that certain optical conditions be met. These conditions are demonstrated with experimental data collected for ethanol at the ambient temperature as a function of the wave number. Once the optical parameters are adjusted correctly, the experimental results show excellent agreement with the literature values. We have also demonstrated that, using microcomputer technology, the entire system can be automated. The instrument is easy to operate and can be used either for research purposes or on a routine basis. The implication of this instrument as a powerful analytical tool for a wide spectrum of liquid interfaces is also discussed.

ISSN:0034-6748    

DOI:10.1063/1.1137825

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

We comment on several aspects of the light scattering technology that have been developed in our laboratory. In particular we show that Shih’s [Rev. Sci. Instrum.55, XXX (1984)] data is consistent once beam propagation is taken into account fully and a small error in the grating constants corrected. The result is that we can make a stronger statement concerning the correspondence between theory and experiment for both the center frequency and width of the spectrum of capillary wave fluctuations at the liquid/vapor interface. We discuss questions of optimal design of the optical system and detection system for these measurements. We collect a set of dimensionless groups that are useful for the design of experiments.

ISSN:0034-6748    

DOI:10.1063/1.1137826

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The design, construction, and performance of a stable temperature controller specifically built for surface studies is described. The controller can be operated either manually as an independent unit or automatically while interfaced to a digital signal analyzer, a computer, or an external programmer. Problems arising from the magnetic field generated by sample heating current are eliminated, allowing detailed studies of surface phenomena by electron spectroscopies over a wide range of temperatures and electron energies.

ISSN:0034-6748    

DOI:10.1063/1.1137827

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A 64‐channel correlator is designed with application to the processing of laser Doppler anemometry signals in the range 200 Hz to 250 kHz. The correlator is processor operated to enable the consecutive sampling of 448 correlation functions at a rate up to 500 Hz. Software is described to identify a Doppler frequency from each correlation and the system is especially designed for transient flow signals. Doppler frequencies are determined with an accuracy of about 0.1%.

ISSN:0034-6748    

DOI:10.1063/1.1137808

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Equations have been developed which allow the design of coils for Faraday rotators. It is shown that the sensitivity of rotation of the plane of polarization to the ampere turns of the coil is a function of ratios of coil dimensions. Equations and graphs are presented which allow the design to be optimized with respect to the power dissipated in the coil or to the temperature rise of the coil. It is shown that disk‐shaped coils are inefficient as rotators.

ISSN:0034-6748    

DOI:10.1063/1.1137809

出版商:AIP    

年代:1984

数据来源: AIP