摘要:

A laboratory apparatus and experimental techniques have been developed to investigate the properties of a 5–30 keV electron beam fluorescence probe system in air, nitrogen, and helium test gases over a pressure range from 10−3to 10 Torr at 302 K. The design and performance characteristics of the electron beam generating system and optical detector system are described. The electron beam system used in this work was especially designed for wind tunnel remote measurements of local gas density in low density high velocity flow fields. A 1 mm diam collimated beam of 5–30 keV electrons was used to irradiate each of the test gases and excite fluorescence radiation, specifically the 391.44 nm (0,0) First negative band ofN2+in air and nitrogen, and the 501.57 nm (21S–31P) He line in helium. A precision optical detector system has been designed and used to observe the spatial distribution and pressure dependence of this fluorescence radiation excited by the electron beam. Calibration and test procedures have been implemented to reduce significantly experimental errors and provide relative fluorescence intensity measurements with a precision better than ±2%. Typical results are presented and discussed which illustrate data obtained using the developed apparatus and test procedures.

ISSN:0034-6748    

DOI:10.1063/1.1686136

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Charge state yield data for the production of Ar ion beams from a Penning ion source have been previously analyzed by Fuchs. These data have been reanalyzed in calculations which take into account the Auger process at any level of ionization, electron recombination, and charge state dependent and independent losses. For a wide range of simple two‐energy electron distributions, and for a discrete approximation to a distribution of thermalized electrons plus a Gaussian distribution of primary electrons, fits can be obtained which are as much as two orders of magnitude better for Ar9+and even more improved for 10+. The fitting parameters all lie near &agr; [inverted lazy s] 10−8for the recombination rate coefficient and &tgr; [inverted lazy s] 1 &mgr;sec for ion lifetime for an electron density of 3×1014/cm3The contribution to the rate of change of charge state populationqidue to electron recombination is assumed to be (&rgr;eqii2&agr;), where &rgr;eis the electron density. The Auger effect is included as a 2‐electron process for most of the calculations. The estimated cross sections for Auger effects are derived similarly to those used in a feasibility study of electron beam sources of very heavy, highly ionized beams.

ISSN:0034-6748    

DOI:10.1063/1.1686137

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A polarizing microscope is described, in which solid state samples can be cooled down to liquid‐helium temperatures and can be observed with a resolution of the order of 1 &mgr;. By means of this microscope and thin magneto‐optical EuS/EuF2films, the intermediate state in type‐I‐superconducting films of lead and tin could be resolved for the first time.

ISSN:0034-6748    

DOI:10.1063/1.1686138

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A sampling linear detector is described which has been developed for measuring one‐shot free precession amplitudes at 1.5 MHz in a pulsed NMR experiment. A 10−3accuracy is achieved over a 30 dB dynamic range with a 60 &mgr;sec gate aperture time. The rectifying circuit is made up of two low threshold hot carrier diodes placed in the feedback loop of a fast operational amplifier. A bias voltage technique is employed for further linearization. Commercial integrated circuits and operational amplifiers are used throughout and make layout and wiring noncritical. Checking and calibration prodedures, as well as circuit operation, are carefully analyzed.

ISSN:0034-6748    

DOI:10.1063/1.1686139

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A four‐channel solid state rf driver, which can provide the complex sequences of rf pulses necessary for recently developed pulse and Fourier transform nuclear magnetic resonance (NMR) experiments, is described. Suitable for use over a wide frequency range, the device features a high ratio of carrier suppression, accurate control of the rf phase in four separate channels, and a 100% duty cycle. The use of gated rf phase shifters allows considerable simplification in design and results in the need for but one rf gate.

ISSN:0034-6748    

DOI:10.1063/1.1686140

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A facility to determine work function changes was developed in a display‐type Varian 120 LEED‐Auger apparatus, using the electron beam retarding potential technique. Using the known work function value of a reference material that is atomically clean, as verified by Auger electron spectroscopy, the average work function of other materials of interest can be evaluated.

ISSN:0034-6748    

DOI:10.1063/1.1686141

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A low resolution scanning multiple Fabry‐Perot spectrometer has been built for the observation of very weak extended light sources. The instrument consists of three sets of 7.6 cm diam Fabry‐Perot plates operated in central order; their spacings are in a 3–4–5 ratio and are servo controlled using reference light provided by a single master grating monochromator. The instrument is scanned by varying the wavelength setting on the grating instrument. The resolution of the instrument is variable through the range 0.5–15 A, and its luminosity is equal to that of a 5 cm interference filter with a 65% peak transmittance. The free spectral range is about 125 times the peak half‐width. Wavelengths in that range are transmitted at a level of 10−4or less of the central transmission peak.

ISSN:0034-6748    

DOI:10.1063/1.1686142

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The dead time of a channel plate has been regarded so far as an inevitable defect in many applications; however, it is pointed out in this paper that it can be considered as the memory time during which the input image is stored. Line drawing, moving object detection, and inversion of images were performed by an experimental preprocessor using the dead time characteristics. The device should be recognized as a two‐dimensional operator with no scanning and without an electronic computer. The features of the device are very high‐speed operation and high sensitivity for dark images.

ISSN:0034-6748    

DOI:10.1063/1.1686143

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Simple analytic formulas that can be used to design a finite width uniform‐field electrode for any desired aspect ratio and field uniformity are derived. The resulting profile is superior to those of Rogowski, Bruce, and Harrison in its smoothness, compactness, and field uniformity. A procedure for designing a three‐dimensional profile is also given.

ISSN:0034-6748    

DOI:10.1063/1.1686144

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An electric field measuring equipment with a capacitive probe of 40 &mgr; resolution was constructed using only ordinary materials and techniques. The operation of this equipment was completely automatic and the electric field profiles were recorded continuously by anx‐yrecorder. The duration of one measurement, consisting typically of the recording of about 50 profiles and of the sample current vs time diagram, in 4 mm long samples, was [inverted lazy s] 50 min. The usefulness of this equipment has been proven through its use for the observation of a large number of new electric field domain formations in photoconducting CdS samples. The detailed description of these observations will be reported elsewhere.

ISSN:0034-6748    

DOI:10.1063/1.1686145

出版商:AIP    

年代:1973

数据来源: AIP