摘要:

There have been several designs proposed for bimodal transmission resonators for use in EPR, Hall effect, and Faraday rotation measurements. Some of these are based on attempts to spatially define the field patterns of the normal modes of cylindrically symmetric resonators. Others try to separate the modes so that in some parts of the resonator, the radio frequency fields of predominantly one mode will be found. In this way, independent adjustment of the mode characteristics is attempted so that an adjustable null transmission resonator results. The property to be measured for a sample placed inside the resonator causes an imbalance and the resulting output appears in place of the null. This paper describes a different approach to the practical realization of such a resonator and gives the appropriate theory for its operation. In the resonator to be described the spatial position of the normal modes can be altered by a simple rotation control, and the input radio frequency field polarization direction can be rotated by another such control. There is a direct analogy between microwave propagation through this device and optical propagation through an anisotropic medium situated before an analyzer. The complete cavity resonator shows a minimum rejection in transmission which can be made arbitrarily large, and a tunable rejection notch whose attenuation has been observed to be greater than 100 dB, and which is theoretically infinite. A practical nonresonant device based on the same approach is also described.

ISSN:0034-6748    

DOI:10.1063/1.1686072

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Two oversized TE01ncavity resonator systems have been constructed that are suitable for measuring the complex permittivity &egr;=&egr;′ (1 −jtan&dgr;) of low loss liquids at millimeter wavelengths. One of them operates at frequencies from 26 to 70 GHz, while the second, which is described in detail, was tested at frequencies around 136 GHz where a quality factor of about 60 000 was obtained. &egr;′ is determined from the wavelengths measured in the filled and unfilled resonator. The loss factor tan&dgr; is obtained from the half‐widths of the resonance curves in both resonator states. For that purpose, the frequency of the oscillator is swept, and the resonance curves vs frequency are displayed on an oscilloscope. Frequency calibration marks are generated by the absorption resonances of a second long open resonator operating in the HE11mdipole mode which is guided by a thin dielectric thread. To restrict the influence of traces of water in the liquids to be measured, the resonator is permanently connected to an apparatus that permits drying the liquids and filling and emptying the resonator without contact with atmospheric moisture. By this method, the complex permittivity at 136 GHz of seven nonpolar liquids (tan&dgr;=3×10−4−30×10−4) has been determined. Insofar as possible the data are compared with published values.

ISSN:0034-6748    

DOI:10.1063/1.1686073

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A two electrode discharge system for use in TEA carbon dioxide lasers is described. Stabilization of the discharge against the formation of spark channels is achieved through the use of resistive composition electrodes. These provide a series ballast resistance preventing the negative dynamic resistance of the plasma from leading to spark formation. Energy depositions of up to 300 J/liter have been achieved in a lasing mixture without spark channels forming.

ISSN:0034-6748    

DOI:10.1063/1.1686074

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The difficulty of obtaining accurate calibrations of electrostatic analyzers employing large aperture channel electron multipliers is discussed. This is due primarily to the varying efficiency of large aperture multipliers depending on point and angle of impact on the aperture. This varying response makes the assignment of an over‐all detector efficiency uncertain by at least a factor of 2. A laboratory calibration scheme is discussed by which the combined efficiency and geometry factor is obtained for flight detectors using a simulated omnidirectional source of particles.

ISSN:0034-6748    

DOI:10.1063/1.1686075

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A near semiconfocal Fabry‐Perot resonator has been integrated with a small chemical laser to permit detection of ground and excited vibrational state rotational transitions of the reaction products within the laser cavity without perturbing the laser system. The effective lifetimes of unstable gas‐phase species can also be followed by monitoring the maximum value of the absorption coefficient.

ISSN:0034-6748    

DOI:10.1063/1.1686076

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A prototype standard mercury manometer using a fringe counting laser interferometer to measure the differential height of the mercury columns has been built and successfully operated. The 10.6 &mgr; wavelength radiation from a CO2laser and specially treated manometer tubes have been used to reduce the effect of disturbances on the mercury surface so that reliable operation of the manometer is possible.

ISSN:0034-6748    

DOI:10.1063/1.1686077

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

We have developed a spectrometer for studying secondary‐electron yields from ion‐to‐electron converter dynodes. Ions, formed by surface ionization, are mass‐analyzed in a small double‐focusing mass spectrometer which is followed by a post‐accelerating lens to increase the kinetic energy of the ions to ∼30 keV before they strike an ion‐converter dynode. The ion‐converter dynode is a flat, narrow strip positioned along the the axis of rotational symmetry of a cylindrical lens and is rotatable about this axis. Secondary electrons are emitted from the thin‐film oxide surface of the converter dynode. They are accelerated to ∼30 keV in the cylindrical lens and are focused onto a silicon solid state detector for pulse‐height analysis of the secondary‐electron spectrum. Idividual secondary‐electron groups containing 1,2,3,…, etc., electrons are resolved and recorded in a 400‐channel pulse‐height analyzer. Deconvolution of the resulting energy spectrum gives precise estimates of secondary electron yields for monatomic or polyatomic ions of different mass, atomic number, energy, and angle of entry. Experimental results are given for thin films of oxidized aluminum, plasma‐anodized aluminum, and for an activated beryllium‐copper surface. Our results support the hypothesis that the Poisson distribution represents the minimum statistical variance (most sharply peaked distribution) that is physically attainable for secondary electron emission from an ion‐converter dynode.

ISSN:0034-6748    

DOI:10.1063/1.1686078

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Bloch equations are solved in amplitude modulation of the rf field, and it is shown how the saturation can be put to use in obtaining a new kind of detection. A practical realization of a saturation effect spectrometer is given and some experimental results shown.

ISSN:0034-6748    

DOI:10.1063/1.1686079

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A rapid field scan apparatus for use with ESR detection of transients produced by flash photolysis is described. Design data and test results are presented.

ISSN:0034-6748    

DOI:10.1063/1.1686080

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The quasistatic technique used to obtain MOS capacitance voltage characteristics and interface‐state density is finding increased use. While the basic technique has been described, it is felt that a detailed description of the apparatus setup and measurement technique will prove useful. This technique allows the rapid evaluation of MOS properties with accuracy of about 1 × 1010states/cm2eV near midgap. Experimental considerations such as MOS geometry, sweep rate, stray light, and series resistance, and their influence on the resultingC‐Vcharacteristic, are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1686081

出版商:AIP    

年代:1973

数据来源: AIP