摘要:

A susceptometer, based on various properties of superconductors, has been developed. It makes possible the resolution of differences in magnetic susceptibility of less than 1% of the diamagnetism of water, in the whole temperature interval between liquid helium temperature and room temperature, on sample volumes of about 0.1 cm3. Two prototypes are presently in routine operation for measurements on solutions, suspensions, powders, and crystals.

ISSN:0034-6748    

DOI:10.1063/1.1134483

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

We describe a rocket‐borne instrument for measurement of the low energy electron and proton distribution function in the magnetosphere. It consists of an optimized programmable electrostatic toroidal analyzer as an energy selector, coupled with an electron multiplier as a particle detector, and of the associated electronics. Much attention has been paid to the experimental calibration of the instrument which gives us some understanding of the real behavior of the detector and the way it influences the analyzer properties.

ISSN:0034-6748    

DOI:10.1063/1.1134494

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A new crossed‐beam apparatus for the study of ion–molecule collision processes is described. Among the novel features of this apparatus are a high pressure ’’chemical ionization’’ ion source, an apertureless exponential ion deceleration lens, a product ion mass/energy analyzer that can be scanned in angle through nearly a full octant of a sphere, and a supersonic nozzle molecular beam source. The high pressure source can be used to produce vibrationally relaxed ground state reactant ions, and the deceleration lens produces focused ion beams with energies as low as 0.1 eV at intensities equal to the space‐charge limit.

ISSN:0034-6748    

DOI:10.1063/1.1134474

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Quantitative evaluations of the noise reduction and signal deformation that are produced in parabolic smoothing are obtained, and their utilization for the optimization of smoothing is discussed. These results ensue from a general method of analysis of smoothing procedures that was developed in a previous paper. As a by‐product a new smoothing method is developed. It has practically the same properties as the parabolic one, but smoothing is achieved with a notable reduction in the number of operations required.

ISSN:0034-6748    

DOI:10.1063/1.1134484

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The object of this method of design is the determination of the smoothing weighting function wf. This approach makes it possible to base the design on minimum total error (signal deformation plus noise) evaluated at every or at any characteristic important point of the experimental signal. In a previous analysis classes of weighting function were defined. In the present paper the optimum wf of each class is calculated. These are universal functions and in the design only the width of the weighting function (the averaging interval) must be determined. The optimum width is calculated as a function ofaprioriinformation on the signal and the noise. Also, the precision with which this information is required is calculated. Examples of design of experimental signal smoothing are developed.

ISSN:0034-6748    

DOI:10.1063/1.1134485

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A straightforward dc circuit has been built for the precise regulation and accurate measurement of the total incident beam current in an elastic low‐energy electron diffraction (ELEED) apparatus. It functions simply by comparing the returning ground current to a reference current and optically coupling the result to control the filament‐to‐Wehnelt cylinder potential difference. Beam currents down to 0.1 &mgr;A are regulated to within 1% at sweep rates up to 8 v/sec and energy ranges up to 200 eV wide. An additional useful feature is the ability to monitor and null out any leakage or displacement currents without confusion with the true beam current.

ISSN:0034-6748    

DOI:10.1063/1.1134486

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A manipulator is described which supplies two independent, orthogonal rotational motions to both a crystal and a Faraday cup (FC) integrally mounted on the same ultrahigh vacuum flange. Three translational and two tilting motions are also applied to the combined crystal–Faraday cup assembly. Following a description of the motions and their derivation, the results of tests for any interactions between the motions are briefly presented. Lastly, the additional features incorporated for retrieval of the FC signal and the self‐consistent stray magnetic field trimming and crystal‐incident beam alignment are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1134487

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The areal detection efficiency of a channel electron multiplier array (CEMA) and the nature of its secondary emission surface were investigated with the ion microprobe mass analyzer (IMMA). Previous speculations of detection efficiency based on simple geometric arguments of channel‐to‐interchannel area ratios are shown to be in error. With a positive bias applied to a front electrode surface of high secondary yield, areal detection efficiency of a CEMA may approach 100% even for single‐ion impacts. The secondary emission properties of a CEMA are shown to be determined by an alkali‐rich surface layer on each channel wall, and not a concentration of Pb or PbO as previously thought. Both reversible and irreversible gain degradation observed when heating a CEMA in vacuum are interpreted as a change in the composition of this layer.

ISSN:0034-6748    

DOI:10.1063/1.1134488

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The shape of the paraboloidal reflector surface is determined by making a large number of measurements of the reflector curvature along several radii of the surface. These measures of curvature are then integrated twice to give the reflector profile along each radius; the results from several radii then allow the reflector surface shape to be mapped in three dimensions. The curvature measurements are made by a three‐wheeled cart with a depth sensor resting on the surface at the midpoint of the wheels. Tests of the method on an 11 m diam antenna show an average repeatability of 0.037 mm in the measurement of the shape of the parabolic reflector.

ISSN:0034-6748    

DOI:10.1063/1.1134489

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

We describe a tunable Fabry–Perot type filter which has application to radio astronomy in the frequency band 80–110 GHz. The filter causes image sideband suppression when used with a heterodyne spectral line receiver having an intermediate frequency of 4.75 GHz. The transmission loss in the signal sideband is about 0.4 dB, while the image sideband rejection is more than 15 dB; there appears to be little if any problem with scattering or distortion of the antenna radiation pattern.

ISSN:0034-6748    

DOI:10.1063/1.1134490

出版商:AIP    

年代:1976

数据来源: AIP