摘要:

A system for producing 300‐&mgr;sec bursts of 1017metal atoms with 3‐eV average energy is described. It is shown that this system can be successfully used to introduce impurities into CTR‐oriented tokamaks for transport and confinement studies.

ISSN:0034-6748    

DOI:10.1063/1.1134432

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A vacuum diode with a rear‐mounted Pilot‐B scintillator has been coupled with a conventional evacuated pinhole camera. The cathode of the diode is fabricated from 2‐&mgr; thick polycarbonate (Kimfol) with a 200‐A˚ aluminum layer on the rear surface. Incident photons with energies above the carbonKedge (284 eV) are highly absorbed in the polycarbonate, but photons with energies below theKedge are absorbed in the aluminum and produce photoelectrons. This yields a photoelectron sensitivity which is peaked at approximately 275 eV. The photoelectrons are accelerated by a 10‐kV cathode potential to an aluminum anode coating on the scintillator, and scintillation photons are observed with an image converter camera. Streak photographs of exploded‐wire x–uv radiation taken with this system are presented.

ISSN:0034-6748    

DOI:10.1063/1.1134433

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The plasma‐cathode electron gun is a new type of electron source which is suitable for applications requiring a large area, high‐energy electron beam. It employs a plasma generated within a cold low‐voltage, hollow‐cathode discharge as the source of electrons. Plasma cathode devices are characterized by their simplicity and versatility, and they offer a number of advantages over other designs. An electron gun producing a beam with dimensions of 5×125 cm has been developed for use with high‐power cw gas lasers. This device has been operated at beam energies of 150 keV and cw beam current densities of 0.1–0.2 mA/cm2.

ISSN:0034-6748    

DOI:10.1063/1.1134434

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

An approximate analytical model of the transient response of a circular foil heat‐flux gauge to a step change in incident radiant heat flux is described. This model demonstrates that the sensitivity and the transient response of the gauge are significantly affected by heat flow from the foil to the center lead wire. Results obtained for the transient response to a step change in incident radiant flux from the model agree closely with experimental results from several gauges with different sensitivities. Convolution of the present model and previous exponential models of the unit step response, with a transient incident flux represented by a terminal ramp, shows that the response predicted by a previous exponential model differs significantly from that predicted by the present model.

ISSN:0034-6748    

DOI:10.1063/1.1134435

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A new interferometric technique has been developed for measuring the amplitude of very small ac displacements. The technique, utilizing a spherical Fabry–Perot interferometer, is more sensitive and less susceptible to acoustic vibrations than previous methods. We have used this technique to measure displacements as small as 4×10−4A˚, and the theoretical sensitivity in a well‐isolated environment is about 10−5A˚.

ISSN:0034-6748    

DOI:10.1063/1.1134436

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

An apparatus is described which allows the preparation of transmission electron microscopy specimens at specified depths of the order of 1 &mgr; below the initial surface of the specimen. The instrument is designed for electropolishing of the surface withinsitumeasurements by optical interference of the depth of material removed. The depth of the electropolish may be determined to an accuracy of approximately ±500 A˚, and high‐quality specimens may be easily prepared.

ISSN:0034-6748    

DOI:10.1063/1.1134430

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Modern weighing practice consists of making comparisons between the gravitational attractive forces exerted on standard and unknown weights. An effect coupling the gravitational force exerted on a weight to the height of the weight’s center of gravity above its base has been found to be significant when weighings of the highest precision are attempted. This effect will cause systematic errors in mass measurements if not properly accounted for. The effect, called the ’’gravitational configuration effect,’’ arises because the centers of gravity of nominally equal weights above their bases, and hence the weights’ effective distances from the center of the Earth, are affected by the weights’ size and shape. Variations of 1 cm in the separation between the centers of gravity of weights and the center of the Earth produce differences in gravitational attractions of 3.14 parts in 109. Currently, mass comparisons at the 1‐kg level can be carried out with standard deviations as small as 1.5 parts in 109. Thus, the gravitational configuration effect must be considered if weighing accuracies approaching weighing precisions are to be obtained when kilogram weights of significantly different sizes and/or shapes are compared. Corrections for the gravitational configuration effect can readily be combined with corrections for better‐known effects, such as air buoyancy, to generate an overall equation to express the results of mass comparisons.

ISSN:0034-6748    

DOI:10.1063/1.1134431

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The low‐temperature behavior of carbon‐glass thermometers in intense magnetic fields is described. At 15 T, the field‐induced error is 0.3 K at 4.2 K and 0.08 K at 2.1 K. An empirical equation is presented which fits the positive magnetoresistance data to better than 0.1% in the liquid‐helium range. No significant (<0.1%) orientation dependence was found at either 4.2 or 77 K.

ISSN:0034-6748    

DOI:10.1063/1.1134437

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A versatile appearance potential spectrometer has been developed to detect photons and electrons, emitted during electron bombardment, for determining the binding energies of the electrons of surface atoms. Primary currents down to 50 &mgr;A yield good signals for the detection of electrons. Furthermore, the detection of desorbed ions can be used for measuring the threshold energy of ion emission. A special preamplifier is used for a high signal‐to‐noise ratio.

ISSN:0034-6748    

DOI:10.1063/1.1134438

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The specific heatcof Evanohm resistance wire has been measured to bec=0.037+0.333TJ⋅kg−1⋅K−1between 0.15 and 1.5 K. The thermal conductivity &lgr; of Evanohm is given by &lgr;=0.020T+0.048T2W⋅m−1⋅K−1in the same temperature range. These results are compared with similar measurements for constantan, manganin, Nichrome, and a platinum–tungsten alloy. The electrical and magnetic properties of these materials are also reviewed.

ISSN:0034-6748    

DOI:10.1063/1.1134439

出版商:AIP    

年代:1975

数据来源: AIP