摘要:

A distributed amplifier employing a straight wire transmission line is described. The amplifier has a gain of 15±3 db from 10 to 400 Mc, and input and output impedances of 50 &OHgr;. Detailed electrical and mechanical design considerations are included.

ISSN:0034-6748    

DOI:10.1063/1.1716348

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A simple continuous He3refrigerator which uses a minimal amount of gas (80 cc STP) has been built. Temperatures below 0.5°K may be attained for as long as He4remains in the cryostat. Commercial components are used throughout.

ISSN:0034-6748    

DOI:10.1063/1.1716365

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A short section of a wave guide is considered as a nonresonant absorption cell and then as a resonant cavity. It is shown that the latter gives a better signal‐to‐noise ratio by a factor which depends upon the relative intensity of the various noise sources but which increases with theQ. It is shown that the voltage signal‐to‐noise ratio is proportional to the square root of the product of the volume and theQand otherwise is independent of the shape. This result leads to the conclusion that it is possible in theory to build microwave spectrometers having signal‐to‐noise ratios some 50 db larger or capable of detecting absorption coefficients some 300 times smaller than spectrometers which are now widely used. However, practical considerations probably would prevent this advantage from being realized completely. These results are applied to a frequency standard using an absorption line. It is shown that it is possible to build a standard using the 3,3 line of NH3with a fractional stability of about 4×10−12over an extended interval of time. Some discussion of spectrometers with long nonresonant cells is also included.

ISSN:0034-6748    

DOI:10.1063/1.1716366

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The second‐order contamination in the BNL neutron crystal spectrometer is measured for the NaCl(220), NaCl(240), Be(101¯1), and Be(123¯1) reflections over the energy range 0.08 to 5 ev. Reflectivity calculations by Holm for neutrons incident on thin crystals of Be and NaCl are verified experimentally. A method is suggested for rapidly calculating the second‐order fraction of the beam using a simple count rate spectrum and the calculated crystal reflectivities.

ISSN:0034-6748    

DOI:10.1063/1.1716347

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A lowering of the development temperature introduces development defects which are characterized by the partial or total destruction of the developed image and by a deep coloration of the emulsion. These defects are eliminated by increasing the sodium sulfite concentration of the developer. Up to now contrast in nuclear emulsions has been evaluated subjectively by the experimenter; this forbids any comparison of the results obtained in different laboratories.This paper shows that to develop reliably at low temperatures with the usual developers, it becomes necessary to increase the ratio (Na2SO3)/(Amidol). For development temperatures of 10–15°C the concentration ratio needs to be 70% greater than the ones commonly used.A study of track and fog grain properties is carried out. It is shown that at a given temperature the mean gap length is practically independent of the development parameters. The optimum conditions at 14°C are determined with the help of a new quantity termed ``track visibility'' (K), a track to fog signal, and defined byK=blob length×track grain diameter/fog density×(fog grain diameter)2.

ISSN:0034-6748    

DOI:10.1063/1.1716349

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Certain quantitative cytological measurements can be made by the addition of relatively simple components to a television flying‐spot microscope. The flying‐spot system avoids ``distributional errors'' inherent in conventional microphotometry measurements. The microscope has been used to measure the desoxypentose nucleic acid in whole nuclei.

ISSN:0034-6748    

DOI:10.1063/1.1716350

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

This mercury‐capsule light‐pulse generator was developed to test and evaluate the high‐speed features of multiplier phototubes and low‐level image tubes. Light pulses and electrical trigger pulses are generated simultaneously in an arc discharge at a usual repetition rate of 60 per second. The electrical pulse is used as a time reference for the light pulse. The time required for both the light and the electrical pulse to rise from 10 to 90% of peak amplitude is less than 5×10−10sec. The light pulse rises to a maximum and falls to 50% peak amplitude in less than 1.5×10−9sec. The electrical pulse power available is large. Time resolution of 10−10sec is typical of measurements made with conventional fast oscilloscopes, while elaboration of technique permits relative time measurements that are better in some cases by at least three orders of magnitude. The light is emitted from a region a few mils in diameter, and thus may often be considered to come from a point source. An S4 photosurface subtending 0.1 sterad at the light source emits photoelectrically about 107electrons per sterad per pulse. For convenience, three decoupled electrical output channels are provided, together with a Polaroid attenuator for the light pulse.

ISSN:0034-6748    

DOI:10.1063/1.1716351

出版商:AIP    

年代:1959

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1716352

出版商:AIP    

年代:1959

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1716354

出版商:AIP    

年代:1959

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1716356

出版商:AIP    

年代:1959

数据来源: AIP