摘要:

This paper describes an instrument which will rapidly and continuously measure raindrop‐size distributions. A slit of light is used as the sensing element of this disdrometer. Electronic circuits analyze information from a phototube and record the number of drops, within certain size ranges, as they fall through the light slit. The disdrometers of other investigators are reviewed, the characteristics of raindrops are listed, and a raindrop‐size distribution recorded by the light slit‐phototube disdrometer is presented. The recorded drop‐size distribution agrees well with the distribution postulated by Laws and Parsons.

ISSN:0034-6748    

DOI:10.1063/1.1717560

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Nanosecond switching of rf power is achieved using a reflex klystron in a nonoscillating state for amplitude modulation. The variation of klystron input admittance with reflector potential is used. A review of reflex klystron theory is presented explaining the technique. Experimental work at X band using a hybrid T to separate reflected power from power incident on the tube shows that flat‐topped rf pulses with rise time of 1.5 nsec and decay time of 6 nsec are possible. Switch ``off'' relative to switch ``on'' attenuation of 30 db was obtained with a reflector voltage swing of 10 v. It is believed that the technique is applicable at any frequency where reflex klystrons are available.

ISSN:0034-6748    

DOI:10.1063/1.1717561

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A cryostat for irradiating at 4.2°K is described. In this device, it is possible to irradiate samples with no intervening foils, to measure at 4.2°K, to study annealingin situto over 100°K, and to achieve recovery beyond 350°K. A sample holder utilizing the high thermal conductivity of copper and sapphire is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1717562

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A small furnace design is described. The furnace is heated by electrical resistance in a refractory metal tube which is surrounded by radiation shields and a water‐cooled housing arranged in a compact assembly. The heater tube can be replaced readily without disassembling the furnace. The furnace can be heated to a temperature of 2200°C or higher in vacuum or nonoxidizing atmosphere.

ISSN:0034-6748    

DOI:10.1063/1.1717563

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

An improved type of continuously sensitive bubble chamber has been constructed. In order to increase the sensitive volume and the sensitive time, the geometrical size and the heating system of the chamber are improved. We have observed that using an organic liquid and carbon dioxide solution as a liquid in the chamber, this chamber is sensitive to fast neutron irradiation.

ISSN:0034-6748    

DOI:10.1063/1.1717564

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The ``Verni‐Ray,'' an instrument using an alpha source and a solid‐state detector in conjunction with a pulse‐height analyzer, has been designed to yield relatively fast topographical mappings of the surface density of thin foils to an accuracy of 5 &mgr;g/cm2.

ISSN:0034-6748    

DOI:10.1063/1.1717565

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The fatigue phenomena of vacuum and gas‐filled cesium‐antimony photocathodes were studied. It is shown that the phototubes can be operated without fatigue at high photocurrent densities, about 90 &mgr;a cm−2, by reducing the temperature rise of the cathode due to high illumination and by lowering the anode voltage to be applied.The photocathodes whose responses ranged from 30 to 60 &mgr;a/lu were used to study the changes of their sensitivities in the following experiments: (a) Effect of intense illumination on the sensitivity; (b) variation in the response by heating at elevated temperatures and (c) relation between the change in photoresponse and the positive potential applied to the anode. The results obtained were as follows: In red radiation the thermal effects dominated, and in blue‐green radiation an effect on the photosensitivity due to the absorption in the cesium anti‐monide film appears. The photoresponse was appreciably reduced when a positive potential above the ionization potential of the gas in the phototubes was applied to the anode. At a very high light level the fatigue phenomena of the cathodes may be caused mainly by the thermal decomposition of cesium antimonides.

ISSN:0034-6748    

DOI:10.1063/1.1717566

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The use of threshold detector foils to measure the external neutron spectrum of two reactors is described. The foils employed are Pu239to measure the total fast flux, U238for the region above 1.5 Mev, S32above 2.5 Mev, and Au197for thermal neutrons. Scintillation counters are used to determine the activity induced in the detectors. The foil‐counting system is calibrated by using a Cockcroft‐Walton accelerator as a fast neutron source. The results indicate a fission‐type spectrum at each reactor.

ISSN:0034-6748    

DOI:10.1063/1.1717567

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The principle of resilient isolation has been employed in the design of a capacity‐type pressure pickup in order to reduce the recording of spurious ringing effects. Continuous operation at high pressures and temperatures is possible. Use of the pickup in engine combustion studies has shown that the natural frequency of 120 kc is sufficient for all but the occasional extremely severe reaction. Frequencies recorded have extended to 430 kc.

ISSN:0034-6748    

DOI:10.1063/1.1717568

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A vacuum furnace is described which possesses the following characteristics: (1) low actual thermal mass, allowing rapid temperature change when desired; (2) high effective thermal mass, resulting in precise temperature control; and (3) minimum gas evolution. In the range 150°–950°C, the maximum temperature deviation is approximately 0.1°C; the mean deviation is less than 0.05°C.

ISSN:0034-6748    

DOI:10.1063/1.1717569

出版商:AIP    

年代:1961

数据来源: AIP