摘要:

A scintillation counter using pure NaI cooled to liquid nitrogen temperature has been developed. The photopeaks of Co57&ggr; rays (122 kev) and Cs137&ggr; rays (662 kev) were found to have a full width at half‐height of 33% and 14%, respectively. A 7‐inch quartz light pipe was used between scintillator and photomultiplier. The decay time of the fluorescent light was found to be 27 m&mgr;sec. For fast time measurements a time‐to‐pulse‐height converter has been constructed, which operates in the range from 0–100 m&mgr;sec. The converter was used in conjunction with two scintillation counters using plastic (PilotB) scintillators. The time resolution for the detection of annihilation &ggr; rays was found to be 2&tgr;0= 2.3 m&mgr;sec. With one plastic and the cooled NaI scintillator the time resolution was found to be 2&tgr;0= 2.7 m&mgr;sec. The possible factors contributing to the time resolution are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1716321

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A method of using an isothermal calorimeter is described in which experimental errors are minimized by the proper selection of the time of measurement. The method was applied to the calorimetric measurement of the activity of a 2‐curie cobalt‐60 source.

ISSN:0034-6748    

DOI:10.1063/1.1716322

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

This paper describes a device called a ``drag unit'' capable of generating turbulent shear flows of prescribed time‐mean velocity distribution. The device can be used as a research tool to study features of turbulence or to ascertain the effects of flow nonuniformities. Typical experimental results are presented.

ISSN:0034-6748    

DOI:10.1063/1.1716323

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A two‐tube, noninverting, linear amplifier is described. It has a gain of 100 and an inherent rise time of 50 m&mgr;sec for outputs up to 125 v. The amplifier recovers promptly from pulses which overload it a factor of 100.

ISSN:0034-6748    

DOI:10.1063/1.1716324

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A stable sensitive single channel pulse‐height analyzer is described, in which 6BE6 pentagrid tubes paralleled by vacuum diodes are used as linear discriminators. The analyzer works with input pulses of 4‐ to 40‐mv amplitude, and it can be operated directly by a scintillation detector. The dead time is approximately 6 &mgr;sec, and the stability of the instrument over a period of several days is better than 1%.

ISSN:0034-6748    

DOI:10.1063/1.1716325

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

The background resulting from nuclear reaction products of the same magnetic rigidity as the particles to be magnetically analyzed is eliminated by preceding the magnetic analyzer by a velocity filter of crossed electric and magnetic fields.

ISSN:0034-6748    

DOI:10.1063/1.1716326

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

The problem of obtaining fast rising temperatures by resistance heating in a filament initially at low temperatures is examined. From a solution of the heat conduction equation the relationships, both steady state and transient, among temperature, heating current, and heating power are derived. These solutions are dependent on the initial temperature, the thermal properties of the filament, and its physical dimensions. For a typical filament the current‐temperature curves are of the formi = F+ (B/T) whereBis negative for 77°K boundary temperature, zero for approximately 50°K, and positive below this temperature.Experimental evidence taken with a 0.1‐mm diam tungsten filament 2.5 cm long confirms these predictions.A circuit capable of raising a filament from any temperature above 4.2°K to any desired temperature below 600°K in less than 0.3 sec is described.

ISSN:0034-6748    

DOI:10.1063/1.1716327

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

The paper describes a rapid high‐sensitivity thermistor thermometer including the circuit details for the activation of the thermistor bridge circuit and associated amplifier. Using a small bead thermistor housed in a hypodermic needle, the 95% response time is about 0.17 sec and noise levels as low as 2×104°C have been obtained.

ISSN:0034-6748    

DOI:10.1063/1.1716328

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

An ultrathin window, permeable to low‐energy electrons, has been developed for use with cathode‐ray tubes and associated devices. This window, some 70 &mgr;in. thick, has the ability to withstand greater than 1‐atmos pressure differential and, at the same time, allow a 15‐kv electron beam to penetrate it. Window structures are composed of a ¼‐in. square matrix (80‐mesh nickel screen) supported bentonite clay film. It is expected that larger area configurations can be developed. The films are relatively gas‐tight and are insensitive to temperatures of at least 400°C.

ISSN:0034-6748    

DOI:10.1063/1.1716329

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

The closed path (trajectory) traversed by a point on a vibrating surface is described in terms of two components normal to each other and contained in a plane perpendicular to the surface. For the analysis of this motion a biaxial vibration pickup (BVP), using acceleration‐responsive piezoelectric transducers, has been developed. The signals for the BVP are combined by anX‐Yoscilloscope to synthesize the amplified trajectory of the surface point to which the pickup is applied. Phase and amplitude of the component signals are measured with a double‐beam oscilloscope so that a motion map of the vibrating surface can be made.

ISSN:0034-6748    

DOI:10.1063/1.1716330

出版商:AIP    

年代:1958

数据来源: AIP