摘要:

A nozzle source which produces beams of neutral molecules, a factor of 102to 103more intense than that from effusive sources, is described. Further, the velocity distribution from this source is much narrower than that from effusive sources. The properties of the source and a description of its use in total cross section measurements for the case of a He beam on a H2scatterer are presented.

ISSN:0034-6748    

DOI:10.1063/1.1720622

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A 4 mm microwave interferometer has been developed for measurements on electron concentrations in low‐density plasmas (ne≥1010cm−3). The microwaves are transmitted via Lecher wires, inserted across the discharge tube, to obtain high spatial resolution (≲one wavelength). The sensitivity of the system is improved by eliminating the influence of possible variations in the klystron frequency. A microwave phase shift as low as 2&pgr;×10−3rad can be detected in this way. Density oscillations can be scanned by means of a sampling technique. An example of applications on low‐pressure arc discharges is given.

ISSN:0034-6748    

DOI:10.1063/1.1720623

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Developments in the field of sensing elements for frost point hygrometers are briefly reviewed. The rod type geometry connecting a refrigerant at one end with the mirror and heater at the other is analyzed mathematically to show the response and temperature distribution limitations of this geometry. A new sensing element is then described which consists of a hemispherical silver (or copper) thermal reservoir attached to a low mass mirror, heat distributor, and resistance heater via a thin layer of Invar. The latter confines most of the thermal gradient to itself due to its low thermal conductivity and optimum design of the hemisphere and refrigerant flow path. The new sensing element was simulated on a Pace 221R analog computer as well as being subjected to transient analysis which showed that the element responded as a first order lag of time constant 1.67 seconds. Actual construction and tests with step changes of input to the heater confirmed the first order response but with a time constant of 1.3 sec which corresponds to an average full scale response of 14.5 C°/sec with a maximum of 74 C°/sec. Subsequent tracking tests revealed smooth response particularly through 0°C where the ice‐water transition takes place.

ISSN:0034-6748    

DOI:10.1063/1.1720624

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A dissociation field effect relaxation method apparatus for measuring rates of very rapid chemical reactions in aqueous and nonaqueous solutions is described. Chemical relaxation times between 0.3 and approximately 5.0 &mgr;sec are measurable on an asymmetric, high voltage Wheatstone bridge, two arms of which are electrolyte cells. The relaxation in weak electrolyte conductance (second Wien or dissociation field effect) caused by a square wave high voltage pulse from a coaxial delay line is detected with an oscilloscope as a changing difference in voltage between opposite points on the bridge. The construction of the bridge and triggering device and the mechanics of balancing the bridge previous to the actual measurement are described in detail.

ISSN:0034-6748    

DOI:10.1063/1.1720625

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A calorimeter is described for the simultaneous measurement of the heat capacity and length changes of absorbent‐adsorbate systems between +25 and −45°C. The heat capacity of sodium chloride between 0 and −28°C is given and is found to agree with previous results within 0.6%. The calorimeter is also suitable for studies of heats of adsorption and solid state reactions such as hydration and phase transition.

ISSN:0034-6748    

DOI:10.1063/1.1720626

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A new type of temperature sensor is suggested, actuated by piezoelectricty generated by means of thermal expansion of suitable materials. A crystal of quartz, preloaded in a special frame, senses the effects of load changes due to the difference between the thermal expansion of the frame and that of the quartz itself. A fixed proportion exists between the difference of potential, measurable on the appropriate faces of the crystal, and the temperature of the sensor. The tests carried out in order to check the characteristics of the new device fully confirm this proportionality. The voltage output of the sensor has been found to be about 0.001 V/C°.

ISSN:0034-6748    

DOI:10.1063/1.1720627

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An apparatus for measuring the relative viscosity of molten glass‐forming oxides at elevated temperatures and pressures is described. It utilizes a concentric cylinder viscometer and electric furnace enclosed in a steel pressure bomb and is gas pressured. Four thermocouples and three heating circuits enable the temperature of the sample to be controlled to within ±0.2°. Data on the pressure dependence of viscosity of molten boron trioxide in the temperature range of 380–470°C and at pressures up to 300 bars are presented.

ISSN:0034-6748    

DOI:10.1063/1.1720628

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An accurate method for measuring the rotational movement of a carriage about an axis parallel to the direction of its translation movement is explained. It is shown that the method can also be used in determining very accurately the tilt of a supporting system.

ISSN:0034-6748    

DOI:10.1063/1.1720629

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The growing need for refrigeration at temperatures below the boiling point of helium—particularly to maintain superfluid helium in a superconducting linear accelerator for long periods of time—has led to the development of a closed‐cycle refrigerator in which the refrigerative powers of the helium vapor at pressures as low as 0.02 atm can be utilized. Effective use of the cold vapor in a heat exchanger makes possible a several‐fold increase in the capacity of a refrigerating system, as compared to conventional open‐cycle techniques.

ISSN:0034-6748    

DOI:10.1063/1.1720630

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An apparatus is described for measuring the Hall effect of low mobility samples at high temperatures. The measuring method is of the double ac type. An alternating current at 510 cps, in conjunction with a low frequency magnetic field at about 2 cps, is used. The use of single or double phase sensitive detection is discussed. A temperature controller with a stability of about 2×10−2C° at 1000°C and a sample holder assembly are described. Results of measurements on NiO samples are given, indicating a noise level equivalent to mobilities of 3×10−4cm2/V sec.

ISSN:0034-6748    

DOI:10.1063/1.1720631

出版商:AIP    

年代:1967

数据来源: AIP