摘要:

Refinements of the single photon technique are reported, which are concerned for the most part with the photon timing photomultiplier, its associated circuitry, and the signal processing equipment between this multiplier and the time to amplitude convertor. A photomultiplier voltage distribution circuit is described which permits one to optimize the performance of the photon counting photomultiplier either for sensitivity, time resolution, or both in order to assure the validity of the convolution integral as the representation of the instrument output. An investigation of the variation of the instrumental response with stop discriminator level is reported, and the origin and elimination of wavelength effects and photocathode area effects associated with the timing photomultiplier are also described.

ISSN:0034-6748    

DOI:10.1063/1.1686062

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The technique of the symmetric double probe lends itself to thein situmeasurement of plasma temperature in the ionospheric D region because it can lead to meaningful results under relatively high collision frequencies where the Langmuir probe has been observed to fail. For a completely thermalized plasma and over parametric ranges 0.1≤&lgr;ia/Rp≤100 and 0.004≤Rp/&lgr;D≤100, where &lgr;iais the ion‐atom mean free path, Rpis the probe radius, and &lgr;Dis the Debye length, it is shown that the modification to the original collision‐free double‐probe theory of Johnson and Malter for the determination of electron temperature is never greater than 12%, with a value of (8 ± 2)% nominally applicable in the case of D‐region diagnostics. This technique has been successfully operated on a Nike‐Cajun payload flown at midday from White Sands, N. M. to an apogee of 78.5 km. The associated electronics and deployed double‐probe configuration are presented, and a current‐voltage characteristic collected in the ascent stage at 73.7 km is briefly discussed. The values of electron temperature indicated by the sampled data are [inverted lazy s] 30% higher than those predicted by theory for the anticipated state of thermal equilibrium with the ambient neutrals. The importance, however, is that these values, of the order of 300 K, are the lowest ever reported by anyin situmethod operative in the D region and consequently point out the strong potential of the double‐probe technique in future applications to regions of planetary ionospheres which cannot be considered as collision‐free.

ISSN:0034-6748    

DOI:10.1063/1.1686063

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An apparatus was constructed to measure directly, to 900 bars, the difference between the isothermal compressibilities of two seawater solutions whose compositions differ with respect to one component. The instrument is being used to determine how specific sea salts affect seawater compressibility; this information will be used to study hydration of ions in seawater. The main design feature of the apparatus is that two equal‐volume bellows‐type densimeters are arranged back‐to‐back inside the same high‐pressure vessel. In operation, one bellows is filled with a test solution and the other bellows is filled with a reference solution. As hydrostatic pressure is applied to the two solutions the bellows compress differentially owing to the difference between the compositions of the reference and test solutions. The differential displacement of the two bellows is measured with a linear differential transformer network, and it is directly related to the difference between the isothermal compressibilities of the test and reference solutions. The apparatus has been calibrated using an absolute technique. In a series of trial runs at 15°C, as a check on the calibration, where the reference solution was distilled water and the test solution was seawater of 35‰, the precision of the method ranged from ±0.03×10−6to ±0.07×10−6bar−1over the pressure range 100–900 bar. The actual compressibility difference values ranged from −3.42×10−6±0.06×10−6bar−1at 100 bar to −2.41×10−6±0.03×10−6bar−1at 900 bar; these values are within +0.01×10−6to −0.39×10−6bar−1, respectively, of one set of present literature values. Some additional seawater measurements made at 10°C were within −0.06×10−6to −0.12×10−6bar−1of the most recently determined compressibility measurements carried out by Bradshaw and Schleicher who used a glass dilatometer. Also some measurements made at 25°C on 0.7615mNaCl vs deionized‐distilled water compared within −0.07×10−6to −0.22×10−6bar−1with the recently reported compressibility data of Milleroet al., who made their measurements using a high‐precision magnetic float densimeter.

ISSN:0034-6748    

DOI:10.1063/1.1686064

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A dual gate system with adjustable delays is described; this system is ideally suited to a wide variety of double resonance experiments in nuclear magnetic resonance. The incorporation of the dual gate system into a typical pulse Fourier transform spectrometer is described, and the timing sequences of a typical double resonance experiment are outlined.

ISSN:0034-6748    

DOI:10.1063/1.1686065

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A technique is discussed for forming liquid drops of uniform size from a syringe needle. The method is unique in that it employs fluidic technology to produce drops with diameter independent of rate of formation over a wide range of rates. The velocity and placement of the drop after formation are controlled. Drops from 100 to 3000&mgr; in diameter may be produced at rates between 0 and 15 drops per second. Standard deviations of diameter below 1% can be obtained.

ISSN:0034-6748    

DOI:10.1063/1.1686066

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A method was developed for measuring the time of flow in an Ubellohde viscometer to an accuracy of 3 ppm. For this purpose the following points were shown to be crucial: (a) use of a thermostat with a long time thermal stability of ±2×10−4°C; (b) closing the viscometer off to the outside during all stages of the experiment; (c) adoption of a standard procedure for cleaning and preparing the glass surface; (d) maintenance of the viscometer bulb and capillary always in contact with the fluid by raising level immediately after each experiment; (e) adjustment of the position of the viscometer reproducibly; (f) measurement of the time of flow to within 1 msec. A full description of all parts of the system except the thermostat is given. The thermostat has been described separately. Examples are given illustrating both the accuracy of the technique and the importance of each and all of the above points.

ISSN:0034-6748    

DOI:10.1063/1.1686067

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A velocity measuring probe that creates a train of heat pulses at one point in the flow and detects their arrival at a sensing wire a short distance downstream has been developed for the measurement of turbulent flows of unknown composition. In such a turbulent flow the detected pulses are highly disturbed, but reconstruction of a mean pulse, by digital computer, from several hundred pulses enables calculation of a mean velocity and a velocity fluctuation level. To illustrate the application of this technique, velocity profiles were measured in inhomogeneous turbulent jets over a wide range of jet ambient density ratios.

ISSN:0034-6748    

DOI:10.1063/1.1686068

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An economical two‐circle orienting external goniometer has been designed and fabricated for an Andonian liquid helium Dewar. The Dewar can be tilted ±30° from the vertical in two perpendicular directions. The geometrical center of the Dewar's optical cavity moves a maximum of 1 mm when the cryostat is tilted the full 30°. The basic design involves the rotation of two concentric cylinders riding on bearing surfaces. Two chain belts and gear boxes are used as drive mechanisms.

ISSN:0034-6748    

DOI:10.1063/1.1686069

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An automatically recording constant volume variable pressure apparatus for measurement of reaction kinetics is described. This instrument has been found to be useful for following rates of reactions in solution that proceed with an increase in pressure of the gas phase over the reaction solution.

ISSN:0034-6748    

DOI:10.1063/1.1686070

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An apparatus based on the spinning analyzer technique is described for the measurement of MORD and MCD as a function of wavelength in the region of 6500–3200 Å. Rotation angles can be measured to an accuracy of 0.002°, while the spectrum can be recorded continuously. A discussion of the signal‐to‐noise ratio is given. It is shown that the performance is very close to the theoretical limit.

ISSN:0034-6748    

DOI:10.1063/1.1686071

出版商:AIP    

年代:1973

数据来源: AIP