摘要:

A feedback stabilization technique is described for a fractional fringe interferometer measuring plasma electron densities. Using this technique, a CO2laser Michelson interferometer with a pyroelectric detector exhibited a sensitivity of 3.4×10−4fringe on a 1‐ms time scale and, due to acoustic pickup, 1.8×10−2fringe on a 10‐ms time scale. The rise time is 45 &mgr;s. Stabilization against slow drifts in mirror distances is achieved by an electromechanically translated mirror driven by a servo system having a 0.2‐s response time. A mechanical chopper in one of the two beam paths generates the signal which drives the servo system.

ISSN:0034-6748    

DOI:10.1063/1.1135938

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A method was developed for the application of direct current comparator apparatus in resistance thermometry and in voltage measurements in combustion calorimetry. The performance of the measuring system was checked by combustions of benzoic acid combined with electrical calibration of the calorimeter.

ISSN:0034-6748    

DOI:10.1063/1.1135939

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A device has been constructed for the study of the interaction between a fast ion beam and a target plasma of separately controllable parameters. The beam of either hydrogen or helium ions has an energy of 1–4 keV and a total current of 0.5–2 A. The beam energy and beam current can be varied separately. The ion source plasma is created by a pulsed (0.2–10‐ms pulse length) discharge in neutral gas at up to 3×10−3Torr. The neutrals are pulsed into the source chamber, allowing the neutral pressure in the target region to remain less than 5×10−5Torr at a 2‐Hz repetition rate. The creation of the source plasma can be described by a simple set of equations which predict optimum source design parameters. The target plasma is also produced by a pulsed discharge. Between the target and source chambers the beam is neutralized by electrons drawn from a set of hot filaments. Currently under study is an unstable wave in a field‐free plasma excited when the beam velocity is nearly equal to the target electron thermal velocity (vbeam≈3.5×107cm/s,Te=0.5 eV).

ISSN:0034-6748    

DOI:10.1063/1.1135940

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A quartz resonator thin film monitor of exceptionally high accuracy and resolution has been developed. It is capable of providing measurements with an effective resolution of 0.001 nm and a corresponding relative accuracy of about 1% for a 0.100‐nm‐thick film of gold. A novel dual oscillator and mixer using integrated circuits is also described.

ISSN:0034-6748    

DOI:10.1063/1.1135941

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A theoretical and experimental study of the helical capacitor sensor for determining theinsitucomponent ratios in two‐phase systems is described. There is excellent agreement between the initial experimental data, the improved design data, and the theoretical analysis.

ISSN:0034-6748    

DOI:10.1063/1.1135942

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Most operable Laser Doppler Anemometry (LDA) systems employ the fringe mode geometrical configuration with a counting type signal processor. The fringes are contained within an ellipsoid volume, which is commonly described as the sensing volume of the LDA. Generally, the dimensions of the focusing volume are determined from the waist diameter of the beams and their intersection angle. However, the electronic processing system exerts several constraints upon the size of the focusing volume. In this study we will address ourselves to the constraints of the dual counter processing system, which is based on the individual realization mode of the LDA. Correction equations will be derived for the sensing volume and the individual realization biasing and applied to two‐component flow fields, measured by a one‐dimensional LDA system.

ISSN:0034-6748    

DOI:10.1063/1.1135943

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

An instrument is described which uses single‐sideband techniques to combine two channels of Doppler flow signals into a form suitable for simultaneous processing by a single‐channel real‐time spectral analyzer. The maximum input frequency range is 50 Hz to 10 kHz.

ISSN:0034-6748    

DOI:10.1063/1.1135944

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A continuous‐temperature infrared calibrator is designed and constructed for providing reference video signals in temperature measurement using an infrared scanner. The calibrator can be controlled for a wide range of temperature settings and to present a continuous span of reference signals for calibration purposes. Both analytical and experimental methods are used to evaluate the performance of the calibrator. Results show that the calibrator has a normal total emissivity of at least 0.984, which is about 1% lower than the predicted value. Methods to improve the emissivity of the calibrator are also discussed. The paper provides for analytical equations useful for parameters estimation in the future design of the calibrator.

ISSN:0034-6748    

DOI:10.1063/1.1135934

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A method is described for building a low‐voltage‐drift differential dc amplifier featuring automatic zero adjustment, a high input impedance, and a bandwidth of 10 kHz. This is achieved by an asymmetric two‐step process between the input signal and ground. Bandwidth can be extended by the use of a second amplifier during the ground‐sampling time. The amplifier can be made with standard electronic components. A major advantage of this method is that an existing amplifier can easily be converted into a low‐voltage‐drift amplifier by adding the essential elements of the described automatic zero‐adjusting amplifier to its input stage. To illustrate the method a practical example is constructed featuring a drift of 0.2 &mgr;V/ °C.

ISSN:0034-6748    

DOI:10.1063/1.1135945

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The theory is given of the voltage output of a Rogowski coil excited by a current pulse flowing along the axis of the coil. In this theory the Rogowski coil is considered as a delay line. The results do not differ from those obtained usually by considering the coil as a voltage sourced&fgr;/dtwith an inductive output impedance. Details are also given of the design of two Rogowski coils and their working modes are fully analyzed.

ISSN:0034-6748    

DOI:10.1063/1.1135946

出版商:AIP    

年代:1979

数据来源: AIP