摘要:

Magnetic probes are commonly used in plasma experiments to measure the magnetic and plasma properties of the configuration. Probes consisting of coils of copper wire encased in one or more layers of stainless‐steel tubing are used both inside and outside the plasma to measure the magnetic field in the Maryland spheromak. A technique has been developed to calibrate the probes over a large frequency bandwidth using digital computer signal processing. The frequency‐dependent effects of the stainless‐steel tubing and the self‐inductance of the coils on the recorded signal are taken into account over the entire bandwidth. This technique may also be used to take into account the eddy currents present in the metal vessel walls.

ISSN:0034-6748    

DOI:10.1063/1.1139440

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

HAIFA is a modular, multichannel, fiber‐optically coupled spectroscopy diagnostic for tokamak plasmas. It operates in the visible, measuringH&agr;radiation, the visible continuum from thermal bremsstrahlung, and selected impurity lines. HAIFA is characterized by high modularity and flexibility, good radiation resistance, high noise immunity, and low cost. Details of design, construction, and calibration are given. The analysis of visible bremsstrahlung radiation measurements to deduce the effective ionic charge in a plasma is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1139441

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

This paper presents the results of a complete series of tests and calibrations of a bleed‐type pressure sensor used in order to determine in‐stream static pressure fluctuations in a turbulent boundary layer just above a pure laboratory wind–wave field. The static calibrations show that for air flow mean velocities lower than 15 m/s, the sensor response depends not only upon the pressure but also upon the velocity and the temperature of the air flow. Dynamic calibrations prove that the temperature and velocity sensitivities depend strongly upon the frequency. They are important for low frequencies and equal to zero only for frequencies greater than 0.1 Hz if the sensor is operated in an isothermal turbulent flow and greater than 1 Hz for a nonisothermal flow. Pressure sensitivity doesn’t depend upon frequency for a range from dc to 600 Hz.

ISSN:0034-6748    

DOI:10.1063/1.1139442

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Amounts of adsorption of helium over some zeolites were determined ranging from 77 to 673 K with a temperature‐compensated, differential tensimeter having symmetrical design. The amount of adsorption of helium was determined by measuring an increase in apparent dead space between the sample adsorption cell containing the sample and the reference adsorption cell containing several glass rods on the assumption that the amount adsorbed of helium at 673 K was negligibly small, the temperature of the adsorption cells being changed after each determination. Discussion has been made of the errors caused by the adsorption of helium to the determination of the density of solids when helium is used as the dilatometric fluid, and the determination of the surface areas of solids based upon the adsorption of nitrogen with a conventional volumetric adsorption apparatus.

ISSN:0034-6748    

DOI:10.1063/1.1139659

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A LED‐based fiber‐optic temperature sensor is developed which uses the change in the wavelength distribution of emission of fluorescence from a small sample of pink ruby as the means of sensing temperature. An all fiber‐optic system is described using simple electronics to measure temperature in the range from 293 to 433 K, with an accuracy of ±3 K.

ISSN:0034-6748    

DOI:10.1063/1.1139443

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The dynamic response of thermistor temperature sensors is known to be sensitive to the relative velocity between the sensor and the surrounding fluid on both theoretical and experimental grounds. The majority of the experimental investigations derive empirical velocity scaling relationships which have little basis in theory. We have determined that the dynamic response of a particular fast response thermistor scales with the square root of velocity, in accordance with the predictions of the boundary layer theory, over a speed range of 0.5–2 m/s with water as the working fluid.

ISSN:0034-6748    

DOI:10.1063/1.1139444

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

An automated adiabatic calorimeter with an internal volume of 5 cm3, operable over the temperature range from 30 to 380 K is described. One of the main advantages of this calorimeter over others in use is the much abbreviated down time during sample changes, due to interchangeable sample vessels that fit into the heater/thermometer assembly. This calorimeter was tested by measuring the heat capacity of benzoic acid, and the results agreed with the literature values to within 0.5%.

ISSN:0034-6748    

DOI:10.1063/1.1139445

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

This paper introduces the design of a signal processing circuit which can be used in conjunction with additional arrangement for measuring gas mass flow rate. Measurement is based on Bernoulli’s equation for subsonic flow. Voltages representing gas static pressure, static temperature, and difference pressure generated across an orifice plate are supposed to be taken from appropriate transducers. These voltages are processed with this circuit in such a way as to produce a digital number representing the mass flow rate value. The circuit shows a good accuracy result with uncertainty of about ±0.1%.

ISSN:0034-6748    

DOI:10.1063/1.1139446

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The precision limits of a waveform processing oscilloscope have been investigated for the situation where the instrument is used to recover a repetitive exponential signal from high levels of noise. In these studies, the oscilloscope was programmed to sample the signal, average it, and then calculate its exponential decay time constant. The measurement errors in the resulting time constants were found to decrease with continued averaging, but not without limit. In fact, we found that there was an optimum number of samples needed to minimize the error for any particular value of the signal‐to‐noise ratio at the input to the oscilloscope. We present here our empirically determined values of those optima, an intercomparison of them with the results of a theoretical model, and a description of the measurement system developed for this work.

ISSN:0034-6748    

DOI:10.1063/1.1139447

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

An apparatus is described whereby physicochemical measurements which involve pressure changes up to about 2 kbar can be made in times of the order of 102s. Pressure changes in short times are achieved by the evolution of a large supply of hydrogen gas into a very small volume.

ISSN:0034-6748    

DOI:10.1063/1.1139448

出版商:AIP    

年代:1987

数据来源: AIP