摘要:

We describe a method for measuring the temperature distribution in high‐temperature furnaces with thermocouples that is independent of thermocouple calibration or inhomogeneity errors, and of the presence of leakage voltages on the thermocouple. The method uses several thermocouples and the wire bridge method of true temperature indication; the distribution is obtained from the rate of change of furnace temperature and the time between successive melts. We illustrate the method using gold as the indicator, and in this case achieve an accuracy approaching ±0.2 °C.

ISSN:0034-6748    

DOI:10.1063/1.1136054

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A method is described for tuning coupled‐cavity structures without the need for iterative machining. Small field displacements caused by the rotation of alternate segments of on‐axis coupled structures are sufficient to change the coupling cell frequency without having a significant effect on the accelerating cell frequency. The results from a nine‐cell experimental model have implications in the suppression of nonaxially symmetric modes which cause beam blow up in cw microtrons.

ISSN:0034-6748    

DOI:10.1063/1.1136055

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The magnetoresistance in the liquid helium temperature range has been determined for a number of Ohmite/Allen–Bradley 1/8 W and older Allen–Bradley 1/10 W resistors in magnetic fields from 0.01 to 0.1 T. The new resistors show &Dgr;R/R∝B1.3±0.2; the older resistors show negative &Dgr;R/Rover a large part of this field range. Both sets show larger fractional changes at higher temperatures. The apparent fractional temperature shifts are also given for typical resistors when used as thermometers.

ISSN:0034-6748    

DOI:10.1063/1.1136056

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

An array of hot tungsten wires is used for surface ionization of potassium atoms introduced perpendicular to the magnetic field. The array is opaque to the neutral beam but is highly transparent to the axially flowing plasma. By placing it in a magnetic mirror configuration, well trapped ions are produced.

ISSN:0034-6748    

DOI:10.1063/1.1136057

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Multidipole plasma devices are operated in an unconventional manner with primary electrons prevented by surface magnetic fields from entering the main plasma volume. Applications of this technique, to provide primary electron‐free unmagnetized plasmas and to furnish a source for a large diameter magnetized plasma column, are given.

ISSN:0034-6748    

DOI:10.1063/1.1136020

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

This paper describes the development of a resistive voltage divider to measure pulsed voltages in excess of 2 MVinvacuofor approximately 100 ns. The monitor can measure either positive or negative polarity by changing the low voltage insulator and reversing the remainder of the insulators and gradient rings.

ISSN:0034-6748    

DOI:10.1063/1.1136021

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A grid‐gated photomultiplier has been used in the construction of a subnanosecond‐time‐resolved photometer. The photocathode is gated on during a sampling window which occupies 4 ns of an 8‐ns mode‐locked ion laser cycle. The 0.5‐ns rise‐time sampling window is derived from the mode‐locker drive signal and can be adjusted in phase relative to the incident laser light pulses. By resolving scattered light pulses from long‐lived fluorescence, the photometer affords a 20‐fold reduction in scattered light interfering with photobleaching recovery measurements of low‐level fluorescence. Moreover, it has permitted the time‐domain measurement with dc circuitry of fluorescence lifetimes as short as 0.7 ns. This time response is achieved using a photomultiplier which, in the absence of grid gating, exhibits an anode pulse rise time of 18 ns. Additional applications of this device and of a related narrow‐window sampling photometer currently under development are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1136022

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

In order to acquire the three‐dimensional information (frequency, depth, and intensity) required for a range resolved Brillouin spectrum, either a multichannel or integration technique must be employed. This paper describes a system in which many laser shots are used to ’’build up’’ one Brillouin spectrum for each range gate in an ocean subsurface experiment.

ISSN:0034-6748    

DOI:10.1063/1.1136023

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A new experimental system to measure the equivalent thermal conductivity of a liquid with regard to the Be´nard–Rayleigh problem was constructed. The liquid is enclosed within walls of polymethylmethacrylate between two copper plates in which there are thermocouples to measure the difference in temperature between the lower and upper surfaces of the layer of liquid. Heat flux is measured by means of a linear heat fluxmeter consisting of 204 thermocouples in series. The fluxmeter was calibrated and the linear relationship that exists between the heat flux and the emf generated was verified. The thermal conductivity of the polymethylmethacrylate employed was measured and measurements of the equivalent conductivity in cylindrical boundaries of two silicone oils were made. The critical value of the temperature difference and the contribution of the convective process to the transmission of heat were determined.

ISSN:0034-6748    

DOI:10.1063/1.1136024

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Two novel types of x‐ray monochromators which eliminate unwanted higher orders usually present in crystal monochromatized synchrotron radiation beams have been used successfully in spectroscopic studies. The design of the monochromators is based on the refractive index correction’s dependence on wavelength and relative orientation of crystal surface to reflecting Bragg planes. In addition to the order sorting property, both types of monochromators can be used to decrease or increase the reflected beam cross section by Bragg focusing, and in one type, to determine the polarization state of the diffracted beam.

ISSN:0034-6748    

DOI:10.1063/1.1136025

出版商:AIP    

年代:1980

数据来源: AIP