摘要:

The pulse‐height‐analysis (PHA) system installed on the Joint European Torus (JET) measures the plasma soft x‐ray emission (2–30 keV) with an energy resolution of 450 eV and a time resolution of 200 ms. This diagnostic includes three Si(Li) detectors, equipped with sets of remotely controlled apertures and filters, which view the plasma in the midhorizontal plane of the torus along a single tangential line of sight. Automatic analysis of the spectra yields the central electron temperature, the central concentrations of chlorine, chromium, and nickel, andZeff. Simulations of the measured spectra using a radiation code provides the basis to construct a consistent picture of the soft x‐ray emission in the central region of JET plasmas.

ISSN:0034-6748    

DOI:10.1063/1.1139812

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A bolometry system for time and spatially resolved energy‐loss measurements on the ZT‐40M reversed‐field pinch is described. This system allows ∼100‐&mgr;s time resolution with a radiation detection limit of ∼100 mW/cm2, in particularly noisy electromagnetic environments. The bolometer element fabrication using evaporative techniques and photolithography is discussed. Increased noise rejection is realized by using an oscillator/FM receiver electronics system based on 5‐MHz ac excitation of the resistor. An improved oscillator is described. Because resistive sensing is done at 5 MHz, pulsed heating currents may simultaneously be passed through the bolometer resistor and this allows for absoluteinsitusystem calibration. We describe a new method of such calibration that is independent of the resistor geometry.

ISSN:0034-6748    

DOI:10.1063/1.1139813

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A novel pendulum design—hollow ballistic pendulum—is suggested for plasma momentum measurements. It has an advantage over the pendula used earlier in laser plasma experiments of being insensitive to a momentum of matter evaporated and scattered by the pendulum wall exposed to the plasma, which usually exceeds plasma momentum to be measured. Simple expressions describing pendulum performance are derived, and requirements of shape and size are established. Using this kind of pendulum in experiments on laser acceleration of thin foils made it possible to measure the momentum of accelerated foil with an accuracy of about 10%.

ISSN:0034-6748    

DOI:10.1063/1.1139814

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A mass spectrometer has been used to study the gas composition in a sealed rf‐excited CO2waveguide laser during operation. CO2dissociation levels, at 53% to 71%, are similar to those reported for dc‐excited waveguide lasers and substantiate prior measurements on rf‐excited discharges. The degree of dissociation decreases with increasing pressure and xenon content, but increases as the proportion of helium in the gas mixture is increased. Dissociation has been found to be insensitive to the rf input power per unit discharge length over the range of 2.7 to 4.7 W/cm. This is believed to be the result of increased rates of water vapor outgassing at higher input power levels.

ISSN:0034-6748    

DOI:10.1063/1.1139815

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A prism light‐scattering spectrometer capable of measuring both the angular distribution of scattered intensity and Rayleigh linewidth is described. The spectrometer employs a unique prism light‐scattering cell capable of making small‐angle self‐beating dynamic light‐scattering measurements down to a scattering angle of 2° and is able to achieve an optical coherence factor &bgr;∼0.9 routinely, with the theoretical limit for &bgr; being 1. The prism light‐scattering cell also permits refractive index measurements in the 1.33–1.60 range to a precision of 8×10−7using a single‐axis lateral position sensor. It is a flow cell with potential as a detector for other analytical techniques once the cell volume can be minimized. The apparatus can be controlled by a computer for measurements, as well as acquisition, display, computation, and storage of data.

ISSN:0034-6748    

DOI:10.1063/1.1139816

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A reflectometer is described that can make accurate measurements of the thickness of a dielectric film on a large‐area substrate. The measured value does not depend on the surface characteristics of the substrate. Two basic principles that the new reflectometer invokes are: (i) the wavelength dependence of the integrated reflectance exhibits a minimum at a wavelength which can be related to the film thickness; and (ii) the reciprocity principle for integrated reflectance (i.e., the sample is illuminated with a light of wide angular distribution and the component of light reflected normal to the sample is measured). The instrument has applications in semiconductor industry in general and, in particular, in solar energy device fabrication. This instrument can also be used to measure the absolute reflectance.

ISSN:0034-6748    

DOI:10.1063/1.1139817

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

An improved device for electrical birefringence measurements is described. The novel features of this apparatus include a new design of the Kerr cell and use of the Pockels cell as a compensator. These features show enhanced sensitivity and great improvement in reproducibility of results. A relationship between the intensity detected and the relative phase shifts in the Kerr and Pockels cells is determined by a matrix analysis of the amplitude of radiation passing through each optical element. Based on this analysis, a comparative study under different experimental configurations, as well as an evaluation of the effects of misalignments and methods to cancel the static birefringence, are made. From the results, the best experimental arrangement and procedure of measurement are deduced. Finally, the apparatus is checked by measuring Kerr constants (B) of several nearly isotropic solvents used for the study of polymers in solution.

ISSN:0034-6748    

DOI:10.1063/1.1139818

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

An instrument is described fork‐resolved ultraviolet inverse photoemission spectroscopy using a LiF lens monochromator and a rotatable high‐perveance electron gun. The energy resolution from all sources at ℏ&ohgr;=11 eV is 0.6 eV (FWHM). The angular spread of the incident electrons is calibrated using the properties of a well‐known and well‐characterized surface state on Cu(111), and is found to be 7°(FWHM).

ISSN:0034-6748    

DOI:10.1063/1.1139819

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

An inverse photoemission detector of the Geiger–Mu¨ller type is described, with a detection energy of 10.6 eV and resolution of 0.6 eV. The window material is MgF2and the detecting gas is dimethyl ether, with argon as the multiplier gas. The detector offers a number of advantages compared with the conventional I2/CaF2detector, including a detection energy higher than that of previous detectors, insensitivity to temperature variations, and ease of handling because the detector gas is neither corrosive nor highly poisonous.

ISSN:0034-6748    

DOI:10.1063/1.1139820

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We describe a new type of electrostatic charged particle analyzer based on toroidal geometry. The analyzer features a 360°×10° (polar×azimuthal) field of view and a focal length in the polar direction significantly longer than that of similar devices based on spherical geometry. Extended focal length is a requirement for matching the electrostatic energy spectrometer with a second, mass‐resolving, analyzer. Laboratory tests show that the toroid design has a large geometric factor per unit of instrument weight, good energy‐angle resolution in the particle deflection plane, and sharp (1.0° FWHM) resolution at focus in the polar angle direction. The analyzer is well suited for use in satellite‐borne mass spectrometry and also as a stand‐alone electrostatic analyzer.

ISSN:0034-6748    

DOI:10.1063/1.1139821

出版商:AIP    

年代:1988

数据来源: AIP