摘要:

A special purpose charge‐exchange analyzer was constructed to measure the spatial distribution of hot‐plasma ions, as a function of energy and time, in the poloidal divertor experiment (PDX). The fast neutrals produced by charge exchange within the tokamak are reionized as they pass through a helium stripping cell in the detector. The energies of these ions are determined by the trajectories they follow between cylindrical deflection plates which are set at known electrostatic potentials. We describe the technique used to calibrate the response of this system as it depends on the energies and the masses of the particles which are being detected.

ISSN:0034-6748    

DOI:10.1063/1.1136535

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The performance of a metastable atomic beam TOF machine as a thermal plasma diagnostic apparatus is described. The machine consists of two differentially pumped chambers, one containing a hot‐cathode, low‐voltage discharge and the other a channeltron electron multiplier to detect Auger electrons produced by the metastable atoms. Data acquisition and analysis is by a computer‐based pulse height analyzer. The utility of the machine is demonstrated with a discharge in neon.

ISSN:0034-6748    

DOI:10.1063/1.1136536

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A time‐resolving spectrograph for the simultaneous measurement of emissions at extreme ultraviolet wavelengths (300–2200 A˚) is described. The spectrograph is a 400‐mm normal incidence f/30 system with seven gratings. Together two of the gratings cover the entire wavelength range at low resolution. The other five gratings have higher dispersion and cover adjacent intervals of the spectrum. The spectral resolution varies between 0.7–4 A˚. The detector consists of a windowless microchannel plate/phosphor screen image intensifier, coupled by fiber optics to a 1024‐element self‐scanning integrated photodiode array. The output from the array is digitized and stored by a small desktop computer which has sufficient memory to record up to 80 spectra during a single plasma discharge.

ISSN:0034-6748    

DOI:10.1063/1.1136537

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A theoretical model and experimental measurements are presented for a hydrogen discharge in a magnetic multipole (bucket) plasma source where the plasma potential is negative with respect to the anode. This plasma potential depends critically on the anode cusp field, and the measurements show clearly that electrostatic ion confinement is obtained when the anode field is strong (1400 G), which leads to a high electrical efficiency for useful ion production. However, when the anode field is reduced, the plasma potential reverts to its normal positive value with respect to the anode with a consequent reduction in electrical efficiency.

ISSN:0034-6748    

DOI:10.1063/1.1136538

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The temporal and spatial information of gaseous breakdowns occurring from the nanosecond to millisecond time scales are important to the basic understanding and applications of gaseous discharges. A streak camera is an ideal tool for acquiring both time‐ and space‐dependent data simultaneously. However, there are several problems associated with using a conventional streak camera for gaseous breakdown studies. Modifications have been made specifically to solve these problems, while the features of the original streak camera are preserved. A signal overlapping problem has been eliminated by extending the dead time to 70 ms. Streak camera response times have been minimized by adjusting the bias voltages. One streak range has been extended to 7 ms to cover the entire event of a gaseous discharge. The modifications and experimental evaluation of the modified streak camera will be presented.

ISSN:0034-6748    

DOI:10.1063/1.1136539

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The influence of space‐charge effects on the nature and extent of intensity‐dependent temporal broadening in picosecond and subpicosecond streak images has been investigated analytically. The results indicate that the limitations on the dynamic range of electron‐optical streak cameras result primarily from space‐charge effects which are most serious in regions of the streak tubes where the photoelectrons travel with low velocities for relatively long times. The predicted values of dynamic range have been found to be in reasonable agreement with experimental measurements for Photochron I and Photochron II streak cameras. Theoretical estimates of the dynamic range of the Photochron IV streak camera which is currently being developed have also been included.

ISSN:0034-6748    

DOI:10.1063/1.1136540

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A high‐resolution photoelectron spectrometer which uses molecular beam sampling is described. Photons from a rare‐gas resonance lamp or UV laser are crossed with the beam from a differentially pumped supersonic nozzle source. The resulting photoelectrons are collected by an electrostatic analyzer of a unique design consisting of a 90° spherical sector preanalyzer, a system of lenses, and a 180° hemispherical deflector. A multichannel detection system based on dual microchannel plates with a resistive anode position encoder provides an increase in counting efficiency by a factor of 12 over the equivalent single channel detector. The apparatus has demonstrated an instrumental resolution of better than 10 meV FWHM, limited largely by the photon source linewidth. A quadrupole mass spectrometer is used to characterize the composition of the molecular beam. Extensive differential pumping is provided to protect the critical surfaces of the analyzer and mass spectrometer from contamination. Because of the near elimination of Doppler and rotational broadenings, the practical resolution is the highest yet obtained in molecular PES.

ISSN:0034-6748    

DOI:10.1063/1.1136541

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

This report describes an apparatus for increasing the light intensity of a Varian VIX‐150 UV xenon lamp. The increase is a factor 100 times greater at 220 nm. The light pulse width can be varied from 1 to 10 ms. The intensity of the light pulse can be controlled in two different modes: (1) the light flux from the lamp is kept constant by means of a parallel close‐loop control on a small fraction, 10%, of the radiated flux from the lamp. The intensity variation of a 10‐ms light pulse detected by a photomultiplier used for detecting the transient absorption signal can be held constant to within 5%. The accuracy is not limited by the lamp intensifier, but by a lack of precision in optical alignment of the absorption spectrometer; (2) the photomultiplier for the transient absorption signal controls the light intensity. During the first period of the light pulse the photomultiplier signal acts to provide feedback for the lamp intensifier and a constant light level is then obtained. In the subsequent period a hold circuit continues to keep the light level constant. Within the hold period the feedback signal from the photomultiplier is switched off and it continues as the detector for the transient absorption signal. In this mode of operation, a useful light pulse of 1 ms is obtained; the intensity variation is within 3%.

ISSN:0034-6748    

DOI:10.1063/1.1136542

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

In this paper the fatigue produced by pulsed light sources on an RCA C31034 photomultiplier connected to a photon‐counting system is studied experimentally. This fatigue is compared to that obtained when utilizing a continuous light source with the same mean intensity value. It is found that the fatigue produced by the pulsed source is of the same order as that produced by the continuous source, even though pulses are very distant between them. This is explained assuming that when fatigue magnitude decreases the relaxation velocity of the fatigue decreases as well.

ISSN:0034-6748    

DOI:10.1063/1.1136543

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A system is described which has been used to measure the near‐normal vacuum ultraviolet reflectivity of Al2O3up to 450 °C. The system consists of a commercially available lamp and monochromator, and a specially designed reflectometer chamber with an internal electrical furnace and heat shields.

ISSN:0034-6748    

DOI:10.1063/1.1136526

出版商:AIP    

年代:1981

数据来源: AIP