摘要:

In order to carry out x‐ray observations of magnetohydrodynamic wave activity of the plasma during DD and DT (deuterium‐beam‐heated deuterium and tritium plasmas, respectively) operation of the Tokamak Fusion Test Reactor (TFTR), we will need detectors not susceptible to nuclear radiation damage. We have investigated the use of gridded ionization chambers as fast nondamageable x‐ray detectors. A prototype chamber is described which was tested on the PDX tokamak. These tests and laboratory tests with a pulsed x‐ray source suggest that the detector has sufficient sensitivity and speed for the required measurements.

ISSN:0034-6748    

DOI:10.1063/1.1138301

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A Michelson interferometer using a 5‐mW He–Ne laser can either be used in a photodiode detector mode to resolve transient fringe shifts ≲10−4fringe or in a streak mode to obtain entire nanosecond resolved density profiles in a single shot. Extreme sensitivity is achieved by avoiding most noise sources. The effects of plasma light and of ray deflection due to density gradients are compensated for by the use of a lens, stop, and filter combination. Vibration induced signals are nearly eliminated by the use of feedback stabilization. A differential light detector system which subtracts signals at opposite sides of a fringe protects against laser noise and other spurious signals while doubling the sensitivity. In the streak mode a cylindrical lens beam expander allows utilization of nearly all of the laser light.

ISSN:0034-6748    

DOI:10.1063/1.1138302

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Design considerations and experimental results are described for a charge exchange neutral particle mass and energy analyzer for JT‐60, which analyzes H, D, and He simultaneously up to a maximum energy of 110 keV. The analyzer has separately a 180° deflection magnet for momentum analysis and an electrostatic deflector for mass analysis. The way to control the effect of the electric fringe fields in order to expand the detectable energy range is studied by numerical simulation. The deflector is then designed, made of two triangular plates and three additional electrodes for the control of the fringe fields. The effect of the deflector is demonstrated experimentally. Energy and mass resolution and the relation between the incident ion energy and the magnetic field strength are measured. The results of the calibration experiments agree with the designed value.

ISSN:0034-6748    

DOI:10.1063/1.1138303

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Different techniques to increase the H−yield in a multicusp source have been investigated. It is shown that the extracted H−current can be enhanced by optimizing the discharge voltage, the neutral gas pressure, or by employing a magnetoelectrostatic containment scheme. A factor of 6 increase in H−output has been achieved by placing the extractor very close to the magnetic filter. It is also found that the extracted electron current is much reduced at this optimum geometry.

ISSN:0034-6748    

DOI:10.1063/1.1138304

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A high‐intensity supersonic nozzle beam source is described, whose beam energy can be varied between 2 and 170 meV (helium). Experimental performance and time‐of‐flight measurements on cold helium beams are reported. Condensation in the free jet expansions of helium has been studied by mass spectrometric detection of He+2. A correlation between the maximum speed ratio and the onset of clustering is observed.

ISSN:0034-6748    

DOI:10.1063/1.1138305

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

This article describes the design of a time‐of‐flight mass spectrometer (TOFMS) constructed for optimum use with resonance‐enhanced multiphoton ionization spectroscopy in supersonic beams. The use of the supersonic beam results in a great improvement in resolution, i.e., at least 800 at mass 93. Ion packets on the order of 10 ns FWHM or less are observed at our flat dual channel plate detector and the resolution ultimately appears to be laser‐pulse‐width limited. The design of this TOFMS utilizes fast‐pulsed molecular beam techniques to allow the use of reservoir pressures >1 atm with a large orifice (0.5 mm) in order to provide high on‐axis intensity for maximizing the photoionization signal produced by our pulsed laser system with the use of only modest pumping capacity. It also uses a skimmed beam, differential pumping, and a liquid‐N2baffle in order to maintain the flight tube at pressures on the order of 5×10−7Torr and to eliminate organic contamination from the ionization region.

ISSN:0034-6748    

DOI:10.1063/1.1138306

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Application of the cross correlation chopper technique to the measurement of a time‐of‐flight (TOF) spectrum of excited atoms by modulation of the exciting laser light is described. The principle and the practical aspects are discussed in a comparison with mechanical systems. Results are given for angular resolved scattering of excited sodium from potassium.

ISSN:0034-6748    

DOI:10.1063/1.1138307

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A very simple, compact, and inexpensive capacitor charging power supply for a 100‐pps laser pulser is described. Unlike dc resonant charging, this power supply does not use a high‐voltage filter capacitor, charging choke, and diode.

ISSN:0034-6748    

DOI:10.1063/1.1138308

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

An electronic circuit has been constructed that generates a positive 3‐kV linear ramp at adjustable slopes 125–500 V/&mgr;s, extendable to at least 1800 V/&mgr;s, for use in time‐resolved selective field ionization of highly excited Rydberg atoms. Its principle of operation is as follows: An inductor, the primary of a 10:1 pulse transformer, is precharged with magnetic flux. The primary circuit is then opened and the collapse of flux is controlled by an integrator circuit with feedback from the secondary. An output circuit eliminates irregularities during the startup of the output pulse. The quiescent output is less than 40 mV. The output ramp, which can be fired at up to 1‐kHz repetition rate and can drive typical capacitor‐plate loads, has a slope that is constant within 2% from bottom to top, adjustable over a 4:1 range by a single potentiometer. The circuit has been extensively used for the detection and resolution of final‐state ensembles in Rydberg spectroscopy and collision experiments.

ISSN:0034-6748    

DOI:10.1063/1.1138309

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The two major contributions to the time spread of electrons detected after energy analysis in coincidence techniques are from the angular spread in the spectrometers and energy dispersion. We describe a compensation technique for each of these contributions. To compensate for the angular spread we would couple the first hemispherical electron spectrometer with an identical one, by means of an electron lens with a magnification of −1. Compensation for the energy spread is possible because in the spectrometers faster electrons have longer transit times, while the opposite is the case for electrons in field‐free space and in electron lenses. In each case there is a linear relationship between the time spread and the spread in kinetic energies.

ISSN:0034-6748    

DOI:10.1063/1.1138310

出版商:AIP    

年代:1985

数据来源: AIP