摘要:

A more reliable 40 kV, 65 A power supply drain at 0.4 A/cm2, neutral‐beam accelerator was developed for the Tandem Mirror Experiment (TMX). Multiple slotted aperture grids of 60% transparency are fabricated from refractory metal wires mounted to form a spherical surface. This geometrically focuses the beam by aiming individual beamlets at the center of curvature of the spherical grid (r= 3.2 m). We attain greater reliability and faster conditioning with geometrical focusing than with the previous technique of electrostatically steering beamlets to a common point. Electrostatic steering, accomplished by offsetting grid wires, is satisfactory if the offset of a beamlet is much less than the distance from the beamlet to the grids. It was found that Pierce Angle entrance grids performed better if sharper edged. A redesigned accelerator grid support structure reduced the number of ceramic‐to‐metal vacuum joints, and eliminated O rings between precisely aligned parts. The suppressor grid feedthrough is required to withstand a maximum voltage of 15 kV occurring during breakdown, greatly exceeding the operating voltage of 1.5 kV. Convenient fabrication and assembly techniques have been developed. Assembly of accelerators and plasma sources in a clean room appears to reduce the conditioning time. Following the successful testing of the prototype, eight 40 kV accelerators were built for TMX. Furthermore, ten 20 kV versions were built that are modifiable to 40 kV by exchanging the entrance grid.

ISSN:0034-6748    

DOI:10.1063/1.1136733

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A new concept for the linear acceleration of high brightness particle beams, and a description of one working model, are presented. The idea involves the simultaneous acceleration of a large number of low current beamlets in individual, small bore, electrostatic quadrupole focussing channels. Large total current can be reached.

ISSN:0034-6748    

DOI:10.1063/1.1136734

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A molecular beam levitation system is described which is presently being used to sputter deposit coatings on hollow glass microspheres for use as laser fusion targets. Stable levitation of the microspheres has been achieved down to 1×10−4Torr and levitated microspheres have been coated successfully using both dc and rf magnetron sputter guns in a pressure range from 1 to 10 &mgr;m. The system has proven to be highly dependable in both levitation and recovery of the coated microspheres. The levitating gas flow does not appear to interfere with the deposition process, and the rotation of the microsphere, which is produced by the gas flow, ensures that uniform coatings are obtained. Microradiography has shown the coatings to have a high degree of uniformity and the SEM reveals local surface finishes, under specific deposition conditions, of better than 250 A˚. Due to the excellent stability of the levitated microspheres, simultaneous deposition using multiple heads may be possible.

ISSN:0034-6748    

DOI:10.1063/1.1136735

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The paper presents an apparatus designed for the absolute measurement of total electron–atom and electron–molecule cross sections at intermediate energy. This is the first reported instrument capable of measurements at energies higher than 1 KeV. The construction and operation of the apparatus are described. The performance of the apparatus is discussed for two configurations. The first was used to measure the already published data for He, N2, NO, and O2. New measurements for the e−–He system extending to 2000 eV are presented and discussed: these data were obtained with the second (improved angular resolution) setup.

ISSN:0034-6748    

DOI:10.1063/1.1136736

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A compact, high repetition rate, closed‐cycle rare‐gas laser has been achieved in a novel design utilizing an annular flow return surrounding the laser flow channel. The 112‐cm long by 30.5‐cm‐diam. laser head is compact and attractive for portable applications. High repetition rate (to 15 kHz) multiline laser operation has been achieved in high‐pressure (to 2 atm) mixtures of Ne–Xe (6 lines), Ar–Xe (7 lines), He–Xe (9 lines), He–Kr (4 lines), and He–Ar (3 lines). Reliable long lifetime performance has been demonstrated by operating a He–Xe laser continuously for 100 hours at a pulse‐repetition rate of 5 kHz (1.8×109pulses) with no degradation of the 1.1‐W average laser output power.

ISSN:0034-6748    

DOI:10.1063/1.1136737

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Using avalanche transistors, a trigger unit capable of producing several kilovolts in 25 nanoseconds—total risetime—has been constructed. We have used such a circuit to drive a nitrogen laser, resulting in a substantial decrement of the delay time between trigger signal input and the attainment of lasing which is common in commercial lasers. The minimum delay obtained is only limited by the switching time of the thyratron employed. In addition, the ±2 ns jitter of the commercial laser has been reduced to ±0.4 ns using the circuits here described. In order to effect a high degree of reliability, special attention was given to ’’burn‐in’’ and selection of the avalanche transistors.

ISSN:0034-6748    

DOI:10.1063/1.1136738

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A picosecond streak camera that can be used in variable repetitive mode in conjunction with a mode‐locked synchronously‐pumped or a cavity‐dumped dye laser has been developed, as well as an acquisition system which allows digitization and accumulation of the streak records. Time resolution better than 20 ps for the overall system has been obtained with a reproducibility in the time scale of the order of 2 ps.

ISSN:0034-6748    

DOI:10.1063/1.1136739

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Single‐mode optical fiber interferometers used with fiber hydrophones and other types of fiber sensors must be feedback stabilized to achieve maximum sensitivity and linearity in the presence of differential phase drift in their arms resulting from temperature fluctuations and other types of disturbances. A simple and effective electronic circuit for stabilizing such interferometers is described. The bandwidth of the feedback loop is 5 kHz, sufficiently wide to include information signals in addition to the drift correction signals. A high pass filter is used to remove the drift correction signals from the information signals.

ISSN:0034-6748    

DOI:10.1063/1.1136740

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

In this paper we describe a simple and useful apparatus used to measure the absolute reflectance of a surface at normal incidence. A rotating beam splitter provides measurement of the intensity reflected by the sample and the intensity of the direct beam which has been previously compensated by a plate identical to the beam splitter, so that no correction for the transmittance of the beam splitter is necessary, which may even be unknown. The instrument can be used with or without a standard plate.

ISSN:0034-6748    

DOI:10.1063/1.1136723

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A microcomputer‐based image processor has been developed for picosecond time‐resolved spectroscopy of single events. The instrument is used with a monochromator, a streak camera, and a TV camera. Video signals of a spectrum‐resolved streak image are divided into up to 32 channels and their intensity profiles are quickly displayed on a TV screen or drawn on a recorder. The design of the hardware and the function of the software are described in detail. Time‐resolved emission spectra of dimethylaminobenzonitrile excited by a mode‐locked YAG laser have been obtained and a remarkable spectral change in the picosecond domain has been found.

ISSN:0034-6748    

DOI:10.1063/1.1136724

出版商:AIP    

年代:1981

数据来源: AIP