摘要:

H−ions formed by volume processes are extracted from a multicusp ion source. It is shown that a permanent magnet filter together with a small positive bias voltage on the plasma grid can produce a very significant reduction in electron drain as well as a sizable increase in H−ions available for extraction. A further reduction in electron current is achieved by installing a pair of ceramic magnets at the extraction aperture. The combined arrangement improves the ratio of extracted H−ion current to electron current to about unity.

ISSN:0034-6748    

DOI:10.1063/1.1137215

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The gain characteristics of a microchannel plate (MCP) operated in the reflection mode are measured for positive ions with energies between 100 and 300 eV. Singly charged alkali ions emitted thermionically are used as the incident ions. The gain in the reflection mode is found to be higher than that in the conventional transmission mode. A preacceleration for the penetrating ions into the channels is responsible for the high gain obtainable. This result suggests the potential usefulness of a MCP operated in the reflection mode for the detection of low‐energy positive ions.

ISSN:0034-6748    

DOI:10.1063/1.1137216

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Multiplexers are described for use with two‐ or four‐channel signal averagers. The multiplexers in conjunction with a signal averager allow accurate comparisons of two or four repetitive signals even in the presence of considerable drift and noise. The multiplexers can be used in a variety of ways. As an example, their use with boxcar integrators is described and compared with signal averagers.

ISSN:0034-6748    

DOI:10.1063/1.1137217

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A spectrometer for momentum‐resolved and polarization‐dependent bremsstrahlung spectroscopy (inverse photoemission) in the vacuum UV range is described and the performance of the apparatus is discussed. A Seya–Namioka monochromator combined with a position‐sensitive channel plate device for parallel detection of a wavelength range of 165 A˚ is used as a photon detector and covers an energy regime from 10 to 40 eV with a resolution of 5 A˚. Due to the polarization‐dependent reflectivity of the gold‐coated gratings, the monchromator is also inherently an analyzer for the polarization of the detected light. A space‐charge‐limited Pierce‐type electron gun comprising a BaO dispenser cathode is used as an electron source with 0.1‐A˚−1momentum resolution. The overall energy resolution of the apparatus is 0.3 eV at 20 eV photon energy. The sensitivity is 1.8×104counts per Coulomb and eV for the unoccupieds,pbands of a polycrystalline gold sample.

ISSN:0034-6748    

DOI:10.1063/1.1137218

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A fast mechanical chopper system is designed for use with a pulsed YAG laser in time‐resolved resonant fluorescence measurements. The firing of the laser is synchronized with the position of the chopping wheel in order to block a photomultiplier from laser scatter. With an optical mapping technique, which does not require tight focusing of the fluorescence on the chopper blade, a turn‐on time of 2 &mgr;s is obtained with a 100‐&mgr;m spectrometer slit aperture.

ISSN:0034-6748    

DOI:10.1063/1.1137227

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A digital system was designed to control a Varian Auger spectrometer to perform automatic data acquisition and data reduction. It is based on the Apple II personal computer. The advantages of the system are: low cost, simple design and construction of interface circuits, and great flexibility and power for different setups. A detailed description is given for the interface circuits, the analog‐to‐digital converter, and the digital‐to‐analog converters. Finally, it is discussed how to make changes in the original design to suit different needs.

ISSN:0034-6748    

DOI:10.1063/1.1137228

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A system was designed to optically measure the physical motion induced by a microwave pulse on a rat eye lens immersed in saline. After consideration of several possible techniques, a Michelson interferometer using a HeNe laser and normal reflection from the lens surface was constructed. The system uses wavefronts matched to the curved lens surface, a vibrating reference mirror for calibration and signal discrimination, a sample chamber mechanically isolated from the microwave waveguide, and a fast photodetector and signal averager. A rotatable half‐wave plate and two polarizers were used to smoothly vary the intensity of the reference beam while maintaining the spatial integrity of its wavefronts. The system was able to measure motion down to 2 nm and performed successfully in the microwave pulse exposure experiments.

ISSN:0034-6748    

DOI:10.1063/1.1137229

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Electrostrictive dilatations in the order of 10−13m are measured in dielectric crystals by an interferometric method based on the Michelson interferometer. The electrostriction constants &ggr;1111of quartz, diamond, and LiF are found to be (−0.6±0.2), (+0.17±0.03), and (−7.9±0.8) 10−21m2/V2, respectively.

ISSN:0034-6748    

DOI:10.1063/1.1137230

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A very simple optical procedure is developed to investigate the morphology of natural convection and the dynamic behavior of drops evaporating on a plate by means of a laser shadowgraphic system. This method is the only nonintrusive means of visualizing flow patterns in a time‐varying ‘‘lens’’ shaped system. Its uniqueness and superiority are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1137231

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A new pulsed laser data‐acquisition system which can perform the normal operations of boxcar integrators is described. The system is based on a CAMAC standard photocurrent charge‐sensitive integrator which is coupled to a laboratory minicomputer. The charge‐sensitive integrator is triggered by a gate pulse which is optically synchronized to the laser output. This greatly reduces asynchronous noise. Details of the hardware configuration, the trigger gate circuit, and data averaging software are presented. Flexibility of hardware and software allow for other applications, such as multichannel analysis and other real time data processing.

ISSN:0034-6748    

DOI:10.1063/1.1137232

出版商:AIP    

年代:1983

数据来源: AIP