摘要:

The description of a new experimental design for microluminescence is presented in this article. The design is based on the optical analysis of a magnified luminescent region and has been proven to be useful for studying the photon transport mechanism in a solid luminescent material. Lock-in detection and a liquid-nitrogen-cooled detector are used to obtain signal-to-noise ratio as good as102.The performance of the system is discussed by using the measurements taken from a natural ruby crystal. Using transport theory to fit our data, we found the photon diffusion length in the ruby crystal to be on the order of 46 &mgr;m. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148007

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Positron-annihilation-induced Auger electron spectroscopy (PAES) uses a beam of low-energy positrons to excite Auger transitions via annihilation of core electrons. This mechanism imbues PAES with a high degree of surface specificity and the ability to eliminate the large collisionally induced secondary-electron background typically present in conventional Auger spectra. Here, we describe a high-resolution PAES system with an energy resolution&Dgr;E/E=2.5&percent;,approximately five times better than previous PAES spectrometers. The system consists of a compact low-energy(∼10 eV)electrostatically focused positron beam and a large cylindrical mirror analyzer. High-resolution PAES spectra from Cu(100) and Ge(100) surfaces are presented to illustrate the capabilities of the system. Energy spectra of secondary electrons and reemitted positrons resulting from bombardment of the surface by low-energy positron are also presented. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148043

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A highly sensitive gas sensor for detection and analytical identification of hazardous gases was developed, by depositing partially crystalline powder from an aqueous suspension of CdS powder on an alumina substrate. When the deposited layers were promoted with catalysts from Pt-group metals, they exhibited high sensitivity to different gas molecules upon modulation with light of certain frequency, depending on catalyst and impurity concentration. Dark resistance and photosensitivity of the sensors were monitored against gas concentration, sensor temperature, and frequency of the modulating light. Depending on the gas and its concentration, a change of up to 100&percent; in sensor response was observed. Variation of photosensitivity with dark resistance showed different slopes for different molecules. Variation of the low frequency phase angle with photosensitivity at different concentrations also produced different slopes, depending on the type of molecule. This differentiation likely comes about by different interactions of gas molecules with surface recombination centers, depending on the nature of physisorption and/or chemisorption on the surface. Thus, in addition to detecting the gas, it can be identified from their slopes of variation with light frequency, and the sensor can be used as an analytical tool. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148044

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Mechanical filters using cantilever springs as elastic elements have been developed for the seismic isolation system of the VIRGO gravitational wave detector. A two-stage suspension has been built in order to study how the attenuation performances of individual filters combine when the filters are cascaded. An attenuation⩾80 dBin the vertical direction and⩾110 dBin the horizontal direction has been attained for frequencies above 10 Hz. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148045

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In this article we describe the hardware and software architecture of the prototypes of the archiving system of the very long base line interferometric Virgo antenna for gravitational wave detection. The characteristics which make this system very interesting and innovative are not only its performances but also the modularity of the architecture which makes it easier to both follow the progress of the technology without dramatic changes of the hardware and software architecture and to match the requirements according to the Virgo needs. This prototype has been tested in the data acquisition of the 3 m pendularly suspended and evacuated Michelson interferometer prototype which is operational in Naples and in the monitoring of physical environmental quantities, like electromagnetic noise, acoustic noise, etc., necessary for the correlation of the output of the interferometer with the environment. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148046

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have developed a simple, low-cost, GPIB programmable precision voltage source for laboratory use with two outputs in the range[0,−5]V and[0,+5]V. The original goal was to allow the interfacing to personal computer of older high-voltage sources that can be remotely driven by an analog signal. This voltage source can be more generally used whenever a GPIB programmable low-power precision voltage source is needed. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148047

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An electrometer using complementary metal–oxide–semiconductor bilateral switches for automatic range control is described. Based on a dual-switching configuration, the electrometer is capable of current measurement over eight orders of magnitude. Together with a voltage shifter, this circuit provides a quasilinear analog output for the measurement of input dc current between10−3and10−12 A.The application of integrated circuits makes the whole system compact and extremely low cost. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148048

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A quadrant photodetector has been added onto a custom differential interference contrast microscope to measure two-axis displacement of silica beads with a noise ⩽0.1 nm/&sqrt;Hz below 150 Hz. A diode-pumped solid-state laser is incorporated to function not only as a light source for displacement detection but also as an optical trap for motility studies of protein motors. This system is designed for studies in which the motility needs to be simultaneously monitored along both axes at nm accuracy. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148049

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A computer-interfaced multichannel scaler consisting of two counters and FIFO chips as an external memory has been fabricated for use in photon counting. This configuration makes it possible to get a minimum bin width of 1 &mgr;s and to continuously acquire a number of bins. The programmable interval timer is used for setting the bin width through a computer. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148050

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A small device for the rapid ultrahigh temperature sterilization of surfaces is described. Microwave power generated by a 2.45 GHz magnetron is delivered via coaxial cable to a silicon carbide block housed within the chamber. Small quantities of water or aqueous hydrogen peroxide are introduced into the chamber. Upon application of power, the liquid flashes to vapor and superheats producing temperatures to 300 °C. The hot vapor permeates the enclosed space and contacts all exposed surfaces. Complete microbial kill of106colony forming units of the spore forming thermophile,Bacillus stearothermophilus, has been demonstrated using a variety of temperatures and exposure times in both steady state and thermal pulse modes of operation. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148059

出版商:AIP    

年代:1997

数据来源: AIP