摘要:

A versatile ultrahigh‐vacuum thin‐film deposition and analysis system is described. Films are deposited by electron beam evaporation with the possibility of ion beam bombardment of the growing film. Measurements of the reflectance and/or transmittance of the coating surface can be made simultaneously at 16 wavelengths across the visible or infrared spectrum. Ellipsometric measurements can also be madeinsitu, at a single wavelength and single angle of incidence, by an ellipsometer which can operate in either an automatic rotating analyzer mode or a manual nulling mode. The system is also equipped with an ion gun producing a submillimeter spot, and with a hemispherical sector, ion energy analyzer for ion scattering spectroscopy studies of the film surface. Results obtained during the deposition of a gold film are presented to demonstrate the capability of the system.

ISSN:0034-6748    

DOI:10.1063/1.1138408

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A fully automated laser light scattering apparatus has been built and is now operational. A specially designed robot moves samples from a thermostatted holding rack to the spectrometer water bath. Use of a smoothly operating robot enables the study of multiphase fluids without disturbing sensitive interfaces. A computer controls virtually all the supporting hardware. Laser input intensity is adjusted by a rotating polarizer and the scattering angle is varied by a stepper motor built into the goniometer. Fiber optics and a silicon photodetector are employed to determine incident and transmitted intensity. Variables such as time base and prescaling on the autocorrelator are optimized by the software according to the characteristics of the sample. Safety and verification procedures are described. The trade off in signal‐to‐noise requirements of both dynamic and classical light scattering are considered in order to enable simultaneous dynamic and classical intensity measurements. An example of the utility of the instrument for studying critical phenomena is given.

ISSN:0034-6748    

DOI:10.1063/1.1138409

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A thyristor, silicon controlled rectifier (SCR), switched multistage magnetic pulse compressor has been successfully developed for KrF excimer laser excitation. Being composed entirely of solid‐state elements, this exciter will provide the extremely long lifetime at high repetition rate operation that cannot be realized by a conventional power supply with a discharge switch.

ISSN:0034-6748    

DOI:10.1063/1.1138410

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

It is shown that a longitudinal CO2laser with two discharge tubes electrically coupled in parallel can be operated in pulsed mode without ballast impedance. This scheme not only yields much higher efficiency (up to 13% at the maximum output energy) and eliminates component failure at high pulse repetition frequency (prf) but also facilitates short pulse availability. In the absence of ballast, current and laser pulse width decrease on increasing the voltage applied to the discharge tubes but these quantities remain unaffected on varying the value of the energy storage capacitor. This enables an independent control of the laser pulse duration and energy. Threshold energy for the onset of nonuniformities in the glow discharge reduces almost exponentially on increasing the discharge current pulse duration but rises on decreasing the operating value ofE/N, the electric field to neutral gas density ratio. The maximum output laser energy of about 1 J/pulse, adjustable pulse duration from 30 &mgr;s to about 2 ms, and prf up to 50 Hz have been obtained.

ISSN:0034-6748    

DOI:10.1063/1.1138411

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Laser Doppler velocimeter (LDV) systems using polarization‐preserving optical fibers are developed by the polarization and the color methods for simultaneous measurement of multidimensional velocity components. By the use of fibers the construction of the optical systems are made easy, the systems are made more flexible, and remote measurement is realized. A signal processor for the LDVs is developed using only a single frequency counter, a high‐speed electronic scanner, and a computer. Using Karman vortex flow and turbulent premixed flame, it is demonstrated that these systems are powerful tools for fluid mechanic measurements.

ISSN:0034-6748    

DOI:10.1063/1.1138412

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

In a heat sandwich oven the metal vapor is confined to be disk shaped and is optically accessible through 360° in the plane of the disk. We have used this feature to optically measure the radial atom density distribution of sodium vapor within this type of oven, under a range of conditions. In particular, we have observed the formation of a donut‐shaped atom density distribution when the heat sandwich oven is operated at high temperatures with an under pressure of the argon buffer gas.

ISSN:0034-6748    

DOI:10.1063/1.1138413

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The characteristics of a molecular beam from a piezoelectric pulsed nozzle source are given and, where appropriate, compared to a continuous beam. These include variation during the pulse in the relative intensity and speed ratio for the gases He, Ar, Ne, and N2. The measurements were made by standard time‐of‐flight and laser‐induced fluorescence techniques. For gas valve pulses of time duration less than 500 &mgr;s, there was a single peak during which the gases reached continuum steady flow behavior. Typical speed ratios (parallel temperatures) for the gases He, Ar, Ne, and N2were 19, 34, 34, and 20 (2.1, 0.7, 0.7, and 1.9 K), respectively. These values are comparable to those from a continuous source with equivalent values ofp0d, the product of source pressure and nozzle diameter. The dimer concentrations for Ne and Ar were also measured and found to be 0.4% and 0.7%, respectively. A major problem with the valve was its inability to open fully because of the limited motion of the piezoelectric element.

ISSN:0034-6748    

DOI:10.1063/1.1138414

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A new nuclear magnetic resonance (NMR) data acquisition and processing system is described. Designed at a fraction of the cost of most commercially available systems, it in many ways exceeds their capabilities. The use of state‐of‐the‐art components in an open‐architecture system where each component is relatively loosely coupled to the rest of the system and thus can be chosen, upgraded, or replaced without major changes to other components, provides for a flexible and expandable system. The principle of incorporating sufficient intelligence into each of the system components allows the use of serial protocols for all noncritical intrasystem communications, simplifying the task of system integration and reducing cost. Such ‘‘unbundling’’ of the hardware also results in a superior adherence to industry standards at the level of individual components. While the technical details are directed primarily at the NMR researchers, a number of general considerations and the description of the principles and criteria used in designing a laboratory data system are of general interest.

ISSN:0034-6748    

DOI:10.1063/1.1138415

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The aim of this investigation was to measure the sensitivity improvement reached on a commercial homodyneX‐band ESR spectrometer by installing a microwave GaAs–FET type preamplifier (8.5–9.6 GHz). Up to a power level of 1 mW a factor of 3 was obtained in signal improvement. Saturation occurred near 30 mW. Both theoretical and experimental results were described and discussed. In addition, a circuit diagram for easy installation of the microwave preamplifier was given.

ISSN:0034-6748    

DOI:10.1063/1.1138416

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

An improvement to the modified Debye–Scherrer camera is described which allows for the accurate determination of the lattice parameter for thin films. The x‐ray collimator assembly has been altered to allow the thin film sample to cut the x‐ray beam in half at zero angle of incidence resulting in a ‘‘D’’ spot on the x‐ray film. The lattice parameter of an aluminum film was measured using this modified camera and compared with that determined by an x‐ray diffractometer scan and the published value. The results agree within 3 mA˚. An additional method using difference angles is also described which can be employed when the origin has not been determined.

ISSN:0034-6748    

DOI:10.1063/1.1138417

出版商:AIP    

年代:1985

数据来源: AIP