摘要:

A technique for instantaneous linear digitalization of plasma electron temperature display using a triple‐probe method is presented. A digitalized feedback is introduced between the floating probe voltage and the voltage applied to the other probes which is proportional to the electron temperature. Transfer of digitalized data by a photocoupler is used to suppress the side current which causes serious error on a triple‐probe method. The results show that the measured electron temperatures are in a fairly good agreement with a Langmuir single‐probe data. Present system can be applied to most of a low‐density plasma when the ratio (probe radius/Debye length) is less than 2 for a wide range ratios of (mean‐free path/probe radius). Detail error estimation is conducted for the orbital motion limited conditions.

ISSN:0034-6748    

DOI:10.1063/1.1143338

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The energy resolution of a planar retarding potential analyzer can be optimized by using multiple retarding grids and varying the potential applied to the outermost grids. When properly biased, such an analyzer configuration can closely approach the energy resolution of an ideal device. As an added benefit, such an analyzer can be made highly transparent without sacrificing energy resolution. Experimental results verify the solutions of particle‐tracking codes for multiple‐grid configurations.

ISSN:0034-6748    

DOI:10.1063/1.1143339

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Pulsed and continuous‐wave microwaves at 2.45 GHz combined in an Asmussen resonant cavity are used to vaporize, dissociate, and excite copper chloride discharges. Steady state microwaves from 50 to 150 W sustain a microwave discharge which heats and dissociates the copper chloride to a sufficient vapor pressure. A variable frequency (2.45 to 2.60 GHz) pulsed microwave source with pulse widths ranging from 0.5 to 2 ms, repetition rates of 500 to 5000 Hz and a peak output power of 4,500 W then excites the copper atomic states. The two microwave signals are superimposed using a hybrid junction before input into the resonant cavity. Microwave frequencies of the pulsed portion of the signal around 2.50 GHz provided maximum absorption by the discharge. This device is being examined as a potential pump source for a copper vapor laser.

ISSN:0034-6748    

DOI:10.1063/1.1143340

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Apparatus for the measurement of the transverse Kerr magneto‐optic effect is described. The instrument was based on a standard research ellipsometer in a polarizer, compensator, sample, analyzer (PCSA) configuration. The light source was a laser whose intensity was acousto‐optically modulated. At the same time the magnetization of the magnetic film sample was modulated by the field of a nearby coil. The frequency of the magneto‐optic modulation was much less than that of the intensity. Both the intensity and magneto‐optic signals were measured as functions of the analyzer and polarizer angles. The automation of the measurement is outlined. The methods are described by means of which the magneto‐optic variation in &psgr; and &Dgr; were calculated. Typical experimental results are presented for ferromagnetic films which were overcoated with a multilayer dielectric stack.

ISSN:0034-6748    

DOI:10.1063/1.1143839

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A magneto‐optical (MO) Kerr tracer based on an ellipsometer was developed for studying the surface magnetic properties of thin films. This system can be used to measure the optical propertiesnandk, which are strongly related to the magneto‐optical parameters &thgr;kand &eegr;k. In order to carry out measurements on materials having a small &thgr;kwe have developed a multiple reflection sample holder which gives an enhancement of the rotation. The behavior of the sample holder is explained in terms of Jones matrices. The optical and magneto‐optical properties for a thickness series of Co‐Cr films were measured. Comparative measurements on other systems gave similar results.

ISSN:0034-6748    

DOI:10.1063/1.1143341

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

An automated flow calorimeter has been developed for the measurement of highly accurate isobaric heat capacities and enthalpies of fluids at elevated temperatures and pressures. The instrument was successfully tested over the range 300–600 K and 0–12 MPa and is readily extensible to 700 K and 30 MPa. The flow calorimeter relied on an adiabatic design with a two‐chambered cell design incorporating several concentric shells of active and passive shields designed to minimize heat losses, facilitate easy component replacement, and eliminate any external temperature regulation baths. A pair of miniature standard platinum resistance thermometers were built to determine the differential calorimeter temperatures. A precision metering pump eliminated the need for direct mass flow‐rate determinations while a complete automation system supplied all of the required data acquisition, monitoring, and control (except for pressure) resources necessary to operate the calorimeter and make measurements from a single personal computer. Measurements of isobaric heat capacities were performed on water (liq.) andn‐pentane (liq. and vap.) to test the new calorimeter. These experiments compared well with the published values, indicating an overall measurement precision of 0.1% and uncertainty in the range of 0.2%–0.3%. The total calorimeter heat leak was small affecting the experimental uncertainty as much as the combined mass flow‐rate and calorimeter temperature difference errors.

ISSN:0034-6748    

DOI:10.1063/1.1143342

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We have constructed an apparatus that radially compresses monolayers on the surface of water. This mode of compression prevents the anisotropy that is sometimes observed in films that are compressed uniaxially. The area is changed using an elastic band stretched around 12 fingers which move synchronously. The ratio of maximum to minimum diameter of the elastic barrier is ∼7:1, so that the compression ratio is ∼50:1. The apparatus can accommodate dishes of various sizes up to 8 in. in diameter. The temperature is controlled by circulating water under the dish. Isotherms obtained using this apparatus illustrate the difference between uniaxial compression and radial compression for a fatty acid monolayer.

ISSN:0034-6748    

DOI:10.1063/1.1143343

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We describe the design, construction, calibration, and operation of a dosing system for controlled exposures of solid surfaces to gases in ultrahigh vacuum. The doser includes seven parallel tubes in a hexagonal pattern, sized to give nearly uniform flux over a 6‐mm‐diam circle on the sample, and arranged to compensate for an oblique incidence direction. This arrangement gives an enhancement in the ratio of total flux to diffuse flux from the background in excess of 10:1, in spite of a 15.5‐mm distance between the doser and the sample.

ISSN:0034-6748    

DOI:10.1063/1.1143344

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We present a device which makes possible accurate determination of the absorption length of saturated metal vapors inside a long cylindrical absorption cell functioning in the heat‐pipe regime. The device is simple to construct and to operate. The absorption length is determined by the spacing between two movable hot windows welded to inner pipes which are open ended in the cold part of the cell. In this configuration there is no differential pressure on the hot windows and thus can be used also in high‐pressure studies. Moreover, thin windows can be used to minimize their effect on absorption measurements. A continuous independent adjustment of the absorption length and the vapor density can be achieved by simple adjustment of the hot windows spacing. This is accomplished by moving the inner pipes from outside the cell without opening it. A movable inner thermocouple is also added to control and measure the temperature and its distribution along the absorption region.

ISSN:0034-6748    

DOI:10.1063/1.1143345

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A simple spark gap has been used to prevent arcing due to lack of preionization in a laboratory discharge‐pumped excimer laser. Adjustment of the self‐breakdown point of the gap can be made in place without allowing any damaging arcs.

ISSN:0034-6748    

DOI:10.1063/1.1143293

出版商:AIP    

年代:1992

数据来源: AIP