摘要:

The dynamic observation of surfaces has been developed by using a scanning Auger electron microscope (SAM). The images of Auger and secondary electrons are photographed continuously with a 16‐mm movie camera. Each frame is photographed for very short time exposures of 24 to 48 s for the Auger and 3 s for the secondary electrons. Particular logic circuits to control the system were made providing for the rejection of the secondary electrons ejected by the ions and for the photons from the filament of the ion gun which greatly degrade the images.

ISSN:0034-6748    

DOI:10.1063/1.1137659

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

High‐contrast TV images of living cells are recorded from a light microscope. The video line signal is converted to binary and used to gate a 12.5‐MHz clock driving a counter. After completion of each video frame the accumulated counts (proportional to the dark image area) are written onto a stack (FIFO) before the counter is reset. Thus, area information is actualized at a rate of 50 values per second and can be read out at speeds suitable for computer interfacing and (after D/A conversion) oscilloscope displays or paper chart recording. With two counting channels the time course of two areas of distinctly different gray shades can be recorded at once.

ISSN:0034-6748    

DOI:10.1063/1.1137660

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

We have designed and built a single‐crystal fiber growth apparatus. The apparatus employs novel optical, mechanical, and electronic control systems that enable the growth of high optical quality single‐crystal fibers. We have grown oriented single‐crystal fibers of four refractory oxide materials, Al2O3, Cr:Al2O3, Nd:YAG, and LiNbO3. These materials exhibit similar growth characteristics and yield fibers of comparable quality. Fibers as small as 20 &mgr;m in diameter and as long as 20 cm have been grown. Measured optical losses at 1.06 &mgr;m for a 10‐cm‐long, 170‐&mgr;m‐diam Cr:Al2O3fiber were 0.074 dB/cm.

ISSN:0034-6748    

DOI:10.1063/1.1137661

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A measurement system for the current–voltage characterization of solar cells has been developed. The instrument is based on an Intel 8088 microprocessor, which allows for enhanced data collection and storage, as well as automated measurement control. A high‐power analog supply makes measurements in the range of −10 to +10 V and −0.75 to 0.75 A possible, and provides the capability for sinking currents up to 1 A at +10‐V output. Measured data may be transferred to an IBM personal computer for immediate display, and for consequent analysis (to obtain the characteristic parameters). The system provides a rapid, effectiveI–Vcurve measurement and analysis method for many devices, and experimental solar cells in particular.

ISSN:0034-6748    

DOI:10.1063/1.1137662

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

An analysis of the frequency distribution of noise of two synchrotrons (CHESS and SSRL) indicates significant increases of noise at frequencies below 10 Hz. Noise energy distributions above 10 Hz and extending through 200 Hz indicate significant regions of noise distributions relatively independent of frequency, presumably ‘‘white noise.’’ We report tests of two carrier modulation systems in which the ratio (or difference) of a reference signal and measure signal is computed. In one case, the reference and measure sample are alternated at equal intervals, for example, where difference spectroscopy is required. In another version, the measure signal is periodically interrupted by the reference signal at a duty ratio of 10%–15%, thereby maintaining high efficiency of measure signal detection. When using a 10‐Hz oscillator for reference and measure samples, the improvement as observed on beam line A‐3 at CHESS over the ‘‘single‐ended’’ signal is 10‐ to 20‐fold in the nonscanning mode. In the case of a vibrating reed modulator, the signal‐to‐noise ratio at a count rate of 6×105per s is equal to the statistical limit to within the error of calculation. The improvement over a conventional fluorescence signal to ionization chamber output ratioF/I0is over tenfold. Application of these modulation techniques to a variety of detectors is included.

ISSN:0034-6748    

DOI:10.1063/1.1137663

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A simple spherical analyzer combination suitable for use in high‐resolution electron energy‐loss spectroscopy (HREELS) is described. The system is designed to be intrinsically insensitive to extraneous magnetic fields. The problems presented by the control of the spectrometer are also discussed and the advantages of Fourier filtering demonstrated.

ISSN:0034-6748    

DOI:10.1063/1.1137664

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A three‐circle goniometer for a large‐hole electron‐paramagnetic‐resonance (EPR) cavity is described which, by a very simple operation, enables us to rotate the crystal around arbitrary direction parallel to the static magnetic field, by rotating a sample holder about a redundant (or the third) axis accommodated in a spur and crown gear. By comparing not only the observed resonance field with the calculated one, but also the absorption intensity with the transition probability, the quantitative determination of the concentration of the unpaired electron center in a single crystal is possible.

ISSN:0034-6748    

DOI:10.1063/1.1137665

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A completely stand‐alone pulse‐echo‐overlap system which can be easily built using commercially available integrated circuits is described. The system uses a broadband pulse to excite the transducer. The equipment is relatively cheap and yet the sensitivity of the transit time (and, hence, velocity of sound measurement), is made high by making use of a digital frequency synthesizer of 0.01‐Hz resolution, specially constructed for this purpose. Except for the oscilloscope the instrument does not require any other equipment for its operation.

ISSN:0034-6748    

DOI:10.1063/1.1137666

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A new instrument for simply and rapidly determining an ammonia concentration in a gaseous mixture has been developed. The principle is based on the fact that ammonia reacts with NO exactly at 1:1 mole ratio in the presence of an appropriate catalyst: NH3+NO+ 1/4 O2=N2+ (3)/(2) H2O. A sample gas containing NH3is mixed with NO and made to contact with a catalyst capable of promoting reaction of NH3and NO to form N2and H2O in an oxidative atmosphere at an elevated temperature, preferably, 300°–400 °C. The catalyst capable of conducting the reaction is composed of TiO2and at least one of the oxides of V, Fe, Cu, W, Mo. The concentration of NH3is determined by measuring concentrations of NO before and after the reaction and calculating the consumption of NO. For the analysis of NO in the gas, a chemiluminescence‐type analyzer can be preferably used. According to the present method, ammonia in a sample gas can be analyzed within a few minutes without any influence of various coexisting gas components.

ISSN:0034-6748    

DOI:10.1063/1.1137667

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A nude ionization gauge adjacent to the closed ion‐source chamber of a quadrupole mass spectrometer is a sensitive detector of the total amount of gas introduced for dynamic analysis. Linear relations between the amount of gas and the area of the ionization gauge pulse record were found for eight gases. For relatively unreactive gases, linearity extended to the smallest samples that could be detected, approximately 10−10atm cm3. Validity of the dynamic method of analysis was established by demonstrating that the same response was obtained for pulsed and for continuous sample introductions from calibrated leak sources of each of the eight gases.

ISSN:0034-6748    

DOI:10.1063/1.1137673

出版商:AIP    

年代:1984

数据来源: AIP