摘要:

A digital integration technique based on the use of V/F and D/A converters accompanied by the digital scanning and the synchronous square‐wave modulation has been introduced in the scanning Auger electron microscopy. This integrator allows us to perform integration in very high efficiency leading to high signal to noise ratio and to high spatial resolution of the Auger pictures.

ISSN:0034-6748    

DOI:10.1063/1.1136027

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Central to the application of fluorescence correlation spectroscopy, to measure the self‐diffusion coefficients and average concentration of fluorescent molecules in a volume determined by a focussed laser beam, is the determination of the focal spot size. As the focal spot size in the sample plane is varied by displacing either the focusing lens or sample position along the beam axis, the diffusion time and average number of molecules vary in a parabolic manner. Analysis of the parameters of the parabola leads to estimates of the beam radius at the waist. The results agree with theoretical predictions and provide an independent measurement of the beam profile.

ISSN:0034-6748    

DOI:10.1063/1.1136028

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Four different sweep devices based on microwave tubes, avalanche transistors, krytrons, and laser‐triggered spark gaps are treated in detail. These control circuits are developed for picosecond image‐converter cameras and generate sweep pulses providing streak speeds in the range of 107to 5×1010cm/s with maximum time resolution better than 10−12s. Special low‐jitter triggering schemes reduce the jitter to less than 5×10−11s. Some problems arising in the construction and matching of the sweep devices and image‐streak tube are discussed. Comparative parameters of nanosecond switching elements are presented. The results described can be used by other authors involved in streak camera development.

ISSN:0034-6748    

DOI:10.1063/1.1136036

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

This apparatus separates populations of cells or other particles suspended in a liquid. The cells are examined individually in a narrow rectangular flow channel, and sorted out by a device using high‐speed microvalves.

ISSN:0034-6748    

DOI:10.1063/1.1136037

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

We describe new techniques that permit the use of low‐impedance manganin stress gauges in chemically reacting shock waves in the 1.0–40.0 GPa range. The rugged, small, and fast response gauge has reproducibility better than 2% when used in conjunction with a pulsed bridge circuit and adjustable, current‐regulated power supplies. Techniques are presented for fabricating the transducer package, calibrating the bridge circuit and oscilloscopes, designing the drive system, and reducing the data. Data are presented for planar impact experiments performed with a 102‐mm gas gun on high‐explosive samples. In particular, we directly measured the Chapman‐Jouquet pressure in the explosive RX03‐BB [92.5% triaminotrinitrobenzene (TATB)/7.5% polychlorotrifluoroethylene (Kel‐F binder)] as 28.2±0.6 GPa. These new developments open the possibility of applying low‐impedance manganin gauges in chemically reactive hydrodynamic flows such as the evolution of a shock wave into a detonation wave.

ISSN:0034-6748    

DOI:10.1063/1.1136038

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

This paper describes a high resolution scanning transmission electron microscope data collection, storage, and display system. Included are a novel analog‐to‐digital converter, a digital hardware divider, a direct memory access interface to a PDP 11/20, a flicker‐free gray scale TV display, two new gray scale hardcopy devices, and a software description of the system. The system described here accepts three 8‐bit channels of image data from a single picture element every 30 &mgr;s. Each picture element intensity is measured simultaneously by three detectors. Scans of 64, 128, 256, or 512 lines of picture elements are provided. All the data are stored on one of eight disk files, and one of the three simultaneous data channels is displayed on a digitally refreshed TV screen in real time. Production of hard‐copy images and magnetic tape images, and other manipulations of the data are provided after data accumulation is terminated.

ISSN:0034-6748    

DOI:10.1063/1.1136039

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A low‐energy electron diffraction instrument has been constructed which allows one to visually observe a LEED pattern, record the pattern photographically and obtain immediate, quantitative intensity data from several diffraction beams in 5–10 s. The instrument operates at incident beam currents of a few picoamperes eliminating electron beam damage effects. This paper describes the design and construction of this new LEED instrument and reports on the operating parameters of sensitivity, signal‐to‐noise, image distortion, and angular resolution.

ISSN:0034-6748    

DOI:10.1063/1.1136040

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A compact clamp‐type high pressure cell for carrying out electrical conductivity measurements on small solid samples of size 1 mm or less at pressures upto 8 GPa (i.e., 80 kbar) and for use down to 77 K has been designed and fabricated. The pressure generated in the sample region has been calibrated at room temperature against the polymorphic phase transitions of Bismuth and Ytterbium. The pressure relaxation of the clamp at low temperatures has been estimated by monitoring the electrical conductivity behavior of lead.

ISSN:0034-6748    

DOI:10.1063/1.1136041

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A molecular beam source of CH2is described. Coaxial beams of methylene halide and alkali metal react and the mixture is formed into a molecular beam. Passage through a mechanical velocity selector rotating at a suitably high speed purifies the beam, separating light, fast CH2from heavier, slower contaminating species.

ISSN:0034-6748    

DOI:10.1063/1.1136031

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A circuit is described for the production of an amplified, single‐ended output signal from a well‐shielded multiphoton ionization cell.

ISSN:0034-6748    

DOI:10.1063/1.1136032

出版商:AIP    

年代:1980

数据来源: AIP