摘要:

We have developed a device that is capable of moving with steps as small as 70 A˚ in any direction over a flat surface. The device that we call the Maggot consists of two permanent magnets attached to the corners of a triangular plate that stands on a flat base with three fixed ball‐bearing feet. The Maggot is propelled across the base by the magnetic fields from two coils that are powered by computer‐controlled current pulses. Steering of the Maggot is made by vector addition of the pulses by the computer. A complete electromagnetic force theory is given in order to find the best magnet and solenoid geometries for maximum performance. The Maggot is UHV compatible, operates from 500 to 4.2 °K, and is most suitable for operation on a vibration‐isolated base. Movement data is measured with both optical and scanning tunneling microscopy.

ISSN:0021-8979    

DOI:10.1063/1.335568

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The intensities of x‐ray transitions in highly charged ions in the Bei, Bi, and Neiisoelectronic sequences have been calculated as functions of electron density. The intensities of the transitions from the 2sn2pm3pconfiguration, relative to the intensities from the 2sn2pm3sand 2snpm3dconfigurations, are strong functions of electron density in high‐density plasmas. The density sensitivity occurs at electron densities between 1016cm−3(for Si ions) and 1022cm−3(for Kr ions). Opacity is unimportant for plasma dimensions that are characteristic of dense laser‐produced plasmas. These x‐ray line ratios represent a promising new density diagnostic for high‐density plasmas.

ISSN:0021-8979    

DOI:10.1063/1.335569

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Optoacoustic measurement of the absorption line shape is carried out for the determination of the homogeneous linewidths and the saturation intensities of a CH3I molecule for a 10‐&mgr;mP(32) CO2laser line. By fitting the numerically calculated Voigt function to the experimentally obtained absorption line shape, we find two absorption lines separated by 90 MHz. The measurement of the pressure dependence of the homogeneous linewidth at pressures lower than 0.8 Torr shows that the rate of increase of the homogeneous linewidth is not linear but larger at lower pressure than that at higher pressure. The natural linewidth of 12 MHz is obtained by extrapolating the experimentally obtained linewidth curve toward zero pressure, and also the pump saturation intensities at the line centers of the CH3I absorption line and CO2laser line are found to be 1.0 and 2.5 W/cm2, respectively.

ISSN:0021-8979    

DOI:10.1063/1.335570

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

New formulas for the components of the electromagnetic surface wave propagating along the boundary between sea water (Region 1) and a one‐dimensionally anisotropic rock (Region 2) have been obtained. The conductivity of the rock is taken to be &sgr;x=&sgr;y=&sgr;T, &sgr;z=&sgr;L, wherezis perpendicular to the boundary. Both &sgr;Land &sgr;Tare constant. When &sgr;L=&sgr;T, the new formulas coincide with those of Wu and King [Radio Sci.17, 521, 532 (1982); J. Appl. Phys.54, 507 (1983)] for an isotropic medium. When &sgr;L≠&sgr;T, the lateral‐wave part of the field is separated into two terms of which the first is of electric type with the wave numberk2=kL, and the second is of magnetic type withk2=kT. The new formulas can be used to interpret recent measurements of the oceanic crust.

ISSN:0021-8979    

DOI:10.1063/1.335571

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The effects of fluorine donor additives and initiation level on the HF laser output characteristics in a strong and short pulse initiation regime are experimentally and theoretically investigated. Typical parameters of the circularebeam used in the experiment are 2 MV, 60 kA, 65 ns FWHM, and 10 cm in diameter, and theebeam is injected longitudinally. The addition of SF6gas to a mixture of F2/O2/H2is found to increase not only the specific laser energy but also the electrical laser efficiency. The maximum laser energy obtained from the low‐pressure mixture of F2/SF6/O2/H2=200/84/60/45 (Torr) is 4.4 kJ in a 70 ns FWHM with an electrical laser efficiency of 203% and a chemical laser efficiency of 18.6%. Based on the experimental results, the scaling of the HF laser was established in terms of specific HF laser energy and electrical laser efficiency.

ISSN:0021-8979    

DOI:10.1063/1.335572

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

In previous papers, U. Feldman, J. F. Seely, and A. K. Bhatia [J. Appl. Phys.56, 2475 (1984)] and A. K. Bhatia, U. Feldman, and J. F. Seely [At. Data Nucl. Data Tables (in press)] have calculated atomic data and gain coefficients for ions of the Ne I isoelectronic sequence. Their calculations of electron impact excitation rates were carried out in the distorted wave approximation. They did not include the effect of resonance excitation, i.e., dielectronic capture by a Ne‐like ion followed by autoionization leaving the Ne‐like ion in an excited state. In this paper, we use the recent calculations of this process by B. W. Smith, J. C. Raymond, J. B. Mann, and R. D. Cowan [Astrophys. J. (in press)] to explore the effect of resonance excitation on gain coefficient calculations for the ion Fe XVII. We find substantial differences (factors of about 1.3–3) between gain coefficient calculations with and without the inclusion of resonances at low temperatures. However, these effects are not important at the temperatures considered by Feldman, Seely, and Bhatia for Fe XVII.

ISSN:0021-8979    

DOI:10.1063/1.335573

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

For a pulsed high‐power laser with unstable resonator, the mode evolution time is important from the viewpoints of beam focusability and laser‐energy usefulness. We observed temporal and spatial behavior of the mode evolution in a several‐tens‐joule KrF laser with a positive branch confocal unstable resonator, which is pumped by electron beams with a pulse width of 65 ns (FWHM). The beam divergence angle was decreased by a factor of 1/M2(M:magnification) per round trip in the resonator and resulted in a full angle divergence of 0.6 mrad.

ISSN:0021-8979    

DOI:10.1063/1.335574

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Detailed performance characteristics of a closed‐cycle subsonic cw CO laser excited by a transverse self‐sustained dc glow discharge are described. Using an electrode configuration which consists of a hollow‐type cathode and a planar anode, the discharge characteristics have been measured under various gas conditions. The measurements show that the discharge instability, and hence the available discharge input, are strongly influenced not only by gas temperature and total static pressure but also by gas composition. From a discharge volume of about 480 cm3, a laser output power of 406 W is extracted with an electrical conversion efficiency of 11.6% for a mixture of CO/N2/He/O2=6/16/78/0.19 at an entrance gas temperature of 156 K. Furthermore, by applying an additional cathode array, the discharge uniformity and the specific input energy have been enhanced. As a result, the maximum extracted laser output reaches as high as 729 W or 1820 W per m of discharge length, with the corresponding conversion efficiency and specific output energy of 16.3% and 125 J/g, respectively. This performance is comparable to or higher than that which has been obtained with an electron‐beam controlled discharge, a pulser‐sustained discharge, etc.

ISSN:0021-8979    

DOI:10.1063/1.335575

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Catastrophically degraded InGaAsP/InGaP double‐heterostructure lasers grown on (001) GaAs substrates by liquid‐phase epitaxy, emitting at 727 and 810 nm are investigated by photoluminescence topography, scanning electron microscopy, transmission electron microscopy, and energy dispersive x‐ray spectroscopy. The degradation is mainly due to catastrophic optical damage at the facet, i.e., development of ⟨110⟩ dark‐line defects from the facet, and rarely due to catastrophic optical damage at some defects, i.e., development of ⟨110⟩ dark‐line defects from the defects inside the stripe region. These ⟨110⟩ dark‐line defects correspond to complicated dislocation networks connected with dark knots, and are quite similar to those observed in catastrophically degraded GaAlAs/GaAs double‐heterostructure lasers. The degradation characteristics of the InGaAsP/InGaP double‐heterostructure lasers are rather similar to those in GaAlAs/GaAs double‐heterostructure lasers concerning the catastrophic degradation.

ISSN:0021-8979    

DOI:10.1063/1.335576

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The effect of UV preionization by a KrF laser on CO2‐laser‐induced optical breakdown is studied experimentally. The electron number density as well as the breakdown probability is measured as a function of KrF‐laser energy. The results show that the KrF‐laser preionization is quite effective in initiating the optical breakdown. Once a breakdown is initiated, however, the number of produced electrons is found to be independent of the KrF‐laser energy.

ISSN:0021-8979    

DOI:10.1063/1.335577

出版商:AIP    

年代:1985

数据来源: AIP