摘要:

Normal spectral emittance measurements from 5000 to 400 cm−1, and normal total emittance measurements, were made for sapphire and polycrystalline aluminas using Fourier‐transform infrared spectroscopy. Samples were dropped from a furnace into the nitrogen ambient of the spectrometer to the position where the internal global source is normally focused. Radiance was measured as the alumina cooled to derived emittances from 900 to 1450 K. The temperatures were determined from radiance measurements at 1027 cm−1where alumina has zero reflectivity and transmittance. Standard deviations of total normal emittance measurements averaged over three drops were ≤0.3% of the averages.

ISSN:0021-8979    

DOI:10.1063/1.341982

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Formulas are derived that express the potential distribution in a layered spherical and spheroidal anisotropic volume conductor: the number of layers is arbitrary and each layer may be anisotropic. These expressions are a generalization of existing formulas for localization of sources underlying evoked potentials or electro‐encephalographic data. The formulas are presented in a convenient form so that if they are applied in practice the likelihood of software errors is minimal.

ISSN:0021-8979    

DOI:10.1063/1.341983

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Theoretical and experimental results are reported on a method for the correction of aberrations in optical elements for high‐power ion beams. The approach involves the use of arrays of wires immersed in large diameter beams. Individually controlled voltages are applied to the wires, resulting in local transverse deflections of beam particles. With regard to wire survivability and voltage requirements, the method appears feasible for application to high‐intensity negative ion beams. A formalism is described for the calculation of optimum wire voltages to achieve a specified beam angular correction in a Cartesian geometry. The results of the calculations were tested in modeling experiments using an 8‐keV electron beam. The experimental array consisted of 46 wires and boundary plates with independent applied voltages up to 3 kV. Voltage profiles for one‐dimensional focusing, two‐dimensional focusing, and beam steering were studied. The observed particle deflections and beam emittance growth due to the facet lens effect are in agreement with predictions.

ISSN:0021-8979    

DOI:10.1063/1.341984

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The propagation of a relativistic electron beam parallel to an array of parallel conductors, which provide charge and current neutralization of the beam, is investigated. Two geometries are studied: uniformly spaced planar foils or screens, and a matrix of parallel wires. The degree of charge and current neutralization and the resulting parallel and transverse fields are calculated for a uniform density pulse. The self‐consistent transverse equilibrium is derived for the planar foil geometry. The effects of injection perpendicular to a planar cathode are investigated. Particle simulations in planar and cylindrical geometries are presented to confirm the analysis and to study edge effects and containment of the beam within the array. Comparison to vacuum drift tube operation shows that such arrays of conductors may allow beam transport with currents far exceeding the vacuum limit.

ISSN:0021-8979    

DOI:10.1063/1.341985

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Stimulated Brillouin scattering characteristics are formulated for the case of a multiple‐short‐pulse pump. Simplified stimulated Brillouin scattering equations in the small‐ and large‐gain limits are solved for the Stokes intensity giving the dependence on the pulse width and delay, and pulse number. Coherent and incoherent intensities were also calculated and a quadratic versus linear dependence, respectively, on the pulse number was found. It is shown that the gain is largely unaffected by the appearance of a pulsed pump; however, the intensity is roughly reduced by the ratio &tgr;p/&Dgr;, where &tgr;pis the pulse width and &Dgr; is the sum of the pulse width and separation.

ISSN:0021-8979    

DOI:10.1063/1.341986

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Some degradation modes of 1.3 and 1.55 &mgr;m buried heterostructure distributed feedback (DFB) lasers grown by liquid‐phase epitaxy are clarified. A degradation mode induced by the inhomogeneous optical‐field distribution along the laser cavity is found to exist in DFB lasers. In most DFB lasers, the interface degradation between first growth‐step (double heterostructure) layers and second growth‐step (burying) layers occurs in the same manner as Fabry–Perot lasers.

ISSN:0021-8979    

DOI:10.1063/1.341987

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The electron energy distributions for energies lower than 17 eV and their time‐dependent evolution are calculated for electron‐beam‐excited Ne/Xe/HCl mixtures. A time‐dependent Boltzmann equation including all interactions between electrons and ground– or excited‐state species is solved together with a detailed full kinetics model for XeCl lasers. The effects of electron‐electron collision, HCl concentration, and excitation rate on the steady‐state electron energy distribution are examined. Under certain conditions, that is, for relatively high excitations and relatively low initial HCl concentrations, the low‐energy electron distributions tend to be Maxwellian, and their average energies depend on various inelastic processes which cool down the electron energy. All electron reaction rates, especially those related to HCl vibrational excitation and dissociative attachment, are a function of the excitation rate and the transient HCl (v), Xe*, Xe**, and electron densities.

ISSN:0021-8979    

DOI:10.1063/1.341988

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Understanding of the neutral channel formation kinetics in excimer laser gas mixtures has been limited by the lack of data on the pertinent excited‐state populations in these mixtures. Presented are time‐dependent measurements of the lower level xenon excited‐state densities in electron‐beam (e‐beam) pumped XeCl and XeF laser mixtures (neon diluent). Measurements are obtained using hook interferometry under nonlasing conditions at an average excitation rate of ≊250 kW/cm3ande‐beam pulse lengths of 0.4 and 1 &mgr;s. The population differences, &Dgr;N*, between four different electronic transitions [three in the Xe*(6s)‐Xe**(6p) manifold, and one in the Xe**(6s’)‐Xe***(6p’) manifold] are examined as a function of halogen concentration. For both XeCl and XeF at high initial halogen concentrations (>4 Torr), the &Dgr;N* densities of the Xe*(6s) and Xe**(6s’) transitions are relatively constant during the 0.4‐&mgr;se‐beam pulse [for &Dgr;N*(6s‐6p): ≊4×1014cm−3for XeCl, and ≊1.5×1014cm−3for XeF]. At lower initial halogen concentrations, the &Dgr;N* densities of 6s‐6pand 6s’‐6p’start at the beginning of the pulse at approximately the same densities as the richer halogen mixtures, but at a certain point during the pulse, the &Dgr;N* densities abruptly increase. This increase can be >10 times for very lean halogen mixtures (1–2 Torr), and occurs at earlier times as the initial halogen concentration is reduced. From other measurements, this increase appears related to the depletion of the halogen. The observed lifetime of the Xe*(6s) densities is ≊2 &mgr;s for the low initital halogen concentration mixtures. Additional density data for halogen‐free Ne/Xe and Ar/Xe mixtures are also presented.

ISSN:0021-8979    

DOI:10.1063/1.341989

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The laser oscillations from 1553 up to 1603 nm have been demonstrated in Er3+‐doped silica fibers with a doping rate of 2500 ppm. Wide changes in laser oscillation wavelengths are due to broad splitting of the upper sublevels in the4I15/2manifold, caused by the random structure of the silica matrix. It has been shown that unpumped parts of the Er3+ions in the end pumped fiber laser configuration play an important role in the wavelength changes of the laser oscillation. For an absorbed pump power of 320 mW at 514 nm, output power of 0.5 mW was obtained at 1603 nm.

ISSN:0021-8979    

DOI:10.1063/1.341990

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We measured the triplet extinction coefficients &egr;Tover the laser action spectral region of Rhodamine 6G; Rhodamine B; Rhodamine 110; Fluorol‐7GA; Coumarin 540A; Coumarin 522; Coumarin 1; Coumarin 120; 4,4’‐diphenyl stilbene; and 2,7‐bis‐(4‐methoxy‐phenyl)‐9,9‐dipropylfluorene. We employed the different lines from an argon ion cw laser for excitation. McClure’s method was used to obtain the triplet extinction coefficients &egr;T. The method requires the measurement of triplet optical densities ODTas a function of different cw laser excitation intensities (powers)Iex. The importance of triplet‐state losses on dye laser efficiency is reviewed. The laser action properties of the laser dyes we studied are briefly discussed as they relate to the measured &egr;Tvalues.

ISSN:0021-8979    

DOI:10.1063/1.341991

出版商:AIP    

年代:1988

数据来源: AIP