摘要:

This review summarizes recent experimental data on implodingz‐pinches and their radiation output, and gives an overview of theoretical issues concerning radiation production in the pinch plasma. Az‐pinch plasma is created when the current from a fast, powerful electrical generator compresses and heats a small amount of material between the electrodes. The hot, dense plasma emits copious amounts of radiation extending from the visible to the x‐ray region. With a 10‐TW electrical discharge the radiative power may be a few TW, with an energy per pulse of up to tens of kilojoules. Our interest is mainly in the photons with energy around 1 keV, which are useful in x‐ray lithography, microscopy, surface studies, and other applications.

ISSN:0021-8979    

DOI:10.1063/1.341808

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Equitemporal optics is a dynamical optical method that makes it possible to reduce the pulse duration of an x‐ray beam without making any changes in the source generating the photons. The total number of photons in a pulse is not significantly reduced by the method. The SPEAR and PEP electron storage rings at Stanford are considered as examples. Time compression factors of one or two orders of magnitude seem feasible, more if the planned emittance reduction is implemented in PEP. In general, x‐ray pulse lengths down to 0.1 ps appear feasible with emittances available today, using conventional materials. This may be reduced another order of magnitude by employing single‐crystal materials.

ISSN:0021-8979    

DOI:10.1063/1.341803

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A simulation of pulsed photoacoustic signals using the finite elements method is demonstrated, using a hypothetical cylindrical brass sample surrounded by air, and a weak energy density laser source to prevent the sample from being destroyed. Both the distribution of temperature and also the distribution of thermal deformation and thermal stress in the sample are discussed.

ISSN:0021-8979    

DOI:10.1063/1.341804

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We have investigated the collisionally induced line shapes corresponding to the1S0→1D24575‐A˚ electric quadropole transition in neutral calcium for a variety of rare‐gas perturber species. We interpret our results in terms of molecular potentials.

ISSN:0021-8979    

DOI:10.1063/1.341805

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A discrete, time‐dependent energy deposition model is used to study high‐energy electron‐beam (100 eV–10 MeV) deposition in N and N+. Both time‐dependent and steady‐state secondary electron distributions are computed. The loss function, mean energies per electron‐ion pair production (W), production efficiencies, and distribution functions are presented for a wide range of energies. The latest experimental and theoretical cross sections are used in the model which predicts thatWis approximately 31 eV for N and 72 eV for N+over a wide range of beam energies. The sensitivity of these results to assumed background ionization fractions is also investigated.

ISSN:0021-8979    

DOI:10.1063/1.341806

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

In this paper we describe the properties of high‐quality, semiconductor laser facet coatings based on yttria‐stabilizied cubic zirconia (90‐m% ZrO2/10‐m% Y2O3). We have found that cubic zirconia films can be reproducibly deposited by electron‐beam evaporation with an index of refraction of 1.98 at 6328 A˚, almost ideal for use as a single‐layer antireflection coating for GaAs/GaAlAs‐based lasers. ZrO2has a monoclinic crystal structure at room temperature, but changes to tetragonal, hexagonal, and cubic phases upon heating to higher temperatures. However, the addition of the Y2O3stabilizes ZrO2in the cubic form, thus allowing electron‐beam deposition of thin films of this material to be more controllable and reproducible without the usual addition of oxygen into the vacuum chamber during deposition. Preliminary aging tests of high‐power GaAs/GaAlAs lasers show that cubic zirconia films suppress the photo‐enhanced oxidation of laser facets that degrades device performance.

ISSN:0021-8979    

DOI:10.1063/1.341807

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Sb‐Te alloy films are developed as rewritable optical recording materials based on amorphous crystalline phase transformations. The crystallization process of Sb‐Te sputtered films is systematically studied through measurement of recording characteristics to solve the trade‐off problem between data (amorphous) stability and erasing sensitivity. Sb2Te3is shown to be the best practical phase change medium, having room‐temperature stability in amorphous states, short erasing times, and potentially good reversibility. The carrier‐to‐noise ratio of 50 dB in writing and a decrease in the carrier level of over 30 dB in erasing are achieved in dynamic measurement with a single beam optical head. These favorable properties are attributable to the wide composition margin for a single phase formation in the Sb‐Te alloy system.

ISSN:0021-8979    

DOI:10.1063/1.341908

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

If a low‐Zplasma is subjected to ionizing radiation, stationary inversions on hydrogenic ion level populations occur. The plasma conditions and pumping requirements to achieve gain on the Lyman‐&agr; and Balmer‐&agr; lines are investigated by means of a collisional‐radiative model. The calculations are carried out for two cases: first, for the case in which the electron temperature is determined solely by radiative cooling, and second, for the case in which additional electron cooling is provided. In the first case, measurable gain on the Balmer‐&agr; line is found, although the Lyman‐&agr; transition remains uninverted. In the second case, the Balmer‐&agr; gain is dramatically enhanced, and sizable Lyman‐&agr; gain is predicted.

ISSN:0021-8979    

DOI:10.1063/1.341909

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The temperature of solid‐state lasers is a critical parameter. Efficiency and output power are strongly influenced by it. The two parameters which determine the temperature are the heat generation efficiency (HGE) and the surface heat transfer coefficient (SHTC) of the laser rod. These parameters allow the scaling of the rod temperature up to high pumping powers. Moreover, from the temperature inside the rod, the temperature gradients and the mechanical stress can be evaluated. Using transient temperature measurements, the SHTC and the HGE were determined for air‐ and water‐cooled Nd:YAG and alexandrite lasers. The SHTC can be confirmed by theoretical considerations.

ISSN:0021-8979    

DOI:10.1063/1.341910

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Emission spectra of a tandem‐type GaAs single quantum well laser diode were investigated under pulsed operating conditions. By controlling the two injection current levels, we could force the device to operate not only at the lowest (n=1) quantized state transition but also at the second (n=2) transition. Anomalous pulse responses, moreover, were found for the two lasing modes which were simultaneously observed in time‐integrated spectra. The dynamic emission behavior was utilized to achieve a variety of intensity combinations of the two radiation modes at the widely different wavelengths.

ISSN:0021-8979    

DOI:10.1063/1.341911

出版商:AIP    

年代:1988

数据来源: AIP