摘要:

The x‐ray emission from a Ni target irradiated with an 8‐ns Nd: glass laser pulse focused to ∼5×1013W/cm2did not change when up to 2‐torr Xe was added to the target chamber. This suggests that the incident laser beam was not affected appreciably as it propagated through the background gas to the target.

ISSN:0021-8979    

DOI:10.1063/1.328477

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Light ion diodes for producing 1–100 TW ion beams are required for inertial confinement fusion. The theory, numerical simulations, and experiments on a self‐magnetically insulated ion diode are presented. The treatment is from the point of view of a self‐magnetically insulated transmission line with an ion loss current and differs from the usual treatment of the pinched electron beam diode. The simulations show that the ratioV/IZ0=0.25 in such a structure with voltageV, local total currentI, and local vacuum wave impedanceZ0. The ion current density is enhanced by a factor of approximately 2 over the simple space‐charge limited value. The simulation results are verified in an experiment. An analytical theory is then presented for scaling the results to produce a focused beam of protons with a power of up to 1013W.

ISSN:0021-8979    

DOI:10.1063/1.328434

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A HgXe(30+) fluorescence efficiency of 12±2% was measured in an electron‐beam‐preionized, volume‐stable discharge with anE/Nvalue of 2×10−17V cm2. This efficiency was obtained for gas mixtures with mercury pressures in the range of 2–10 Torr and a constant xenon pressure of 3000 Torr. This efficiency was compared with Boltzmann‐kinetics code calculations. It was found that processes involving molecular mercury formation had to be included in the kinetics code in order to obtain agreement between the measured and calculated HgXe (30+) fluorescence efficiency.

ISSN:0021-8979    

DOI:10.1063/1.328445

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A simple analytic central potential with two adjustable parameters is proposed for the helium atom. The potential parameters are obtained by appealing to the precise values of optical oscillator strengths calculated by Schiffetal. Using the Born approximation we calculate 1 1S–n 1Pelectron‐impact excitation cross sections up to 5 keV. Good agreement with experiment is obtained.

ISSN:0021-8979    

DOI:10.1063/1.328476

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Soft x rays have been observed from three transition radiators using 90‐MeV electrons. The radiators consisted of 30 1.0‐&mgr;m foils of A1, 25 1.5‐&mgr;m foils of Mylar, and 23 1.0‐&mgr;m foils of Be. The photon energy spectra for each radiator peaked at 1100, 1000, and 800 eV, respectively.

ISSN:0021-8979    

DOI:10.1063/1.328481

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The characteristics of the magnetic waves guided by a planar film of ferrimagnet in free space are investigated by the ray‐optical techniques for the case of the magnetization direction lying in a plane normal to the surfaces of the film and containing the propagation direction. The dispersion relation is deduced using the zig‐zagging wave‐normal directions within the film and analyzed to obtain the main features of the guided magnetic waves. The time delay produced when the wave packet of a magnetic wave is totally reflected at an interface between a ferrimagnetic medium and free space is included and a ray‐optical description of the group delay of the guided magnetic wave is developed. The group delay is caused partly in the bulk of the ferrimagnet and partly at the surfaces of the film, and the relative importance of these two contributions are examined. The important features of the direct and the reflected rays within the film are brought out. The optimum directions of magnetization for the devices based on the forward and the backward guided magnetic waves are obtained.

ISSN:0021-8979    

DOI:10.1063/1.328486

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The resonance theory of scattering, recently developed for the diffraction of acoustic and elastic waves, is applied here to radar scattering from penetrable targets, with a view toward solving the inverse scattering problem. For the example of a dielectrically coated conducting sphere, it is shown that the thickness and the dielectric constant of the target can be obtained from a determination of the spacing and of the widths of the scattering resonances in the radar echo returns.

ISSN:0021-8979    

DOI:10.1063/1.328501

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The spatial photon intensity distribution is calculated for geometries pertinent to tapered‐wiggler free‐electron lasers. A large‐radius incident photon field interacts with a small‐radiuse‐beam gain medium, and the diffraction of extracted energy from the gain medium to larger radii is analyzed in the limit of small gain. The results are compared with a simple fill‐factor approximation.

ISSN:0021-8979    

DOI:10.1063/1.329806

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

We demonstrate that reduced reflectivity facet coatings of Al2O3on both mirrors can increase the output power levels at which ’’kinks’’ in the light‐current characteristics of proton‐delineated 12‐&mgr;m stripe‐geometry (Al,Ga)As lasers occur without causing a significant softening of the ’’turn‐on.’’ The dielectric coating is intermediate between half‐ and quarter‐wavelength thicknesses. The advantage of this solution to the kink problem is that it can restore to usefulness lasers which had been previously rejected solely because their kinks occurred just at the power output desired for optical communication application. Although the spontaneous emission output just below threshold is increased somewhat, operation with an extinction ratio equal to 15:1 and reasonable limits on the amplitude of the modulating current is still quite possible. It is also found that reduced reflection coatings can decrease the depth of modulation of self‐induced pulsations and decrease the effects of ’’light jumps.’’ The benefits previously connected with half‐wavelength coatings should remain unaffected if reduced reflection coatings are deposited instead; such benefits are increased catastrophic‐damage thresholds, suppression of light‐jump development, suppression of an initially occurring temporally saturable mode of degradation, blocking in‐diffusion of degradation‐promoting copper, stabilization of self‐induced pulsations, and retardation of facet erosion.

ISSN:0021-8979    

DOI:10.1063/1.329814

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The optical gain coefficient is calculated as a function of the nominal current density for In0.72Ga0.28As0.6P0.4(&lgr;g=1.3 &mgr;m) using a Gaussian fit to the Halperin‐Lax band tails and Stern’s matrix element. The calculation is done forp‐type,n‐type and undoped material at 297 and 350 K respectively. The results show thatn‐type layers may give lower threshold currents than do comparablep‐type layers. The gain or loss at the lasing frequency is found to be a nonlinear function of the injected carrier density so that regions of strong carrier depletion may act as saturable absorbers. The results show that the effect of the Fermi factors alone cannot explain the observed temperature dependence of threshold.

ISSN:0021-8979    

DOI:10.1063/1.328456

出版商:AIP    

年代:1981

数据来源: AIP