摘要:

A method is proposed to forecast the catastrophic changes of the states of bistable systems with the use of externally applied Gaussian random force. The prediction is based on the fact that the probability distribution function of the states of a bistable system under the influence of Gaussian random force becomes far from Gaussian in the vicinity of its catastrophe. In other words, the anomalous increase of the variance of the probability distribution function in the vicinity of the catastrophe can be utilized as a precursory phenomenon to predict the catastrophe. The anomaly of the probability distribution function is caused by the nonlinear property of the bistable system.

ISSN:0021-8979    

DOI:10.1063/1.325414

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

An analysis has been performed of charged transmission‐line configurations for use in high‐current electron accelerators. Conditions for maximum efficiency and maximum energy transfer to the beam load are derived for ideal constant‐impedance lines. It is shown that, in the lossless‐line approximation, asymmetric line‐pair configurations exist with which both a high accelerating voltage and nominal 100&percent; efficiency can be achieved. The configurations would also have application as a pulse‐forming network for use with other switched loads.

ISSN:0021-8979    

DOI:10.1063/1.325415

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The divergence of a neutral beam due to imperfect magnetic shielding of the gas‐cell neutralizer is considered. Coupled kinetic equations for the ion and neutral velocity distribution functions are solved. The deflection and divergence of the neutral beam are obtained from moments of the neutral distribution function.

ISSN:0021-8979    

DOI:10.1063/1.325416

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

We have observed the Doppler‐free dichroism and birefringence induced by a linearly polarized laser beam (pump beam) by monitoring the polarization and amplitude changes of a weak probe beam through an analyzer. The effects have been observed in two‐level systems and also in three‐level systems of Ne I. At rather low pump power, a typical refractive‐index anisotropy of 10−8has been measured. We have shown that, when the normal resonance curve exhibits a broad background due to collisions, our method allows the elimination of this background. In addition, using a rotating analyzer, we have obtained simultaneously the dichroism and birefringence curves, i.e., the imaginary and real part of the anisotropic‐induced susceptibility.

ISSN:0021-8979    

DOI:10.1063/1.325417

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

An analysis is presented for the repetitively pulsed dual‐beam thermo‐optical absorption spectrometer, which has been used recently to determine the absorption strengths of several organic liquids in the visible spectral region covered by the cw tunable dye laser. The model succeeds in describing the development of the thermal lens on a pulse‐by‐pulse basis. The equations derived are then used to optimize the spectrometer design with respect to the parameters which are under the control of the experimenter. It is further demonstrated how one identifies the region of linear operation of the spectrometer. Finally, it is shown how the relative absorptivities of compounds may be determined.

ISSN:0021-8979    

DOI:10.1063/1.325418

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Magnetic insulation obtained by employing the magnetic field of the line current in coaxial vacuum‐transmission lines is studied in experiments on two different relativistic electron‐beam accelerators, spanning the voltage range 0.4–10 MV. Effective magnetic insulation at fields up to 1.3 MV/cm is demonstrated. The self‐limiting impedance is measured and compared to a number of theories for magnetic insulation and it is found that none of the ’’standard’’ theories successfully describes the data. However, computer simulations using a self‐consistent two‐dimensional particle code give good agreement with the experimental data, as does a proposed modification of the parapotential flow model.

ISSN:0021-8979    

DOI:10.1063/1.325419

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Lead‐laser operation has been demonstrated at 7229 A˚ in all‐hot sealed‐off quartz discharge tubes for 50‐h cumulative operating times without tube degradation or failure. The maximum output energy of 230 &mgr;J or 2.0 &mgr;J cm−3was obtained at ∼1.5 kHz, and the discharge efficiency was 0.12&percent;. Average‐power levels of 750 mW at 6 kHz were maintained under burst mode excitation conditions for extended periods at temperatures of ∼1050 °C. Lead‐laser emission at ∼500 °C was also obtained using lead iodide as the starting material.

ISSN:0021-8979    

DOI:10.1063/1.325420

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The known properties of GaAs and AlxGa1−xAs have been used to calculate the threshold‐current density of double‐heterostructure (DH) lasers at room temperature without adjustable parameters. In the absence of leakage currents due to unconfined carriers, the room‐temperature threshold‐current density for broad‐area DH lasers may be repesented byJth(A/cm2) =4.5×103d+(20d/&Ggr;)[&agr;i+(1/L)  ln(1/R)], wheredis the active‐layer thickness in microns, &Ggr; is the waveguide confinement factor, &agr;iis the internal loss,Lis the cavity length, andRis the facet reflectivity. The experimentally observed increase ofJthforx<0.2 given by Rode is shown to be due to the diffusive electron and hole leakage currents, and a best fit to the data was obtained with an electron minority‐carrier diffusion length in AlxGa1−xAs (x≲0.3) of ∼1 &mgr;m. The above expression forJthfits Kressel and Ettenberg’sJthversus active‐layer‐thickness data atx=0.65, while forx=0.3, the experimentalJthis 300 A/cm2larger than the calculatedJthatd=0.1 &mgr;m. This difference appears to be due to greater scattering loss atx=0.3 thanx=0.6.

ISSN:0021-8979    

DOI:10.1063/1.325421

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Optical insertion losses in embedded strip waveguides fabricated in LiNbO3by Ti diffusion have been examined at a 0.633‐&mgr;m wavelength, taking into account resultant near‐field patterns. It is confirmed that the main factors influencing optical insertion losses are radiation loss by the deficient refractive‐index change of a waveguide, scattering loss by insufficient diffused residual titanium oxide film on a waveguide, and coupling loss between a waveguide and a fiber. A diffusion condition for making a low‐loss waveguide is presented, although suppression of lateral diffusion is necessary to achieve further insertion‐loss reduction.

ISSN:0021-8979    

DOI:10.1063/1.325409

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

For optically pumped FIR lasers the frequency of the pump beam is in close coincidence with an absorbing transition of the active medium. Saturable absorption results in an intensity‐dependent local refractive index, leading to self‐focusing or defocusing. The latter effect has been demonstrated experimentally in CH3F, in which a beam divergence of the order of several mrad was measured, in agreement with theoretical predictions. This phenomenon has important consequences in the design of high‐power FIR amplifiers.

ISSN:0021-8979    

DOI:10.1063/1.325410

出版商:AIP    

年代:1978

数据来源: AIP