摘要:

The resolution of Thomson spectrometers is examined. Charge, mass energy, and momentum resolutions are found as functions of collimation parameters and field strengths. The results are generally applicable to all Thomson spectrometer systems. In conjunction with this analysis, a compact Thomson spectrometer with high resolving power is described.

ISSN:0021-8979    

DOI:10.1063/1.335389

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Alternative solutions for the vector potential and the magnetic‐field components produced by a toroidal conductor of rectangular cross section are considered. Series expansions are obtained and found to agree with those obtained independently by M. W. Garrett [J. Appl. Phys.22, 1091 (1951)]. Results are obtained for a particular coil geometry by using only a few terms from the series expansions and, by comparing with the exact results, are found to be highly accurate at points close to the coil axis.

ISSN:0021-8979    

DOI:10.1063/1.335398

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The effects of space charge and lens aberrations on a 5‐keV, 80–200‐mA electron beam focused by a solenoid lens are investigated theoretically and experimentally. A third‐order radial trajectory equation is derived with space charge added in the form of discrete annular current elements. This equation is numerically solved for the trajectories of focused electrons in a short solenoid lens. Trajectories launched near the axis are ‘‘reflected’’ from the axis at the waist due to space charge, and trajectories launched farther from axis, cross the axis. The resulting discontinuity is best illustrated in a transverse phase‐space plot where it may be described as a ‘‘tearing’’ of the electron distribution. Due to the combined action of the nonlinear lens forces and the space charge, the initially uniform radial current density distribution becomes markedly nonuniform (hollow or peaked depending on distance) downstream from the lens. Detailed experimental measurements of the density profiles at different positions are found to be in very good agreement with computations.

ISSN:0021-8979    

DOI:10.1063/1.335382

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

In this paper the classical theory of the transverse optical klystron is presented. The gain is obtained by solving analytically the Vlasov equation which governs the evolution of the electron beam along the undulator magnet. The initial energy distribution of the electron beam is assumed gaussian. Both the small signal and the saturation regime are investigated.

ISSN:0021-8979    

DOI:10.1063/1.335388

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

An investigation has been conducted to determine the feasibility of generating conditions favorable to population inversion, gain, and x‐ray lasing in a two‐component plasma consisting of sodium and neon. An intense laser beam is assumed incident on both sides of a Na/Ne slab target separated by a carbon thermal buffer. Temperature and density profiles of the laser target interaction are calculated using a Lagrangian hydrodynamics model. Level populations and radiative emissions are evaluated using a collisional‐radiative equilibrium model including opacity effects. It appears possible to achieve measurable gain at 82, 58 and 230 A˚ from the 3‐2, 4‐2, and 4‐3 transitions of heliumlike neon, respectively. Additionally, by pulse tailoring and target design, it should be possible to enhance the Na pumping power. off

ISSN:0021-8979    

DOI:10.1063/1.335390

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Some of the properties of InxGa1−xAs‐GaAs strained‐layer quantum‐well‐heterostructure (SL‐QWH) injection lasers are described. The laser structures are grown by molecular beam epitaxy onn+GaAs substrates. Following the growth of a 0.5‐&mgr;mn+GaAs buffer layer, a 2‐&mgr;m Al0.45Ga0.55Asn‐type cladding layer is grown. Next an undoped active region is grown, consisting of ∼1600 A˚ of GaAs with three ∼40‐A˚ In0.35Ga0.65As quantum wells separated by two ∼30‐A˚ GaAs barrier layers. Following the active region, a 2‐&mgr;m Al0.45Ga0.65Asp‐type cladding layer and a 0.5‐&mgr;mp+GaAs cap layer are grown. Broad‐area SL‐QWH lasers operate under pulsed conditions at room temperature with threshold current densities as low as 465 A/cm2. The operating wavelength is near 1 &mgr;m. Lasers have operated for up to 1000 h with less than 25% increase in current density to maintain a constant output of 2 mW/facet. Data are also presented describing the temperature dependence of threshold current density. Values ofT0between 80 and 103 K are observed near room temperature, indicating that these SL‐QWH lasers are somewhat more sensitive to temperature changes than conventional laser structures.

ISSN:0021-8979    

DOI:10.1063/1.335391

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Direct photoelectrochemical (PEC) etching of diffraction gratings onn‐InP andn‐GaInAsP in a 2‐MHF/0.5‐MKOH solution has been demonstrated using laser interference holography. Development of a maskless technique for producing gratings has potential application in the fabrication of distributed feedback lasers which are currently made by a multistep photoresist process. Submicron diffraction gratings having a period of 0.5 &mgr;m, corresponding to second‐order feedback in GaInAsP at &lgr;=1.55 &mgr;m, have been achieved. Measurements were obtained on the exposure characteristics, diffraction efficiency, and PEC etching sensitivity of gratings produced in InP and GaInAsP as a function of the writing beam intensity, laser wavelength, material doping level, and grating spatial frequency. For grating frequencies greater than 100 mm−1the sensitivity was observed to decrease approximately as the inverse square of the spatial frequency. In addition, undoped InP and GaInAsP exhibited significantly lower sensitivities thann‐doped material.

ISSN:0021-8979    

DOI:10.1063/1.335392

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

We analyze the free‐running and tunability characteristics of the Cr3+:Gd(Sc,Ga) garnet laser under laser pumping at different wavelengths. Slope efficiencies up to 28%, tunable cw output powers of 200 mW, and a tuning range from 742 to 842 nm were achieved. Excited state absorption of the pump light leads to pumping efficiencies smaller than one, depending on the pump light wavelength and the threshold inversion density. First results of laser experiments with Cr3+:GdGa garnet and Cr3+:(La,Lu)(Lu,Ga) garnet are reported.

ISSN:0021-8979    

DOI:10.1063/1.335393

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Excitation and detection of surface acoustic waves by means of interdigital transducers are studied here in the case of general anisotropic media with low piezoelectric coupling. Relations between mechanical wave amplitude and applied and detected voltage are established. The electromechanical coupling coefficient is calculated from the equivalent electrical circuit of the transducer for different quartz‐crystal orientations. Experimental results are given for different quartz‐crystal cuts, in agreement with the theoretical values.

ISSN:0021-8979    

DOI:10.1063/1.335394

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The experimental study of capacitive radio‐frequency (rf) discharges was performed in mercury vapor at low pressures (10−4–10−2Torr) and at rf applied voltage below 200 V. It was found that at pressures less than 10−2Torr, plasma electrons gain rf energy basically through a noncollisional mechanism at the oscillating potential barrier formed in electrode sheaths. The rf power dissipated in this process turned out to be much larger than that received by electrons through their collisions with neutral atoms in the plasma bulk. Experimental results are in good agreement with the theoretical model of low‐pressure rf discharges developed earlier by one of the authors.

ISSN:0021-8979    

DOI:10.1063/1.335395

出版商:AIP    

年代:1985

数据来源: AIP