摘要:

The basic operating principles of Cˇerenkov maser oscillators are briefly reviewed and the experimental performance of a 3‐mm device is discussed. A power level of approximately 100 kW was achieved at 88 GHz and voltage tuning from 84 to 128 GHz on the fundamental TM01mode was observed. Operation on higher‐order modes at frequencies up to 300–320 GHz was demonstrated, and a two‐stage buncher‐amplifier configuration was investigated.

ISSN:0021-8979    

DOI:10.1063/1.336200

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The increase in the total ionization produced by high‐energy &agr; particles in Ar/C2F6mixtures, which have conduction and insulation properties appropriate for use in diffuse discharge switching applications by addition of low ionization energy additives has been quantitatively studied. The energy to produce an electron‐positive ion pair (ip)Win C2F6was found to be 34.7 eV/ip; this rather high value is attributed to the large cross section for electron impact‐induced dissociation of C2F6. TheWvalues of Ar/C2F6mixtures have also been measured and are reported; they increase with increasing C2F6content. TheWvalues of Ar/C2F6binary gas mixtures have been found to decrease by addition of C2H2or 2‐C4H8. Quantitative measurements of theWvalues of the ternary gas mixtures are reported. The amounts of C2H2or 2‐C4H8in Ar/C2F6, which maximize the increase in total ionization have been estimated; some of these ternary gas mixtures may be useful for diffuse discharge switches sustained by external electron beams. The experimental results on theWvalues for the binary and ternary gas mixtures studied have been modeled and good agreement has been found between the experimental and the calculated results. From an analysis of the data it has been found that the &agr;‐particle energy is partitioned between C2F6and Ar approximately in the ratio 4.2:1. It has also been found that at the argon pressures employed, the probability of deexcitation of excited argon atoms by C2F6(or C2H2or 2‐C4H8) molecules is more than three orders of magnitude larger than the probability of radiative deexcitation of the excited argon atoms.

ISSN:0021-8979    

DOI:10.1063/1.336201

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Intense energetic beams of hydrogen cluster ions characterized by an atom flux density of several A0/cm2, a kinetic energy per atom of several eV, and a number of atoms per charge in the cluster ions of about 105are markedly influenced by collisions of the cluster ions among themselves and with background gas particles. This is demonstrated by acceleration of a partially ionized cluster beam with high voltages in the range of 75–350 kV and measurement of the attenuation of the neutral component. The attenuation varies exponentially with the ionizing electron current; the attenuation constantbis proportional toU1.7a, whereUais the acceleration voltage. Straightforward extrapolation of  bto the conditions prevailing in fully ionized cluster beams leads to attenuations down to about 20% which is not too far from the measured value scattering around 40%.

ISSN:0021-8979    

DOI:10.1063/1.336202

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Electromagnetic wave scattering from a dielectric‐coated sinusoidal diffraction grating is considered. The incident field is assumed to be TE (P) polarized. The analysis technique is based on the extended boundary condition method. Numerical tests show that both energy conservation and reciprocity principles are obeyed. Mode coupling efficiencies as a function of angle of incidence are presented for dielectric coated gratings consisting of: (i) a perfect conductor, (ii) silver, and (iii) aluminum. These three cases exhibit anomalous behavior at a predicted angle of incidence.

ISSN:0021-8979    

DOI:10.1063/1.336203

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The focused beam from a Nd:YAG laser (&lgr;=0.532 &mgr;m) is used to generate cavitation bubbles in water. Optics of short focal length have been shown to be the most suitable for producing a single bubble in a definite place. Some typical photographs of bubbles obtained are presented. These prove that the laser is a useful tool for the study of simulated cavitation in the laboratory.

ISSN:0021-8979    

DOI:10.1063/1.336204

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

rf impedance, dc self‐bias, and ion sheath (dark space) thicknesses are measured in an O2discharge for 7–53 Pa pressure and 50–800 W rf power (13.56 MHz). Special attention is paid to corrections for reactor stray impedances. It is concluded that the discharge can be described as a capacitance (the ion sheath) with both a parallel and a series resistance, the series element being the more important one. Good agreement is found between optical and electrical measurements of the ion sheath thickness. Evidence is presented that the dc potential difference between plasma and ground and rf electrode can be estimated with reasonable accuracy from the dc self‐bias and the optical dark space thicknesses. Positive ion acceleration in the ion sheath and electron‐neutral collisions in the bulk of the plasma glow account for only part of the total rf power transfer. It is suggested that significant dissipation takes place near the glow‐sheath boundary, although a quantitative description cannot be given yet.

ISSN:0021-8979    

DOI:10.1063/1.336177

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

600‐keV Bi was implanted into an Al/Ti bilayer structure. There is good agreement between the Bi depth profile measured by Rutherford backscattering and corresponding theoretical prediction (Monte Carlo codetrim). After annealing at low temperatures, the pronounced structure of Bi concentration at the Al/Ti interface vanishes, and the buildup of a surface precipitation is observed. At 500 °C annealing, strong Bi diffusion sets in, associated with the intermixing of the substrate components. A thin oxide layer present at the surface acts as a diffusion barrier for Bi, resulting in Bi segregation at the oxide/alloy interface.

ISSN:0021-8979    

DOI:10.1063/1.336178

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A method for the vitrification of pure liquid water and dilute aqueous solutions is described which is the only one without a liquid cryomedium for heat transfer: rapid cooling of aqueous aerosol droplets on a solid cryoplate. This method is not limited to water and aqueous solutions, but can be used for the vitrification of any liquid aerosol, the only impurity being some codeposited vapor. The method can be applied in diverse fields such as cryobiology, cryomicroscopy, and low‐temperature spectroscopy of water and dilute aqueous solutions to avoid the formation of crystalline ice.

ISSN:0021-8979    

DOI:10.1063/1.336179

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

It is found that light ions (6Li,10B) distribute neither according to their calculated range nor to their nuclear damage distributions but according to their ionization distributions after implantation into organic polymers. Also, the profile of chemical destruction after low dose light ion implantation (typically 1012–1014ions/cm2) into organic foils obeys the ionization distribution rather than the range or nuclear damage distributions. After annealing, or at higher implanted doses, a slight shift of the implantation or destruction profiles towards the nuclear damage distribution is found. The reason for this implantation behavior may be partly understood in terms of diffusion and subsequent recombination with the created radicals. Li and B distributions in carbon (which may be regarded as the final product of polymer destruction) show a shape which can be described by range profiles with subsequent diffusion and trapping at homogeneously distributed defects. In contrast to light ions, implanted heavy ions distribute in polymers essentially according to their range profiles, due to negligible diffusion after implantation.

ISSN:0021-8979    

DOI:10.1063/1.336180

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The growth of dark line defects (DLD’s) has been observed in epitaxial AlGaAs wafers under optical pumping. The growth velocity as a function of optical intensity is given byV=AI1.8. In addition to recombination‐enhanced defect motion, stress‐induced dislocation glide is shown to contribute to the elongation of DLD’s in ⟨100⟩ and ⟨110⟩ directions. A climb mechanism may be responsible for the thickening of DLD’s after growth in ⟨100⟩ directions. The asymmetric growth of DLD’s between ⟨110⟩ and ⟨11¯0⟩ directions is attributed to the existence of &agr; and &bgr; dislocations and the absence of 90° rotational symmetry in the zinc‐blende structure.

ISSN:0021-8979    

DOI:10.1063/1.336181

出版商:AIP    

年代:1985

数据来源: AIP