摘要:

A beam of D−ions has been produced at 7–13 keV, with currents up to 2.2 A, using charge exchange in sodium vapor. The beam profile is bi‐Gaussian with angular divergence 0.7°×2.8° and peak current density 15 mA/cm2. The characteristics of the beam are in excellent agreement with predictions based on atomic cross sections. The sodium vapor target is formed by a jet directed across the beam. The sodium density drops rapidly in the beamline downstream from the charge exchange region, decreasing three orders of magnitude in 15 cm. Measurement and analysis of the plasma accompanying the beam demonstrate that plasma densities nearly equal to the beam density are obtained 1 m from the charge exchange medium. The plasma produced in the sodium is thus well confined to the charge exchange region and does not propagate along the beam.

ISSN:0021-8979    

DOI:10.1063/1.328697

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Measurements and calculations of the energy full width at half maximum (FWHM) of a 300‐eV electron beam are presented as a function of current. The measurements utilize a low‐energy telefocus electron gun and a 127° cylindrical energy analyzer. The calculations combine theories of Knauer and Zimmermann with beam envelope determinations obtained from a combination of electron ray tracing and measurements on the beam. The energy width is numerically integrated along the beam envelope, and the FWHM is calculated. The calculations agree in magnitude with the measurements, but there is a discrepancy in the current dependence.

ISSN:0021-8979    

DOI:10.1063/1.328698

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The construction and successful operation of a helical transversely excited copper bromide laser is reported. Satisfactory laser performance has been obtained over a wide range of discharge parameters. As a consequence of the helical electrode geometry, the copper laser‐beam cross section is circular symmetric and exhibits a radial energy profile that is near to Gaussian.

ISSN:0021-8979    

DOI:10.1063/1.328699

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The influence of the preionizer and initiating discharge circuit parameters on the performance of a UV preionized pulsed HF/DF chemical laser with relatively low active volume (about 20 cm3) has been investigated. The laser has been operated with gas mixtures of SF6and H2, C2H6, and D2at pressures ?90 Torr, giving laser output energies up to ∼70 mJ with a maximum efficiency of about 2.2%. We observed that the insertion of a peaking capacitor bank across the main discharge gap strongly affected the laser output characteristics. The laser output energy was seen to vary with the capacitance of the peaking capacitor bank, whose influence is a function of the SF6partner in the laser mixture, the gas pressure, and the input energy density into the discharge.

ISSN:0021-8979    

DOI:10.1063/1.328700

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

This paper supports an earlier suggestion that saturation of the optical nonlinearity of a medium by a plane wave will suppress filamentation of the wave. A variational approach and exact solutions of the slowly‐varying‐envelope approximation of the linearized wave equation describe the growth of localized filaments on plane waves. The solutions show that a wave will be stable against filamentation if the wave is weakorif it is intense enough to saturate the nonlinearity of the medium. Experiments are proposed to demonstrate suppression of filamentation of CO2laser beams exceeding 1010W and Nd laser beams exceeding 1012W in fully ionized hydrogen plasmas. The beams saturate the nonlinearity of the plasma by ponderomotive forces; absorption is negligible in the rarefied channel produced by the laser. Applications may include lossless filters that remove intensity hot spots from beams or convert mulitmode beams to nearly single mode.

ISSN:0021-8979    

DOI:10.1063/1.328701

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Low‐loss plastic optical fibers (POF) have been prepared with the attenuation loss of 114 dB/km at the wavelength of 670 nm employing polystylene core and ethylene‐vinylacetate copolymer cladding. The POF can allow the use for short‐distance optical signal transmission. The theoretical loss limit of polystylene core POF is calculated to be 70 dB/km at 670 nm.

ISSN:0021-8979    

DOI:10.1063/1.328702

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The time dependence of the potential distribution in a parallel plate discharge is discussed in terms of a model which indicates the plasma potential oscillates with the applied voltage only over the positive part of the cycle. Measurements of this oscillation have been made, and the response of the ions to the oscillating field has been studied as a function of excitation frequency.

ISSN:0021-8979    

DOI:10.1063/1.328703

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The bandwidth broadening effect of mixing two slow‐wave modes in a dielectric loaded gyrotron is investigated for a small axial momentum spread. The usual intermediate wavelength mode (IWM) integrates with the short wavelength mode (SWM) by reducing the electron beam radius, and creates a mixed slow wave. The resulting bandwidth for the mixed mode gyrotron becomes at least twice broader than that for the pure IWM at the small velocity spread (≲1%) with a substantial contribution of the SWM. Moreover, the presence of the SWM reduces considerably the troublesome heat dissipation in the dielectric layer. Therefore, the mixed mode operation can allow up to several times more power than the usual IWM mode operation.

ISSN:0021-8979    

DOI:10.1063/1.328422

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Spectrometry ofK&agr;radiation emitted during the interaction of an intense particle beam with matter is proposed as a diagnostic. Temperature measurement is possible through the detailed analysis of theK&agr;satellite spectrum. The role of line self‐absorption for this and otherK&agr;measurements is discussed. The feasibility of such measurements is demonstrated in an electron beam‐target interaction experiment.

ISSN:0021-8979    

DOI:10.1063/1.328415

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The influence of a background plasma on the diocotron instability of a relativistic hollow electron beam is investigated within the framework of a cold fluid model. The background plasma is taken to have a uniform density except at the mean radius of the electron beam where the density is assumed to be discontinuous. Of the charged species comprising the plasma, only the electrons influence the dynamics of the beam‐plasma system; the effect of the ions is negligible because of their small plasma frequency. A dispersion relation for the eigenfrequencies of the system is derived and employed to examine instabilities. It is found that the fundamental (l= 1) mode, which is unconditionally stable for a hollow electron beam in a vacuum, is now unstable for certain parameter regimes. The appearance or growth of instabilities with increases in the plasma density discontinuity is observed, while increases in the relativistic factor &ggr;bare seen to exert a stabilizing influence. It is also found that thin beams are generally more unstable than thick ones.

ISSN:0021-8979    

DOI:10.1063/1.328416

出版商:AIP    

年代:1981

数据来源: AIP