摘要:

Two magnetically insulated ion diodes that utilize a radial applied‐Bfield are described. Both diodes generate an annular beam that is extracted along the diode axis. The first diode operated at 1.2 MV and 600 kA for 25 ns and generated a 300‐kA ion beam. The second operated at 300 kV, 100 kA and generated 15 kA of ion current. The first diode was used to study diode performance as a function of inner and outer anode‐cathode gaps, the applied‐Bfield, and transmission line current ratios. The second diode was used to study anode plasma formation. The diodes were operated belowBcrit, resulting in electron leakage to the anode, especially near the outer cathode. A definition ofBcritapplicable to extraction diodes is given and methods of improving ion production efficiency in these diodes are suggested. The strong correlation of ion production with visible light emission suggests, however, that the electron loss played an important role in anode turn‐on. The breakdown of neutral gas desorbed by electron impact is thought to be the anode plasma production mechanism. The grazing incidence leakage electrons affect the breakdown by significantly enhancing space‐charge‐induced electric fields in the dielectric‐filled anode grooves.

ISSN:0021-8979    

DOI:10.1063/1.334728

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

An array of soft x‐ray diodes has been used to obtain central nickel densities for discharges in the Doublet III tokamak, during operation with an inconel primary limiter, in which nickelL‐line radiation dominated the diode signals. The nature of the diode signals is determined primarily by comparison with soft x‐ray spectra. The contribution of the continuum portion of the spectra to the central diode signal can be calculated and compared to the observed signal. When the diode signal is dominated by nickelL‐line emission, the observed signal is considerably larger than the calculated continuum contribution. Chordal data from the array of diodes are inverted to provide the spatial profile of soft x‐ray emission. Because the diodes are absolute detectors of radiation, the soft x‐ray emission profile is used to obtain the absolute nickel concentration and density profile in the center of the plasma. A computer code, including over 100 nickelL‐line transitions, has been developed to obtain the nickel density. The nickelL‐line cooling rate, calculated with the code, is presented. The nickel density obtained by this technique agrees well with that obtained from theK&agr;line intensity measured with a soft x‐ray spectrometer and that obtained from a bolometric measurement of central radiated power coupled with a coronal equilibrium model of the radiation.

ISSN:0021-8979    

DOI:10.1063/1.334729

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The discharge and ion extraction properties of a beam‐plasma ion source have been studied experimentally. The extractable ion current is maximized when the discharge column length is chosen to be an optimum length. The peak extracted ion current can exceed the Child–Langmuir current as much as an order of magnitude.

ISSN:0021-8979    

DOI:10.1063/1.334730

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

We solve the Poisson–Vlasov equations for volume‐produced ions, fast neutrals, and backstreaming electrons in a Mirror Fusion Test Facility 80‐keV preprototype neutral beam source. Neutral pressure distributions are estimated from known gas feed rates and calculated accelerator column conductance, and are calibrated by comparing measured and calculated electron backstreaming power (computed by solving another Vlasov equation). The depletion of atomic yield from these volume processes is computed for sources in which the atomic yield is 100% in the extraction region. The energy distribution of neutrals and ions is also established.

ISSN:0021-8979    

DOI:10.1063/1.334731

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The modulation instability evolving from a continuously amplitude‐modulated perturbation is observed in the ionization waves excited in the He positive column of a glow discharge. The degree of modulation increases with wave propagation, and an isolated pulse‐like wave evolves. The so‐called envelope soliton propagates toward the anode, retaining its own waveform. The measured growth rate of the modulational instability agrees well with that of the calculated one. The growth rate becomes maximum at a certain modulation frequency, as is predicted by a coupled mode theory.

ISSN:0021-8979    

DOI:10.1063/1.334732

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A simple method of producing a relatively large volume of metal vapor for laser‐plasma interaction studies is described. The method uses the explosive removal of a thin metal film from a glass substrate with a low‐intensity laser pulse.

ISSN:0021-8979    

DOI:10.1063/1.334733

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The Proto‐II accelerator has been used to implode krypton and xenon annular gas puffs. A significant fraction of the machine electrical energy was converted first to plasma kinetic energy and then to x rays when the plasma pinched on axis. Quantitative measurements using time‐resolved bolometers have shown as much as 10% of the total radiation yield near 1 keV in Xe and 2 keV in Kr. We have compared this radiation yield to the predictions from one‐dimensional magnetohydrodynamic code calculations. The implosions were also observed with both time‐integrated pinhole cameras and spectrographs. No hard x‐ray (E>10 keV) output was observed.

ISSN:0021-8979    

DOI:10.1063/1.334734

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Infrared absorption bands which can be related to conformational defects in long polymethylene chains are calculated both in frequency and in intensity. End‐gauche, kink, and U‐fold conformational distortions are considered; a complete characterization is given in the frequency range from 700 to 1400 cm−1.

ISSN:0021-8979    

DOI:10.1063/1.335480

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Lattice parameters of LiNbO3were measured at room temperature over the pressure range 0–35 GPa by x‐ray diffraction using the diamond anvil cell. In the region below 13 GPa (where a hydrostatic pressure was maintained) the pressure dependence of the volume can be well described by the Birch–Murnaghan equation of state, yieldingB0=134±3 GPa for the zero‐pressure bulk modulus andB’0=2.9±0.5 for its pressure derivative. A phase transformation was detected at 30±3 GPa both by x‐ray diffraction and by optical observation of the change from a transparent to an opaque state. The pattern of the high‐pressure phase was tentatively indexed on the basis of a cubic cell witha=6.78 A˚.

ISSN:0021-8979    

DOI:10.1063/1.334682

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Argon ions with energy 250 keV were implanted at fluences of 2×1016cm−2at temperatures of 500, 250, and 21 °C, in a specimen of relatively pure polycrystalline nickel. Deuterium was introduced into the surface and implanted regions by making the specimen the negative electrode of an electrolytic cell containing 1‐Npure deuterated sulfuric acid. Deuterium trapped in the vacancy complexes of the implanted regions was analyzed as a function of temperature using the2H(3He,1H)4He nuclear reaction during an isochronal annealing process. The results indicate that the types of traps and trap densities found in the regions implanted at 21 and 250 °C were essentially identical while the trap density found in the region implanted at 500 °C was approximately 40% of that found in the other regions. Math model comparison with the experimental results suggests the existence of at least two types of traps in each region. Trap binding enthalpies used in the math model to fit the experimental data were slightly higher for the region implanted with argon at 500 °C than for the regions implanted at the lower temperatures. TEM studies revealed the presence of small voids in the region implanted at 500 °C as well as dislocation loops similar to those found in the regions implanted at the lower temperatures.

ISSN:0021-8979    

DOI:10.1063/1.334683

出版商:AIP    

年代:1985

数据来源: AIP