摘要:

The driver and target parameters required to extend the successful results from an exploding foil Ne‐like‐Se soft x‐ray laser at 206 A˚ towards wavelengths of 40 A˚ are investigated. The power requirements are found to scale as &lgr;−4, which is quite costly. The principal constraint is the refraction of the x‐ray laser beam in these high density, single pass, exploding foil targets. Correcting mirrors or nonrefracting target designs could reduce this costly scaling.

ISSN:0031-9171    

DOI:10.1063/1.866797

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The general analytical solution of a collisional‐radiative model, including atom–atom inelastic collisions, for nonequilibrium, partially ionized, steady‐state plasmas is presented. This is applied to argon plasmas and the results are compared with previous numerical calculations. The model includes three atomic energy levels; the ground level, one excited level, and continuum, and assumes a Maxwellian electron and atom distribution functions. All rates for collisional and radiative processes are expressed as analytical functions. The model is solved algebraically to obtain analytical expressions for the electron and excited atom densities as a function of the plasma parameters. In the limit of an optically thick plasma the solution agrees with results for complete thermodynamic equilibrium. Solutions are presented for a wide range of conditions (3000≤Te≤24 000 K, 105≤Ne≤NAcm−3, 1014≤NA≤1018cm−3).

ISSN:0031-9171    

DOI:10.1063/1.866798

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Experiments on the spherical expansion of a plasma into an underdense plasma are described. The initial spherical plasmas are stable anode spots that expand into the ambient region. The anode spots are formed in low pressure noble gas plasmas that have been impregnated with acetone. The formation mechanism is interpreted in terms of electron attachment on the acetone molecules.

ISSN:0031-9171    

DOI:10.1063/1.866799

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Toroidal rotation of the central plasma core has been observed prior to and during electron cyclotron heating (ECH) in the Doublet III tokamak [inPlasmaPhysicsandControlledNuclearFusionResearch1984, Proceedings of the Tenth International Conference, London (IAEA, Vienna, 1985), Vol. 1, p. 131]. Measurements were made using a curved‐crystal Bragg x‐ray spectrometer with spectral resolution of &lgr;/&Dgr;&lgr; of greater than 19 000 and temporal resolution of 20 msec. Ion rotation velocity was determined from the Doppler shift of x rays emitted from the plasma impurity Ti XXI resonance line. Ion temperatures were determined from the Doppler broadening of this line. A study of purely Ohmic discharges suggests that nonrotating discharges exhibit magnetohydrodynamic activity other than sawtooth oscillations, while those that rotate exhibit sawteeth. Discharges with plasma rotation prior to the appliction of ECH appear to heat more effectively than those that do not. Velocity and temperature histories show that there are temporal characteristics corresponding to whether the plasma was or was not effectively heated.

ISSN:0031-9171    

DOI:10.1063/1.866800

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Several kinds of experiments have been done relating to the second harmonic emission from a plasma produced by a 1 &mgr;m laser pulse of 30 psec. Complicated spectra of the second harmonic have been observed above ∼1013 W/cm2. It has been concluded that their production mechanisms are dependent on the self‐focusing of the laser beam. In the absence of the self‐focusing of the laser beam, it was determined that the complicated spectrum was caused by the parametric decay instability of an electron plasma wave excited by the resonance absorption. In the presence of the self‐focusing of the laser beam, on the other hand, other mechanisms have been found to be dominant. It was tentatively concluded that they are the unstable motion of the critical surface of the plasma or the self‐phase modulation of the laser pulse.

ISSN:0031-9171    

DOI:10.1063/1.866801

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

When induced by pitch‐angle scattering, waves of the middle branch of the extraordinary mode will give up their energy to a plasma by magnetically pumping electrons. The damping decrement for small‐amplitude extraordinary waves is calculated and the decrement for finite‐amplitude waves is estimated. Because heating a plasma makes it a better absorber of extraordinary waves, such waves can produce localized hot cavities in plasmas. The evolution of electron distribution functionsf(v) is examined and it is found that magnetic‐pumping‐mediated absorption leads tof∝v−3tails.

ISSN:0031-9171    

DOI:10.1063/1.866802

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

For the first time, the temporal structure of ion energy in a plasma focus is revealed using a time‐resolving Thomson spectrometer. The velocities and arrival times of ions are determined from the spectrogram. The resulting distribution of ions in velocity–time space at the source is found to be a line distribution, as if the ions were accelerated in a diode by a pulsed voltage.

ISSN:0031-9171    

DOI:10.1063/1.866803

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Kaufman’s formula [Phys. Fluids15, 1063 (1972)] for the first‐order distribution function obtained via the action‐angle formalism is shown to be correct. The proof requires that it be noted that the transformation from canonical coordinates to physical variables has terms of all orders. Neglect of this fact has led to an incorrect formula for the linear susceptibility in previous work.

ISSN:0031-9171    

DOI:10.1063/1.866804

出版商:AIP    

年代:1988

数据来源: AIP

ISSN:0031-9171    

DOI:10.1063/1.867027

出版商:AIP    

年代:1988

数据来源: AIP