The electron temperature of a quiescent plasma in a metal discharge chamber, where the walls serve as the anode, can be raised by introducing a second anode consisting of 0.0025-cm-diam tungsten wires held at potentials as high as 100 V with respect to the walls. Hot electrons orbit the wires and return to the plasma. Cold electrons are absorbed. Smooth temperature variation, without introduction of noise, has been achieved between 0.5 and 4.0 eV.

Highly nonlinear ion acoustic solitons are produced by the superposition of a 15\ Dwide photoionized plasma slab on a dc background. The Mach number increases with the initial step ratio R up to M » 1,95 for R « 10. Above M « 1.8, R^6, however, the profiles diffuse rapidly as they propagate. For Mach numbers M&1.8, a linear interaction is observed in the collision of two solitons traveling in opposite directions, whereas two solitions moving in the same direction exhibit a nonlinear interaction.A plasma composed of isothermal electrons and cold ions was first shown by Moiseev and Sagdeev 1 to be capable of supporting a symmetric solitary pulse, a soliton. Subsequent analysis of soliton formation and interaction, for small but finite amplitudes via the Korteweg-de Vries equation, was carried out by several authors. 2 " 5 Recently, large-amplitude solitons have been treated by computer numerical and simulation techniques. 6 " 9 Mason 7 has considered soliton formation from an initial slug of plasma (in close analogy with our experimental method). Further, soliton interactions have been considered for two important cases: (a) two solitons of different amplitude moving in the same direction with the larger catching up to the smaller, and (b) the collision of two oppositely directed solitons. Sakanaka 8 has considered case (a) with the assumption of isothermal electrons and warm ions. Using the fluid equations for cold ions and isothermal electrons, Biskamp and Parkinson 9 have treated cases (a) and (b). Ikezi et al}° have experimentally studied the reversible interactions in cases (a) and (b) for Mach numbers M% 1.2. The present experiment examines the formation of solitons with Mach numbers 1.24

Large-amplitude ion-acoustic shocks are produced by superposition of a pulsed photoionized plasma slab on a dc background. The Mach number M increases as a function of the step ratio R up to a maximum of M « 2.5 for R =20. Above R =5 and a shock jump of An/n »1, the shock widths start to broaden severely with distance from the source.

Abstract. We have developed a method for using hyperspectral (HS) data to identify and locate chemical materials on arbitrary surfaces using the materials' reflection or emission spectra that makes no prior modeling assumptions about the presence of pure pixels or the statistics of the background clutter and sensor noise. To our knowledge, this is the first time that surface detection without dependence on background information has been achieved. There are three main components to the method: (1) an HS unmixing algorithm based on the alternating direction method of multipliers that is applied over local subsets of the imaging to resolve the HS data into a set of linearly independent spectral and spatial components; (2) the fitting of those unmixing spectra to a set of candidate template spectra; and (3) a support vector machine classifier for chemical detection, identification, and location. The algorithm is illustrated on HS data collected by a Telops Hyper-Cam infrared camera on data resulting from the deposition of chemical agent simulants on various surfaces.

The results obtained from a comprehensive theoretical model for an electrically excited laser are compared with experimental data obtained from a large-volume KrF laser device, excited by an e−-beam only, or with enhancement from an electric discharge.