High-temperature iT, > 150 e'V), small-diameter (--200 J..lm) plasma columns have been efficiently generated by very fast (13 ns rise time, 28 ns full width at half maximum) pulsed discharge excitation of capillary channels filled with preionized gas. Discharges in argon-filled capillaries at currents between 20 and 60 kA produced plasmas with Ar x-Ar XIV line emission, in which the degree of ionization was controlled by the magnitude of the current pulse. The characteristics of these plasmas differ from those created by vacuum discharges in the same capillaries and approach those necessary for soft-x-ray amplification in low-Z elements. PACS numberts): 52.80. -s, 42.55.Vc

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A cold plasma switch scheme with opening and closing capabilities is reported. An externally applied magnetic field causes a low pressure hollow cathode discharge to transition from a low impedance mode sustained by oscillating beam electrons into a virtually collisionless high impedance mode. The impedance of a 10 A discharge was demonstrated to increase by 20 with the application of a field of 0.018 T.Switches and modulators are fundamental components in most pulse power applications. Compact high power closing switches have been successfully developed based on discharges which utilize hollow cathodes. 1 -3 These devices have been operated in a glow discharge mode at currents in excess of 100 kA. 2 It has been recognized that the ability to interrupt a high current hollow cathode discharge (HCD) would have a significant impact in pulse power technology.4•5 Magnetic fields are known to affect the impedance of HCDs. 6-9 A plasma switch based on controlling the plasma density in the axis of a HCD by means of an axial magnetic field has been investigated by Schoen bach et a!. 4 • 5 In those experiments the applied magnetic field confined the energetic electrons, which normally oscillate radially between the walls of a cylindrical HCD creating an axial region of enhanced ionization, to the periphery of the discharge. An applied magnetic field of 1.2 T was observed to reduce the plasma density in the axis of the discharge, increasing by a factor of six the impedance of a 10 A discharge. 5 In this letter we report a new cold cathode glow discharge plasma switch configuration which requires a significantly smaller magnetic field, of the order of 0.01 T, to modulate the discharge current. In this scheme an externally applied magnetic field causes a HCD to transition from a low impedance regime, sustained by the ionizing collisions of oscillating beam electrons, into a high impedance mode which is virtually collisionless. This is achieved by deflecting to the anode the entire flux of energetic beam electrons. The resulting decrease in the ionization efficiency, which at low pressure can reach two orders of magnitude, quenches the discharge. To implement this scheme a discharge geometry must be selected such that the trajectory of the beam electrons intercepts the anode when a small magnetic field is applied. The discharge geometry shown in Fig. 1, which consists of a pair of parallel plate cathodes placed perpendicular to a pair of parallel plate anodes, is one of the several possible configurations that meet this requirement.The physical processes that determine the behavior of the discharge are discussed below. It is well known that in cold cathode HCDs the majority of the applied voltage falls in a positive space charge region, the cathode sheath, which develops in front of the cathode. 10 The rest of lhe space enclosed by the cathode structure is filled by the •>on leave from Phillips Laboratory, Kirtland Air Force Base, NM. negative glow, which is practically electric field free and is sustained by the ionizatio...

ArF(B-X) laser emission has been observed under long pulse electron-beam excitation at relatively low pump rate. ArF lasing only occurred with Ne buffered gas mixtures. Optimum performance of 1.93 J/ℓ at an intrinsic efficiency of 1.35% occurred with an Ar/F2 mixture of 1/0.075% using a Ne buffer to 4.0 amagats. Total energy of 290 mJ in a 2-cm2 beam with a 1.0-μs full width at half maximum pulse width was recorded.