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The performance of a pulsed CO2 laser using the capacitor transfer circuit is generally known to improve with an optimum peaking-to-storage capacitor ratio Cp/Cs which varies from around 0.1 to almost 0.5. There has been no reported attempt to account for precisely the origin of this optimum ratio and the large difference amongst them with different experimental setups. In this paper, the optimum capacitor ratio is shown to depend uniquely on the distributed circuit inductances. This may be understood from a simple consideration of the impedance matching for achieving an optimum power transfer at a quasiconstant E/N ratio into the main discharge. [ABSTRACT FROM AUTHOR]

This article presents an in situ calibration of a streak camera from 500 ps/mm to 20 ns/mm of streak speeds with an adjustable time-sequenced multispark switch. This switch is comprised of a trigatron which drives two other secondary sparks separated in time from several nanoseconds to almost 1 μs by simply varying their respective breakdown gaps. The spark light sources of ≤7-ns rise time from these two secondary breakdowns are coupled into the streak camera using optical fibers and the null streak span separating two parallel streak images corresponding to the time delay between their measured spark currents, thus allowing a streak speed to be calibrated. The main advantage of this calibration technique, besides simplicity and cost effectiveness of the multispark switch, is that the streak camera is easily synchronized without using any electronic delay unit. [ABSTRACT FROM AUTHOR]

A simple trigatron spark-gap chamber is modified to accommodate two cascading highvoltage breakdowns, separated by the time lag of the second spark formation. The time lag is employed as a temporal delay for synchronizing the ultraviolet preionization and the main discharge in the transversely excited atmospheric CO[sub 2] laser. Owing to prompt triggering and in situ preionization of the second breakdown, reliable delay up to 500 ns is possible by simply varying the separation of the second spark-gap electrode to that of the first spark gap. [ABSTRACT FROM AUTHOR]

A simple, cost-effective image-intensifying fluorescent probe designed for mapping the magnetic surfaces in the heliac sheila is described. It consists of a phosphor-coated metal plate which is enclosed in a grounded U-channel that provides electrostatic shielding. An adjustable accelerating voltage is applied to the metal plate to greatly increase the cathodoluminescence produced by the directed electron beam from an electron gun, and the visible electron-beam image is recorded by a CCD camera. The gain in the image brightness allows significant reduction of the electron-beam energy to minimize the deviation of the measured drift surfaces from the true magnetic surfaces, and to improve resolution for detailed studies of surfaces in the newer stellarator experiments. This technique is particularly suited to electron energies below the phosphor activation threshold, when external image intensifying systems are likely to be very inefficient. Up to 36 toroidal rotations have been observed, limited mainly by the effective cross sections of the fluorescent probe and the electron gun. Mapping at low magnetic field strengths allows detection of small fixed amplitude field errors. Measurements of the gain characteristics and resolution are presented, with an example of the electrically variable resolution achievable with this design. The effect of electron energy on drift surfaces of a heliac is demonstrated. [ABSTRACT FROM AUTHOR]

A microscope slide with several transparent slits installed in a streak camera is used to record time-resolved two-dimensional information when a curved luminous plasma sheath traverses these slits. Applying this method to the plasma focus experiment, the axial run-down trajectory and the shapes of the plasma sheath at various moments can be obtained from a single streak photograph. [ABSTRACT FROM AUTHOR]

Streaked shadowgraphy based on a simple coaxial flashlamp-pumped dye laser as the probing light source is applied to a plasma focus pinch in argon fill gas. This resolves a major problem in using the normal streak photography for capturing the gross dynamics of argon focus pinch, in which its plasma luminosity as a function of time is highly nonuniform. [ABSTRACT FROM AUTHOR]