In an electron beam sustained discharge Xenon laser the discharge energy deposition has been varied in order to investigate the saturation effect on the Xenon laser. The current density of the electron beam is varied separately in the range of 0.1-2.7 A/cmz to obtain optimized discharge excitation conditions as a function of electron beam current density and gas pressure. An optimal fractional ionization f = 3.5-4 x lo-' is found, independent of the electron beam parameters.The synergy of electron beam and discharge excitation has resulted in a maximum specific energy of 15 J/I at a total gas pressure of 9 bar.

In this paper we present results we obtained in mine detection, in the course of a multi-national European research program.Trials were performed in the Joint Research Center in ISPRA, using polarimetric infrared imagers. Usually the 3-5 im spectral band is used for this application, however we explain that the 8-12 im band is physically a better choice. We thus obtained information on the polarization of the self emitted radiations of the objects so that our method should be more versatile regarding the environment. Images of the global intensity, the radiation global ellipticity and orientation are presented on several types of mines. The obvious increase of contrast between the observed mines and the clutter demonstrates the usefulness of this technique in mine and UXO detection.

Abstract.Experimental investigations on an e-beam sustained near infrared Ar :Xe laser have been carried out to determine the intrinsic efficiency at optimized conditions. A parametric study at different sustainer currents reveals a maximum output energy depending on current density. Up to 8 bar the optimized laser output power per unit volume increases linearly with 1.1 M W / l b a r . Intrinsic efficiencies of up to about 8% are feasible. The near infrared A r : X e laser has attracted much interest because this type of laser shows a high intrinsic efficiency and a high specific energy. It uses rare gases for the active medium resulting in a long gas lifetime. The wavelengths due to transitions between the 5d and 6p levels of Xe are between 1.73 and 3.51 gm and are short compared to that of a CO2 laser. There is no gas dissociation and no thermal population of the lower laser level so that cooling provisions are less critical. In this paper results will be presented from measurements on an e-beam sustained electrical discharge Ar :Xe laser. PACSThis technique has been successfully applied in the past for excimer laser studies [1] and for the Ar :Xe laser [2~4]. It uses the e-beam both to ionize the medium and to maintain the stability of the discharge. The sustainer discharge ionizes the xenon atoms again from the metastable (6s) state. In this way the system works as a four-level system with the metastable state as the ground state in the excitation scheme. The e-beam excitation from the atomic ground state assures sufficient replenishment for metastable atoms that are quenched to the ground state.In the present studies we investigated the optimum conditions with respect to efficiency and laser output as a function of experimental parameters such as gas pressure and current densities of e-beam and sustainer.

The high pressure atomic xenon laser is becoming the most promising light source in the wavelength region of a few microns. The merits are high efficiency (so far up to 8 percent), high output energies (15 J/liter at 9 bar), high continuous output power (more than 200 W/litre), no gas dissociation and thermal heating of the lower laser level. Compared with the well-known low pressure xenon laser the power performance is now roughly a factor thousand higher. The operation of the system, based on three-body-collisions, uses the metastable state of the xenon atom as the ground state so that in the recirculation of energy a high quantum efficiency is obtained. Furthermore the homogeneous line broadening caused by the high collision frequency has also a strong beneficial effect on the efficiency. However, the required intense homogeneous excitation of the gas medium at high density is from a technical point of view a great challenge. From our experimental and theoretical work we found that at optimum performance the input power must be 1 to 2.5 [KW cm3 atm 2j. We describe our results obtained with c-beam sustained and x-ray preionized systems delivering pulsed energies in the range of joules per litre. Furthermore we describe our recent results on continuous RF excited wave guide systems of about 37 cm length with output powers in the range of watts.Keywords: high atomic lasers, cw and pulsed 2-3 j.m lasers.

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