P.J.M. Peters

Small‐signal gain measurements in an electron beam pumped F2 laser

The net‐small‐signal gain of a molecular fluorine F2 * laser pumped by a coaxial electron beam has been measured in gas mixtures of He/F2 and He/Ne/F2. A peak net‐small‐signal gain of 0.63 cm−1 has been measured in a mixture of He/Ne/F2 at a pressure of 8 bar and a pumping power density of 13 MW/cm3.

New continuous wave infrared Ar‐Xe laser at intermediate gas pressures pumped by a transverse radio frequency discharge

An atomic Xe laser with a transverse rf excitation has been operated in a cw mode in the intermediate pressure regime. The laser output spectrum consisted of 5 Xe lines with wavelengths of 2.03, 2.63, 2.65, 3.37, and 3.51 μm. The unoptimized total output power of 330 mW was obtained for a gas mixture Ar:He:Xe=59:40:1 at a pressure of 85 Torr and a rf input power of 150 W and excitation frequency of 121 MHz.

Pressure-dependent optical delay time measurements in a coaxial electron beam pumped Ar:Xe laser

Optical delay times and pulse widths of five Ar:Xe laser lines have been measured as a function of the total gas pressure. Both the delay time and the pulse width appeared to be almost linearly dependent on the inverse gas pressure. For a total gas pressure of 14 bars the delay times were around 100 ns, at a total gas pressure of 1 bar the laser output typically appeared after 1–3 μs.

Current filamentation in discharge-excited F2-based excimer laser gas mixtures

Discharge instabilities in x-ray preionized F2-doped excimer laser gas mixtures are investigated using an intensified charge coupled device camera with a gating time of 300 ps. In contradiction with earlier theories and observations, it is found that the discharges in He/F2 mixtures are homogeneous only at very low concentration of F2 0.025%. We present experimental results, which prove that in He/Kr/F2 mixtures the appearance of discharge filaments is coupled with the presence of F2 rather than Kr.

Vacuum ultraviolet fluorescence of (XeRb)+ produced in an electron‐beam‐pumped gas mixture

With a pulsed electron beam a gas mixture of Ar, Xe, and Rb was excited producing (XeRb)+ ionic excimer molecules. To study the formation kinetics the (XeRb)+fluorescence pulse was measured as a function of the gas composition and the pumping density. From the observed fluorescence signal decay a value of 6±1×10−30 cm6/s for the formation rate constant of (XeRb)+ from Xe+, Ar, and Rb was determined.

Generation of powerful electron beams in a dense gas with a dielectric-barrier-discharge-based cathode

An electron beam source based on a dielectric barrier discharge and a perforated anode working in a dense gas is described. Electron beams with current densities up to 60 A/cm2 and pulse durations of 150 ns were generated. Stable operation of the device at a repetition frequency of 200 Hz has been demonstrated.

Continuous wave near‐infrared atomic Xe laser excited by a radio frequency discharge in a slab geometry

Near‐infrared atomic Xe laser lines have been generated from an Ar:He:Xe laser gas mixture excited by a radio frequency (rf) discharge in a slab geometry. A maximum continuous wave (cw) output power of 1.5 W (270 W/l) was obtained at an rf frequency of 125 MHz from a gas mixture containing Ar:He:Xe (50:49:1) at a total gas pressure of 90 Torr.

A study of the electron quenching of excimers in a KrF* laser excited by a coaxial electron beam

Measurements of the output energy, the optical pulse length and the build-up time of the laser pulse, obtained with a coaxially e-beam pumped KrF* laser, were performed varying the total gas fill pressure, the F2 content and the e-beam current from 1–5 bar, 0.1–0.8% and 13.3–26.6 kA, respectively. The maximum specific extraction energy amounts to 64 J/l. The large range of measurements, especially at low F2 concentrations, reveals the necessity to extend the kinetics of the F2 chain in the usual computer model. With the introduction of electron quenching of KrF* and ArF* by dissociative attachment the predictions are also for low F2 concentration in agreement with experiments.

Effect of preionization, fluorine concentration, and current density on the discharge uniformity in F2 excimer laser gas mixtures

The discharge homogeneity in F2-based excimer laser gas mixtures and its dependence on various key parameters, such as the degree of preionization, preionization delay time, F2 concentration and current density, is investigated in a small x-ray preionized discharge chamber. The spatial and temporal evolution of the discharges is monitored by taking photographs of the discharge fluorescence with a fast intensified CCD camera. It is found that a preionization electron density of about 107 cm−3 bar−1 is sufficient to initiate a streamer-free homogeneous discharge in gas mixtures of helium and fluorine with multiatmospheric gas pressure. The accompanying optimum time delay between the application of the x-ray pulse and voltage across the discharge electrodes is determined to be about 20 ns. It is shown that in spite of these optimum initial conditions, a homogeneous glow discharge eventually transforms into an inhomogeneous discharge containing numerous filaments. Our experiments show that the higher the initial F2 concentration, the initial current density or the pump power density, the shorter the time interval over which the discharge stays homogeneous. By a quantitative characterization and defining a detailed measure of the observed discharge inhomogeneity we find that halogen depletion, as suggested from the theory, is responsible for the temporal instability of discharges in such laser gas mixtures, as the experimental results are in good agreement with the theory on the halogen depletion instability mechanism

RF discharge in CO2 laser mixtures at moderate pressures

The voltage-power characteristics and spatial structure of an RF discharge in the mixtures of CO2 and N2 molecular gases with He at total pressures of tens of torr are studied. One-dimensional numerical simulations of an RF discharge are carried out within two approaches: (i) the distribution function and the related kinetic coefficients are assumed to be functions of the local reduced field, and (ii) the kinetic coefficients are functions of the electron mean energy, which is calculated with allowance for both electron heat conduction and diffusion. The latter approach is shown to better describe the existing experimental dependence of the discharge voltage and the phase shift between the discharge current and voltage on the driving power.