Results are presented from experimental and theoretical studies of the efficiency of using a CO 2 laser to create a high-power source of 13- to 14-nm EUV radiation for lithography. For a laser intensity of ∼2 × 10 11 W/cm 2 , a conversion efficiency of k EUV ≃ 1.5% was achieved on a plane solid Sn target. The calculated gas dynamics and population kinetics of Sn plasma ions agree qualitatively with experimental results.

In the experiments on the CO2-laser facility TIR with output pulse duration similar to15 ns and pulse energy similar to100 J high-current beams of ions with charge Zsimilar to20divided by 30 and energy up to similar to1 MeV were obtained. High quality of spatial and temporal light beam characteristics as well as possibility to vary its parameters in accordance with required target irradiation conditions provide an opportunity for generation of ion beams with high charge and large number of particles. Results of measurements of ion energy spectra and ion fluxes for different expansion angles are presented. Technological and medical applications of such beams are discussed.

Time evolution of the X-ray spectrum of a lead ion plasma generated by CO2 laser pulses with an energy of 100 J and a duration of 15 ns was measured using an X-ray polychromator with six channels covering the quantum energy range from 180 to 1850 eV. The plasma temperature was determined by comparing the results of measurements with the calculated X-ray emission spectra. The electron temperature measured well agrees with the calculated data.

CO2-laser-produced plasma ion component parameters were studied for aluminium and lead targets at laser intensity of P = 4×1013 W cm−2 and pulse duration of τ = 15 ns experimentally and numerically. Angular dependences of ion number density for different charge states, average velocity and its spread were measured by time-of-flight method. Ion charge state distribution shows high-charge and low-charge state groups at normal expansion direction. Ions in these groups have different average expansion velocity and longitudinal velocity spread. Angular distribution of high-charge states is narrower than that of the low-charge state ion group, maximum yield of low-charge states occur at some angle from normal. For Al target results show similar trends as for Pb target, but simulations have indicated that the effect of laser ponderomotive force is more pronounced in this case.

CO2 laser-produced plasma ion component parameters were studied experimentally and numerically for aluminium and lead targets at peak laser intensity of 4 x 10(13) W cm(-2) and FWHM pulse duration of 15 ns. Angular dependences of ion number density, average velocity, and its spread were measured for different charge states by time-of-flight method. Ion charge state distribution shows high-charge and low-charge state groups. Ions in these groups have different average expansion velocity and longitudinal velocity spread. Angular distribution of high charge states is narrower than that of the low-charge state ion group, maximum yield of low charge states occurs at some angle from normal. For Al target the results show similar trends as for Pb target, but simulations have indicated that the effect of laser ponderomotive force is more pronounced in this case.

Temporal evolution of X-ray spectra of lead plasma produced by a CO2 laser pulse with energy of 100 J and a duration of 15 ns has been measured using a six-channel X-ray polychromator. The polychromator registered the radiation intensity in the range from 180 to 1850 eV. Plasma temperature was determined by comparison of measured results with radiation spectra obtained by numerical simulation. The values of electron temperature are in good agreement with results of hydro simulations.

By means of spatially resolved high-resolution X-ray spectroscopy, we have investigated the generation of fast ions at various laser installations with different flux densities and laser wavelengths. It is demonstrated that the fast ion generation in laser-produced plasma can be achieved for a very low level of the averaged laser intensity on the target. The time-of-flight mass spectrometry ion diagnostics and X-ray spectrographs give very close results for the energy distribution of the thermal ion component. For higher energies, however, we found significant differences: the spatially resolved high-resolution spectrographs expose the presence of suprathermal ions, while the time-of-flight method does not. Suprathermal ion energies Eion plotted as a function of the qλ2 parameter show a large scatter far above the experimental errors. The cause of these large scatters is attributed to a strong nonuniformity of the laser intensity distribution in the focal spot. The analysis by means of hydrodynamics and spectral simulations show that the X-ray emission spectrum is a complex convolution from different parts of the plasma with strongly different electron density and temperature. It is shown that the highly resolved Li-like satellite spectrum near Heαcontains significant distortions even for very low hot electron fractions. Non-Maxwellian spectroscopy allows determination of both the hot electron fraction and the bulk electron temperature.

In the system consisting of a master oscillator, a three-pass telescopic amplifier, and saturable absorbing cells, CO2 laser pulses with an energy of 100 J and duration variable from 15 to 80 ns were obtained. A theoretical model for the calculation of interaction of CO2 laser radiation with resonance absorbing and amplifying media was developed. The system consisting of an absorber saturated at the leading edge of the pulse and an amplifier working in the deep-saturation mode was shown to provide a considerable increase in the gain and pulse compression.

The measurement results are presented for angular dependency of the CO2 laser produced plasma parameters at power density of 4.10(13)W/cm(2) and laser pulse duration of 14 ns. 2D numerical simulations are in sufficiently good agreement with experiment. It is shown that the light pressure effects on plasma expansion dynamics and the number of particles generated at the target normal direction.

The evolution of the ion composition of a laser plasma during its expansion over a large distance is studied. The plasma is produced by a TIR CO2 laser with a pulse energy up to 100 J and duration of ∼20 ns. X-ray diagnostics with the use of a spectrograph and X-ray PIN diodes was applied to study the plasma near the target surface. At large distances from the target surface, time-of-flight neutral-particle diagnostics with the use of an electrostatic analyzer and ion collector was applied. Calculations performed with the GIDRA-1 code agree well with experimental data.

A CO2 laser system with self-modulation of the intracavity losses was developed. This system was capable of generating efficiently pulses free of a radiation 'tail' typical for CO2 lasers. A simple method was used to detect the optical inhomogeneity of the medium of a gas-discharge TEA module. The results of the measurements are presented.

2D simulation of a composite Z-pinch was performed by the complete radiative magnetohydrodynamic code ZETA including detailed calculation of EOS, spectral properties of materials and radiation transport in non-LTE multicharged ions plasma.

Simulations of gain in recombining laser-produced plasma of Li-like ions of aluminum were performed using the 2-D code GIDRA-5. Symmetrical 4-beam scheme of fiber irradiation was modeled in accordance with experimental arrangement described in Rei. (1). These simulations show good agreement with earlier 1-D simulations for optically thin plasma. Maximal angle-averaged value of gain on 3d(5/2) -4f(7/2) transition in Li-like aluminum calculated using Sobolev approximation for photon escape probability and the Doppler line profile was 0.95 cm(-1). These 2-D simulations also show more realistic laser energy absorption (25-30% in 2-D simulations compared to nearly 90% in 1-D simulations and 6% in experiments).

It is shown that in a dense, not very hot, multiply charged plasma the satellite structures of resonance lines can become more intense than the resonance lines themselves. Experimental and theoretical investigations show that the conditions under which the satellite structures dominate in the emission spectrum of the plasma are quite easily realized experimentally and, furthermore, apparently they will be the most typical case in investigations of compressed plasma regions in inertial-confinement fusion experiments and in the study of plasma produced by high-contrast pico-and femtosecond laser pulses.

Resonant and intercombination spectral lines formation of He-like magnesium is analyzed both experimentally and numerically.It is shown that in plasma created by XeCl laser at flux density 8.10(12) W/cm(2) the peak of electron temperature is placed downstream from the critical surface at density significantly smaller than critical, and radiation in both resonant and recombination lines is also produced by the plasma region with density below critical. Simulations also show significant line radiation at large distances (1 - 2 mm) from the target as it was observed in experiments. This secondary peak is produced by a compression wave forming near the plasma front.As opposite, radiation in these lines in plasma created by Nd-glass laser at flux density 5.10(13) W/cm(2) comes from the plasma region placed deeper than the critical surface and has no tail at large distances.

The results of lead ion generation with charge state from Pb10+ to Pb35+ from laser-heated plasma are presented. CO2 lasers producing 10.6-μm wavelength radiation at power densities in the range 4.1011-6.1014 W/cm2 in TBKI and CERN were used. Results of detailed numerical simulations presented in the paper are in good agreement with the experimental data. Work done in collaboration with CERN, ITEP, and TBKI was aimed at the specification of requirements for a laser system that will be able to drive an ion source for the hadron collider (LHC) at CERN.

For light ions, Laser Ion Sources have already found their application (e.g. Dubna). At CERN a source for heavy ions with the final characteristics Pb25+, with current of 5 - 10 mA, a pulse length of 5 - 6 mu s, a normalised 4 x rms emittance of 0.2 - 0.4 mm*mrad, is under development. Topics like the required laser energy and performance, the ion beam transport and the acceleration are discussed. The different phases of the realisation of this source and its status are presented.