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Extreme Ultraviolet Source

#3648


Creation of a Compact and Effective Short-Wave EUV Source of Recombination Type with Using Current-Carrying Radiationally Collapsing Radially Converging Shock Waves in Low-Inductive High-Current Discharges

Tech Area / Field

  • PHY-OPL/Optics and Lasers/Physics

Status
3 Approved without Funding

Registration date
21.11.2006

Leading Institute
NIIEFA Efremov, Russia, St Petersburg

Supporting institutes

  • FIAN Lebedev, Russia, Moscow

Collaborators

  • Czech Technical University / Faculty of Nuclear Sciences and Physical Engineering, Czechia, Prague\nUniversity Colorado State/Electrical & Computer Engineering, USA, CO, Fort Collins

Project summary

The main purpose of the Project is to create a compact and effective short-wave EUV model source of recombination type in which for obtaining nonequilibrium plasma the current-carrying radiationally collapsing radially converging shock waves in low-inductive high-current discharges are used. Under short-wave EUV radiation it is understood the radiation in region of 13,5 and 11,5 nm, where there are multilayer narrow-band mirrors on the basis of Mo/Si and Be/Si coats, offering the challenge in applications of similar lasers in different fields of sciences and engineering.

The use of capillary discharges is one of the main ways in creation of compact (table-top) and nonexpansive sources of coherent EUV radiation on plasma of the multiply charged ions which would be accessible for scientific organizations of various descriptions. So, the laser on neon-like argon Ar8+ with wave length of 46,9 nm, created in Colorado State University, USA, is really compact and effective enough EUV source, the output energy of which has been carried to record quantity of 0,88 mJ. Even more compact and transportable source it was found a neon-like argon laser in which the laser pulse energy of 13 μJ generated with repetition rate of 12 Hz, greatest of all known experiments in the field of creation EUV lasers. With using these lasers its applicability in many fields of sciences including interferometric diagnostics of dense laser plasmas, interferometric lithography in nanoelectronics, measurements of optical constants, ablation of various materials, definition of characteristics of soft X-ray optics, etc. was successfully demonstrated.

However attempts of creation of more short-wave electrodischarge lasers, necessary for of some applications, including metrology in nanoelectronics on a wave length of 13.5 nm, till now have not crowned success. The matter is that with reducing in wave length of EUV radiation the needed specific power of pumping sharply increases, and efficiency of transformation of electrical energy stored in generators in thermal and potential energy of inverted medium falls. It leads to necessity of increasing stored electrical energy that reduces life time of capillary tubes and impedes their exploitation.

The lasers specified above work on plasma of fast z-pinches with ionization non-equilibrium. However the history of the development of EUV lasers on capillary discharges began with attempts in realization of recombinational nonequilibrium plasma in polymer tubes with ablating walls. But small gain gl, defined by an amplification coefficient and capillary length, and also low durability of polymer tubes did not allow to create practically comprehensible laser of the given type. Now owing to the development of engineering of fast discharges and numerical methods of their modeling an opportunity arises to return to the idea of recombination EUV lasers. Carried out in NIIEFA numerical RMHD calculations with account not only radiation transport, but also nonequilibrium ionization in fast low-inductive capillary discharges have allowed to find conditions of the occurrence of recombination non-equilibrium in near-axis plasma.

The proposed approach to the achievement of the set purpose, following from preliminary calculations, carried out by NIIEFA with using RMHD code, consists in the apply of current-carrying radiationally collapsing shock waves for obtaining near-axis recombinational nonequilibrium plasma column. The surrounding cylindrical dense and cold plasma layer, created by radiationally collapsing shock wave, restricts its radial expansion and increases the time of the existence of recombinational non-equilibrium near-axis plasma. With the purpose of more effective generation of similar shock waves and restrictions of energy input into the discharge it is offered to use low-inductive electrical discharges with the close spacing of electrodes. The running wave of a sliding avalanche-type discharge will be applied for preionization of gas at a voltage on the capillary equal to a double voltage of an incident wave in the transporting line. The main discharge is realized with a current, nearing to a double current of an incident wave. Main principles of such organization of low-inductive z- discharges have been checked up in NIIEFA on the model source of EUV radiation.

For researching of a hot and dense plasma column obtained by means of low-inductive capillary discharges, it is supposed to use EUV optics based on Schwarzschild objective. The objective, developed in FIAN and consisting of two hemispherical multilayer mirrors, will allow obtaining the spatial resolution better than 1 μm that will enable to study physical processes, occurring in plasma column and their influence on the quality of output radiation. Spectroscopic researches of laser radiation are planed to carry out by means of compact EUV spectrometer developed recently in FIAN and based on sliced multilayer gratings (SMG) which are compact optical devices with a high dispersion. The spectroscopic resolution of such lattices is not less than 250.

Expected results of works under the given Project:

  • theoretical and experimental confirmation of correctness of the chosen approach,
  • realization of effective regimes of obtaining active media with a recombination non-equilibrium on the example of hydrogen-like nitrogen with wave length of radiation of 13.4 nm, achievement of the linear amplification coefficient of g ≈1.5-2 cm-1 and gain of gl ≈15-20 in single path (energy of output radiation of 100 μJ).

The participating organizations have a wide experience in the given field.

NIIEFA for the long time researched radiating z- and θ-discharges for optical pumping of gas lasers, has created and preliminary explored model EUV source on neon-like ions of argon Ar8+ with using low-inductive capillary discharges at close placed return coaxial current conductor. In the Efremov Institute one-dimensional one-liquid two-temperature RMHD program has been developed with account of nonequilibrium ionization, radiation transport and the pulsed power supply system for complex numerical modeling of capillary sources. Here, with application of this program propositions on increasing efficiency of capillary sources working on recombination scheme with using of shock waves were developed.

FIAN for long time researched kinetics of EUV lasers based on plasma of multiply charged ions with electrodischarge and laser pumping. Last time Lebedev Institute successfully is developing X-ray optics and diagnostic instruments for EUV lasers, and also studies applications of EUV lasers for X-ray microtomography, reflectometry and elipsometry.

The main contents of works

Experimental research will be carried out mainly on the available in NIIEFA compact model source with low-inductive ceramic capillary, supplied from the 8-channel generator of high-voltage pulses through transmitting cable long line. Preionization of gas is carried out by means of a traveling wave of the sliding avalanche-type discharge which after reaching the output electrode transfers in the high-current main discharge. Charging voltage of the double forming line is of 100 kV, stored energy of 100 J, wave impedance of 9 Ohm, pulse length of 100 ns, inner diameter of alumina tube of 5.5 mm, linear inductance of capillary load of 1.5 nH/cm. The emphasis will be made on studying of energy balance and dynamics of plasma in low-inductive discharges, and also its radiative characteristics. With this purpose FIAN develops and manufactures imaging, focusing and dispersing optical elements and systems for wave length range of 10-48 nm, particularly x-ray optical elements and diffraction gratings for spectroscopic researches of optically active pulse plasma. In spectroscopic measurements the participation of Czech Technical University, Prague Czechia is foreseen.

Then it is planed the carry out of complex numerical calculations of dynamics and kinetics of electrodischarge plasmas, orientated on the elaboration of recommendations on development of a new high power EUV source of the recombination type with using cumulative shock waves and radiative cooling for obtaining near-axis recombinational nonequilibrium plasma. Cooperation with Czech Technical University, Prague in the field of calculations of all-level kinetics of recombining plasma on hydrogen-like ions are proposed.

On the final stage of works creation and research of a new compact EUV source on low-inductive high-current discharges with primary stored energy of ~500 J, wave impedance of 1-2 Ohms (charging voltage for DFL of 100 kV, duration of leading front in incident wave voltage of ~ 1 ns) are proposed. Modernization of the laboratory building for this experimental installation is required. Experiments on realization of recombination pumping of active medium, generating in short wave range of EUV radiation are planed on the example of hydrogen-like nitrogen N6+with wave length of 13.4 nm. Two parts of this stage are provided; the first part is carried out in NIIEFA, St.-Petersburg. After finishing electrophysical researches and preliminary spectroscopic measurements the installation is transported in Fort Collins, USA for carrying out detailed spectroscopic and optical measurements jointly with Colorado State University. After finishing these researches the source is returned in Saint-Petersburg.

The presented Project will make its contribution to fulfillment of purposes of ISTC, namely:

  • in conservation of the highly professional staff in the participating scientific organizations,
  • in development of conversion activity of these organizations and making of new laser engineering for scientific researches and high technologies,
  • in involving the Russian scientists occupied early in development of weapons, in the international scientific and technical cooperation in the peace purposes.

The Russian participants of the Project are interested in cooperation with foreign collaborators on following positions:
  • carrying out of joint numerical calculations of all-level kinetics of hydrogen-like ions, and also experimental spectroscopic researches with Czech Technical University, Prague, Czechia,
  • carrying out of joint experimental spectroscopic researches and optical measuring of characteristics of EUV radiation on the high power source, delivered specially for these purposes from St. Petersburg to Colorado State University, Fort Collins, USA,
  • rendering of assistance to participants of the Project in visiting the international conferences on related themes,
  • carrying out of joint symposiums and workshops for discussion of partial progress and elaboration of recommendations on their continuation.


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