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Coherent X-radiation Source for Microelectronics and Medicine

#2035


Creation of a 5–50 nm Coherent Radiation Source with the Discharge-Laser Formation of Active Medium for Microelectronics and Medicine Applications

Tech Area / Field

  • PHY-OPL/Optics and Lasers/Physics
  • PHY-PLS/Plasma Physics/Physics

Status
3 Approved without Funding

Registration date
01.11.2000

Leading Institute
NIIEFA Efremov, Russia, St Petersburg

Supporting institutes

  • Vavilov State Optical Institute (GOI) / Research Institute for Complex Testing of Optical Devices, Russia, Leningrad reg., Sosnovy Bor

Collaborators

  • Electro-Optics Research Center TRW, USA, CA, Redondo Beach\nCymer,Inc. , USA, CA, San Diego\nCentre National De La Recherche Scientifique/Laboratoire De Physique Et Technologie Des Plasmas/, France, Palaiseau\nAIXUV GmbH, Germany, Aachen\nASM Lithography B.V., The Netherlands, Veldhoven\nOsaka University / Institute of Laser Engineering, Japan, Osaka

Project summary

Introduction and Overview.

The development of coherent emitting sources of soft X-ray spectrum is one of the most urgent and complicated problems of the laser physics. The range of possible applications includes not only the up-to-date physics but also chemistry, technology, biophysics and medicine. In recent years particular emphasis has been placed on production of coherent X-ray radiation with the wavelength lying in the biologically important spectral “water” window l=2.32–4.376 nm. In particular, the coherent X-ray emitting sources are of great interest for microelectronics application for production of chips. The coherent X-ray radiation opens the way for development of microchips with a characteristic size of patterns less than 100 nm and, in general, for elaboration of the technological methods in the range of 1–100 nm (nanotechnology). Another extremely important application of the coherent short-wave emitting sources is biology and medicine. In medicine this is the study of the drugs effect at the molecular level and the elaboration of novel treatment methods. One of the most important problems in biology is the investigation into the DNA structure and decipher of the human genetic code (“Human Genom” International Program) and the succeeding stage, i.e. “correction” of the genetic structure (DNA-diagnostics, DNA-correction and longevity problems).

In connection with the foregoing understandable is the activity undertaken in scientific world centers with the aim to develop coherent emitting sources in the X-ray range. Different approaches to the solution of this problems are analyzed. But, by now, the most developed are the schemes for production of coherent X-ray radiation based on the highly-ionized dense hot plasma used as an active medium.

As of now, the most powerful laboratory pulse energy sources are lasers. Only high-current discharges rank below the lasers in the possibility to obtain high power density in the material. Therefore, the most advanced approaches to the production of the hot dense plasma with the parameters (density, temperature, sizes, etc.) necessary for generation of the active medium of the coherent X-ray source are related mainly to the application of powerful pulse lasers and high-current discharges.

As of now, the most developed, theoretically and experimentally, are the schemes of laboratory X-ray lasers on transitions of Ne- and Ni-like ions with collision pumping in the dense hot laser plasma. But the application of pure laser single-pulse method for active medium pumping requires energies of hundred joules and even more. To reduce the required laser energy in the collision pumping scheme and to compensate partially for the refraction of enhanced spontaneous radiation the two-pulse or even multi-pulse method has been widely used in recent years. By selecting the moments, when a comparatively low-intensity long pulse producing the elongated plasma (forplasma) and a super-powerful short pulse producing in this plasma the necessary and sufficient amplification conditions for laser generation arrive at the target, it is possible to considerably reduce the required pumping laser energy. Nevertheless, the pure-laser schemes have some essential disadvantages, i.e. bulky facility and complicated control.

Among the high-current discharges the most promising are the capillary discharges, the subject matter of this Project. The powerful capillary discharges are advantageous, if compared with the high-current Z-discharges of other types, in the stabilizing effect of the capillary walls reducing the danger of instability development in the plasma and in higher homogeneity of produced elongated plasma bunches. As compared with the pure laser systems the generation of coherent X-ray radiation in the capillary discharge plasma does not require unique lasers and offers such advantages as technical simplicity, low cost and, conceivably, compactness. Different schemes for inversion achievement in the capillary discharge plasma were analyzed and considerable progress was made towards realizing the mode of spontaneous radiation amplification. The investigations revealed that higher gain factors could be achieved in the radiation-collision scheme, coherent radiation was obtained in the range of ~ 30–50 nm. In our opinion the capillary discharge potentialities for production of shorter coherent radiation wavelengths have not beet exhausted. Shorter wavelengths can be provided, in particular, by increasing the discharge power and by using the capillaries, the inner walls of which are covered with materials with a large evaporation heat and a large Z nucleus charge. There are other ideas on reducing the wavelength of X-ray source radiation on capillary discharges related to a more accurate control over the plasma dynamics and radiation in the capillary discharge when programming the pulses of power introduced into the plasma. These ideas need to be verified.

At the same time the capillary discharges, in specific power contribution into the substance, rank below the pure laser systems, this affecting the minimum achievable wavelength of X-ray radiation. Therefore, interest is taken in the systems with two-staged combined discharge-laser formation of the active medium. In such systems the effect of super-powerful short-pulse laser radiation on the capillary discharge plasma offers considerable possibilities for generation of population inversion in the plasma of multi-fold ions, for advance into the region of shorter wavelengths of X-ray spectral range and for achievement of the “water window”. In such systems the capillary discharges might generate the preliminary plasma with optimal energy distribution of ions characterized by a high density of the necessary ionization state. And then a short laser pulse, which heats free electrons in the plasma to a temperature optimal for the collision pumping of the upper operating level and produces the required population inversion, initiates the generation stage.

The main objective of the Project is to develop and to produce the coherent X-ray radiation source in the range of 2–50 nm on the basis of multi-charge ion transitions in the dense plasma produced in microcapillaries under combined action of a powerful electric charge and a super-short radiation pulse of a solid laser.

The following activities will be undertaken under the Project:

– computer code development and numerical investigation into the active media formation on multi-charge ion transitions (Ne- and Ni-like ions Ta, W, Cs) in the capillary discharge plasma;

– investigations of the capillary discharge and elaboration of compact sources of coherent radiation of soft X-ray range with formation of the active medium in the capillary discharge. We hope to obtain the coherent radiation with wavelengths of l < 30 nm;

– investigation into the interaction of super-powerful solid laser radiation with the capillary discharge plasma and development of the coherent radiation sources of soft X-ray range with the combined discharge-laser formation of the active medium in the capillary discharge. We hope to obtain the coherent radiation with minimum possible wave lengths and to approach to the area of the “water window”.

Two institutions, NIIEFA and NIIKI, will participate in realization of this Project:

– development and production of powerful electric-pulse generators making possible the generation of programmable power pulses at physical loads (NIIEFA);


– computation of multiple plasma ionization, kinetics of multi-charge ion radiation (NIIEFA, NIIKI);
– comprehensive numerical simulation of high-current emitting discharges of different types and configurations (NIIEFA);
– comprehensive numerical simulation of capillary discharges taking into account the radiation transition, wall erosion and processes in the electric circuit (NIIEFA);
– the interaction of laser radiation with the dense highly-ionized plasma (NIIEFA, NIIKI);
– elaboration of the methods for generation of super-powerful and super-short pulses of laser radiation (NIIKI);
– development of the X-ray optics elements (NIIKI);
– elaboration of the original plasma diagnostics methods (NIIEFA, NIIKI);
– design and production of powerful pulse electrophysical facilities (NIIEFA).

On the basis of the Project objective and their own potentialities and experience the participating institutions are planning to perform the coordinated numerical and experimental researches, the joint analytical discussion of these results and to work out scientific recommendations of general character on the methods for reduction of the coherent radiation wave length. These recommendation will be taken into account when developing the mock-up of coherent X-ray radiation source generating in the wavelength range of 2–50 nm.

The distinguishing features of the proposed development activities, as compared with the activities in other scientific centers, are the possibility to obtain the programmable high energy density in the capillary discharge plasma and application of the unique laser facility PROGRESS, making it possible to approach the spectral area of the “water window”.

The main technical approach to attaining the goal consists in developing the computer codes, numerical simulation and self-consistent numerical optimization of the basic physical processes determining the energy pumping of the active plasma media, which can be realized both by the capillary discharge and the combined method during the consistent laser energy input into the capillary discharge plasma, as well as in performing the model physics experimental investigations so as to validate the theoretical predictions and proposals on enhancing the efficiency of both inpidual systems and lasers on the whole.

Experimental studies aiming at attainment of coherent X-ray radiation with the wavelength as short as possible are based on the self-consistent selection of the operating parameters – the parameters of the capillary discharges and laser system. Attainment of this goal is associated with the possibility to create in the capillary discharge a sufficiently elongated uniform plasma column with high plasma parameters and with the organization of high-effective interaction of super-powerful laser pulse with the capillary discharge plasma.

The experimental studies will be performed on the existing facilities to be modernized:

– low-inductive energy capacitor storage with a stored energy of > 100 kJ, ¼-period duration t ~ 1 ms and a voltage of ~ 100 kV (NIIEFA);


– current pulse peaking unit using the properties of electrically exploded conductors allowing the power at plasma loads to be increased by an order of magnitude;
– electric pulse generator allowing for generation of current pulses with the front edge t ~ 2–3 ns and an amplitude of ~ 30 kA at a voltage of ~ 100 kV (NIIEFA);
– PROGRESS Nd-glass laser facility consisting of the PROGRESS-M six-beam laser focusing 1.5 kJ energy within 1.5 ns or 3.5 TW power within 200 ns, the 30 TW single-beam picosecond laser with an output amplification cascade of 85 mm with the pulse compressed on two holographic gratings and the vacuum target chamber allowing focusing of radiation to a line (NIIKI).

These facilities open up wide possibilities for investigation of various active media in the plasma of multi-charge ions, conditions for their excitation for generation of coherent radiation in the short-wave spectral range under different operating conditions.

The low-inductive capacitor storage with the electric-explosion current peaking unit offers wide possibilities for realization of different regimes of energy input into the capillary discharge plasma. This circumstance will be used in experimental investigations into the effect of the pulse parameters of the power introduced into the capillary discharge on the plasma dynamics and radiation with the aim to obtain the necessary geometrical sizes and inner parameters of the active medium. The use of one more power peaker, i.e. plasma current breaker of erosion type intended for formation of the current pulse edges t < 10 ns, will provide additional opportunities for these researches. The low-inductive capacitive module with the power pulse peaking system will be used for model investigations of physical processes in the capillary discharge and for definition of the conditions necessary to generate the coherent radiation with a wavelength of < 30 nm.

The short-pulse electric generator will be used mainly to optimize the engineering solution necessary for development of more compact X-ray sources, as well as to perform model experiments on the combined discharge-laser pumping of the active medium with the aim to generate the coherent radiation with the maximum short wavelength. We have at our disposal gigantic pumping powers provided by the PROGRESS laser system, making it possible to work with Ni-like ions of tantalum, tungsten and cesium and to approach to the spectral range of the “water window”. Among the advantages of this effect is the possibility for independent control over the initial electron plasma density by changing the initial capillary discharge parameters and by optimizing further plasma heating up to the necessary temperature by changing the intensity of the short laser pulse.

The present proposal refers to the category of applied investigations. The elaboration of the technical proposals on the development of coherent X-ray source with discharge-laser pumping of the active medium performed on the basis of the numerical and experimental investigations will be the Russian Federation contribution to the international cooperation in this field. The draft design elaborated under the Project and the developed mock-up of the coherent X-ray source with a wavelength of 2–50 nm can be used for joint development, together with the Collaborators and other foreign institutions, of technological facilities for application in microelectronics and research facilities for application in medicine and biology.

The project will contribute to achievement of the ISTC goals, namely:

– highly skilled professionals will be retained in the participating institutions;


– the conversion activity will develop in these institutions and novel laser equipment will be elaborated for scientific researches and high technologies;
– opportunity will be provided for scientists with previous weapons expertise to be engaged in the international cooperation for peaceful purposes.

The Russian participants of the Project are interested in the cooperation with foreign collaborators in the following fields:

– exchange of the scientific and technical information during the progress of the Project;


– rendering assistance to the Project participants in attending international meetings on this and related subject matters.
– joint symposia and workshops.


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