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1

Ambient fields generated by a laser spark

Rohlena K., Mašek M.

Nukleonika

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2016

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Vol. 61, No. 2

119--124

EN

The electric and magnetic fields surrounding a laser spark formed after an optical breakdown due to a focused nanosecond laser beam in a gaseous environment are examined in order to assess their possible influence on the processes going on in the gas medium, mainly chemical reactions triggered by the spark plasma radiation. The magnetic field is generated by the standard mechanism of crossed electron density and temperature gradients, the electric field is supposed to be produced by the plasma polarization due to its radial expansion across the self-generated magnetic field. A simple model of spark plasma formation near the tip of the focal cone is assumed, with a delayed breakdown, which allows the focused laser light to sweep the whole volume of the forming spark right down to the focal caustic and thus to form a centimeter long plasma cone. In this conical geometry, the value of plasma electric dipole moment is evaluated as a measurable quantity as well as approximate values of the electric and magnetic field near the focal caustic, where they both tend to grow in magnitude.

2

Plasma jet generation by flyer disk collision with massive target

Kasperczuk A., Pisarczyk T., Borodziuk S., Gus'kov S. Y., Ullschmied J., Krousky E., Masek K., Pfeifer M., Rohlena K., Skala J., Kalal M., Limpouch J., Pisarczyk P.

Optica Applicata

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2007

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Vol. 37, nr 1-2

73-82

EN

In this paper, results from experiments with Al flyer targets (disks with a diameter of 300 mm and a thickness of 6 mm) accelerated at first to high velocities by PALS iodine laser pulses (with an energy of 130 J, pulse duration of 400 ps, a wavelength of 1.315 mm, and laser spot diameter of 250 mm), subsequently creating craters after their collisions with massive Al targets (placed at a distance of the order of 200 mm) are presented. To measure the plasma density evolution a three frame interferometric system was employed. The experimental results demonstrate that the flyer disk-massive target collision generates an axial plasma jet corresponding to a flat shock wave propagating in a massive target. This form of the shock wave was deduced from a crater trapezoidal shape which was reconstructed by means of crater replica technique.

3

High power laser interaction with single and double layer targets

Borodziuk S., Demchenko N. N., Guskov S. Y., Jungwirth K., Kalal M., Kasperczuk A., Kondrashov V. N., Kralikova B., Krousky E., Limpouch J., Masek K., Pisarczyk P., Pisarczyk T., Pfeifer M., Rohlena K., Rozanov V.B., Skala J., Ullschmied J.

Optica Applicata

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2005

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Vol. 35, nr 2

241-262

EN

Results of extended complementary experimental and computer simulation studies of craters formation produced by high power lasers in single and double layer targets are presented. The experimental investigation was carried out using the PALS (Prague Asterix Laser System) facility working with two different laser beam wavelengths: L(lambda)1 = 1.315 žm and L3 = 0.438 žm. Two types of targets made of Al were used: single massive targets and double targets consisting of foils or disks (6 and 11 žm thick for both cases) placed in front of the massive target at distances of 200 and 500 žm. The targets were illuminated by laser energies EL= 130, 240 and 390 J always focused with diameter of 250 žm. In all experiments performed the laser pulse duration was equal to 400 ps. The 3-frame interferometry was employed to investigate the plasma dynamics by means of the electron density distribution time development, as well as the disks and foil fragments velocity measurements. Dimensions and shapes of craters were obtained by crater replica technology and microscopy measurement. Experimental results were complemented by analytical theory and computer simulations to help their interpretation. This way the values of laser energy absorption coefficient, ablation loading efficiency and efficiency of energy transfer, as well as 2-D shock wave generation at the laser-driven macroparticle impact, were obtained from measured craters parameters for both wavelengths of laser radiation. Computer simulations allowed us to obtain an energy absorption balance of incident laser energy for both wavelengths employed.

4

Fast ion generation by a picosecond high-power laser

Badziak J., Parys P., Wołowski J., Hora H., Krasa J., Laska L., Rohlena K.

Optica Applicata

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2005

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Vol. 35, nr 1

5-22

EN

Recent progress in ultrashot-pulse high-power laser technology has resulted in the production of exstremely high light intensities aproaching 1020 W / cm2. The great non-linear forces generated by the laser pulse during its interaction with plasma can be used to accelerate electrons and ions to energies from hundreds of keV to hundreds of MeV over distances of only microns. This creates the prospect of construction of compact laser-based particle acceleraton rs and thier application in material science, medicine, nuclear physics, and inerial confinement fusion. In this paper, the results of our recent studies on fast ion generation in plasma produced by an intense 1-ps laser pulse, performed using the terawatt Nd:glass laser at Institute of Plasma Physics and Laser Microfusion (IPPLM) in Warsaw, are briefly reviewed. The properties of fast proton beams generated from thin foil targets of various structures as well as the heavy ion fluxes emitted from massive high-Z targets are discussed. The possibility of producing picosecond ion beams of ultrahigh ion current densities (1010 A/cm2 close to the target) is considered. The most important features of fast ion generation in the plasmas produced by ultrashort ( 1 ps ) and long ( 0.5 ns ) laser pulses are also compared.

5

Investigation of plasma ablation and crater formation processes in the Prague Asterix Laser System laser facility

Borodziuk S., Kasperczuk A., Pisarczyk T., Gus'kov S., Ullschmied J., Kralikova B., Rohlena K., Skala J., Kalal M., Pisarczyk P.

Optica Applicata

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2004

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Vol. 34, nr 1

31-42

EN

The present investigation of the processes of ablative plasma generation and formation of craters was carried out at the Prague Asterix Laser System (PALS) iodine laser facility. Experiments were performed with broad range of laser beam intensities (1013-1016 W/cm2), focal spot radii (35–600 mm), and two laser wavelengths (l1 = 1.315 mm and l3 = 0.438 mm). The laser beam was focused on the surface of the massive solid aluminum targets. The main goal of our study was to estimate conversion efficiency of the laser beam energy into the energy of shock waves for different mechanisms of laser beam–target interaction. The expansion of plasma generated as a result of the interaction process was observed by means of the 3-frame interferometry. Dimensions and shapes of the craters were determined using optical microscopy and wax-replica technique.

6

Application of the 3-frame interferometry and the crater replica method for investigation of laser accelerated macroparticles interacting with massive targets in the Prague Asterix Laser System (PALS) experiment

Borodziuk S., Kasperczuk A., Pisarczyk T., Demchenko N.N., Gus’kov S., Rozanov V. B., Kalal M., Limpouch J., Ullschmied J., Rohlena K., Skala J., Kondrashov V. N., Pisarczyk P.

Optica Applicata

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2004

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Vol. 34, nr 3

385-403

EN

In the present paper results from our experiments with macroparticles, accelerated at first to high speeds by the PALS iodine laser and subsequently hitting massive targets and creating craters, are presented. The main aim of these investigations concerned the influence of wavelength on the efficiency of macroparticles acceleration and creation of craters. To this end, two different harmonics of the PALS laser beam (l1 = 1.315 mm and l3 = 0.438 mm) and several types of targets (simple massive planar Al targets as well as much more elaborated double targets consisting of 6 mm thick Al foils or disks placed in front of the massive target at the distance of either 200 mm or 500 mm) were used. All these targets were irradiated by the iodine laser beam with its parameters very much the same for both harmonics: the energy of 130 J, the focal spot diameter of 250 mm, and the pulse duration of 400 ps. Velocities of accelerated extracted foil fragments or disks as well as electron density distributions of plasma streams were determined by means of the 3-frame interferometry. Shapes and volumes of craters were obtained employing the crater acetate cellulose replica technology and microscopy measurements. The data from these experiments provided valuable information concerning the ablative plasma generation and crater creation processes.

7

Experimental and theoretical investigations of crater formation in an aluminium target in a PALS experiment

Borodziuk S., Doskach I., Gus'kov S., Jungwirth K., Kálal M., Kasperczuk A., Kralikova B., Krousky E., Limpouch J., Masek K., Pfeifer M., Pisarczyk P., Pisarczyk T., Rohlena K., Rozanov V., Skala J., Ullschmied J.

Nukleonika

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2004

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Vol. 49, nr 1

7-14

EN

Experimental and theoretical results of investigations of the iodine laser - Al solid target interactions on the PALS (Prague Asterix Laser System) facility are presented. The experimental investigations of laser interaction with massive Al targets devoted to shock wave propagation in solids and crater formation physics are presented. Experiments were performed with the use of high intensity laser pulses (1013 15 W/cm2) for two laser wavelengths (0.438 mi m and 1.315 mi m) and four laser beam radii (from 35 mi m up to 600 ěm). The crater dimensions were measured using optical microscopy and a wax-replica technique. Plasma expansion out of the target was measured via three-frame interferometry. Theoretical model of the postpulse crater formation by the shock wave propagating and decaying in solids after the end of the laser pulse is presented and applied for the explanation of the results obtained in experiments.

8

Studies of plasma and craters produced by the interaction of high-energy sub-nanosecond laser with silver target

Woryna E., Badziak J., Parys P., Suchańska R., Wołowski J., Krása J., Láska L., Pfeifer M., Rohlena K., Ullschmied J.

Nukleonika

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2002

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Vol. 47, nr 4

147-150

EN

The results of measurements of microablation from a silver target irradiated by the high-power PALS laser system in Prague are presented. In this experiment the laser beam of energy of about 110 J in a 400 ps pulse was focused perpendicularly to the massive silver target. The target surface position was changed with respect to the focal spot of the laser beam in the range from -2.5 to 2.5 mm. A set of four ion collectors was used for plasma ion emission measurements. The effect of the laser pulse interaction with the target, i.e. craters and damages formed in the vicinity of the craters, were investigated with the use of scanning electron microscopy (SEM) and optical microscopy methods. The characteristics of the crater were compared with the essential parameters of ion streams emitted from the plasma produced in the same laser shot.

9

Effect of a laser beam focus position on ion emission from plasmas produced by picosecond and sub-nanosecond laser pulses from solid targets.

Woryna E., Badziak J., Makowski J., Parys P., Wołowski J., Krasa J., Laska L., Rohlena K., Vankov A.B.

Optica Applicata

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2001

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Vol. 31, nr 4

791-798

EN

The dependences of parameters of laser-produced ion fluxes on the laser focus position with respect to the target surface for picosecond laser pulses are presented and compared with the ones for sub-nanosecond pulses at nearly the same densities of laser energy. The experiments were performed with the use of chirped-pulse-amplification Nd:glass laser system. Thick Au targets were irradiated by normally incident laser pulses. The maximum intensities of the focused laser beams were 8 * 10/sup 16/ and 2 * 10/sup 14/ W/cm/sup 2/ for ps and sub-ns laser pulses, respectively. The particle fluxes were analysed with the use of ion collectors and an electrostatic ion-energy analyser. The ion current densities and the charges carried by ions as well as the maximum and peak velocities of fast and thermal ion groups as a function of the focus position for ps and sub-ns pulses were determined.

10

Laser ion sources for various applications.

Wołowski J., Parys P., Woryna E., Krasa J., Laska L., Rohlena K.

Optica Applicata

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2000

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Vol. 30, nr 1

69-82

EN

Presents the results of studies of ion emission from the high-Z plasma generated using short wavelength, short pulse lasers: Nd:glass laser at the IPPLM in Warsaw and iodine laser PERUN at the IP ASCR in Prague. These studies were motivated mainly by the laser-produced plasma applications as a heavy ion source for particle accelerators and for ion implantation. The properties of highly charged ion streams were investigated by ion diagnostic methods: ion collectors and a cylindrical electrostatic energy analyzer. The results proved the existence of highly charged ions with charges 2[right angle bracket]40 (measured z/sub max/=55 for Ta) and with energies of several MeV in a far expansion zone. Ion current densities higher than 20 mA/cm/sup 2/ at about 1 m from the target were demonstrated. Construction of an effective laser heavy ion source seems thus to be not a principal, but rather a technological problem. ECLISE experiment (ECR ion source coupled to a laser ion source for charge state enhancement) has been founded by INFN LNS in Catania and preliminary experiments have been carried out at the IPPLM in Warsaw, in order to confirm the beneficial effects of the axial magnetic field of the ECR ion source on the extraction of ions from the LIS, and to evaluate the ion energy, which is the critical parameter for the coupling process. Direct implantation of ions from laser produced plasma has been investigated using the PERUN laser system at the IP ASCR in Prague. Attention was devoted mainly to the properties of the ion streams from the laser-produced plasmas (Sn, Pb, Ag) as well as to the direct implantation of those ions into different materials.