[Show abstract][Hide abstract] ABSTRACT: A space-resolved charge density of ions is derived from a time-resolved current of ions emitted from laser-produced plasma and expanded into the vacuum along collision-free and field-free paths. This derivation is based on a similarity relationship for ion currents with “frozen” charges observed at different distances from the target. This relationship makes it possible to determine a map of ion charge density at selected times after the laser plasma interaction from signals of time-of-flight detectors positioned at a certain distance from the target around a target-surface normal. In this work, we present maps of the charge density of ions emitted from Cu and polyethylene plasmas. The mapping demonstrates that bursts of ions are emitted at various ejection angles ϕ n with respect to the target-surface normal. There are two basic directions ϕ1 and ϕ2, one belonging to the fastest ions, i.e., protons and carbon ions, and the other one to the slowest ions being a part of each plasma plume.
Laser and Particle Beams 03/2014; 32:15-20. · 2.02 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Efficiency of the laser radiation energy transport into the shock wave generated in layered planar targets (consisting of massive Cu over coated by thin CH layer) was investigated. The targets were irradiated using two laser pulses. The 1ω pulse with the energy of ̃50 J produced a pre-plasma, imitating the corona of the pre-compressed inertial confinement fusion target. The second main pulse used the 1ω or 3ω laser harmonics with the energy of ̃200 J. The influence of the pre-plasma on parameters of the shock wave was determined from the crater volume measurements and from the electron density distribution measured by 3-frame interferometry. The experimental results show that the energy transport by fast electrons provides a definite contribution to the dynamics of the ablative process, to the shock wave generation, and to the ablation pressure in dependence on the target irradiation conditions. The strong influence of the pre-plasma on the investigated process was observed in the 1ω case. Theoretical analysis supports the explanation of experimental results.
[Show abstract][Hide abstract] ABSTRACT: A scheme to enhance the target foil velocity has been investigated for a
direct drive inertial fusion target. Polymer PVA (polyvinyl alcohol or
(C2H4O)n) target foils of thickness
15-20 μm were used in plain form and also embedded with gold in the
nano-particle (Au-np) or micro-particle (Au-mp) form. Nano-particles
were of 20-50 nm and micro-particles of 2-3 μm in size. 17% higher
target velocity was measured for foils embedded with nano-particle gold
(Au-np) as compared to targets embedded with micro-particles gold
(Au-mp). The weight of gold in both cases was in the range 40-55% of the
full target weight (atomic percentage of about 22%). Experiments were
performed with the single beam of the Prague Asterix Laser System (PALS)
at 0.43 μm wavelength (3ω of the fundamental wavelength), 120
Joule energy and 300 psec pulse duration. Laser intensity on the target
was about 1015 W/cm2. A simple model has been
proposed to explain the experimental results.
[Show abstract][Hide abstract] ABSTRACT: Generation of ion fluxes in the laser-induced cavity pressure acceleration (LICPA) scheme is investigated by the time-of-flight method and compared with the one in the conventional laser-planar target interaction scheme. It is shown that the ion current density and intensity of the ion flux produced in the LICPA scheme from CD2 foil target irradiated by a 0.3-ns laser pulse of intensity ∼1014–1015 W/cm2 are by an order of magnitude higher and the mean and maximum ion energies by a factor 4–5 higher than those for the conventional scheme.
[Show abstract][Hide abstract] ABSTRACT: The efficiency of the laser energy conversion to a shock wave has been investigated in solid targets irradiated by a single or two consecutive laser beams. The first laser pulse was used to produce the plasma simulating conditions relevant to shock ignition approach. One-and two-layer planar targets (bulk Al and Cu alternatively covered by a thin CH layer) were used. The laser provided a 250 ps pulse within the intensity range of 1-50 PW/cm 2 at the first and third harmonics with wavelengths of 1.315 and 0.438 μm, respectively. Three-frame interferometry and measurements of crater parameters were used as the main diagnostics. The contribution of fast electrons to ablation and the laser energy conversion into shock wave have been investigated for different conditions of the target irradiation, including the pre-plasma presence. 2D numerical simulations and theoretical analysis were carried out to support explanation of experimental results.
40th EPS Conference on Plasma Physics, Espoo, Finland; 07/2013
[Show abstract][Hide abstract] ABSTRACT: The effect of preformed plasma on a laser-driven shock produced in a planar target at the conditions relevant to the shock ignition scenario of ICF was investigated at the kilojoule PALS laser facility. Characteristics of the preformed plasma were controlled by the delay ∆t between the auxiliary beam (1ω, 7×10 13 W/cm 2) and the main 3ω, 250 ps laser pulse of intensity up to 10 16 W/cm 2 , and measured with the use of 3-frame interferometry, ion diagnostics, an X-ray spectrometer and K α imaging. Parameters of the shock produced in a CH(Cl) target (25 µm or 40 µm thick) by the intense 3ω laser pulse with energy ranging between 50 J and 200 J were determined by measuring the craters produced by the shock in a massive Cu target behind the layer of plastic. The volume and the shape of these craters was found to depend rather weakly on the preplasma thickness, which implies the same is true for the total energy of shocks and pressure generated by them. From the comparison of the measured crater parameters with those obtained in 2D simulations using the PALE code, it was estimated that for I 3ω ≈ 10 16 W/cm 2 the pressure at the rear (non-irradiated) side of the 25-µm plastic layer reaches about 100 Mbar.
EPS Conference on Plasma Physics, Espoo, Finland; 07/2013
[Show abstract][Hide abstract] ABSTRACT: The paper presents research on the optimization of the laser ion implantation method with electrostatic
acceleration/deflection including numerical simulations by the means of the Opera 3D code and experimental
tests at the IPPLM, Warsaw. To introduce the ablation process an Nd:YAG laser system with
repetition rate of 10 Hz, pulse duration of 3.5 ns and pulse energy of 0.5 J has been applied. Ion time
of flight diagnostics has been used in situ to characterize concentration and energy distribution in the
obtained ion streams while the postmortem analysis of the implanted samples was conducted by the
means of XRD, FTIR and Raman Spectroscopy. In the paper the predictions of the Opera 3D code are
compared with the results of the ion diagnostics in the real experiment. To give the whole picture of
the method, the postmortem results of the XRD, FTIR and Raman characterization techniques are discussed.
Experimental results show that it is possible to achieve the development of a micrometer-sized
crystalline Ge phase and/or an amorphous one only after a thermal annealing treatment.
[Show abstract][Hide abstract] ABSTRACT: The PALS high power iodine laser system in Prague (� = 1.315 �m) was used to study non-linear processes
in a laser-produced plasma at intense laser beam interactions with planar targets. The focus setting allows
to alter the non-linear interaction of the main laser pulse with the ablated plasma produced by the front
edge of a nanosecond laser pulse (300 ps FWHM). The arisen non-linear effects significantly influence
the behavior of electrons, which accelerate fully striped or highly charged fast ions. Variations in time of
the expanding plasma, recorded at the target surface by the use of Kentech low-magnification soft X-ray
streak camera on
∼2 ns time scale, are presented and discussed. Narrowing, arching and even splitting
of expansion paths in the target-normal space-time diagram are shown. These phenomena are ascribed
to the magnetic field, self-generated at high laser intensities, which may become strong enough to cause
pinching of the expanding plasma.
[Show abstract][Hide abstract] ABSTRACT: Shock ignition (SI) is an appealing approach in the inertial confinement scenario for the ignition and burn of a
pre-compressed fusion pellet. In this scheme, a strong converging shock is launched by laser irradiation at an
intensity Iλ2 >1015 Wcm−2 μm2 at the end of the compression phase. In this intensity regime, laser–plasma
interactions are characterized by the onset of a variety of instabilities, including stimulated Raman scattering,
Brillouin scattering and the two plasmon decay, accompanied by the generation of a population of fast electrons. The effect of the fast electrons on the efficiency of the shock wave production is investigated in a series of dedicated experiments at the Prague Asterix Laser Facility (PALS). We study the laser–plasma coupling in a SI relevant regime in a planar geometry by creating an extended preformed plasma with a laser beam at ∼7 × 1013 Wcm−2 (250 ps, 1315 nm). A strong shock is launched by irradiation with a second laser beam at intensities in the range 1015–1016 Wcm−2 (250 ps, 438 nm) at various delays with respect to the first beam. The pre-plasma is characterized using x-ray spectroscopy, ion diagnostics and interferometry. Spectroscopy and calorimetry of the backscattered radiation is performed in the spectral range 250–850 nm, including (3/2)ω, ω and ω/2 emission. The fast electron production is characterized through spectroscopy and imaging of the Kα emission. Information on the shock pressure is obtained using shock breakout chronometry and measurements of the craters produced by the shock in a massive target. Preliminary results show that the backscattered energy is in the range 3–15%, mainly due to backscattered light at the laser wavelength (438 nm), which increases with increasing the delay between the two laser beams. The values of the peak shock pressures inferred from the shock breakout times are lower than expected from 2D numerical simulations. The same simulations reveal that the 2D effects play a major role in these experiments, with the laser spot size comparable with the distance between critical and ablation layers.
[Show abstract][Hide abstract] ABSTRACT: Previous experimental results demonstrated that the plasma pressure decreases with the growing atomic number of the target material. In this context, a question arose if the Al plasma outflow could be collimated using the plastic plasma as a compressor. To solve this problem, an experiment using a plastic target with an Al cylindrical insert was performed. The focal spot diameter substantially larger than that of the insert ensured simultaneous heating both target materials. This experiment proved that a production of Al plasma jets collimated by an action of outer plastic plasma is feasible [Kasperczuk et al., Laser Part. Beams 30, 1 (2012)]. The results of investigations presented here provide additional information on distributions of electron temperature in the outflowing plasma and time and space characteristics of ion emission, both registered at bare and constrained-flow Al targets. The experiment was carried out at the Prague asterix laser system iodine laser facility. The laser provided a 250 ps (full width at half maximum) pulse with the energy of 130 J at the third harmonic frequency (λ3 = 0.438 μm). A plastic target with an Al cylindrical insert of 400 μm in diameter as well as a bare Al target (for comparison) was used. The focal spot diameter (ΦL) 1200 μm ensured the lateral pressure effect of the plastic plasma strong enough to guarantee the effective Al plasma compression. The electron temperature measurements have shown that such Al plasma compression is accompanied by the increase of its temperature, dominance of which starts at distance of 0.5 mm from the target surface. Measurements of ion emission characteristics confirm the earlier numerical simulation prediction that in these conditions the plasma expansion geometry is closer to planar. The constrained Al plasma jet is very narrow and its axial velocity is considerably larger than the velocity of freely expanding Al plasma stream. It means that the plastic plasma envelope, besides the Al plasma compression, also strongly accelerates the Al plasma in its axial motion.
Physics of Plasmas 09/2012; 19(9). · 2.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Acceleration of dense matter to high velocities is of high importance for high energy density
physics, inertial confinement fusion, or space research. The acceleration schemes employed so far
are capable of accelerating dense microprojectiles to velocities approaching 1000 km/s; however,
the energetic efficiency of acceleration is low. Here, we propose and demonstrate a highly efficient
scheme of acceleration of dense matter in which a projectile placed in a cavity is irradiated by a
laser beam introduced into the cavity through a hole and then accelerated in a guiding channel by
the pressure of a hot plasma produced in the cavity by the laser beam or by the photon pressure of
the ultra-intense laser radiation trapped in the cavity. We show that the acceleration efficiency in
this scheme can be much higher than that achieved so far and that sub-relativisitic projectile
velocities are feasible in the radiation pressure regime.
Physics of Plasmas 05/2012; 19(5):053105. · 2.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The results of a detailed study of the ion emission from Al target irradiated with a high-intensity (up to 5 · 1016 W/cm2)1−ps Nd: glass laser pulse are presented. The ion emission measurements were based on the time-of-flight method. An electrostatic
ion energy analyzer and ion collectors were employed. The maximum ion energy of about 132 keV and fully striped Al ions were
registered. The ion current density of 3 mA/cm2 was measured at the distance of 1 m in the direction of the target normal. Both the measured ion charge distribution and
the angular distribution of ion emission are discussed. The dependencies of the parameters of ions emitted from the plasma
on the laser-pulse energy as well as on the location of the focus of the laser beam with respect to the target surface were
Czechoslovak Journal of Physics 05/2012; 50:213-216. · 0.42 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Results on iodine laser production of Ag, Au, Pb, Sn and Ta ions are presented and experiments on their implantation into
steel, Al and plastics are compared and discussed. Ions were implanted without additional acceleration into metals to the
depth of several hundreds of nanometers, and into plastics to a depths of up to several micrometers.
Czechoslovak Journal of Physics 04/2012; 50:81-90. · 0.42 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The generation of fast highly charged metal ions with the use of the sub-nanosecond Prague Asterix Laser System, operated at a fundamental wavelength of 1315 nm, is reported. Particular attention is paid to shot-to-shot reproducibility in the ion emission. Au and Pd targets were exposed to intensities up to 5 × 10(16) W∕cm(2). Above the laser intensity threshold of ∼3 × 10(14) W∕cm(2) the plasma is generated in a form of irregular bursts. The maximum energy of protons constituting the leading edge of the fastest burst reaches a value up to 1 MeV. The fast ions in the following bursts have energy gradually decreasing with the increasing burst number, namely, from a value of about 0.5 MeV∕charge regardless of the atomic number and mass of the ionized species.
The Review of scientific instruments 02/2012; 83(2):02B302. · 1.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ge crystals were prepared by means of laser-induced ion implantation technique. A Nd:YAG pulsed laser (repetition rate: 10 Hz; pulse duration: 3.5 ns; pulse energy: ∼0.5 J) was used both as an ion source and to carry out the ablation processes. The optimization of the laser-generated ion beam parameters in a broad energy and current density range has been obtained controlling the electrostatic field parameters. Numerical simulations of the focusing system, performed adopting an OPERA 3D code, and an investigation of the ion characteristics, using the ion time-of-flight method, have allowed to optimize the preparation parameters. The structural properties of the samples were investigated by means of x-ray photoelectron, micro-Raman spectroscopies, and scanning electron microscopy techniques. Experimental results show that, by appropriately varying the ion implantation parameters and by a post-preparation annealing treatment, it is possible to achieve the development of a micrometer-sized crystalline Ge phase and∕or an amorphous one.
The Review of scientific instruments 02/2012; 83(2):02B305. · 1.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: An overview of the last experimental campaigns on laser-driven ion acceleration performed at the PALS facility in Prague is given. Both the 2 TW, sub-nanosecond iodine laser system and the 20 TW, femtosecond Ti:sapphire laser, recently installed at PALS, are used along our experiments performed in the intensity range 10(16)-10(19) W∕cm(2). The main goal of our studies was to generate high energy, high current ion streams at relatively low laser intensities. The discussed experimental investigations show promising results in terms of maximum ion energy and current density, which make the laser-accelerated ion beams a candidate for new-generation ion sources to be employed in medicine, nuclear physics, matter physics, and industry.
The Review of scientific instruments 02/2012; 83(2):02B307. · 1.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The application of single-crystal CVD diamond and SiC detectors for the measurement of ions generated from laser-produced plasmas is reported. It was found that detectors are mostly sensitive to fast ions and protons. Optimization of the diagnostic system based on the detectors is discussed.