B. Králiková

The Prague Asterix Laser System

The Prague Asterix Laser System (PALS) is a new international laboratory where research teams are invited to compete for the beam time. The PALS Center runs an iodine photodissociation high-power laser system delivering up to 1.2 kJ of energy in ∼400 ps pulses at the wavelength of 1.315 μm. Optional doubling and tripling of the frequency is assured by large-diameter nonlinear crystals. The ASTERIX IV laser [H. Baumhacker et al., Appl. Phys. B 61, 325 (1995)], transferred from Garching into a new laser hall in Prague, was updated and put into operation on 8 June 2000. These upgrades include new beam delivery options and a twin interaction chamber, which is designed flexibly for a broad spectrum of applications. Results of the first series of experiments are presented and some planned upgrades are briefly described. These include implementation of adaptive optics, replacement of the iodine master oscillator by a more flexible solid state oscillator based on fiber optics, and a femtosecond extension of the l...

Effects of ps and ns laser pulses for giant ion source

Abstract Laser driven ion sources produce giant ion emission current densities at the emission area which exceed the few mA/cm 2 of classical ion sources (MEVVA or ECR) by many orders of magnitude. Very energetic highly charged fast ions, separated by their charge number Z , from ns laser pulses were explained by relativistic self-focusing and nonlinear force effects. Recently a strong difference with ps pulses was found in contrast to the ns pulses depending on the prepulses. We present an explanation based on a skin layer process. This has consequences to sub-picosecond laser-plasma interaction for the studies of the fast ignitor physics for laser fusion and to the new field of nuclear physics opened by these laser pulses which produce up to 100 MeV particles and gammas of high density as well as for ion source applications.

Laser produced Ag ions for direct implantation

The amount and properties of ions produced by laser ablation of Ag targets have been analyzed. The maximum ion current density jmax=21.0 mA and maximum charge state Ar37+ of the ions produced by a laser power density of about 1×1014 W cm−2 at 1.315 and 0.657 μm on an Ag target have been determined. Direct implantation of the Ag ions from the laser-produced plasma has also been studied. An implanted ion density of 3.5×1016 cm−2 at a depth of 500 nm in Al samples was determined by RBS.

IODINE LASER PRODUCTION OF HIGHLY CHARGED Ta IONS

The results of systematic studies of multiply charged Ta ion production with the fundamental frequency of an iodine laser (λ=1.315μm), and its 2nd (0.657μm) and 3rd (0.438μm) harmonics are summarized and discussed. Short laser pulse (350 ps) and a focus spot diameter of 100μm allowed for the laser power densities in the range of 5×1013–1.5×1015 W/cm2. Corpuscular diagnostics were based on time-of-flight methods; two types of ion collectors and a cylindrical electrostatic ion energy analyzer were used. The Ta ions with charge state up to 55+ were registered in the distance of 210 cm; the maximum amplitude of the signal of a high energy ion group was found to belong to the ions with the charge state around 43+, depending on the laser power density. The ion energy distribution was measured for all three wavelengths, however, in a different energy range; the maximum registered ion energy was 8.8 MeV. The occurrence of highly charged ions in the far expansion zone is discussed in view of the mechanism of charge distribution “freezing” during two-temperature isothermal plasma expansion.

Au49+, Pb50+, and Ta48+ ions from laser‐produced plasmas

Results of generation of intense currents of highly charged ions of heavy elements from laser‐produced Au, Pb, and Ta plasmas are reported. High‐power iodine laser PERUN operating with λ=1.315 μm was used for that purpose. Using a parabolic mirror with a hole in the center instead of a focusing lens increased the efficiency of the illumination system and made the ion measurements along the target normal possible. Multiply charged ions were recorded with an ion energy analyzer in a distance of 240 cm.

Ion production by lasers using high-power densities in a near infrared region : Laser-Ion Sources

Results are presented of experiments on ion production from Ta targets using a short pulse (350-600 ps in focus) illumination with focal power densities exceeding 10 14 Wcm -2 at the wavelength of an iodine photodissociation laser (1.315 μm) and its harmonics. Strong evidence of the existence of tantalum ions with the charge state +45 near the target surface was obtained by X-ray spectroscopy methods. The particle diagnostics point to the existence of frozen high charge states ( 4 MeV) for the highest observed charge states. A tentative theoretical explanation of the observed anomalous charge state freezing phenomenon in the expanding plasma produced by a subnanosecond laser pulse is given.

Highly charged Ta ions produced by the photodissociation iodine laser with subnanosecond pulses

The results of the generation of tantalum ions with a charge state of 46+ are reported. Iodine laser pulses of about 15 J energy and 350 ps in duration were used for a Ta plasma production. Multiply charged ions were recorded by the diagnostic techniques based on the time‐of‐flight method in the distance of approximately 200 cm. The plasma temperature estimated from the ion measurements was found to be about 1750 eV.

Properties of iodine laser-produced stream of multiply charged heavy ions of different elements

Properties of laser produced stream of ions of high- and medium-Z elements were analyzed in the far expansion zone using time-of-flight method and Thomson parabola spectrograph in experiments performed with the iodine laser system PERUN at IP ASCR, Prague (λ=1.315 μm, EL∼45 J,τL∼300–700 μs). Ta, Au, and Pb, as well as Co, Sn, and Ag were mainly used as targets onto which a laser power density up to 1×1015 W cm−2 was delivered. Attention is paid to the evolution and comparison of different produced ion groups, and to the number, charge state, energy, and angular distribution of emitted ions.

Multiply charged ion generation from NIR and visible laser‐produced plasma

Results of experiments on ion production from Ta target using ∼350 ps pulses of the iodine photodissociation laser PERUN are presented and analysed. Ta ions with charge states higher than 45+ and with energies 8 MeV were registered in a far expansion zone (∼2 m). Theoretical interpretation of the results is possible by considering that the plasma temporal evolution follows the mechanism of two‐temperature isothermal expansion.

Iodine photodissociation laser system Perun II

A construction and exploitation of a medium size iodine photodissociation laser system Perun II is reported. This laser produced pulses of infrared light (λ=1.315μm) up to 50 J in energy and 300 ps in duration. The diameter of the beam is 82 mm. The beam divergence is about 4×10−4 rad. The laser beam can be focused in a focal spot of a power density exceeding 1014 W/cm2. The resuls of measurements of basic plasma parameters on an Al foil target are also presented. A recent improvement of the system includes a conversion to the second harmonic by a DKDP crystal.