39 research outputs found
Experimental studies of generation of ~100 MeV Au-ions from the laser-produced plasma
AbstractUsing the PALS iodine laser system, Au ions with the charge state up to 58+ and with the kinetic energy as high as ~300 MeV were generated. The production of these ions was tested in dependence on the laser frequency (1ω, 3ω), on the irradiation/detection angles (0°, 30°), on the focus position with regard to the target surface, and on the target thickness (500 µm, 200 µm, 80 µm). A larger amount of the fastest ions was produced with 1ω than with 3ω, the most of the fast ions were recorded in the direction ~10°from the target normal, the optimum focus position is in front of the target and should be set on with a precision of 50 µm. The forward emission is weaker than the backward one for both of the thinner targets (which burn through) at our experimental conditions
Self-focusing in processes of laser generation of highly-charged and high-energy heavy ions
Laser-beam interaction with expanding plasma was investigated using
the PALS high-power iodine-laser system. The interaction conditions are
significantly changing with the laser focus spot position. The decisive
role of the laser-beam self-focusing, participating in the production of
ions with the highest charge states, was proved
Expansion of tungsten ions emitted from laser-produced plasma in axial magnetic and electric fields
The experimental results of the investigations on the influence
of external magnetic and electric fields on the characteristics
of a tungsten ion stream emitted from a plasma produced by the
Nd:glass laser (1 J, 1 ns) performed at IPPLM, Warsaw are
presented. A negatively biased target up to −15 kV and
a magnetic field up to 0.45 T were used in the experiment. A
set of ion collectors and an electrostatic cylindrical ion energy
analyzer located at small angles with respect to the laser beam
axis and at large distances from the target were applied for
ion measurements. The effect of an external magnetic field is
essential to plasma expansion, but the effect of the retarding
potential of the target is very weak in our experimental
conditions. The aim of the studies was to prove the possibility
of the optimization of ion beam parameters from laser-produced
plasma for the particular application as a laser ion source
coupled with the electron cyclotron resonance ion source for
particle accelerators
Angular distributions of ions emitted from laser plasma produced at various irradiation angles and laser intensities
AbstractAngular distributions of currents and velocities (energies) of ions produced at various target irradiation angles and laser intensities ranged from 1010 W/cm2 to 1017 W/cm2 were analyzed. It was confirmed that for low laser intensities the ion current distributions are always peaked along the target normal. However, at laser intensities comparable to or higher than 1014 W/cm2, the preferred direction of ion emission strongly depends on the irradiation geometry (laser focus setting, the irradiation angle), and can be off the target normal. This is very likely caused by the non-linear interaction of the laser beam with produced plasma, in particular, by the action of ponderomotive forces and the laser beam self-focusing
Factors influencing parameters of laser ion sources
Various applications demand various kinds of ions. Charge state, energy and the amount of laser produced ions depend, primary, on the wavelength, the energy, the pulse duration, and the focusing ability of the laser used. Angle of the target irradiation, angle of the ion extraction (recording), and mainly the focus setting may significantly influence especially the portion of ions with the highest charge states. The participation of non-linear processes on the generation of ions with extremely high parameters is demonstrated. The observed effects support the idea of a longitudinal structure of the self-focused laser beam with a space period of ∼200 µm
The influence of an intense laser beam interaction with preformed plasma on the characteristics of emitted ion streams
AbstractIntense laser-beam interactions with preformed plasma, preceding the laser-target interactions, significantly influence both the ion and X-ray generation. It is due to the laser pulse (its total length, the shape of the front edge, its background, the contrast, the radial homogeneity) as well as plasma (density, temperature) properties. Generation of the super fast (FF) ion groups is connected with a presence of non-linear processes. Saturated maximum of the charge states (independently on the laser intensity) is ascribed to the constant limit radius of the self-focused laser beam. Its longitudinal structure is considered as a possible explanation for the course of some experimental dependencies obtained
Ambient fields generated by a laser spark
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