Generation of multiply charged ions at low and high laser-power densities

Abstract

The PERUN and PALS iodine laser systems and a Nd : YAG laser have been used for studies of ions emitted from various single element laser plasmas, at both low (I L ∼ 10 9 W cm −2 ) and high (I L ∼ 10 16 W cm −2 ) laser intensities. Sufficiently high current densities of low-charge ions, with energies only of hundreds of electronvolt, were produced for starting tests of a considered new hybrid ion source, based on coupling of laser ion source to electron cyclotron resonance plasma. Highly charged ions with charge states about 50+ and with energies even higher than 20 MeV were generated at the highest laser intensities (I L > 2×10 14 W cm −2 ). Seven ion sub-groups at least (faster and slower) were recorded and distinguished at these conditions. The existence of an 'optimum focus position' in front of the target surface is consistent with the idea that laser interaction with a prepulse-produced plasma improves the conditions for self-focusing. The experimental arrangements and ion diagnostics used for the various laser ion generation experiments are briefly reviewed, as well as our both older and more recent results on the characteristics of the ions, produced at the various laser irradiances, are presented. The results of laser ion implantation experiments using these ions directly (without additional electrostatic acceleration) are also mentioned.

Laser ablation loading of a radiofrequency ion trap

“…Refs. [18,19]). It has been shown that the distribution of ions over the charge states depends on the laser intensity and shifts to higher charges for higher intensity [19].…”

Laser-driven generation of fast particles

“…These ions form a fast ion group, as opposed to the thermal, slower ion group accelerated by thermokinetic forces. The mechanism of acceleration using the double-layer in plasma corona dominates in the case of long driving pulses [7][8][9][10], but it can be also efficient in the case of short pulses of relatively low contrast (producing sufficiently thick underdense preplasma layer) [44,45]. Both the double-layer and S-LPA mechanisms were demonstrated to be efficient in generation backward-emitted heavy ion beams.…”

“…Studies of laser-driven generation of highly charged ions with the use of long-pulse (ns or subns) lasers have a much longer history and have been performed by several research groups [7][8][9][10][52][53][54][55][56][57][58]. Some results obtained by the Czech-Polish group with the use of subns high-energy iodine lasers are presented in Table 3 [10].…”

“…However, powers and intensities, I L , of the used lasers were low (I L < 10 12 W/cm 2 ), so energies of produced particles were low (~keV) as well. The high-intensity experiments began in the seventies and up to the middle of the nineties they were performed almost exclusively with long nanosecond and subnanosecond laser pulses of intensities up to 10 16 W/cm 2 [7][8][9][10]. A real breakthrough in the field, especially in laser-driven generation of fast ion beams, took place, however, on the turn of the century, when short picosecond and subpicosecond laser pulses of powers from TW to PW level were employed in the experiments.…”

Ion charge state distributions in plasma produced by pulsed laser irradiations

“…Recently, at the Plasma Asterix Laser System (PALS) Laboratory of Prague, for example, by using a pulsed laser at a fluence of 300 kJ/cm 2 , 400 ps pulse width, to irradiate tantalum in vacuum, the ion charge state distribution shown in Figure 6(b) [13] has been obtained. This distribution is very wide and it indicates a very high ion charge state production, up to 58 + , showing three ion charge state regions.…”