Search

Nowadays charged-coupled device (CCD) detectors are widely used for the registration of multicharged ions x-ray spectra. These spectra are generated in a plasma during interaction of ultrashort, ultraintense laser pulses with solid targets. Strong parasitic radiation from the plasma affects CCD detectors and contaminates resulting spectra, so that spectral features can be completely covered by noise even during measurements with a very short accumulation time. In this work we propose a “mean to median” (M2M) algorithm for noise suppression in femtosecond laser plasma x-ray spectra. Series of spectra is necessary for the identification of corrupted data points by the developed method. The algorithm was tested with model spectra which reflect main features of experimental data. In practice we used it for extracting information about spectral lines of Ne-like Fe ions and He-like Al ions which allowed us to calculate plasma parameters. It is demonstrated that M2M method is able to clean spectra with more than 10% of corrupted pixels. Fluctuations in intensity of spectral lines induced by laser instability do not affect validity of the proposed method. [ABSTRACT FROM AUTHOR]

High-resolution soft X-ray spectra of H-like and He-like ions were produced from laser irradiated silicon and aluminum targets. Plasma size was about 100 µm. X-ray spectra were analyzed to determine plasma parameters. We compared the line shape of resonance transitions and their intensity ratios to corresponding dielectronic satellites and the intensities of the inter combination lines of He-like ions, with the results of model calculations. Such comparison gave average values of the electron density N e =(1-1.9)×10 21 cm -3 and the electron temperature T e =460–560 eV for Si plasmas and about 560 eV for Al plasmas produced by the first and the second laser harmonics. According to our estimations, more than 10 12 photons were produced within the resonance line spectral width and in the solid angle 2p steredian during the total decay period. [ABSTRACT FROM AUTHOR]

Experimental data are reported on the generation of fast ions in a picosecond laser plasma at a laser-radiation intensity of 2×1018W/cm2. The results are obtained by measuring the Doppler spectra of hydrogen-like fluorine ions. An important feature of the energy distribution of fast ions is a slow decrease up to an energy of 1.4 MeV. In addition, the directional motion of fast ions deep into a target is found due to the redshift of the Doppler profile of the Lyα line. The parameters of the energy distribution of the ions are theoretically estimated. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

The X-ray lines of ions in a solid target interacting with picosecond laser pulses of moderate intensity (2 × 10[sup 17] W/cm[sup 2]) were measured on the “Neodim” laser facility. X-ray Ly[sub α] emission spectra of hydrogen-like fluorine ions were observed. Satellite lines were also observed, evidencing the presence of intense plasma oscillations. The positions and separation between the satellites allow their assignment to the intense electrostatic oscillations with an amplitude larger than 10[sup 8] V/cm and a frequency of about 7 × 10[sup 14]s[sup –1] that is noticeably lower than the laser frequency ω[sub las] ∼ 1.8 × 10[sup 15] s[sup –1]. It is suggested that these oscillations may be due to strong plasma turbulence caused by the development of plasma oscillations of the Bernstein-mode type under the action of a strong magnetic field generated in plasma. The experimental results are compared with the calculated spectra of multicharged ions. © 2003 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The satellite structure of 1s2p[sup 1, 3]P[sub 1]–1s[sup 2 1]S[sub 0] lines of the He-like argon ion in plasma produced by a 45-fs laser pulse in a gas-jet cluster target is measured with a high spectral resolution. Radiation transitions 2p → 1s from autoionizing states (AISs) are detected for ions ranging from Li-like to F-like. The spectrum observed is theoretically simulated with the use of the spectroscopic data for the AISs of multicharged ions obtained within the multiconfiguration relativistic Hartree–Fock method. Good agreement with experimental data is obtained when the main population channels of these states are taken into account for typical values of cluster-target plasma parameters. © 2002 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

It was established experimentally that the number and energy of fast ions in laser plasma increased with increasing angle of focusing laser radiation onto a flat target. Numerical calculations showed that the increase in angle of focusing brought the mean angle of incidence of laser radiation closer to the optimal angle corresponding to the maximal efficiency of the resonance absorption mechanism and, as a result, increased the fraction of absorbed laser energy in the energy of fast electrons and increased the number of fast electrons. In turn, the increase in the energy and number of fast electrons resulted in an increase in the number of fast electrons involved in the formation of a self-consistent electric field at the target edge and led to the growth of the field strength, which, eventually, was the reason for the increase in the number and energy of fast ions. © 2001 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The x-ray spectra of a plasma generated by heating CO[sub 2] and Ar clusters with high-intensity femtosecond laser pulses with q[sub las] ... 10[sup 18] W/cm² are investigated. Spatially resolved x-ray spectra of a cluster plasma are obtained for the first time. Photoionization absorption is observed to influence the spectral line profiles. The recorded features of the x-ray emission spectra definitely indicate the existence of a large relative number of excited ions (... 10[sup -2] - 10[sup -3]) with energies of 0.1 - 1 MeV in such a plasma. Possible mechanisms underlying the acceleration of ions to high energies are discussed. It is shown that the experimental results can be attributed to the influence of ponderomotive forces in standing waves generated by the reflection of laser radiation from the clusters. [ABSTRACT FROM AUTHOR]

Experimental demonstration of multi-charged heavy ion acceleration from the interaction between the ultra-intense short pulse laser system and the metal target is presented. Al ions are accelerated up to 12 MeV/u (324 MeV total energy). To our knowledge, this is far the highest energy ever reported for the case of acceleration of the heavy ions produced by the < 10 J laser energy of 200 TW class Ti:sapphire laser system. Adding to that, thanks to the extraordinary high intensity laser field of ~1021 Wcm-2, the accelerated ions are almost fully stripped, having high charge to mass ratio (Q/M). [ABSTRACT FROM AUTHOR]