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In this work, the deposition of Y thin films by laser beams with 0.5 ps and 5 ps pulse durations at different laser fluences (1.2-6.4 J/cm(2)) is reported. The morphology of the deposited films and of the ablated target surface is investigated by scanning electron microscopy analyses. The present results show that the films, well adherent to the substrates, are characterized by a high abundance of sub-micrometric particulates with average size less than 0.3 mu m, whose density decreases with increasing laser fluence. The formation of columnar structures observed on the target surface seems to be responsible of the poor film homogeneity. Acceptable deposition rate in the range of 0.08-0.16 A/pulse with 5 ps pulse duration is found; on the contrary with 0.5 ps pulse duration, it is not possible to get information on deposition rate as a function of the laser fluence due to the high non-uniformity of the films. A comparison with the results previously obtained in ns regime is presented and discussed. The achievements of our investigation will be useful to optimize the synthesis of photocathodes based on Y films for the production of bright electron beams in radio-frequency photoinjectors.

In this work, we report on the characterization of pulsed soft X-rays emitted from laser-produced plasma by different targets. The measurements were performed in a vacuum stainless-steel chamber at 10-7 mbar .The plasma was generated by a pulsed KrF excimer laser of 248 nm laser wavelength, operating at single shot and having a pulses of 23 ns FWHM. The beam was focused on pure Si, Cu and Ta targets. The laser energies were 40, 80 and 120 mJ, concentrated onto a spot of about 0.01 cm2, with a resulting irradiance of 1.7, 3.5 and 5.2x108 Wcm-2. The utilized detector was a very sensitive Faraday cup which opportunely biased was able to record time resolved signals of X-rays and to estimate their energy. The found X-rays energy values were compared to the ion temperature of the target plasma fitting the time resolved ion current signals by the shifted Maxwell-Boltzmann velocity distribution.

We developed an ion accelerator with a double accelerating gap system supplied by two power generators of different polarity.-The ions were generated by laser ion source technique. The laser plasma induced by an excimer KrF laser, freely expanded before the action of accelerating fields. After the first gap action, the ions were again accelerated by a second gap. The total acceleration can imprint a maximum ion energy up to 160 keV per charge state. We analyzed the extracted charge from a Cu target as a function of the accelerating voltage at laser energy of 9, 11 and 17 mJ deposited on a spot of 0.005 cm2. The peak of current density was 3.9, 5.3 mA for the lower and medium laser energy at 60 kV. At the highest laser energy, the maximum output current was 11.7 mA with an accelerating voltage of 50 kV. The maximum ion dose was estimated to be of 1012 ions/cm2. Under the condition of 60 kV accelerating voltage and 5.3 mA output current the normalized emittance of the beam measured by pepper pot method was 0.22 π mm mrad.

In this work two different techniques to modify the polymeric surfaces are compared; Laser irradiation and ion implantation were performed on Ultra High Molecular Weight Polyethylene (UHMWPE) samples. The irradiation treatment was performed by using two different laser sources operating in the UV and IR range, applying many laser shots in air atmosphere on the polymer surface. Ion implantation was performed using a new LIS (Laser Ion Source) accelerator with an accelerating voltage of 40 kV. Contact angle, roughness and Fourier Transform Infra Red (FT-IR) measurements were performed on the samples before and after the two treatments in order to obtain information on the UHMWPE modification.

We study the velocity distribution of ions delivered by plasma whihs is induced by UV Laser.

Ions of different elements were generated by laser-induced-plasma and accelerated by a two adjacent cavities. Therefore, the ions were undergone a double acceleration imparting a maximum ion energy of 160 keV per charge state. We analyzed the extracted charge from a Cu target as a function of the accelerating voltage. At 60 kV of total accelerating voltage, the maximum current peak was of 5.3 mA. The ion flux resulted of 3.4x1011 ions/cm2. The normalized emittance measured by pepper pot method at 60 kV was of 0.22 π mm mrad. By this machine, biomedical materials as UHMWPE were implanted with carbon and titanium ions. At a total ion flux of 2x1015 ions/cm2 the polyethylene surface increased its micro hardness of about 3-hold measured by the scratch test. Considering the ion emission cone dimension, we estimated a total extracted charge per pulse of 200 nC.

The properties of pulse laser ablation of Cu and Cu98/Be2 materials are studied and the differences in emission of Cu ions are emphasized. The iodine high-power laser system PALS and a KrF laser were used to perform the experiments at the fundamental harmonics λ = 1.315 µm and  = 248 nm delivering energy up to 500 J and 600 mJ, respectively. Pure Cu and Cu98/Be2 alloy targets of 50 µm, 500 µm and 1000 µm in thickness were ablated to measure the influence of the Be admixture on the emission of Cu ions. The alloy Cu98/Be2 was chosen due to the well defined amount of a beryllium admixture in the plasma in contrary to the incidental amount of carbon, oxygen and hydrogen impurities chemisorbed on target surfaces of Cu and Cu98/Be2 samples. It was approved that the emission of Cu ions driven by the KrF laser exhibits a higher gain from the Cu98/Be2 plasma in contrary to the Cu plasma. The fast ion emission induced by laser intensities near the threshold value is significantly affected by the emission of ionized impurities chemisorbed on the target surface and by repetitive outbursts of fast generated ions. Under these conditions the influence of the 2% Be admixture on the emission of Cu ions plays only a minor role.

A single-crystal CVD diamond detector (DD) of a sandwich structure was used for measurement of soft X-rays and ions emitted from plasmas obtained with the use the PALS laser system in Prague. The detector was fabricated in the Institute of Nuclear Physics PAN in Cracow with the use of diamond material obtained from Element Six, Inc. In the laser experiment, the responses of the detector to X-rays and ions were compared to the responses of an ion collector (IC). The signals from the DD proved to be much different to the ones from the IC which is explained by different mechanisms of producing current in both detectors. Due to high sensitivity, the DD is useful for measurement of fast protons. Both detectors can be used for simultaneous measurement of soft X-rays and ions from the same laser shot and the data obtained are complementary.

Il trovato è un divisore capacitivo di dimensioni tali da registrare impulsi molto brevi inferiori a 100 ps. Le applicazioni sono da trovare nel campo delle macchine acceleratrici e di diagnostica digitale.

The purpose of this work is the characteristic modification by ion implantation of ultra high molecular weight polyethylene, and a preliminary study of its surface. This biomedical material has been chosen for its excellent chemical and physical properties. An ultraviolet-pulsed laser of 248 nm was employed to produce, by laser ablation, C and Ti ions of different charges with current densities of the order of 10 mA/cm(2). The ions were accelerated by the application of a positive high voltage, 30 kV, on the target support to accelerate ions to implant the polyethylene surfaces up to a depth of about 200 nm. Preliminary results about surface properties indicate that implanted surfaces have higher wettability and micro-hardness values with respect to unimplanted ones