M. Vrbova

XUV radiation from gaseous nitrogen and argon target laser plasmas

Laser plasma created in gaseous target is studied as a source of radiation in the water window wavelength range. Plasma is created by focusing an 800 mJ/7 ns Nd:YAG laser pulse into the gas-puff target. Using nitrogen gas results in emission of an intense quasi-monochromatic radiation with the wavelength 2.88 nm, corresponding to the quantum transition 1s2p → 1s2 of helium –like nitrogen ion. The emission spectrum with argon target covers all the water window range. Laboratory and computer experiments have been performed for both target gases. The spatial distributions of emitted energy in the water window spectral range were compared. The total emitted energy with argon was one order higher than with nitrogen.

Picosecond relaxation time measurement from the Q-switched threshold

A method is presented for measurement of the relaxation time of a passive Q -switch dye in the picosecond region which is based on the determination of the Q -switch threshold. The relaxation times of 24 ± 5 ps for cryptocyanine and 28 ± 5 ps for modified dicarbocyanine iodide were obtained.

Dynamics and Emission Characteristics of Xenon Capillary Discharge

Xenon filled fast capillary discharge is studied as a source of intense EUV radiation. Experiments are performed with GREMI apparatus. One‐dimensional two temperatures MHD code is used to evaluate time and radial dependences of capillary plasma properties. Plasma thermodynamic and radiative characteristics are evaluated by means of steady state IONMIX code. Measured and estimated emission spectra are compared.

EUV Emission Spectra and Gain in Polyacetal Capillary Discharge

Experimental and computer studies of polyacetal capillary discharge are reported. Time resolved spectra in the wavelength region 3 – 25 nm are measured. Space‐time dependences of plasma electron density and temperature are calculated by means of MHD code. Time profiles of selected lithium‐, helium‐ and hydrogen‐like carbon and oxygen ion populations and time resolved spectra are evaluated by means of the FLY code. Gain factors for a capillary initially either evacuated or filled by polyacetal vapors are calculated.

Mid-infrared lasers for transmyocardial laser revascularization

Transmyocardial laser revascularization was fount to be a new emerging technique for the treatment of end-stage coronary artery diseases. In our study, a comparison has been made of mid-IR solid-state laser radiation interaction with a myocardium tissue. For this purpose, the Tm:YAG, CTH:YAG and Er:YAG laser systems were designed, constructed and used for the interaction experiments. The ablation coefficients were measured to be 3 mm/J for Tm:YAG; 0.03 mm/J for CTH:YAG, and 10.5 mm/J for Er:YAG interacting laser radiation. From the histological examination follows that the channels ablated by Er:YAG laser radiation are without any thermal damage of the surrounding tissue and with the minimal mechanical injury, therefore Er:YAG laser could be considered as a good candidate for the TMLR.

XUV Radiation Emitted by Capillary Pinching Discharge

Fast capillary discharge in nitrogen is studied as a source of incoherent monochromatic radiation in “water window” wavelength range. Discharge system with current amplitude 13.5 kA and half period 140 ns was designed, realized and modeled. Strong spectral line at 2.88 nm corresponding to the quantum transition 1s2p→1s2 of helium -like nitrogen ions was detected. The initial pressure nitrogen in the alumina capillary was varied from 10 to 220 Pa. Peak value of the line intensity at about 50 Pa was found and proved by the computer modeling.

Modelling of Capillary Z-Pinch Recombination Pumping of Hydrogen-Like Ion EUV Lasers

We report here new results of simulations of Z-pinch recombination pumping for capillary filled by boron and compare them with previous nitrogen results. In both cases the same capillary radius and current pulse shape are taken into account. Evaluated pressure optimized gains for boron and nitrogen are 1.04 cm−1 and 0.11 cm−1, respectively. Influence of possible wall ablation is also analyzed.

Optical diagnostics of evacuated polyacetal capillary discharge

In this paper our new capillary discharge device built for the soft x-ray laser studies is described and the first experimental results obtained from electrical, optical and UV diagnostics together with code simulations are presented.

Infrared laser-tissue interaction during transmyocardial laser revascularization

Transmyocardial laser revascularization was found to be a new way how to convey oxygen-rich blood directly from the left ventricular cavity to the myocardium. In our study, a comparison has been made of the interaction of mid-IR solid state laser radiation with a myocardium tissue. For this purpose, the CTH:YAG, Tm:YAG and Er:YAG laser systems were designed, constructed and used for the interaction experiments. Besides those mid-IR lasers, the commercially produced CO2 laser was used for the comparative study. The ablation coefficients were measured to be 0.029 mm/J for CTH:YAG laser radiation; 0.061 mm/J for Tm:YAG; 0.75 mm/J for CO2, and 10.5 mm/J for Er:YAG. From the histological examination follows that only the channels ablated by Er:YAG laser radiation are without any thermal damage of the surrounding tissue and with the minimal mechanical injury. As a conclusion - Er:YAG laser could be considered as a good candidate for the TMR besides CO2 laser.

Intravenous irradiation of blood by N2 laser: rabbit organism immunity increase using a staphylococcal model

The capacity of erythrocytes to photohemolysis was researched in physiological solution with increasing percents of blood plasma by spectrophotometer Specord UV-VIS. The screening effect of plasma was founded during illumination of erythrocyte suspensions by completed light of the mercury lamp DRT-375. Much less effect was observed during the illumination of the light with (lambda) equals 365 nm. The screening effect of plasma was due to presence of a protein and aminoacid groups in plasma.