|
| |
|
|
Deformation of thin self-standing mask at inhomogeneous irradiation.
Koláček, Karel ; Schmidt, Jiří ; Frolov, Oleksandr ; Štraus, Jaroslav ; Chalupský, Jaromír ; Choukourov, A.
Flatness of the mask is one of key features influencing the quality of image. Among factors that can affect mask flatness belongs inhomogeneous illumination. This does not apply to lithography, but to experiments that use only discrete parts of mask e.g. for nanostructuring or other type of material research. It is shown that even single EUV laser shot (laser wavelength ~46.9 nm, pulse duration ~1.5 ns, focused pulse energy ~20 .mu.J, peak fluency 48 J/cm2) not only deforms the mask, but also changes mask-substrate distance. In our case two kinds of grids (one circular with rectangular windows 7.5x7.5 μm and bars 5 micro m (period 12.5x12.5 micro m), other rectangular with rectangular windows 3.2x1.2 μm and bars 0.8 micro m (period 4x2 micro m)) were attached to PMMA substrate and exposed to one or five superimposed focused laser shots. The mask (grid) deformation was inferred from the changes of diffraction pattern engraved into PMMA.
|
|
|
Double pulse capillary discharge assessment for nitrogen soft X-ray laser.
Hübner, Jakub ; Nevrkla, M.
The work examines possibilities of capillary discharge pinching plasma driven by combination of two electric current pulses ("pedestal" slow exponentially damped sinus t1/4 > 200 ns, peak current Ipeak < 50 kA and fast triangular pulse with a rise time about 38 ns, Ipeak > 60 kA) to obtain the maximum possible gain at wavelength l = 13.4 nm (hydrogen-like nitrogen recombination scheme). The optimal initial density ρ0 (or pressure) and start time tstart of second triangular pulse (second pulse start at peak current Ipeak of the first pulse) were determined for two capillary radii (0.5 and 1 cm) and four current peaks of the first pulse (20, 30, 40 and 50 kA).\n
|
|
|
Reflectivity of a mirror in XUV spectral region (46.9 nm).
Schmidt, Jiří ; Koláček, Karel ; Štraus, Jaroslav ; Frolov, Oleksandr ; Prukner, Václav ; Melich, Radek ; Psota, Pavel ; Sobota, Jaroslav ; Fořt, Tomáš
A focusing mirror as an optical element is used in our applications that require light collection (e.g. for laser ablation studies). A knowledge of the mirror reflectivity is important for determination of focused laser pulse energy, or for determination of local fluencies near the laser focus. The reflectivity of our spherical focusing mirror with(/without) multi-layer coating was measured. Reflection coefficients of this mirror in a long period of time are also reported. Further, the incidence-angle dependence of the XUV reflectivity of flat mirrors is presented as well.
|
|
|
XUV Spectra from High Current Nitrogen Z-Pinch Capillary Discharge.
Vrba, Pavel ; Vrbová, M.
We have performed computer modeling of the pinching plasma of capillary discharge using the 1d NPINCH code, that considers ablation of the capillary wall. At high currents we have observed that, the ablation has significant effect on the plasma electron temperature evolution and on the rate of pinch decay. To estimate the emitted spectra in XUV range, the FLYCHK code was used as a post processor. The capillary wall ablation represents the principal obstacles of recombination pumping during pinch decay.\n
|
|
|
Sub-Nanosecond Laser Induced Plasma as Water Window Radiation Source.
Vrbová, M. ; Vrba, Pavel
Laser plasma created in a krypton gas puff target is studied as a source of radiation in the water window spectral range (lambda= 2.3 - 4.4 nm). The spatial development of the plasma induced by a sub-nanosecond Nd:YAG laser pulse focused on the gas puff target is modeled using 2d RMHD code Z*. Space-time distributions of plasma quantities, namely electron temperature, electron density, mass density and plasma expansion velocity were evaluated. Instantaneous spectra during the laser pulse and during plasma decay period are also calculated. Temporal evolutions of the krypton ions relative populations prove that ions from Kr21+ and Kr22+ are responsible for dominant spectral intensity emitted at a wavelength around lambda= 3 nm. Evaluated time resolved spectra are compared with time integrated spectra obtained experimentally.
|
guest ::
