|
|
Optimization of a high current pulse discharge in gas filled capillary for application purposes - Ar8+ laser 46.9 nm
Štraus, Jaroslav ; Koláček, Karel (advisor) ; Jančárek, Alexandr (referee) ; Wild, Jan (referee)
The aim of the thesis was to complete the development of the Czech version of the extremal ultraviolet (XUV) argon capillary laser working at the wavelength 46.9 nm and its adaptation for the first practical applications. A multi-discipline complex of mutually interconnected problems was analyzed and studied: The reasons for a capillary low life-time were investigated using defectoscopic methods, a pre- pulse regime influence was studied with the help of spectroscopy on a physical model. By performing necessary construction and technology changes as well as by the multi-parametric optimisation of working regime, the indicated weaknesses were suppressed. The XUV laser was focused into a footprint of the size about 100 µm and the apparatus was extended by a set of practical aids and accessories for special applications, especially for exposition of the samples at extreme temperatures. As practical applications of the XUV laser, measurements of multilayer mirror reflectivity and filter transmissivity were performed. Using the XUV laser for a thin layer deposition and radiation resistance testing was verified to be practicable in principle. Probably a first temperature dependence of an XUV laser ablation rate was measured, in the temperature range from -180 deg.C to +200 deg.C, on BaF2.
|
|
|
Optimization of a high current pulse discharge in gas filled capillary for application purposes - Ar8+ laser 46.9 nm
Štraus, Jaroslav ; Koláček, Karel (advisor) ; Jančárek, Alexandr (referee) ; Wild, Jan (referee)
The aim of the thesis was to complete the development of the Czech version of the extremal ultraviolet (XUV) argon capillary laser working at the wavelength 46.9 nm and its adaptation for the first practical applications. A multi-discipline complex of mutually interconnected problems was analyzed and studied: The reasons for a capillary low life-time were investigated using defectoscopic methods, a pre- pulse regime influence was studied with the help of spectroscopy on a physical model. By performing necessary construction and technology changes as well as by the multi-parametric optimisation of working regime, the indicated weaknesses were suppressed. The XUV laser was focused into a footprint of the size about 100 µm and the apparatus was extended by a set of practical aids and accessories for special applications, especially for exposition of the samples at extreme temperatures. As practical applications of the XUV laser, measurements of multilayer mirror reflectivity and filter transmissivity were performed. Using the XUV laser for a thin layer deposition and radiation resistance testing was verified to be practicable in principle. Probably a first temperature dependence of an XUV laser ablation rate was measured, in the temperature range from -180 deg.C to +200 deg.C, on BaF2.
|
|
| |
|
|
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.
|
|
|
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.
|
|
| |
|
|
Exploze drátku ve vodě
Prukner, Václav ; Koláček, Karel ; Schmidt, Jiří ; Frolov, Oleksandr ; Štraus, Jaroslav
The paper reports on the first experimental results of a new-built apparatus which is designed as soft X-ray source of coherent radiation with wavelength 14 nm. The radiation could be produced by the wire explosion in a liquid where the proximity of liquid wall can stabilize plasma similarly as proximity of solid wall stabilizes a Z-pinch in a capillary. The first part of this paper describes construction of the new device. In the second part are published first experimental data of wire explosion tests of the device which means time dependences of charging voltage and current.
|
|
|
Čtyř-segmentová vakuová XUV fotodioda
Schmidt, Jiří ; Koláček, Karel ; Frolov, Oleksandr ; Prukner, Václav ; Štraus, Jaroslav
A soft X-ray/XUV diode (XRD) is a powerful diagnostic tool for system alignment, among others, in capillary discharge experiments, which generate directional soft x-ray radiation, eventually a laser pulse. In our experimental devices (CAPEX and CAPEX-U) we usually used PIN diode or vacuum photodiode (one-segment). These diagnostics are not very suitable, mainly because many shots (more than 50) are necessary to find the optical axis. During last year we have designed and manufactured a four-segment soft X-ray vacuum diode with a golden photocathode, which detects the soft X-ray radiation emitted in the axial direction. This new diagnostic tool is capable to locate the axis of soft X-ray laser in a few capillary shots (less than 10). The description and the experimental measurement of the four-segment soft X-ray vacuum diode are a subject of this paper.
|
|
|
Využití modelových spekter ke stanovení vhodných parametrů kapilárního výboje pro zesílenou emisi Balmerova alfa – přechodu H–like N (13,4 nm)
Štraus, Jaroslav ; Koláček, Karel ; Schmidt, Jiří ; Frolov, Oleksandr ; Prukner, Václav
Our capillary-discharge driver CAPEX-U, as many other pulsed-power devices, requires very accurate triggering of high-voltage gas switch. Laser-triggered switches offer many advantages over electrical triggered ones in terms of reproducibility, reliability, suitability for multi-gap or multi-channel operation and electrical isolation from the main high-voltage pulse. Results on the simultaneous initiation of four-channel high voltage spark gap by a neodymium dopped yttrium aluminium garnet (Nd:YAG, λ=1064 nm) laser are presented. The switch is pressurised with SF6 and N2 and holds off voltage about 500 kV at a gap separation of 13 mm. Electrical parameters of the spark channels are obtained from the comparison of experimental and modelling (equivalent circuit) results.
|
|
| |
guest ::
RSS feed.