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Nedávné příspěvky

Software pro analýzu teplotního namáhání tunelových konstrukcí
(ČVUT v Praze., 2025) Beránek, D.; Štefan, R.; Holan, J.
Softwarový nástroj pro stanovení rozložení teplot v nosné konstrukci tunelu. Umožňuje parametrické zadávání pro rychlé předběžné výpočty.
Metodika pro modelování požárů v tunelech
(ČVUT v Praze, 2025) Benýšek, M.; Moucha, P.; Dvořáková, N.; Štefan, R.; Kučera, P.; Thomitzek, A.
Výstupem je necertifikovaná metodika obsahující soubor doporučených postupů pro modelování požáru v tunelech popisující, v jakých případech lze modelovat požár pomocí méně komplexních modelů, a v jakých případech je nutné používat pokročilé modely. Dále obsahuje praktické rady pro modelování požáru pomocí pokročilých i méně komplexních modelů.
Measurement of strong electromagnetic pulses generated from solid targets at sub-ns kJ-class PALS laser facility
(IOP Publishing, 2021) Raczka P.; Cikhardt J.; Pfeifer M.; Krása J.; Krupka M.; Burian T.; Krůs M.; Pisarczyk T.; Dostál J.; Dudžák R.; Badziak J.
Measurements had been performed of strong electromagnetic pulses (EMPs) generated as a result of laser-target interaction at the sub-ns kJ-class Prague Asterix Laser System facility. Two conductive Prodyn FD5C D-dot pencil probes were used. Measurements were performed inside the experimental chamber and outside the chamber in a large chamber window 40 cm in diameter in a setup that guaranteed 6 GHz bandwidth. A very good signal-to-noise ratio (17:1) was obtained after some steps were taken to ensure proper EMP shielding of the data collection setup. The EMP signal in the time domain was found to have the form of a sharp initial spike followed by gradually decaying oscillations interspersed with some secondary spikes. The values of the vertical component of the electric field strength were estimated. The highest value recorded in this experiment was 620(-180)(+260) kV m(-1) at a distance of 40 cm from the target. It was observed that plastic targets-particularly the 100s of mu m thick plastic foils-tend to generate stronger EMP fields than Cu and Au targets. A time-frequency analysis was performed for a typical shot, clearly showing some spectral features that appear only sometime after the start of the signal and hence indicate EMP generation from secondary sources. Electrons ejected from the target were recorded with the energies exceeding 1.5 MeV, which indicates that highly energetic processes are triggered as a result of the laser-target interaction.
Laser produced electromagnetic pulses: generation, detection and mitigation
(Cambridge University Press, 2020) Consoli F.; Tikhonchuk V.T.; Bardon M.; Bradford P.; Carroll D.C.; Cikhardt J.; Cipriani M.; Clarke R.J.; Cowan T.E.; Danson C.N.
This paper provides an up-to-date review of the problems related to the generation, detection and mitigation of strong electromagnetic pulses created in the interaction of high-power, high-energy laser pulses with different types of solid targets. It includes new experimental data obtained independently at several international laboratories. The mechanisms of electromagnetic field generation are analyzed and considered as a function of the intensity and the spectral range of emissions they produce. The major emphasis is put on the GHz frequency domain, which is the most damaging for electronics and may have important applications. The physics of electromagnetic emissions in other spectral domains, in particular THz and MHz, is also discussed. The theoretical models and numerical simulations are compared with the results of experimental measurements, with special attention to the methodology of measurements and complementary diagnostics. Understanding the underlying physical processes is the basis for developing techniques to mitigate the electromagnetic threat and to harness electromagnetic emissions, which may have promising applications.
Neutron fluence distribution in experiments with 3 MA deuterium gas-puff z-pinch
(American Institute of Physics, 2020) Cikhardt J.; Klír D.; Shishlov A.; Kokshenev V. A.; Řezáč K.; Cherdizov R.K.; Dudkin G.N.; Fursov F.I.; Kravárik J.; Kubeš P.; Kurmaev N.E.; Munzar V.; Novotný J.; Ratakhin N.A.; Varlachev V.A.; Turek K.
Deuterium gas-puff z-pinches are very efficient laboratory sources of neutron pulses. Using a novel hybrid gas-puff load on the GIT-12 generator, a significant increase in the neutron yields up to