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Desorption/ablation of lithium fluoride induced by extreme ultraviolet laser radiation

Blejchař T., Nevrlý V., Vašinek M., Dostál M., Kozubková M., Dlabka J., Stachoň M., Juha L., Bitala P., Zelinger Z., Pira P., Wild J.

Nukleonika

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2016

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Vol. 61, No. 2

131--138

EN

The availability of reliable modeling tools and input data required for the prediction of surface removal rate from the lithium fluoridetargets irradiated by the intense photon beams is essential for many practical aspects. This study is motivated by the practical implementation of soft X-ray (SXR) or extreme ultraviolet (XUV) lasers for the pulsed ablation and thin fi lm deposition. Specifically, it is focused on quantitative description of XUV laser-induced desorption/ablation from lithium fluoride, which is a reference large band-gap dielectric material with ionic crystalline structure. Computational framework was proposed and employed here for the reconstruction of plume expansion dynamics induced by the irradiation of lithium fluoridetargets. The morphology of experimentally observed desorption/ablation craters were reproduced using idealized representation (two-zone approximation) of the laser fluence profile. The calculation of desorption/ablation rate was performed using one-dimensional thermomechanic model (XUV-ABLATOR code) taking into account laser heating and surface evaporation of the lithium fluoridetarget occurring on a nanosecond timescale. This step was followed by the application of two-dimensional hydrodynamic solver for description of laser-produced plasma plume expansion dynamics. The calculated plume lengths determined by numerical simulations were compared with a simple adiabatic expansion (blast-wave) model. The availability of reliable modeling tools and input data required for the prediction of surface removal rate from the lithium fluoridetargets irradiated by the intense photon beams is essential for many practical aspects. This study is motivated by the practical implementation of soft X-ray (SXR) or extreme ultraviolet (XUV) lasers for the pulsed ablation and thin fi lm deposition. Specifically, it is focused on quantitative description of XUV laser-induced desorption/ablation from lithium fluoride, which is a reference large band-gap dielectric material with ionic crystalline structure. Computational framework was proposed and employed here for the reconstruction of plume expansion dynamics induced by the irradiation of lithium fluoridetargets. The morphology of experimentally observed desorption/ablation craters were reproduced using idealized representation (two-zone approximation) of the laser fluence profile. The calculation of desorption/ablation rate was performed using one-dimensional thermomechanic model (XUV-ABLATOR code) taking into account laser heating and surface evaporation of the lithium fluoridetarget occurring on a nanosecond timescale. This step was followed by the application of two-dimensional hydrodynamic solver for description of laser-produced plasma plume expansion dynamics. The calculated plume lengths determined by numerical simulations were compared with a simple adiabatic expansion (blast-wave) model.

2

Energy transformation in Plasma Focus discharge with wire and liner as a load

Kubeš P., Kravárik J., Klír D., Scholz M., Paduch M., Tomaszewski K., Karpinski L., Ryc L., Juha L., Krása J., Szydlowski A., Romanova V.

Nukleonika

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2002

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Vol. 47, nr 4

151-153

EN

We present the results of experiments focused on energy transformations during the implosion of the hydrogen current sheath towards an Al wire (120 ěm in diameter) positioned on the top of the inner electrode of the PF-1000 plasma focus facility at the IPPLM in Warsaw. A wire corona is formed at the current sheath impact and ~60 ns after the impact a soft X-ray pulse is emitted. Its spectrum contains AlVI-XII lines accompanied by their satellites. The amount of emitted energy is recorded by two filtered PIN diodes and thermoluminescent dosimeters and depends on symmetry of the current sheath and quality of the current sheath focus. The mean value of energy of keV photons emitted in the runs done without the wire (~1 J) is higher than the energy obtained with the wire (~0.4 J). A time delay between the impact of the current sheath and X-ray pulse, the plasma focus dynamics and soft X-ray emission are interpreted by an axial magnetic field generation and transformations.

3

Time-integrated diagnostics of X-ray emission from PALS and PF 1000 : preliminary results

Ryć L., Krása J., Juha L., Kaczmarczyk J., Paduch M., Parys P., Tomaszewski K., Scholz M.

Nukleonika

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2001

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Vol. 46, suppl. 1

41--43

EN

Thermoluminescent and semiconductor detectors operating in an integrating mode have been applied to the measurement of X-ray flashes of high intensity from large plasma facilities. A detection head of special kind has been developed to perform comparison measurements with the use of the detectors of both kinds.

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Limitations of thermoluminescent dosimeters in soft X-ray diagnostics of pulsed plasma

Krása J., Fárníková M., Juha L., Cejnarová A.

Nukleonika

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2001

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Vol. 46, suppl. 1

49--51

EN

Responses of thermoluminescent dosimeters (TLDs) of CaF2:Dy, CaF2:Mn, and LiF:Mg,Cu,P to the deposited energy of monochromatic 1.75–3.5 keV radiation were measured with respect to an increase in the local dose due to the attenuation length that was much shorter than the TLD thickness. The responses of TLDs to X-ray emission from the laserproduced aluminium plasma were found to be independent of the dose rate within a wide range.