Hydrogen interaction with tungsten is becoming a highly relevant topic since tungsten was recognized as the most promising candidate for the first wall of future fusion reactors. Prediction of hydrogen isotopes migration and their abundance in the reactor after plasma exposure is uncertain. Namely, a part of gaseous tritium is not interacted completely with deuterium and is also not completely removed in the gas phase after the plasma shots. A part of it may be retained everywhere inside reactor surface. A great role represents the structural disorder that is formed on the W surface or by W and Be/W deposits. Vacancy sites are theoretically predicted to trap multiple H atoms exothermically, but their density and their potential influence on permeability has not been experimentally investigated yet. In our work, long-term hydrogen outgassing and permeation studies of structurally highly disordered tungsten films, deposited on 40 mm diameter highly permeable Eurofer substrates, using the Pulsed Laser Deposition technique have been realized. Permeability of W films having different thicknesses (1 and 10 micrometers) was initially extremely low, and was gradually increasing over a several-day campaign. The final values at 400 °C, lying between P = 1.46x10-15 mol H2/(m s Pa^0.5) and P = 4.8x10-15 mol H2/(m s Pa^0.5), were substantially lower than those known for well ordered films. Surprisingly, the 10 micrometer thick W film initially contained a very high amount of hydrogen, ~ 0.1 H/W, which was gradually releasing during the twenty-day campaign.
COBISS.SI-ID: 25908263
We present experimental data and numerical simulations in order to show that the mechanism of spinodal dewetting is active during ion beam irradiation of thin solid films. The expected scaling law for the characteristic wavelengths versus the initial film thickness is modified by the presence of sputtering. The conclusion is fully supported by model simulation which shows a square law dependence for null sputtering yield and a bimodal trend when sputtering is included. This result is in contrast to earlier studies and opens the possibility to control and use ion induced dewetting for the fabrication of functional nanostructures.
COBISS.SI-ID: 914090
In this paper we described new experimental data on hydrogen interaction with the first wall of a nuclear fusion reactor. By applying a very sensitive method we were able to measure most relevant parameters which govern hydrogen transport through tungsten films.
COBISS.SI-ID: 24636967
This paper presents a gas-sorption method, based on an in situ calibrated throughput, for characterizing nonevaporable getters (NEGs) of Ti- and Zr-based alloys. The main characteristics of the method are the adjustment of a constant injected gas flow, the prompt calibration of a throughput, and the measurement of an increasing sorption pressure. It is essential that inert vacuum gauges be selected for measurements of total pressure to prevent contamination of a test gas and poisoning of an NEG under test. A capacitance diaphragm gauge is used for preparation of the injected gas flow by filling the gas reservoir with a test gas and adjusting the conductance of a variable leak valve. A spinning rotor gauge (SRG) is used for in situ calibration of the throughput by means of an integrated gas-flow calibration facility and the rate-of-pressure-rise method, and by continuous measurement of the sorption pressure in a test chamber. A getter pumping speed and a sorbed quantity are calculated while considering the trhoughput, the sorption pressure, and the sorption time. The throughput must be selected in accondance with both the sorption characteristics of a particular Neg TYPE and the measurement capabilities of the SRG. At room temperature, porous thick-film NEGs and structured thin-film NEGs exhibit an initial getter pumping speed on the order of 1 and 0.1 1 s[sup]{-1} cm[sup]{-2}, respectively. The corresponding sorption capacity of a few times 10[sup{-4} mbar 1 cm[sup]{-2} is comparable for all chemically active gases except for H[sub]2, which amounts to a few times 100 x 10[sup]{-3} mbar 1 cm[sup]{-2} in the case of porous NEGs and ~ 1 x 10[sup]{-3} mbar 1 cm[sup]{-2} in the case of structured NEGs. Detailed analysis of uncertainties of SRG pressure measurements below 1 x 10[sup]{-3} mbar gives an expanded uncertainty of the getter pumping speed and the sorbed quantity of 1.9% and 3.5%, respectively. While temporally interrupting the throughput, the setup enables discrete measurements of the background pressure, which increases because of the acumulation of nongetterable gases. After completion of the gas-sorption test, a qualitative determination of the accumulated inert gas composition is performed by the gas-burst method using a quadrupole mass spectrometer (QMS) mounted on a vacuum system. The quantitative analysis is enabled by the use of a QMS calibrated in situ by known amounts of a certain gas such as H[sub]2, CH[sub]4, CO, Ar and Kr.
COBISS.SI-ID: 874154
We study the consequences of a class M1.0 Xray solar flare (0.1 - 0.8 nm) recorded by GOES15 satellite on February 18, 2011 between 14:00 and 14:15 UT, by analyzing the amplitude and phase real time variations of very low frequency (VLF) radio waves emitted by transmitter DHO/23.4 kHz (Germany) and recorded by the AWESOME receiver in Belgrade (Serbia). The electron density has been recovered by applying the LWPC simulation code to the different stages of the flare development, as registered by the amplitude and phase perturbations, whereupon the electron continuity equation has been used to estimate the effective recombination coefficient in the range around 70km height. The increase of the effective recombination coefficient with both decreasing height and flare intensity is confirmed.
COBISS.SI-ID: 2058491