Manufacturing of magnetron sputtering tungsten coatings and irradiation damage behavior under helium plasma exposure

The effects of high-energy protons produced in the plasma focus device on molybdenum and copper metals were studied. Molybdenum and copper samples were simultaneously irradiated with 20 hydrogen ion shots after the initial preparation and polishing of their surface. Molybdenum and copper samples were analyzed before and after irradiation by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Lee code was used to characterize the ion beam generated in the plasma focus device. The XRD results showed that the size of crystals in molybdenum samples increased from 33.1 to 41.4 nm and for copper samples from 28 to 37.2 nm. Also, the location of peaks in molybdenum and copper samples was shifted to larger angles by 0.041 and 0.174, respectively. The SEM micrographs revealed that cracks and cavities were formed on the surface of molybdenum due to the radiation of high-energy protons, while dense blisters were formed on the surface of copper, and in some areas on the surface of copper, melting and physical sputtering occurred due to the collision of high-energy ions with copper surface atoms. Lee code results indicated that each shot of the plasma focus device emits 7.9 × 1014 ions from the plasma column.

The investigation of the destructive effects of high-energy hydrogen ions on molybdenum and copper

Graphite samples, used in first-wall and divertor of nuclear fusion reactors like tokamaks, were irradiated using hydrogen and argon ions produced in an MTPF-2 plasma focus device in 20 shots to study radiation damages. Ion energy spectra are $dN_{\text {H}}\left ({E_{\text {H}} }\right)/ dE_{\text {H}}\approx E_{\text {H}}^{-2.8}$ with a minimum energy of 120 keV to a maximum of 1 MeV for hydrogen ions and ${dN_{\text {Ar}}\left ({E_{\text {Ar}} }\right)} / {dE_{\text {Ar}}}\approx E_{\text {Ar}}^{-3.5}$ with a minimum energy of 200 keV and a maximum energy of 2 MeV for argon ions. Based on the results of the SRIM code, the maximum destruction of hydrogen ions is at a depth of 900 nm, and a rate of 0.025 DPA/shot and highest hydrogen density is 0.5% at 920 nm. Conversely, the highest degradation of argon ions is at a depth of 120 nm and 0.23 DPA/shot, and the highest density of argon ions at a depth of 200 nm is 0.07%. Different maximum degradation locations and the maximum density of argon ions are due to their heavy mass compared to hydrogen. SEM micrographs show holes with high population density and some sublimated areas on hydrogen-irradiated surfaces. The predominant phenomenon due to argon ion irradiation is physical sputtering, leading to cavities with a depth of several micrometers. Based on the X-ray diffraction (XRD) spectrum, the location and intensity of peaks are changed, and irradiation reduces graphitization and increases the size of the graphite crystal.

Radiation Damage of Graphite Surface, Used in First-Wall and Divertor of Tokamaks, Irradiated by Hydrogen and Argon in Plasma Focus Device

Abstract In this study, nanoparticles of neodymium oxide were deposited on NaX zeolite powder using a 5.3 kJ Mather‒type plasma focus device. The NaX zeolite samples were exposed to the 10, 15, and 20 shot numbers of the plasma focus device at a distance of 14 cm from the anode tip and 0 angular positions with respect to the anode axis. Parent NaX zeolite and NaX:Nd composites with different Nd 2 O 3 percent weights were characterized using different techniques such as; XRF, XRD, SEM, FT‒IR, and UV‒vis. It was shown that the amount of Nd 2 O 3 in the samples increases with increase of the shot number. It was also found from the results that variations in amount of Nd 2 O 3 can have significant effects on the degree of the crystallinity and optical properties of final products such as refractive index, band gap energy, dielectric constant, and absorption coefficients. 

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B. Shirani Bidabadi

Papers

Study of surface damage and hydrogen distribution in irradiated tungsten by protons in plasma focus device