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The transport of tungsten vapour evaporated from the electrode surfaces of a high-pressure xenon short-arc lamp, which is dominated by the gas convection in the lamp, determines the location and extent of the blackened area on the inner bulb wall. We have investigated factors affecting the vapour transport and other important phenomena related to the gas convection using a unified numerical model. The influence of the lamp operating parameters and also the thermodynamic and transport properties of the gas is discussed. The predicted lamp characteristics and phenomena agree well with experimental results. The gas velocity in the lamp is strongly affected by the Lorentz force and the gas density, which respectively depend on the current and the filling pressure. The viscosity and density of the gas adjacent to the anode surface were found to depend on the anode energy balance and to affect the resistance of the gas flow, which in turn affects the separation point of the gas flow from the anode surface. This indicates that the anode surface temperature, which is determined by the energy balance between the gas and the anode, also affects the blackening location.

Black silicon formed by helium plasma irradiation has attractive surface morphologies in terms of solar cell fabrication, because it has good photon absorption property across the solar spectrum. It also does not need any masking process, which is sometimes employed in the fabrication of pyramid-like microstructures. Black silicon formed by helium plasma irradiation has potential not only for solar cell applications, but also in the fields of photonics, optics, and ultrasonic wave generation. Here, the nano-cone structure formation process, detailed observations of surface morphologies with TEM as well as SEM, the optimal He irradiation conditions, surface reflectivity over UV–visible-NIR wavelengths, and scattered light enhancement with Raman spectroscopy in addition to X-ray diffraction measurements were studied. Investigation of electronic properties is reported, including good resistivity of the Si black surface without an ITO electrode.

Fiber-form nanostructures grown on tungsten (W) surfaces with helium (He) plasma irradiation exhibit an excellent thermal radiative property at low sample temperatures up to 1200 °C. To maintain this radiative property at higher temperatures, the recovery to undefected surface and annealing effect of nanostructured W surfaces need to be investigated while focusing on the dopant effect. TFGR-W-1.1%TiC/H (toughing, fine-grained recrystallized tungsten with TiC dispersoids) was experimentally found to have the best characteristics among the tested doped W samples. However, it was noted and discussed that a further improvement at higher temperatures needs an additional surface treatment. Possibilities of maintaining complicated structures with nano-scale lengths are discussed in terms of dopant pinning effect and self-diffusion on tungsten surface.

When operating a xenon short arc lamp, tungsten (W) vapour that evaporates from the electrodes is transported by gas convection to blacken the inner bulb wall. Since this reduces the output light intensity and increases the risk of lamp breakage, it is crucial to thoroughly understand the factors that govern gas convection to optimally control it to reduce blackening. Gas convection is complex, especially in horizontal lamps, because it is strongly affected by buoyancy. This study used 3D numerical simulation to investigate buoyancy's influence on the gas convection of a horizontal xenon short arc lamp, which directly affects the blackening location. Gas convection, especially in the low flow velocity region, was strongly affected by the buoyancy, whose strength was mainly determined by the anode surface temperature. The gas convection in turn affected the bulb wall temperature and the W vapour transport and was reflected in the blackening location. This result indicates that the surface temperature of the anode, which was determined by the energy balance between the gas and anode, also affected the blackening location. Therefore, the emissivity of the anode surface was an important factor controlling the horizontal lamp's gas convection.

Growth mechanisms of complex tungsten (W) fuzzy nanostructure on helium-plasma-irradiated W surface have been extensively studied since the discovery of the phenomenon in 2006. However, the growth process of complicated W nano-fibers from the atomistic and crystal structure standpoints is not well understood. In this study, the X-ray diffraction (XRD) and transmission electron microscopy (TEM) were performed to investigate complexity of nano-fibers as well as their crystallinity. Small-angle-incident XRD on the substrate with fuzz and He-defected bulk surface was used to determine grain distribution among contributions of different crystal orientation families, showing the difference in grain distribution of surface fuzz layer and the basing W bulk surface with helium defects compared with the distribution of pristine powder metallurgy W (PM-W). Peak shifts and broadenings of X-ray diffracted spectra with respect to pristine PM-W substrate and TEM observations were discussed in terms of crystallinity and He-bubbles induced strain. It is speculated that the grain distribution of the He-defected W with nano-fibers would be very similar to that of bulk α-phase W globally. Moreover, the scraped-off fuzz aggregate without basing plate makes it possible to conduct XRD using a thin glass capillary tube. The grain distribution of pure fuzz aggregate was found to be very similar to natural α-phase W with intensification of high grain orientation modes. The process of such high modes may bring morphological complexity to nano-fibers because grain boundaries play a role of turning surfaces along nano-fibers.

Microwrinkle structures with a pitch of less than 100 nm and up to 600 nm on refractory metals like tungsten (W) and molybdenum, which are irradiated by noble gas ions such as neon and helium, have been studied systematically. The wrinkle formation mechanism is thought to be a buckling of the hard surface layer supported by the soft elastic substrate, which is induced by a penetration of noble gas species from the irradiated surface. Microwrinkle forms on this structure under lateral compressive strain/stress fields coming from thermal constriction on the way to substrate cooling. Such a process should be anticipated when walls in a fusion reactor are attacked by heat pulses such as edge localized modes and/or vertical displacement events, and therefore might be an initial stage of W surface damage.

A new technology for obtaining nanostructure on silicon surface for potential applications to optical devices is represented. Scanning electron microscope analysis indicated a grown nanostructure of dense forest consisting of long cylindrical needle cones with a length of approximately 300 nm and a mutual distance of approximately 200 nm. Raman spectroscopy and spectrophotometry showed a good crystallinity and photon trapping, and reduced light reflectance after helium plasma exposure. The present technique consists of a simple maskless process that circumvents the use of chemical etching liquid, and utilizes soft ion bombardment on silicon substrate, keeping a good crystallinity.