The damage and erosion of plasma-facing components (PFCs) due to extremely high heat loads and particle bombardment is a key issue for the nuclear fusion community. Currently high current ion and electron beams are used in laboratories for simulating the behaviour of PFC materials under ITER-like conditions. Our results indicate that high-power nanosecond lasers can be used for laboratory simulation of high heat flux PFC material degradation. We exposed tungsten (W) surfaces with repetitive laser pulses from a nanosecond laser with a power density ∼ a few GW cm−2. Emission spectroscopic analysis showed that plasma features at early times followed by intense particle emission at later times. Analysis of laser-exposed W surface demonstrated cracks and grain structures. Our results indicate that the typical particle emission features from laser-irradiated tungsten are consistent with high-power particle beam simulation results.

The optimum conditions for efficient extreme ultraviolet (EUV) sources in laser-produced plasma (LPP) depend on the ideal combination of several parameters such as laser wavelength, intensity, spot size, and pulse duration. These parameters need to be optimized in relation to the actual target size and geometry. The laser wavelength can play a major role in this regard. While target related effects are not significant in the case of a Nd:YAG laser, the achievable conversion efficiency (CE) of EUV sources produced by a CO₂ laser from small Sn droplets can be several times lower compared to that from a flat Sn target. Improving the efficiency and performance of EUV sources requires detailed investigation of various laser/target combinations using comprehensive integrated models. We simulated and characterized in detail plasmas produced from the Sn droplet irradiated by lasers with various wavelengths. The optimum laser intensity with respect to the laser and target sizes was determined for a range of laser wavelengths from 1 μm to 10 μm. This work was inspired by the recent developments of lasers with a 2 μm wavelength. The laser pulse duration is another important parameter in the optimization of LPP for EUV sources. Our comprehensive HEIGHTS modeling showed that increasing the pulse duration of the 2 μm laser leads to an increase in the CE of EUV sources. Our results also indicate that a significant reduction in the kinetic energies of ions generated from LPP can be achieved by optimizing the laser pulse duration.

The international thermonuclear experimental reactor (ITER) is a worldwide project currently being built in France for the demonstration of the feasibility of thermonuclear technologies for future realization of successful commercial fusion energy. ITER is of the tokamak based design using strong magnetic fields to confine the very hot plasma needed to induce the fusion reaction. Tokamak devices are currently the front leading designs. Building a successful magnetic fusion device for energy production is of great challenge. A key obstacle to such design is the performance during abnormal events including plasma disruptions and so-called edge-localized modes (ELMs). In these events, a massive and sudden release of energy occurs quickly, due to loss of full or partial plasma confinement, leading to very high transient power loads on the reactor surface boundaries. A successful reactor design should tolerate several of these transient events without serious damages such as melting and vaporization of the structure. This paper highlights, through comprehensive state-of-the-art computer simulation of the entire ITER interior design during such transient events, e.g., ELMs occurring at normal operation and disruptions during abnormal operation, potential serious problems with current plasma facing components (PFCs) design. The HEIGHTS computer package is used in these simulations. The ITER reactor design was simulated in full and exact 3D geometry including all known relevant physical processes involved during these transient events. The current ITER divertor design may not work properly and may requires significant modifications or new innovative design to prevent serious damage and to ensure successful operation.

Dynamics of metal ions during laser-produced plasmas was studied. A 1064 nm, Nd: YAG laser pulse was used to ablate pure Al, Fe, Co, Mo, and Sn samples. Ion flux and velocity were measured using Faraday cup ion collector. Time-of-flight measurements showed decreasing ion flux and ion velocity with increasing atomic weight, and heavy metal ion flux profile exhibited multiple peaks that was not observed in lighter metals. Slow peak was found to follow shifted Maxwell Boltzmann distribution, while the fast peak was found to follow Gaussian distribution. Ion flux angular distribution that was carried out on Mo and Al using fixed laser intensity 2.5 × 10¹⁰ W/cm² revealed that the slow ion flux peaks at small angles, that is, close to normal to the target ∼0° independent of target's atomic weight, and fast ion flux for Mo peaks at large angles ∼40° measured from the target normal, while it completely absents for Al. This difference in spatial and temporal distribution reveals that the emission mechanism of the fast and slow ions is different. From the slow ion flux angular distribution, the measured plume expansion ratio (plume forward peaking) was 1.90 and 2.10 for Al and Mo, respectively. Moreover, the effect of incident laser intensity on the ion flux emission as well as the emitted ion velocity were investigated using laser intensities varying from 2.5 × 10¹⁰ W/cm² to 1.0 × 10¹¹ W/cm². Linear increase of fast ion flux and velocity, and quadratic increase of slow ion flux and velocity were observed. For further understanding of plume dynamics, laser optical emission spectroscopy was used to characterize Sn plasma by measuring the temporal and spatial evolution of plasma electron density N_e and electron temperature T_e. At 3.5 mm away from the target, plasma density showed slow decrease with time, however electron temperature was observed to decrease dramatically. The maximum plasma density and temperature occurred at 0.5 mm away from target and were measured to be 8.0 × 10¹⁷ cm⁻³ and 1.3 eV, respectively.