The first wall in an inertial confinement fusion (ICF) reactor is eroded by charged particles, neutrons, and X-rays as the nuclear fusion output within an extremely short period. Because damage to plasma-facing materials (PFMs) determines the lifetime of a nuclear fusion system, it is crucial to examine the internal state of PFMs. We irradiated a pulsed laser to simulate the heat load generated by the ICF output using tungsten as the wall material. No cracks were observed on the surface of the sample using an optical microscope, whereas cracks appeared near the surface inside the sample manufactured in the depth direction using a focused ion beam device. The observed cracks were formed in deeper locations than in previous studies. The cracks were generated owing to the temperature difference between the surface and the interior generated by the thermal load within an extremely short period.

Optical emission spectroscopy as well as time-of-flight (TOF) measurements were performed in the diagnostics of nanosecond laser produced plasmas. The target is rotated during pulsed laser ablation at 5 GW/cm², where the optical emission spectroscopy is performed along, as well as perpendicular to the target axis. Parallel to the target axis, the continuum radiation intensity increases up to 6000 pulses, and emission line intensities from C I and C II increase for with number of pulses. Perpendicular to the target axis, decrease in emission line and continuum intensities were observed. TOF measurements resulted to carbon cluster ions detection from C_n⁺, n ≥ 2, where peak shift of 4 µs towards later times were observed after 10000 pulses ablation. Charge collection experiments showed approximately 80 percent energy loss after 10000 shots. Collision-induced recombination mechanisms were suggested as causes of energy loss and line intensity decrease.

A frozen laser target that is in the gaseous phase at room temperature is advantageous for a laser ion source because it can avoid the accumulation of damage from laser irradiation by regeneration of the target surface by additional gas freezing. In this study, the possibility of forming a xenon ion beam with a current sufficient for heavy-ion inertial fusion (HIF) was investigated. The relationship between the frozen target growth and resulting ion current was analyzed to determine the optimal condition of laser irradiation that ensures stable supply of ion beams for a long time. A frozen target of xenon was formed on a mount cooled to 20 K using a Gifford McMahon cryocooler, and plasma was generated using a Nd:YAG laser. The results showed that it is possible to supply a sufficient ion current for application of singly charged ions as a driver for HIF. Additionally, it was indicated that the xenon responsible for forming the plasma existed only at a certain depth from the target surface. The results imply that it is possible to obtain a stable ion supply for a long time by irradiating the target with a laser after the frozen xenon grows to a sufficient thickness.

Quantum science and technology Kansai group has found new harmonics X-ray radiation from the relativistic laser-produced plasma, burst intensification by singularity emitting radiation (BISER). As a next step, the BISER pulse width is one of the unclear parameters, and its measurement is essential for applications of BISER to scientific and engineering fields. Therefore, we designed and constructed a magnetic bottle time-of-flight electron spectrometer to characterize the BISER pulse width using a pump-probe method (attosecond streaking). The spectrometer configuration was determined through numerical calculations to obtain a high-energy resolution of approximately 0.2 eV. The electron spectra of the xenon atom irradiated with the BISER X-rays were measured to verify the performance. Consequently, we successfully measured 8.26-eV Auger spectra associated with 4d inner-shell electrons in the test experiment. We demonstrate the experimental results and discuss the signal-to-noise ratio affected by electromagnetic noise generated by the relativistic plasma.

Surface wave oscillator (SWO) is an intense subterahertz wave source based on the interaction of an electron beam with a surface wave in a cylindrical corrugated waveguide (CCW). The oversized factor is a key parameter of SWO and is the ratio of the CCW diameter to the wavelength of a generated wave. In this study, we experimentally examine 0.1 THz SWO with different oversized factors of 10 and 7. For an oversized factor of 7, a kilowatt class radiation with a maximum efficiency of 8% is observed. SWO operation can be improved by decreasing the factor from 10 to 7.

The effect of water vapor plasma upon the surface morphology of the Zn target contained in a reactive magnetron sputtering source is investigated. The surface roughness and composition at different regions of the target were characterized using laser microscopy and X-ray diffraction, and an in-situ method for optical evaluation using laser differential reflectance is explored. The formation of a redeposited layer was observed, and the target center where direct plasma erosion was minimized showed an enhanced redeposition layer at low water vapor content. The roughness of the center and racetrack, where the plasma touched down along the magnetic field,was found to decrease at increasing water vapor content. An increasing trend in the laser differential reflectance of the target at different plasma exposure and varying water vapor content were observed.

Thermal Plasma processing has many applications in medical and environmental fields like melting, smelting and waste disposal. Here, the primary vessel known as plasma chamber is preheated to a high temperature of around ∼1000^◦C using plasma arcs. In this design process, CFD (Computational Fluid Dynamics) analysis has played a major role in defining the design of the plasma chamber. The simulation methodology has been benchmarked based on comparison of experiment and CFD simulation carried out for an experimental system available at IPR (Institute for Plasma Research). Transient thermal profile of the chamber has been evaluated using CFD analysis to design a higher capacity plasma chamber for scaled up systems. The analysis helped in identifying the desired material properties, dimensions of chamber and thickness of insulation, refractory materials to be used for the construction of chamber. The design focusses on uniformity of temperatures inside the chamber, identification of hotspot locations and faster ramp up time to desired process temperatures. Temperature at the outer most surface of plasma chamber have also been evaluated using the CFD analysis for human safety. The CFD analysis is computationally expensive and time consuming due to large size, transient behaviour and inclusion of radiation transport.

This contribution provides an overview of the core diagnostics as they are required for W7-X steady-state high-density operation with a divertor and profile control. The inferred profiles then address the stellarator optimization. A particular task is the characterization of fast ion slowing down and -losses, which in a classical stellarator reactor could result in unacceptable wall loads and ultimately are deleterious for the heating efficiency. The energy dissipated during operation, 10 MW · 1800 s impacts on the technical diagnostic realization via loads to in-vessel components, quasi steady-state operation requires adequate data acquisition and control systems.