Impact of Energetic Ion Driven Global Modes on Toroidal Plasma Confinements

Excitation of energetic-ion-driven Alfv6n eigenmodes (AEs) and their impact on energetic ion confinement are widely and intensively studied in helical devices such as CHS and LHD as well as major tokamaks. The excitation of AEs sensitively depends on the parameter space defined by the averaged beam beta and the velocity ratio V6nlV6 (V611 : injected beam ion velocity, Va: Alfv6n velocity). In LHD, these two relevant parameters are widely scanned without suffering from current disruptions. So far, toroidicity induced AE (TAE), global AE (GAE) and energetic particle mode (EPM) or resonant TAE (R-TAE) were identified during tangential neutral beam injection (NBI) in CHS and LHD. Moreover, a new coherent mode with the frequency by about 8 times higher than the TAE frequency was observed in NBI heated plasmas of LHD at low magnetic field (<0.6T). This mode may be induced by helical field components of the confinement field. Nonlinear phenomena of bursting amplitude modulation and fast frequency chirping are clearly seen for TAEs and EPMs in CHS and LHD. EPMs in CHS and bursting TAEs in LHD enhance radial transport of energetic ions in certain plasma conditions

Self-consistent long-time simulation of chirping and beating energetic particle modes in JT-60U plasmas

Recurring bursts of chirping Alfvén modes that were observed in JT-60U tokamak plasmas driven by negative-ion-based neutral beams (N-NB) are reproduced in first-principle simulations performed with an extended version of the hybrid code MEGA. This code simulates the interactions between gyrokinetic fast ions and magnetohydrodynamic (MHD) modes in the presence of a realistic fast ion source and collisions, so that it self-consistently captures dynamics across a wide range of time scales (0.01–100 ms). The simulation confirms that the experimentally observed phenomena known as \u27fast frequency sweeping (fast FS) modes\u27 are caused by bursts of energetic particle modes (EPM) with dominant toroidal mode number n  =  1. On the long time scale (1–10 ms), the simulation reproduces the chirping range (40–60 kHz), the burst duration (few ms) and intervals (5–10 ms). On the short time scale (0.01–0.1 ms), it reproduces pulsations and phase jumps, which we interpret as the result of beating between multiple resonant wave packets. Having reproduced at multiple levels of detail the dynamics of low-amplitude long-wavelength Alfvén modes driven by N-NB ions, the next goal is to reproduce and explain abrupt large-amplitude events (ALE) that were seen in the same experiments at longer time intervals (10–100 ms)

Administration of Kampo medicine through a tube at an advanced critical care center

In emergency and critical care medical centers, tube administration is employed for patients who have difficulty swallowing oral drugs owing to decreased consciousness or mechanical ventilation. However, tube clogging due to drug injection is a concern. We compared the crushing method with the simple suspension method for the passage of amlodipine, an antihypertensive drug, in combination with rikkunshito, which has been used to treat upper gastrointestinal disorders such as functional dyspepsia and gastroesophageal reflux in emergency and critical care medical centers, to ascertain the effect of Kampo products on the passage of other drugs during tube administration. When the crushing method was employed, poorly water-soluble solid products were formed, while a uniformly dispersed suspension was obtained using the simple suspension method. In addition, the passage rate of amlodipine through the tube was 64% and 93% in the crushing and simple suspension methods, respectively, thereby indicating that the simple suspension method provided more favorable than the crushing method. The results of this study suggested that the passage rate of amlodipine for patients who received Kampo products concurrently was higher when the simple suspension method was used, and an appropriate drug amount might well be able to administered to patients using this method

Impurity emission characteristics of long pulse discharges in Large Helical Device

Line spectra from intrinsic impurity ions have been monitored during the three kinds of long-pulse discharges (ICH, ECH, NBI). Constant emission from the iron impurity shows no preferential accumulation of iron ion during the long-pulse operations. Stable Doppler ion temperature has been also measured from Fe XX, C V and C III spectra

Manufacturing of lower divertor cassette of JT-60SA

A lower divertor cassette of JT-60SA, which is the largest superconducting tokamak, has been designed, and the first divertor cassette covering a 10◦ sector in the toroidal direction has been manufactured. Modularized plasma facing components such as vertical targets, baffles, and domes will be assembled into the divertor cassette. All plasma facing components will be actively cooled. Carbon armor tiles bolted to water-cooled copper alloy heat sinks are used to remove heat loads of 0.3–2MW/m2 for 100 s and 10MW/m2 for less than 10 s. The divertor cassette integrated with coolant pipe connections will be used for remote handling / hands-on maintenance. A remote pipe welding tool, which is accessed from the inside of the pipe, has been developed to assemble the inboard vertical target. The space around the cooling pipes is so limited that they are cut and welded remotely from the inside for maintenance. The laser welding method was used, and the focusing mirror inside the pipe was rotated to perform circumferential welding. As a countermeasure for welding groove misalignment, the aiming accuracy of the laser was improved by simultaneously controlling the rotation and lifting of the tool. Thereby, reliable welding has been achieved even with a groove that is misaligned by 0.5 degrees or more. The outer diameter of the cooling pipe is 59.8 mm, the wall thickness is 2.8 mm, and the material is SUS316L. After connecting the inboard vertical target, the other plasma facing components have been assembled into the first lower divertor cassette. When installing the divertor cassette towards the vacuum vessel, the laser welding tool described above is used to connect the cooling pipe between divertor cassette and vacuum vessel in JT-60SA, because the outer diameter and wall thickness of the cooling pipe are the same as the inboard vertical target.31st Symposium on Fusion Technology (SOFT2020

In-bore laser welding tool for actively cooled divertor cassettes in JT-60SA

In-bore remote pipe welding tool has been upgraded for divertor cassettes of JT-60SA, where all plasma-facing components are actively cooled. Because the cooling pipes are surrounded by divertor cassette frame, pipe welding should be done from the inside of the pipe. The tool was equipped with a mirror to reflect the laser radially. Circumferential welding was performed by rotating the tool while injecting the laser. If fumes and spatters adhere to the laser reflecting mirror during welding, the laser will not reach the groove and the welding will not be stable. Upgrading the welding tool has realized to perform welding tests with a well-protected mirror and stable laser power. A misalignment between pipes at the groove is unavoidable in actual divertor cassettes of JT-60SA. The results of butt welding of short pipes indicated that it was possible not only in the gap but also in the combined state with angular and axial misalignment, covering a larger range than required by the actual cassette. It is notable that welding was possible even with an angular misalignment of 0.9◦ and an axial misalignment of 0.3 mm, where the maximum gap between pipes was about 0.9 mm