Production of overdense plasmas by launching 2,45 GHz electron cyclotron waves in a helical device

For production of low temperature plasmas with low collisionality, 2.45GHz microwave power up to 20kW is injected perpendicularly to the toroidal field at very low toroidal field BtComment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France

Experimental Simulation of High Temperature Plasma Transport Using Almost Dimensionally Similar Cold Plasmas in the Compact Helical System

In the Compact Helical System (CHS), experimental simulation of high temperature plasma transport is attempted by using cold plasma having similar dimensionless parameters such as electron-ion collision frequency normalized by bounce frequency v*ei, averaged toroidal beta value βt and the normalized gyro radius ρs*. The cold plasma is produced by 2.45 GHz electron cyclotron waves at very low toroidal field less than 0.1 T, and has v*ei ~ 0.05?1, βt < 0.02 % and ρs* ~ 0.02?0.05. The radial profiles of fluctuation amplitude have similarity to those in a high temperature plasma. In the cold plasma with low v*ei < 0.1, internal transport barrier is clearly formed in electron density and temperature profiles when the radial electric field rapidly evolves to positive value

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

Progenitor Constraint Incorporating Shell Merger: The Case of Supernova Remnant G359.0-0.9

It is generally hard to put robust constraints on progenitor masses of supernovae (SNe) and remnants (SNRs) observationally, while they offer tantalizing clues to understanding explosion mechanisms and mass distribution. Our recent study suggests that ``shell merger'', which is theoretically expected for stellar evolution, can appreciably affect final yields of inter-mediate mass elements (IMEs; such as Ne, Mg, and Si). In light of this, here we report results of X-ray spectral analysis of a Galactic SNR G359.0-0.9, whose abundance pattern may possibly be anomalous according to a previous study. Our spectroscopy using all the available data taken with XMM-Newton reveals that this remnant is classified as Mg-rich SNRs because of its high Mg-to-Ne ratio (Z_Mg/Z_Ne=1.90+0.27-0.19; mass ratio 0.66+0.09-0.07) and conclude that the result cannot be explained without the shell merger. By comparing the observation with theoretical calculations, we prefer the so-called Ne-burning shell intrusion and in this case the progenitor mass M_ZAMS is likely <15M_sun. We confirm the result also by our new molecular line observations with the NRO-45 m telescope: G359.0-0.9 is located in the Scutum-Centaurus arm (2.66--2.94 kpc) and in this case the resultant total ejecta mass ~6.8M_sun is indeed consistent with the above estimate. Our method using mass ratios of IMEs presented in this paper will become useful to distinguish the type of the shell merger, the Ne-burning shell intrusion and the O-burning shell merger, for future SNR studies

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)

Assessment of linear disruption predictors using JT-60U data

Disruptions are dangerous events in tokamaks that require mitigation methods to alleviate its detrimental effects. A prerequisite to trigger any mitigation action is the existence of a reliable disruption predictor. This article assesses a predictor that relates in a linear way consecutive samples of a single quantity (in particular, the magnetic perturbation time derivative signal has been used). With this kind of predictor, the recognition of disruptions does not depend on how large the signal amplitude is but on how large the signal increments are: small increments mean smooth plasma evolution whereas abrupt increments reflect a non-smooth evolution and potential risk of disruption. Results are presented with data from the JT-60U tokamak and high-beta discharges. Two training methods have been tested: a classical approach in which the more data for training the better and an adaptive method that starts from scratch. In both cases the success rate is about 95%. It should be noted that predictors based on signal increments and their adaptive versions can be of big interest for next devices such as JT-60SA or ITER

Imipenem/cilastatin sodium (IPM/CS) as an embolic agent for transcatheter arterial embolisation: a preliminary clinical study of gastrointestinal bleeding from neoplasms

PURPOSE: To evaluate the feasibility and usefulness of imipenem/cilastatin sodium (IPM/CS) as an embolic agent for intestinal bleeding from neoplasms. MATERIALS AND METHODS: Seven patients who underwent 11 transarterial embolisations (TAEs) using IPM/CS as an embolic material for duodenal or small/large intestinal tumour bleeding from January 2004 to December 2011 were retrospectively evaluated. A mixture of IPM/CS and contrast medium was introduced through the microcatheter positioned at the feeding artery to the tumour until extravasation disappeared or stasis of blood flow to the tumour staining was observed. RESULTS: Haemostasis was obtained in all patients. Therefore, the technical success rate was 100%. Rebleeding was observed in four patients. All of them underwent repeat TAE using IPM/CS, and haemostasis was obtained successfully. No complication was identified following laboratory and clinical examinations. No haemorrhagic death occurred. Haemorrhagic parameters, including blood haemoglobin and the amount of blood transfusion, improved after TAE. CONCLUSION: The safety, feasibility, and effectiveness of TAE using IPM/CS as an embolic material for intestinal bleeding from neoplasms were suggested by this study. The mild embolic effect of IPM/CS may be adequate for oozing from tumours. Although rebleeding may occur after embolotherapy using IPM/CS, repeat embolisation is effective as treatment for rebleeding

Reference values for the locomotive syndrome risk test quantifying mobility of 8681 adults aged 20–89 years: A cross-sectional nationwide study in Japan

Background The locomotive syndrome risk test was developed to quantify the decrease in mobility among adults, which could eventually lead to disability. The purpose of this study was to establish reference values for the locomotive syndrome risk test for adults and investigate the influence of age and sex. Methods We analyzed 8681 independent community dwellers (3607 men, 5074 women). Data pertaining to locomotive syndrome risk test (the two-step test, the stand-up test, and the 25-question geriatric locomotive function scale [GLFS-25]) scores were collected from seven administrative areas of Japan. Results The reference values of the three test scores were generated and all three test scores gradually decreased among young-to-middle-aged individuals and rapidly decreased in individuals aged over 60 years. The stand-up test score began decreasing significantly from the age of 30 years. The trajectories of decrease in the two-step test score with age was slightly different between men and women especially among the middle-aged individuals. The two physical test scores were more sensitive to aging than the self-reported test score. Conclusion The reference values generated in this study could be employed to determine whether an individual has mobility comparable to independent community dwellers of the same age and sex

心房粗動性頻拍に対する冷凍外科治療経験

Two cases of atrial tachyarrhythmias with atrial flutter requiring cryosurgical treatment are reported. In two cases, preoperative electrophysiological studies revealed supraventricular reentrant tachyarrhythmias during atrial flutter and showed enhanced conduction through the AV node that conducted atrial impulses rapidly to the ventricle. Based on intraoperative endocardial mapping, the earliest excitation site was localized along the AV node and His bundle during supraventricular tachyarrhythmias in one case. The cryosurgical treatment was administered at Koch\u27s triangles and in one case additionally at coronary sinus. After the operation, supraventricular tachyarrhythmias were not inducible and no clinical recurrences have occurred. Normal atrioventricular conduction was preserved in two cases. We concluded that cryosurgical treatment is useful for the treatment of the atrial tachyarrhythmias