Runaway electron generation during plasma shutdown by killer pellet injection
Tokamak discharges are sometimes terminated by disruptions that may cause large mechanical and thermal loads on the vessel. To mitigate disruption-induced problems it has been proposed that ‘killer’ pellets could be injected into the plasma in order to safely terminate the discharge. Killer pellets enhance radiative energy loss and thereby lead to rapid cooling and shutdown of the discharge. But pellets may also cause runaway electron generation, as has been observed in experiments in several tokamaks. In this work, runaway dynamics in connection with deuterium or carbon pellet-induced fast plasma shutdown is considered. A pellet code, which calculates the material deposition and initial cooling caused by the pellet is coupled to a runaway code, which determines the subsequent temperature evolution and runaway generation. In this way, a tool has been created to test the suitability of different pellet injection scenarios for disruption mitigation. If runaway generation is avoided, the resulting current quench times are too long to safely avoid large forces on the vessel due to halo currents.
Fast plasma shutdown by killer pellet injection in JT-60U with reduced heat flux on the divertor plate and avoiding runaway electron generation
A killer pellet is an impurity pellet that is injected into a tokamak plasma in order to terminate a discharge without causing serious damage to the tokamak machine. In JT-60U neon ice pellets have been injected into OH and NB heated plasmas and fast plasma shutdowns have been demonstrated without large vertical displacement. The heat pulse on the divertor plate has been greatly reduced by killer pellet injection (KPI), but a low-power heat flux tail with a long time duration is observed. The total energy on the divertor plate increases with longer heat flux tail, so it has been reduced by shortening the tail. Runaway electron (RE) generation has been observed just after KPI and/or in the later phase of the plasma current quench. However, RE generation has been avoided when large magnetic perturbations are excited. These experimental results clearly show that KPI is a credible fast shutdown method avoiding large vertical displacement, reducing heat flux on the divertor plate, and avoiding (or minimizing) RE generation.
Comparative Industrial Sociology and the Convergence Hypothesis
Industrial sociology grew spectacularly after World War II, concentrating on three areas: workers' relations with each other, their managers, and their unions; the social organization of the factory; and the impact of technology on social systems extending from the factory to the society. Unable to sus­ tain leadership in all of these areas, industrial sociology shrivelled as other fields invaded its domains. Human relations became the ideological property of the business schools; labor economics maintained its grip on industrial relations; industry-community relations waned as interest in community power soared; industrial organizations were absorbed into the study of com­ plex organizations; occupational sociology maintained research impetus in labor force analysis; and the sociology of the economy dominated the study of industry's institutional relationships. Industrial sociology survived on remnants: worker-machine relationships (job satisfaction, alienation, un­ employment), organizational responses to technological changes. and a bit of working-class ethnology. Enduring interest in technology, however, en­ abled industrial sociology to take part in sociology's expanding interest in comparative studies.