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Abstract: After more than 20 years of operation and numerous modifications, a substantial modernisation of the inboard pellet injection system on ASDEX Upgrade was carried out. This enhancement was necessary to meet new functional requirements and to benefit from technical progress as well. New requirements are the integration in discharge control system, variation of settings of pellet train parameters during one discharge, temperature control of ice extrusion and overcome process limits caused by out-dated vacuum components. The programmable logic controller system is now fully migrated to S7-300 using High Speed Boolean Processor FM352-5 to replace hard-wired logic elements and enable flexible control of process parameters. First applications on ASDEX Upgrade concerning high density operation and ELM control are presented to confirm usefulness of implemented features. [Copyright &y& Elsevier]

Edge-localized mode (ELM) triggering and pacing in an all-metal wall environment shows significant differences to a first-wall configuration containing carbon. Here we report on experiments performed at ASDEX Upgrade revisiting the issue with all plasma-facing surfaces now fully replaced by tungsten. This investigation was motivated by experimental findings indicating that ELM triggering becomes more intricate when the carbon is replaced by a metal wall. ELM pacing could no longer be achieved by magnetic triggering in ASDEX Upgrade under conditions that previously showed a positive response. Also, recent investigations at JET indicate that a lag time occurs in pellet ELM triggering when operating with the new ITER-like wall. The ASDEX Upgrade centrifuge-based launching system was revitalized and upgraded for this study, now allowing detailed analysis of the ELM trigger response. The appearance of a lag time for pellet ELM triggering in an all-metal wall environment was confirmed. While different lag time durations were found for several type-I ELMy H-mode scenarios, the magnitude of the pellet perturbation was found to cause no difference. Reducing the auxiliary heating power for ELM triggering clearly makes the pellet tool less efficient for ELM control purposes; however, this affords a major benefit when applied for fuelling. Plasma operation with benign ELM behaviour at core densities far beyond the Greenwald limit was demonstrated, this being fully reversible and not affecting the energy confinement. [ABSTRACT FROM AUTHOR]