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The pre-conceptual design for a European pulsed fusion reactor (DEMO1) is ongoing and one of the most challenging activities within scenario modeling studies deals with numerical investigations of DEMO1 transient phases. This paper presents an investigation on both ramp-up and ramp-down phases by selected plasma trajectories. Plasma evolution has a clear impact on the engineering design of the reactor, e.g. on auxiliary power systems, current ramp-rates and requirements on the coil system. Studies on ramp-up have been carried out with the fast tokamak simulator METIS to highlight the effects of different ramp-up options in terms of robustness of access to the desired flat-top scenario. Particular attention has been paid to requirements on heating systems and plasma position controllability. A dedicated heating power during ramp-up, in addition to the one required during flat-top, appears to be necessary for reliable access to H-mode. The ramp-down phase poses specific issues on vertical stability due to the complex plasma evolution. Ramp-down trajectories with controllable plasma boundaries generated by the CREATE NL code have been coupled to 1.5D transport simulations by means of the JINTRAC transport suite of codes. The results show the necessity of additional ramp-down heating power to avoid a radiative plasma collapse and to control the current density profile. Reducing the current ramp-rate in the ramp-down phase can help the controllability of the plasma. [ABSTRACT FROM AUTHOR]

Abstract: The plasma control system simulation platform (PCSSP) for ITER shall support the analysis and development of methods to be used by the ITER plasma control system (PCS) for handling exceptions to optimize pulses and assist in machine protection. PCSSP will permit to investigate physical and technical events, such as component failures, control degradation, operation domain excess, plasma state bifurcation or instabilities, and interlock activity. Serving that purpose, the plasma, actuator, diagnostics and PCS simulation modules in PCSSP will be enhanced to compute nominal and off-normal data. Configured by an event schedule, an event generator will orchestrate the activation and manipulate the characteristics of such off-normal computation. In the simulated PCS exceptions will be handled in a pulse supervision layer operating on top of the pulse continuous control (PCC) feedback loops. It will monitor events, decide on which exceptions to respond, and compute new control references to modify PCC behavior. We discuss basic concepts for the event generation in PCSSP, and a preliminary architecture for exception handling in PCS, and show how these will be configured with event and pulse schedules. [Copyright &y& Elsevier]