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A Volumetric Neutron Source (VNS) is proposed as a compact tokamak to serve as a qualification testbed for fusion in-vessel components, breeding blanket in particular. The main goal is to determine the minimum size of the machine while maximizing the Neutron Wall Load (NWL). This paper discusses the design parameters and constraints involved in specifying the magnetic cage for VNS. The focus of the study is on sizing the TF (toroidal field) coils and related structures with the plasma magnetic field, as well as assessing how various design constraints influence the machine performance at higher magnetic field strengths. In particular, the trade-off between TF neutron heat load and dose and shielding efficiency. A very preliminary (and still evolving) design point for VNS is presented and discussed.

AbstractXenon is a potential candidate as a pedestal and edge radiator in DEMO, but it is considered troublesome in cases where larger amounts have to be handled in the fuel cycle. Hence, direct and efficient codeposition inside the confined plasma with the fuel injected by means of solid cryogenic pellets is regarded as more favorable than simple gas puffing. At ASDEX Upgrade, investigations are underway to develop a versatile reactor-relevant pellet actuator. Equipped with an accordingly set up pellet launching system and well diagnosed, this all-metal-wall tokamak is well suited for this task. Here, we report on efforts to produce and inject pellets made from deuterium with a reasonable amount of admixed xenon. Results indicate xenon supply via carrier fueling pellets is possible while showing advanced performance. Compared to xenon gas puffing where long latency is observed, presumably due to wall sticking, doped pellets provide much shorter response times. Hence, this first exploration suggests fueling pellets with admixed auxiliary gases can be a versatile, efficient, and fast actuator for additional control features such as, e.g., radiative plasma cooling.