High Field Tokamaks as Compact Neutron Sources

Fusion reactor scaling laws can be used to define plasma parameters of high field compact tokamak for low fusion gain applications as it is the case of compact neutron sources. The attractive physics of the high field tokamaks explored on Alcator devices and FTU has demonstrated that tokamaks (at magnetic field B 7 T) can be operated in L-mode with substantial increase of confinement. In particular the operation with pellets is attractive in this respect because it opens up the possibility of operating the machine in ohmic plasmas at very high density (plasma density n e 110 20 m -3 ) with improved confinement properties. The compact high field tokamaks are characterized by a fundamental ohmic confinement with possibly a low RF heating power because of the limited space available. This paper is dedicated to i) a summary of the physics of high field tokamaks as derived from the database of FT, FTU and Alcator devices (including Alcator-C-MOD); ii) a discussion of their confinement properties in scenarios operated with pellets; iii) the scaling laws for fusion reactors, which allow for the evaluation of the geometry and plasma parameters of compact high field (B 7 T) tokamaks at aspect ratio A 2.5 and at low aspect ratio (A < 2); iv) the technical feasibility of these neutron sources and their technology readiness level.