Spatial profiles of fusion product flux in the gas dynamic trap with deuterium neutral beam injection

Recently, a plasma with energetic deuterons has been produced in the Gas Dynamic Trap (GDT) experiment under skew injection of 4 MW, 15-17 keV deuterium neutral beams. The GDT is a long, axially symmetric magnetic mirror device with a high mirror ratio. The deuterium neutral beams have been injected at the midplane of the device under 45o to the axis. High anisotropy of the fast ion angular distribution results in a strong peaking of the fast ion density at the turning points near the end mirrors. The axial profile of DD fusion product fluxes has been measured and found to be strongly peaked in the same regions. The characteristics of the profiles are consistent with the classical mechanism of fast ion relaxation caused by two-body Coulomb collisions with plasma particles. This observation validates an approach used in a GDT based neutron source, in which the regions of high neutron flux would be surrounded by the testing zones for fusion material irradiations.