Beam formation and transport in the BATMAN Upgrade test facility

摘要

In the BATMAN Upgrade test facility, an RF-driven negative hydrogen ion source is developed in support of the ITER NBI. Its 5 x 14 apertures represent approximately one ITER beamlet group. Diagnostics include a tungsten wire calorimeter, a copper calorimeter, and two arrays of beam emission spectroscopy lines of sight.When the RF-power is increased at fixed extraction potential, the extracted current density saturates. This is due to scraping of the beamlet by the extraction grid; a method is developed to characterize the injected current density. This current density can vary locally, e.g. due to the ExB drift induced by the filter field. A procedure is introduced to infer the vertical injected current density profile from the behaviour of the different beam emission spectroscopy lines of sight during an RF-power scan.The injected current density profile is used to calculate aperture specific beamlet properties with IBSimu. The beamlet properties are projected towards the calorimeters with the ABC3D code, and compared with measurements to benchmark the current density profile and IBSimu calculations. Beamlet-to-beamlet variations of power and width in the tungsten wire calorimeter are well reproduced. It is crucial to include heat transfer in the copper calorimeter to reproduce the measured profiles.