Beamlet Tilting due to Magnetic Field in Beam Accelerator of NBI Source

Beamlet - monitoring experiment with a combination of the NIFS teststand and "mini - STRIKE", which is a test device of the beam monitor to be installed at "SPIDER", has been carried out as an international collaboration program between NIFS and Consorzio RFX . The monitor plates of the mini - STRIKE are made of one - directional CFC tiles, whose fib e res are directed to the beam axis and the beamlet footprints exposed on the plates are observed with IR camera on the opposite side of the exposed surface as shown in Fig. 1. A negative ion source with the a half size of the LHD source is applied for this experiment, and the monitor plates are placed at 0.76 m apart from the exit of the grounded grid of the ion source. The beamlets are extracted from 5 (H) x 3 (V) apertures of the plasma grids by masked with Mo plates. Each beamlet distribution is clearly identified as a thermal image on the monitor plate, and beamlet tilting has been observed. The titling is affected with electron deflection field and the tilting directions flip alternatively row by row. In this talk, we compare the tilting characteristic s with the beamlet - monitoring results obtained at the LHD beamline [1] as well as simulation results of the beamlets.