The neutron production in ASDEX Upgrade(AUG) neutral beam injection (NBI) heated discharges is dominated by beam-target fusion reactions. Hence, the neutron rate and energy distributions are footprints of the fast ion distribution. This motivates the achievement of reliable neutron measurements and good agreement between experiment and theoretical calculations. However, comparisons at AUG between the experimental neutron rate and the one predicted by TRANSP show systematic discrepancies. Potential reason for this is the delicate absolute calibration of the neutron detectors. Therefore, a different calibration technique was performed, allowing for longer calibration time, better statistics and thus less uncertainty. A toy train carrying a radioactive source (238Pu/B) over two poloidal positions on the equatorial plane shows a clearly periodical neutron rate on the epithermal 3He neutron detector. The calibration results are compared to a Monte Carlo (MC) transport simulation using the Serpent code.
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