Beam transmission dependence on beam parameters for TJ-II Neutral Beam Injectors

•Neutral Beam power density profiles are obtained from thermographic images of a CFC target.•Beam perveance determines beam divergence, independently of the voltage and current values.•Beam simulation with detailed 3D geometric models yield the power and current through the port.•In plasma experiments involving NBI generated fast ions, beam parameter scans are often performed.•When performing Beam parameter scans, beam divergence must be determined for each set of parameters.