A 6 MeV heavy ion beam probe (HLBP) is being designed for potential me
asurements on the Large Helical Device (LHD). This article describes a
method to control the 3-D probing beam trajectories in the helical ma
gnetic field, an estimate of beam attenuation and energy reduction ari
sing from the long paths in the plasma, and a cylindrical analyzer as
a candidate for the energy analyzer.