Heavy Ion Beam Probe for the Study of Plasma Confinement in Nagoya Bumpy Torus

The heavy ion beam probing system has been constructed for the study of plasma confinement in Nagoya Bumpy Torus (NBT-1/1M). Not only the plasma space potential but also the electron density multiplied by a function of the electron temperature nf(Te) can be measured with good spatial resolution. The feedback controlled detection technique and the time resolved fast detection technique are used, depending on the operation mode. The effects of the hot electron beta and the potential on the beam orbit are analyzed. It was confirmed that these effects on the observation points are usually small, and that the hot electron beta can be estimated from the shifts of the primary beam orbits of many cords.