Operational characteristics of NBI cryo-condensation pumps

Neutral Beam Injector (NBI) is used as an effective tool for heating plasma in magnetic confinement devices, namely the Tokamak. Cryo-condensation pump is an important component of the NBI system. These pumps are required to handle a high throughput of Hydrogen gas of 50–80 Torr.L/s. The Cryo-condensation pump comprise of panel cooled at ∼4.2 K by flowing LHe (liquid helium). The required vacuum of ∼10⁻⁵ torr is achieved by condensation of hydrogen gas on the panel. The panel is thermally shielded from ambient by a set of chevron baffles cooled by LN2 (liquid nitrogen) at ∼80K. In IPR cryo-condensation pumps were developed indigenously for long duration pumping ∼4000s. Two such cryo- condensation pumps are installed in the NBI's vacuum chamber. Recently an experiment has been conducted to obtain operational experience and to study its characteristic performance.The operation was carried out successfully for hydrogen gas feed up to 100 torr.l/s. In this paper we describe the experimental setup, the operational procedure and results of the experiments.