RECYCLING CONTROL FOR LHD USING CARBON SHEET PUMP

Carbon Sheet Pump(CSP) has been proposed to be installed on the vacuum vessel wall of the Large Helical Device(LHD) in order to reduce the h ydrogen recycling and improve the energy confinement. The CSP of C/C c omposite with temperature below 200 degrees C can pump high energy hyd rogen particles such as charge exchange fast neutrals by trapping them . The saturated hydrogen particles can be removed simply by heating th e carbon sheet above 800 degrees C. One of the requirement on the CSP design for LHD is that the temperature of the vacuum vessel must be ma intained to be below 70 degrees C to avoid excessive heat flux to the LHD superconducting magnet system. The first design of CSP for LHD is presented, and a successful demonstration of heating the CSP carried o ut.