Y. Nakashima et al., Characteristics of carbon sheet pump in application experiments to a high-temperature plasma device, J NUCL MAT, 269, 1999, pp. 901-905
Carbon sheet pump (CSP), which has been developed for reduction of hydrogen
recycling in the large helical device (LHD) of National Institute for Fusi
on Science, is applied to an actual plasma device for the first time to eva
luate the pumping characteristics. A small scale of pump module is manufact
ured and installed in the GAMMA-10 tandem mirror device and the module is e
xposed to charge-exchange neutrals emitted from ICRF-heated hot-ion plasmas
. Temporal evolution of the pressure is measured with a fast ionization gau
ge installed in the test chamber during the plasma discharge and a signific
ant difference between CSP-on and CSP-off is observed under good reproducib
ility. The dependence on the ICRF power is investigated and the pressure di
fference between on and off is found to increase with the ICRF power. These
phenomena indicating the pumping ability of CSP are observed to continue d
uring more than 300 plasma shots, which shows the effectiveness of CSP in c
ontrolling hydrogen recycling. The result of thermal desorption experiments
of CSP after being exposed to charge-exchange neutrals is also described.
(C) 1999 Elsevier Science B.V. All rights reserved.