High heat flux Langmuir probe array for the DIII-D divertor plates

作者：Watkins J G^*; Taussig D; Boivin R L; Mahdavi M A; Nygren R E

来源：Review of Scientific Instruments, 2008, 79(10): 10F125.

DOI：10.1063/1.2982423

• ceramics
• cryopumping
• divertors
• graphite
• heat conduction
• Langmuir probes
• plasma toroidal confinement
• plasma transport processes
• Tokamak devices

Two modular arrays of Langmuir probes designed to handle a heat flux of up to 25 MW/m(2) for 10 s exposures have been installed in the lower divertor target plates of the DIII-D tokamak. The 20 pyrolytic graphite probe tips have more than three times higher thermal conductivity and 16 times larger mass than the original DIII-D isotropic graphite probes. The probe tips have a fixed 12.5 degrees surface angle to distribute the heat flux more uniformly than the previous 6 mm diameter domed collectors and a symmetric "rooftop" design to allow operation with reversed toroidal magnetic field. A large spring-loaded contact area improves heat conduction from each probe tip through a ceramic insulator into a cooled graphite divertor floor tile. The probe tips, brazed to molybdenum foil to ensure good electrical contact, are mounted in a ceramic tray for electrical isolation and reliable cable connections. The new probes are located 1.5 cm radially apart in a staggered arrangement near the entrance to the lower divertor pumping baffle and are linearly spaced 3 cm apart on the shelf above the in-vessel cryopump. Typical target plate profiles of J(sat), T(e), and V(f) with 4 mm spatial resolution are shown.

• 出版日期2008-10