TPX Diagnostics for Tokamak Operation, Plasma Control and Machine Protection
Authors: P.H. Edmonds, S.S. Medley, K.M. Young, Et al.
The Tokamak Physics Experiment (TPX) is planned to be an advanced performance, high beta, steady state, high heat flux, double null divertor tokamak. Machine parameters are R0=2.25m, ap=0.5m; A=4.5; k~2; d~0.8; BT=4T and Ip=2 MA. Operation in both hydrogen and deuterium is planned. The design is required to incorporate end-of-life tritium capability. The experiments includes 8 MW of neutral beam power, 6 MW of ion cyclotron and 3 MW of lower hybrid rf power for auxiliary heating and current drive. Experimental scenarios include non-inductive current drive with an initial 1000 sec long pulse mode and an upgrade to steady state (105 sec), divertor heat loads of up to 7.5MW/m3 and maximum neutron rates up to 7.5 Y 1016/sec. First plasma is scheduled for mid-2001. Diagnostics are required for real time plasma control, physics measurements and machine protection. Fundamental to initial operation are measurements of plasma equilibrium and position, basic plasma properties, current density and pressure profiles, surface heat loads on plasma facing components and provision for disruption avoidance. An extensive set of diagnostics is planned, divided between a baseline set required for the first phase of operation and an upgrade set which includes fluctuation diagnostics as well as those required for extended pulse length operation. Present diagnostic design is concentrated on the first phase diagnostics. Preliminary designs for the magnetics, Thomson scattering, motional Stark effect and divertor infra-red imaging diagnostics are described. TPX diagnostic design, construction, installation and operation will be a national effort, with participation by National Laboratories, industry and universities under the direction of the TPX project.