ABSTRACT
A thin-foil infrared bolometer has been developed to measure the plasma radiation quantitatively during plasma disruptions in the KSTAR tokamak. We present analytic solutions of a 0D heat transfer model, which enable the estimation of the plasma radiation from the bolometer signal. The analytical solutions for the linear response regime give practical ways by which the radiation power and energy can be estimated from the cooling time scale of the bolometer signal. A useful way of evaluating the linear response of the system is also introduced. The analysis is complemented by 2D heat transfer simulations. The bolometer signals from the shattered pellet injection experiments in the 2020 KSTAR campaign are analyzed and interpreted according to the heat transfer models.
ABSTRACT
For the first time it is experimentally demonstrated on the JET tokamak that a combination of a low impurity concentration bulk plasma and large magnetohydrodynamic instabilities is able to suppress relativistic electron beams without measurable heat loads onto the plasma facing components. Magnetohydrodynamic simulations of the instability and modeling of the postinstability plasma confirm the prompt loss of runaways and the absence of regeneration during the final current collapse. These surprising findings motivate a new approach to dissipate runaway electrons generated during tokamak plasma disruptions.
