Spurious radiated power signal following massive material injections in JET and the effect of neutral gas pressure on resistive bolometers.

Massive material injections in the JET tokamak have been observed to substantially affect resistive bolometer measurements, resulting in a spurious radiated power signal proportional to the quantity injected and reaching up to 8 MW. These bolometers are calibrated and designed to operate in near vacuum but certain scenarios requiring large gas injections can push the neutral pressure past nominal values. This study demonstrates that the bolometry measurement can be affected at neutral pressures above 0.

Implementation of low temperature spectrometers for the JET high resolution Thomson scattering diagnostic for disruption plasma measurements.

This work presents a system upgrade of the High Resolution Thomson Scattering (HRTS) diagnostic [Pasqualotto et al., Rev. Sci.

Demonstration of Safe Termination of Megaampere Relativistic Electron Beams in Tokamaks.

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.

Fast imaging system on Tore Supra.

A new endoscope aiming at transferring the image of a poloidal section of the Tore Supra plasma to a fast camera able to record frames at a speed up to 4800 frames per second at full resolution, or much faster for a limited number of pixel, has been installed on Tore Supra. First movies showing the light emission associated to fast phenomena such as plasma start up, disruptions or gas and pellet injections have been produced.