Disruption generated runaway electrons in TEXTOR and ITER

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Abstract
Runaway generation during a major disruption has been observed in TEXTOR. Measurements of the synchrotron radiation yielded number, energy and pitch angle of the runaways. A simple model, which assumes that the runaways take over the current density in the centre of the discharge, successfully describes these measurements. This model is applied to JET and ITER. One interesting result of the model is that it could be favourable for ITER to have a high runaway production. This leads to a lower runaway energy and less runaway damage. Quantitative predictions are sensitive to the value of the runaway parameter = E/Ecrit, which is determined by the post-disruption temperature. The present estimate for ITER gives = 0.02, which results in a maximum runaway energy of 300 MeV in a runaway beam with a total energy of 500 MJ. However, if is enhanced, these values will be reduced. An increase to = 0.04 is sufficient to decrease the maximum runaway energy to 55 MeV and the total beam energy to 130 MJ. Secondary generation plays an important role in these predictions