Enhancement of the contrast of laser plasma emission spectra accompanying two-pulse irradiation of a surface by neodymium laser radiation

Abstract

Two H-mode regimes have been identified in JET in which edge localized modes @LM's) maintain steady-state conditions. In the first regime, strong gas puffig was used in combined (ICRF plus NBI) heating experiments at powers of up to 2OMW. Rapid ELM activity occurred and at moderate powers (-8MW) steady-state H-modes with durations of up to 18s and energy codmement times of up to 95% of the JETiD-DID scaling were established. At high toroidal beta (PN 2 1.5) H-mode plasmas were also found to exhibit regular ELM behaviour which resulted in steady-state H-modes with confinement enhancement of -90% of the JETD-IIID scaling. This paper examines the plasma properties of these regimes and assesses their implications for steady-state H-mode operation in ignited plasmas.