Incremental energy confinement time during H⁰beam heating in JT-60

Abstract

Characteristics are presented of the energy confinement time resulting from neutral hydrogen beam heating of JT-60 tokamak plasmas with a plasma current, Ip, of 1-2 MA, a line averaged electron density, n e , of 1.5-7 X 10 19 m~3 and an absorbed beam power, P a b S , up to 20 MW. The plasma energy content follows an offset linear relation to the absorbed power. The incremental energy confinement time for thermal components, rg c , is almost independent of I p and n e at 60 ms, while the incremental energy confinement time for the total plasma energy, TJJ<£, decreases with plasma density. The value of rg c in JT-60 coincides with the prediction of the Shimomura-Odajima scaling of L-mode discharges.

Bootstrap current during perpendicular neutral injection in JT-60

“…1. The energy confinement properties of the discharges follow the saturated Ohmic confinement scaling (the energy confinement time is typically up to 450 ms) and the L-mode scaling during neutral beam heating [11]. The Ohmic data are taken near the end of the flat-top of the plasma current where the discharges are nearly stationary.…”

Enhancement of energy confinement by acceleration of fast ions in combined lower hybrid and neutral beam heating on JT-60

“…A comparison of the power flow of the three different heating systems in shot E7928 is given in Table I, where Pft, • P ^ + P& s + P 0H > Padd • PLH + P N b B s + AP 0H and AW* = W**, -W 0H -AW 6lTc (AW finc is the change in stored energy due to the density increase deduced from the OH scaling [23]). Since the incremental energy confinement time of the bulk plasma in the combined NB + LH heating case is considered to be the normal value (~53 ms), as mentioned before, it is possible to estimate the stored energy of the tail (Table I).…”

Model of heat pinch transport in the JT-60 tokamak

“…The incremental thermal diffusivity is independent of the average density; this is clear from our previous study [7] where the energy loss has been shown to be dominated by the conduction loss, and the incremental energy confinement time for the thermal component is…”

“…As shown in Ref. [7], the plasma stored energy during Ohmic heating increases with the average plasma density. The incremental energy confinement time for the thermal component is independent of (or weakly dependent on) the plasma density and the plasma current; however, no full current scan was made.…”

“…Goldston [6] pointed out the importance of the density dependence in the heat pinch analysis. We have shown previously the importance of the density dependence in a study of the offset linear scaling [7]. The stored Ohmic energy which would represent the strength of the heat pinch increases strongly with the plasma density and the plasma current.…”