A study of high-energy ions produced by ICRF heating in LHD

Abstract

This paper reports on the behaviour of high-energy ions created by ion cyclotron range of frequency (ICRF) heating on the Large Helical Device (LHD). In the third experimental campaign conducted in 1999, it was found that minority heating has good heating performance, and high-energy particles were observed. In the fourth campaign in 2000, the temporal behaviour of high-energy ions was investigated in the minority heating regime using turnoff or modulation of ICRF power. The time evolution of the highenergy particle distribution was measured using a natural diamond detector (NDD) and a time-of-flight neutral particle analyser (TOF-NPA). It was found that the count number of higher-energy particles declines faster than that of lower-energy particles after ICRF turnoff. In the modulation experiments, the phase difference of the flux of high-energy particles with respect to the ICRF power modulation increased with energy. These results were explained qualitatively by the Fokker-Planck equation with a simple model. The

Third harmonic ICRF heating in LHD hydrogen experiments

“…The ICRF heating efficiency is approximately 30%-50% estimated by the breakin-slope at the ICRF turn off timing. This value of the efficiency and increasing tendency when the density is increased are similar results of previous research in second harmonic ICRF heating experiments [20]. One reason for this increasing tendency is that the ICRF perpendicular wave number k ⊥ increases with the density increasing [21].…”

Perpendicular and tangential angularly resolved multi-sight neutral particle analyzer system in LHD

“…Saito et al measured them by a scanning system of the TOF-NPA shot-by-shot. 9,10 However, ARMS can observe them in only one discharge. Figure 4(a) shows the data of the tangential ARMS during the NBI plasma intermittently overlapped by the ECH.…”

Two-dimensional scanning high-energy particle diagnostic system in Large Helical Device

“…A higher energy particle can be confined in the coinjection case than in counterinjection case. 3 Horizontal scan measurements were performed in ICH plasmas as well. The result is that the spatial distribution of the neutral particle flux had a butterfly shape predicted theoretically.…”

“…The result is that the spatial distribution of the neutral particle flux had a butterfly shape predicted theoretically. [3][4][5] Resonant loss (see Sec. IV) can be observed at about 5 keV, especially in low magnetic fields and with the outer magnetic axis configuration.…”