Force balance and hysteresis effects during L-H transitions in the H-1 Heliac

Full text: In this poster, we use the ion force balance equation to infer the radial electric field (E1) from the poloidal and toroidal flow, density and temperature profiles, measured using passive techniques on the H-1 Heliac. The density profile is measured with the scanning FIR interferometer, and temperature and flow profiles are measured from the Doppler shift and broadening of spectral lines using the MOSS camera. Abel inversions (which assume that flux surfaces have constant density, emissivity and temperature) are performed on this data to convert line-integrated measurements into radial profiles. In order to check the accuracy of this method, Ef is then measured using probe techniques. With this tool, we then examine the rearrangement of the plasma and change in Er between L and H modes in low field Ar discharges the H-1 Heliac. Furthermore, we explore hysteresis effects on the plasma as we quasi-statically change the RF heating power. A complicated hysteresis behavior is found: a typical L-H / H-L transition hysteresis loop can be identified, but other intriguing hysteresis loops appear in various discharge conditions. By examining the possible plasma states as a function of magnetic field, gas fill pressure and RF power, mode structures in this phase space are identified. Copyright (2002) Australian National University- Research School of Physical Sciences and Engineering