Ballistic contributions to heat-pulse propagation in the TFTR tokamak

Long Range Temperature Fluctuation in LHD

“…ITOH 1,2) , Naoki TAMURA 3) , Satoru SAKAKIBARA 3) , Naohiro KASUYA 3) , Akihide FUJISAWA 1,2) , Shin KUBO 3) , Takashi SHIMOZUMA 3) , Takeshi IDO 3) , Seiya NISHIMURA 3) , Hiroyuki ARAKAWA 4) , Tatsuya KOBAYASHI 4) , Masatoshi YAGI 1,2) , Kenji TANAKA 3) , Yoshio NAGAYAMA 3) , Kazuo KAWAHATA 3) , Shigeru SUDO 3) , Hiroshi YAMADA 3) , Akio KOMORI 3) and LHD Experiment Group We report a detailed correlation technique to identify the long-range temperature fluctuation in the Large Helical Device. Correlation hunting has successfully realized the observation of electron temperature fluctuations, which are characterized by their correlation length comparable to the plasma minor radius, with low frequency of ∼ 1-3 kHz, ballistic radial propagation (at a speed of ∼1 km/s, of the order of diamagnetic drift velocity), spatial mode number of m/n = 1/1 (or 2/1), and amplitude of ∼2% at the maximum.…”

“…In future experiments on thermonuclear fusion, such as the Internal Thermonuclear Experimental Reactor (ITER), the performance and controllability of plasmas are predicted and designed based on the basis of such a presumption. However, the fast radial propagation of temperature perturbations in toroidal plasmas, i.e., the so-called "transient transport problem", has been observed in many tokamaks and helical devices during the course of the last two decades [2][3][4][5][6][7]. The temperature perturbation, which is applied to the plasma edge region, propagates inward at a speed that is 10-50 times faster than that expected from diffusive transport models.…”

Observation of multi-scale turbulence and non-local transport in LHD plasmas

“…In addition, the studies of relation between heat/particle/momentum flux and temperature/density/flow gradient are shown that the flux is not necessarily determined by the local plasma parameters. [10][11][12][13][14][15][16][17] In cold pulse propagation experiments, for example, the core plasma temperature shows the fast change after the edge cooling. [18][19][20] The change of temperature is much faster than the expected value from the diffusive process in a thermal transport.…”

Experimental Measurement of ECH Deposition Broadening: Beyond Anomalous Transport

“…Firstly, an exponential modulated diffusion appears frequently in the literature to fit heat pulse transport in experiments [16]. Time variation ofξ can be expressed in an exponential basis as well as a sine wave basiŝ ξ = n a n exp(−nt)…”

“…Fitting to a variety of discharges has found the ∇T e driven portion ofξ dominates. This makesξ reminiscent of an anomalous diffusion [16]. Because fitting will be performed across harmonics, some form of time dependence must be applied, as ∇ñ e andñ e are not known.…”