The heat flux is one of the key theoretical concepts used to quantify and understand transport in fusion devices. In this paper, a new method is introduced to calculate the heat flux including its confidence with high accuracy based on perturbed measurements such as the electron temperature. The new method is based on ideal filtering to optimally reduce the noise contributions on the measurements and piece-wise polynomial approximations to calculate the time derivative. Both methods are necessary to arrive at a heat flux and effective diffusion coefficient with high accuracy. The new methodology is applied to a measurement example using ECRH block-wave modulation at the Large Helical Device showing the merit of the newly developed methodology.

VL - 58 IS - 9 U1 -FP

U2 -IMT

U5 - 9aecc9fdfa64362d2e98948e554ac487 ER - TY - JOUR T1 - New evidence and impact of electron transport non-linearities based on new perturbative inter-modulation analysis JF - Nuclear Fusion Y1 - 2017 A1 - van Berkel, M. A1 - Kobayashi, T. A1 - Igami, H. A1 - Vandersteen, G. A1 - Hogeweij, G. M. D. A1 - Tanaka, K. A1 - Tamura, N. A1 - Zwart, H. J. A1 - Kubo, S. A1 - Ito, S. A1 - Tsuchiya, H. A1 - M. R. de Baar A1 - LHD Experiment Group AB -A new methodology to analyze non-linear components in perturbative transport experiments is introduced. The methodology has been experimentally validated in the Large Helical Device for the electron heat transport channel. Electron cyclotron resonance heating with different modulation frequencies by two gyrotrons has been used to directly quantify the amplitude of the non-linear component at the inter-modulation frequencies. The measurements show significant quadratic non-linear contributions and also the absence of cubic and higher order components. The non-linear component is analyzed using the Volterra series, which is the non-linear generalization of transfer functions. This allows us to study the radial distribution of the non-linearity of the plasma and to reconstruct linear profiles where the measurements were not distorted by non-linearities. The reconstructed linear profiles are significantly different from the measured profiles, demonstrating the significant impact that non-linearity can have.

VL - 57 IS - 12 U1 -FP

U2 -IMT

U5 - 253a5b36e4c90b5327e0cb8eb01a914e ER - TY - JOUR T1 - Summary of EC-17: the 17th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating (Deurne, The Netherlands, 7-10 May 2012) JF - Nuclear Fusion Y1 - 2013 A1 - Westerhof, E. A1 - Austin, M. E. A1 - Kubo, S. A1 - Lin-Liu, Y. R. A1 - Plaum, B. AB -An overview is given of the papers presented at the 17th Joint Workshop on Electron Cyclotron Emission (ECE) and Electron Cyclotron Resonance Heating (ECRH). The meeting covered all aspects of the research field ranging from theory to enabling technologies. From the workshop, advanced control by electron cyclotron heating and current drive is emerging as probably the main application of ECRH in fusion devices. Large progress is reported from various experiments on real-time control applications. At the same time ECE is developing into a multi-dimensional plasma diagnostic taking advantage of new technological developments. The resulting multi-dimensional ECE data reveal exciting new details of the complicated plasma dynamics in fusion devices.

VL - 53 SN - 0029-5515 IS - 2 U1 -FP

U2 -CPP-HT

U5 - 36dbe91a66f8654bb038c2b9c5f18687 ER - TY - JOUR T1 - Experimental studies towards long pulse steady state operation in LHD JF - Nuclear Fusion Y1 - 2001 A1 - Noda, N. A1 - Nakamura, Y. A1 - Takeiri, Y. A1 - Mutoh, T. A1 - Kumazawa, R. A1 - Sato, M. A1 - Kawahata, K. A1 - Yamada, S. A1 - Shimozuma, T. A1 - Oka, Y. A1 - Iiyoshi, A. A1 - Sakamoto, R. A1 - Kubota, Y. A1 - Masuzaki, S. A1 - Inagaki, S. A1 - Morisaki, T. A1 - Suzuki, H. A1 - Ohyabu, N. A1 - Adachi, K. A1 - Akaishi, K. A1 - Ashikawa, N. A1 - Chikaraishi, H. A1 - de Vries, P. C. A1 - Emoto, M. A1 - Funaba, H. A1 - Goto, M. A1 - Hamaguchi, S. A1 - Ida, K. A1 - Idei, H. A1 - Ikeda, K. A1 - Imagawa, S. A1 - Inoue, N. A1 - Isobe, M. A1 - Iwamoto, A. A1 - Kado, S. A1 - Kaneko, O. A1 - Kitagawa, S. A1 - Khlopenkov, K. A1 - Kobuchi, T. A1 - Komori, A. A1 - Kubo, S. A1 - Liang, Y. A1 - Maekawa, R. A1 - Minami, T. A1 - Mito, T. A1 - Miyazawa, J. A1 - Morita, S. A1 - Murai, K. A1 - Murakami, S. A1 - Muto, S. A1 - Nagayama, Y. A1 - Nakanishi, H. A1 - Narihara, K. A1 - Nishimura, A. A1 - Nishimura, K. A1 - Nishizawa, A. A1 - Notake, T. A1 - Ohdachi, S. A1 - Okamoto, M. A1 - Osakabe, M. A1 - Ozaki, T. A1 - Pavlichenko, R. O. A1 - Peterson, B. J. A1 - Sagara, A. A1 - Saito, K. A1 - Sakakibara, S. A1 - Sasao, H. A1 - Sasao, M. A1 - Sato, K. A1 - Seki, T. A1 - Shoji, M. A1 - Sugama, H. A1 - Takahata, K. A1 - Takechi, M. A1 - Tamura, H. A1 - Tamura, N. A1 - Tanaka, K. A1 - Toi, K. A1 - Tokuzawa, T. A1 - Torii, Y. A1 - Tsumori, K. A1 - Watanabe, K. Y. A1 - Watanabe, T. A1 - Watari, T. A1 - Yanagi, N. A1 - Yamada, I. A1 - Yamada, H. A1 - Yamaguchi, S. A1 - Yamamoto, S. A1 - Yamamoto, T. A1 - Yokoyama, M. A1 - Yoshimura, Y. A1 - Ohtake, I. A1 - Akiyama, R. A1 - Haba, K. A1 - Iima, M. A1 - Kodaira, J. A1 - Tsuzuki, K. A1 - Itoh, K. A1 - Matsuoka, K. A1 - Ohkubo, K. A1 - Satoh, S. A1 - Satow, T. A1 - Sudo, S. A1 - Tanahashi, S. A1 - Yamazaki, K. A1 - Motojima, O. A1 - Hamada, Y. A1 - Fujiwara, M. AB - In the Large Helical Device, stable discharges lasting longer than one minute have been obtained using the complete heating scheme, including ECH. The plasma is sustained with NBI or ICRF of 0.5-1 MW. The central plasma temperature is higher than 1.5 keV with a density of (1-2) x 10(19) m(-3) maintained until the end of the pulse. Full installation of the carbon divertor has contributed to this achievement. This provides a sufficient basis for physics and technology studies for the next campaign. Long pulse operation opens new possibilities in diagnostics and in physics studies. Higher accuracy and reliability are obtained with a diagnostics parameter scan, longer integration of signals or two dimensional measurement. The mechanism of a slow oscillation called 'breathing' is discussed. Hydrogen recycling analysis has been carried out and preliminary results have been obtained. On the basis of these results, the future programme is divided into two categories: (i) physics and technology experiments utilizing long pulse discharges lasting up to 5 minutes, and (ii) extension of the pulse length up to one hour. VL - 41 SN - 0029-5515; 1741-4326 U5 - 3347e2694d4225255b5acce27fce657c ER -