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Title: Quasi-single helicity state by a small positive pulse of toroidal magnetic field in TPE-RX reversed field pinch experiment

Abstract

By applying a small positive pulse ({delta}B{sub ta}) in toroidal magnetic field, the quasi-single helicity (QSH) state can be obtained with a controllable and reproducible manner in a reversed-field pinch (RFP) experiment on the large RFP machine, TPE-RX [Y. Yagi et al., Fusion Eng. Des. 45, 421 (1999)]. The QSH state in RFP is one of the states where the improved confinement can be observed, and is important for development toward the pure single helicity (SH) state. In the SH state, the dynamo-action for sustaining the RFP configuration will be driven by a single helical mode and its harmonics, and the anomalous plasma loss can be avoided which is caused by the multi-helicity dynamo action in ordinary RFPs. In the operating condition presented here, the reversal of toroidal magnetic field (B{sub ta}) is maintained at a shallow value ({approx}-1 mT) for a certain period ({approx}20 ms) after the setting up of the RFP configuration and then the positive {delta}B{sub ta} ((less-or-similar sign)5 mT magnitude and {approx}2 ms width) is applied to the B{sub ta}, which is usually negative during the sustaining phase of RFP. Just after applying the pulse, the m/n=1/6 mode (m and n being the poloidal and toroidalmore » Fourier mode numbers, respectively) grows dominantly and the configuration goes into QSH state. This QSH state can be sustained for a long period (up to {approx}45 ms) almost until the end of discharge by applying a delayed reversal of B{sub ta} with appropriate timing and magnitude. The setting up of the QSH states shows a reproducibility of almost 100% with the same timing corresponding to the applied positive pulse. This observation can confirm the interpretation in the former report [Y. Hirano et al., Phys. Plasmas 12, 112501 (2005)], in which it is claimed that the QSH state is obtained when a small positive pulse in toroidal magnetic field spontaneously appears.« less

Authors:
; ; ; ;  [1]
  1. National Institute of Advanced Industrial Science and Technology, Tsukuba-shi, Ibaraki 305-8568 (Japan)
Publication Date:
OSTI Identifier:
20860445
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 13; Journal Issue: 12; Other Information: DOI: 10.1063/1.2405343; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; HARMONICS; HELICITY; KINK INSTABILITY; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; PLASMA; PLASMA CONFINEMENT; PULSES; RADIATION TRANSPORT; REVERSE-FIELD PINCH; TEARING INSTABILITY; TPE-RX DEVICE

Citation Formats

Hirano, Y., Koguchi, H., Yambe, K., Sakakita, H., and Kiyama, S. Quasi-single helicity state by a small positive pulse of toroidal magnetic field in TPE-RX reversed field pinch experiment. United States: N. p., 2006. Web. doi:10.1063/1.2405343.
Hirano, Y., Koguchi, H., Yambe, K., Sakakita, H., & Kiyama, S. Quasi-single helicity state by a small positive pulse of toroidal magnetic field in TPE-RX reversed field pinch experiment. United States. doi:10.1063/1.2405343.
Hirano, Y., Koguchi, H., Yambe, K., Sakakita, H., and Kiyama, S. Fri . "Quasi-single helicity state by a small positive pulse of toroidal magnetic field in TPE-RX reversed field pinch experiment". United States. doi:10.1063/1.2405343.
@article{osti_20860445,
title = {Quasi-single helicity state by a small positive pulse of toroidal magnetic field in TPE-RX reversed field pinch experiment},
author = {Hirano, Y. and Koguchi, H. and Yambe, K. and Sakakita, H. and Kiyama, S.},
abstractNote = {By applying a small positive pulse ({delta}B{sub ta}) in toroidal magnetic field, the quasi-single helicity (QSH) state can be obtained with a controllable and reproducible manner in a reversed-field pinch (RFP) experiment on the large RFP machine, TPE-RX [Y. Yagi et al., Fusion Eng. Des. 45, 421 (1999)]. The QSH state in RFP is one of the states where the improved confinement can be observed, and is important for development toward the pure single helicity (SH) state. In the SH state, the dynamo-action for sustaining the RFP configuration will be driven by a single helical mode and its harmonics, and the anomalous plasma loss can be avoided which is caused by the multi-helicity dynamo action in ordinary RFPs. In the operating condition presented here, the reversal of toroidal magnetic field (B{sub ta}) is maintained at a shallow value ({approx}-1 mT) for a certain period ({approx}20 ms) after the setting up of the RFP configuration and then the positive {delta}B{sub ta} ((less-or-similar sign)5 mT magnitude and {approx}2 ms width) is applied to the B{sub ta}, which is usually negative during the sustaining phase of RFP. Just after applying the pulse, the m/n=1/6 mode (m and n being the poloidal and toroidal Fourier mode numbers, respectively) grows dominantly and the configuration goes into QSH state. This QSH state can be sustained for a long period (up to {approx}45 ms) almost until the end of discharge by applying a delayed reversal of B{sub ta} with appropriate timing and magnitude. The setting up of the QSH states shows a reproducibility of almost 100% with the same timing corresponding to the applied positive pulse. This observation can confirm the interpretation in the former report [Y. Hirano et al., Phys. Plasmas 12, 112501 (2005)], in which it is claimed that the QSH state is obtained when a small positive pulse in toroidal magnetic field spontaneously appears.},
doi = {10.1063/1.2405343},
journal = {Physics of Plasmas},
number = 12,
volume = 13,
place = {United States},
year = {Fri Dec 15 00:00:00 EST 2006},
month = {Fri Dec 15 00:00:00 EST 2006}
}