Stork, D. and Baranov, Y. and Belo, P. and Bertalot, L. and Borba, D. and Brzozowski, J.H. and Challis, C.D. and Ciric, D. and Neu, R and O'Mullane, M and Contributors, JET EFDA (2005) *Overview of transport, fast particle and heating and current drive physics using tritium in JET plasmas.* Nuclear Fusion, 45 (10). S181-S194. ISSN 0029-5515

## Abstract

Results are presented from the JET Trace Tritium Experimental (TTE) campaign using minority tritium (T) plasmas (n(T)/n(D) <3. Thermal tritium particle transport coefficients (D-T, nu(T)) are found to exceed neo-classical values in all regimes, except in ELMy H-modes at high densities and in the region of internal transport barriers (ITBs) in reversed shear plasmas. In ELMy H-mode dimensionless parameter scans, at q(95) 2.8 and triangularity delta = 0.2, the T particle transport scales in a gyro-Bohm manner in the inner plasma (r/a <0.4), whilst the outer plasma particle transport scaling is more Bohm-like. Dimensionless parameter scans show contrasting behaviour for the trace particle confinement (increases with collisionality, nu* and beta) and bulk energy confinement (decreases with nu* and is independent of beta). In an extended ELMy H-mode data set, with rho*, nu*, and q varied but with neo-classical tearing modes (NTMs) either absent or limited to weak, benign core modes (4/3 or above), the multiparameter fit to the normalized diffusion coefficient in the outer plasma (0.65 <r/a <0.8) gives D-T/B-phi similar to rho*(2.46) nu*(-0.23) beta(-1.01) q(2.03). In hybrid scenarios (q(min) similar to 1, low positive shear, no sawteeth), the T particle confinement is found to scale with increasing triangularity and plasma current. Comparing regimes (ELMy H-mode, ITB plasma and hybrid scenarios) in the outer plasma region, a correlation of high values of D-T with high values Of nu(T) is seen. The normalized diffusion coefficients for the hybrid and ITB scenarios do not fit the scaling derived for ELMy H-modes. The normalized tritium diffusion scales with normalized poloidal Larmor radius (rho(theta)* = q rho*) in a manner close to gyro-Bohm (similar to rho(sigma)*(3)), with an added inverse P dependence. The effects of ELMs, sawteeth and NTMs on the T particle transport are described. Fast-ion confinement in current-hole (CH) plasmas was tested in TTE by tritium neutral beam injection into JET CH plasmas. gamma-rays from the reactions of fusion alpha and beryllium impurities (Be-9(alpha, n gamma)C-12) characterized the fast fusion-alpha population evolution. The gamma-decay times are consistent with classical alpha plus parent fast triton slowing down times (tau(Ts) + tau(alpha s)) for high plasma currents (I-p > 2 MA) and monotonic q-profiles. In CH discharges the gamma-ray emission decay times are much lower than classical (tau(Ts) + tau(alpha s)), indicating alpha confinement degradation, due to the orbit losses and particle orbit drift predicted by a 3-D Fokker-Planck numerical code and modelled using TRANSP.

Item type: | Article |
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ID code: | 31301 |

Notes: | Symposium on Theory of Magnetic Confinement held at the 20th IAEA Fusion Energy Conference, Vilamoura, PORTUGAL, NOV 01-06, 2004 |

Keywords: | fast particle effects , fusion products, spherical tokamaks, helicity injection, ignition , Physics |

Subjects: | Science > Physics |

Department: | Faculty of Science > Physics |

Related URLs: | |

Depositing user: | Pure Administrator |

Date Deposited: | 13 Jul 2011 09:56 |

Last modified: | 12 Mar 2012 11:27 |

URI: | http://strathprints.strath.ac.uk/id/eprint/31301 |

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