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Knowledge of the particle source strength is of great importance if the particle transport mechanisms in a tokamak are to be understood. Since the ion plasma sources are due to ionisation (and recombination) of neutral atoms, numerical codes may be used to calculate the neutral atom density profile which, through the well known ionisation and recombination cross-sections, allows the particle source strength to be found. The results of such codes, however, depend on information that may be difficult to obtain, such as the impurity content and the distribution of external sources. Moreover, the measurement of neutral atom density, based on spectroscopic techniques, is only possible in the edge of the plasma. In this paper a method is described for measuring the local neutral density and, consequently, the particle source strength directly induced by gas puffing. The measurement is performed by modulating the gas valve flow and measuring the perturbation induced in the fast neutral emission as a function of energy.

Additional information

Authors: ZANZA V, ENEA, Centro Ricerche Energia Frascati, Roma (IT)
Bibliographic Reference: Paper presented: 20th EPS Conference on Controlled Fusion and Plasma Physics, Lisboa (PT), July 26-30, 1993
Availability: Available from (1) as Paper EN 37543 ORA
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