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Spatial profiles of the neutron emission from deuterium plasmas are routinely obtained at the Joint European Torus (JET) using the line-integrated signals measured with a multi-channel instrument. It is shown that the manner in which these profiles relax following the termination of strong heating with neutral beam injection (NBI) permits the local thermal diffusivity (Chi(i)) to be obtained with an accuracy of about 20%. The profiles of Chi(i) for small minor radius (r/a is less than 0.6) were found to be flat and to take values between 0.3 and 1.1 m2/s for H-mode plasmas with plasma current I(p) = 3.1 MA and toroidal field B(T) = 2.3 T. The value of Chi(i) was smallest for Z(eff) = 2.2 and increased weakly with increasing Z(eff). The predictions of neoclassical theory are much smaller than the experimental values for low Z(eff) but increase rapidly until they become comparable with the experimental values at the highest Z(eff) obtained.

Additional information

Authors: SASAO M, National Institute for Fusion Science, Nagoya (JP);ADAMS J M, AEA Technology, Harwell Laboratory, Didcot, Oxon. (GB);CONROY S, JET Joint Undertaking, Abingdon, Oxon. (GB);JARVIS O N, JET Joint Undertaking, Abingdon, Oxon. (GB);MARCUS F B, JET Joint Undertaking, Abingdon, Oxon. (GB);SADLER G, JET Joint Undertaking, Abingdon, Oxon. (GB);VAN BELLE P, JET Joint Undertaking, Abingdon, Oxon. (GB)
Bibliographic Reference: Report: JET-P(92)75 EN (1992) 14 pp.
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
Record Number: 199211585 / Last updated on: 1994-11-29
Original language: en
Available languages: en