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Local thermal diffusivity can be expressed in terms of the Bohm diffusivity and a function of dimensionless parameters. Tests of transport models, theoretical, empirical or heuristic, expressed in terms of such parameters, often produce ambiguous answers which arise from collinearities in the experimental data. In experiments on dimensionally similar discharges, the scaling of confinement with one single dimensionless parameter can be examined in a less ambiguous fashion. Experiments on JET were carried out in which only the normalised Larmor radius rho(*) was varied. This was achieved by varying the plasma current, the toroidal field, the density, the ion cyclotron frequency and power level in a predetermined pattern so that other dimensionless parameters such as normalised collisionality and the safety factor are kept constant. The experiments on JET demonstrate that L-mode confinement both globally and locally scales with rho(*) according to the long wavelength or Bohm scaling. The implications for theory and future experiments are outlined.

Additional information

Authors: CHRISTIANSEN J P ET AL., JET Joint Undertaking, Abingdon, Oxon. (GB)
Bibliographic Reference: Report: JET-P(93)16 EN (1993)
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
Record Number: 199310727 / Last updated on: 1994-11-29
Original language: en
Available languages: en