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 multichannel 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 minor radii in the range 0.25<r/a<0.55 were found to be flat and to take values between 0.3 and 1.1 m2 s-1 for H-mode plasmas with plasma current Ip=3.1 MA and toroidal field BT=2.3 T. The value of chi i was smallest for Zeff=2.2 and increased weakly with increasing Zeff. The predictions of neoclassical theory are much smaller than the experimental values for low Zeff but increase rapidly until they become comparable with the experimental values at the highest Zeff obtained.
中性束注入（NBI）强加热终止后，利用多通道仪器测得的线积分信号，常规获取联合欧洲环（JET）氘等离子体的中子发射空间分布。结果表明，这些分布在加热终止后的弛豫过程使得局部热扩散系数（χᵢ）能够以约20%的精度获得。在等离子体电流Iₚ=3.1 MA、环向磁场Bₜ=2.3 T的H模等离子体中，小半径范围0.25<r/a<0.55内的χᵢ分布平坦，数值介于0.3至1.1 m² s⁻¹之间。当有效电荷数Z_eff=2.2时，χᵢ取最小值，并随Z_eff增大而缓慢增加。新经典理论预测值在低Z_eff时远低于实验值，但随着Z_eff增大而迅速上升，在达到的最高Z_eff值下与实验值相当。