当同时使用离子(或电子)回旋及中性束注入方式加热等离子体时，高能量粒子的能量分布函数一般应为尾部隆起(简称尾隆)分布。这种具有正能量梯度区域的分布函数更容易激发不稳定性，同时由于分布函数尾部隆起，在色散关系中引入了新的色散函数。主要研究了这种新色散函数的计算方法，结果表明：色散函数实部是关于原点对称的奇函数；而虚部则是关于纵轴对称的偶函数。色散函数的实部有2~4个极值点且极值点的位置与尾隆分布函数的能量梯度Δ有关、虚部有1~3个极值点但极值点位置与Δ无关。当其宗量趋于无穷大时，色散函数的值趋于零。当尾隆分布趋近于麦克斯韦分布时，用该方法计算的结果与色散函数表中给出的结果非常吻合。%In general, the energy distribution of energetic particles is bump-on-tail when both the neutral beam injection and electron/ion cyclotron resonant heating are used in tokamak plasma experiment. It is easier to induce instability for energy distribution profile with positive energy gradient regions existing such as the bump-on-tail. Therefore, a new dispersion function is introduced in dispersion relation due to bump-on-tail of the energy distribution. The calculation method of the new dispersion function is studied. T results show that the real and imaginary parts of dispersion functions are odd and even functions respectively. There are 2 to 4 extremes for real parts of the dispersion function and the positions of the extremes are dependent on Δ, the gradient of the energy distribution, whereas there are 1 to 3 extremes for imaginary parts and the positions of these extremes are independent ofΔ. Both the real and imaginary parts of the dispersion function go to zero when the arguments of Zt go to infinity. The calculated values agree very well with those given in dispersion function table when the bump-on-tail distribution goes to Maxwellian distribution.
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