The Effect of Plasma Density Profile on Two-Plasmon Decay in Tokamak Plasma

Electron cyclotron extraordinary-wave decay into two upper hybrid waves in an inhomogeneous magnetized plasma is studied theoretically and numerically. The analytic expressions for the local coupling constant and convective amplification factor of two-plasmon decay (TPD) are obtained. It shows that the TPD threshold intensity is very high (about 15 MW) with the linear density profile in a tokamak plasma. However, within the nonmonotonicity density profile, the power threshold of TPD can significantly be reduced more than one order of magnitude (about 1.2MW). The comparison of the numerical and simulation results of the local coupling constant shows that they agree well with each other.