The nonlinear saturation levels of parametric instabilities critically impact their detrimental effects in fusion applications. We uncover new insights into absolute two-plasmon decay (TPD) instability in inhomogeneous plasmas of inertial confinement fusion, identifying the resonance density range as a key factor governing the amplitudes of ion density fluctuations and Langmuir waves at nonlinear saturation, which holds despite the broad TPD spectrum extending beyond conventional absolute modes and the interplay of multiple saturation mechanisms. Based on the Langmuir wave amplitude at saturation, we further develop a physical model predicting hot electron energy fractions, with the results reproducing key features of prior experimental measurements.

Parametric Instability，,two-plasmon decay，,Nonlinear Saturation