Abstract: Jets injection in the TRIP gain generator can be either pure helium or mixture of helium and deuterium. Both of the cavity flowfield were numerically simulated to investigate their difference. The simulation results show that mixing enhanement of trip jets is obvious, the static pressure and static temperature have evident rising. Small signal gain’s peak value of each spectrum increases and its location moves upstream, while the small signal gain falls faster than that of cases without trip jets, and region of negative gain appear soon. Reaction between deuterium and fluorine is weak, which would not affect the main stream. Comparing the cases of trip jets and pure helium, the small signal gain of spectrum rises faster upstream, while the peak value preserves basically.