The distribution function of suprathermal ions is found to be self-similar under conditions relevant to inertial confinement fusion hot spots. By utilizing this feature, interference between the hydrodynamic instabilities and kinetic effects is for the first time assessed quantitatively to find that the instabilities substantially aggravate the fusion reactivity reduction. The ion tail depletion is also shown to lower the experimentally inferred ion temperature, a novel kinetic effect that may explain the discrepancy between the exploding pusher experiments and rad-hydro simulations and contribute to the observation that temperature inferred from DD reaction products is lower than from DT at the National Ignition Facility. Recent exploding pusher experiments [1-6] reveal substantial kinetic effects on the implosion performance. Specific mechanisms potentially responsible for these observations include the inter-ion-species diffusion [7][8][9][10] and reactivity reduction due to ion tail depletion [11][12][13][14][15][16][17][18]. Theoretical evaluation of these phenomena is challenging, however, and while fully kinetic simulations allow study of a certain stage of implosion in specific configurations [19,20], such calculations are computationally prohibitive for the modeling of a realistic inertial confinement fusion (ICF) experiment. A substantial simplification results from treating thermal and suprathermal ions separately [21]. For the former, the mean free path λ ð0Þ is often much smaller than the characteristic scale of the system L, making fluid equations (including interspecies diffusion) a valid model. The latter constitute only a small fraction of the ion density, momentum, and energy and do not appear explicitly in the fluid equations. However, it is the suprathermal ions that are most likely to undergo fusion reactions, so they do affect the fluid equations implicitly as an energy source. For these ions, the mean free path is much larger than λ ð0Þ and can be comparable to L even if λ ð0Þ ≪ L. Hence, self-consistent modeling of ICF implosions would appear to require a kinetic treatment of suprathermal ions capable of predicting the fusion reactivity at each time step of the fluid equations' evolution.While suprathermal ions can be described by a reduced linear (as opposite a to fully nonlinear) kinetic equation [22], this task is still nontrivial. All prior studies rely on either a direct numerical solution [15][16][17][18] or phenomenological assumptions that affect the structure of the kinetic equation [13,14]. Until now, no simple solution to the firstprinciples kinetic equation for the suprathermal ions has been found even in the one-dimensional (1D) planar case. The issue becomes particularly pressing in light of hydroinstabilities at the fuel-pusher interface [23][24][25][26][27][28][29][30]. It is near this interface that the suprathermal ion distribution is modified most, so one should expect substantial interference between the instabilities and the fusion reactivity. However, applying direct...