We report on measurements of the ion-electron energy-transfer cross section utilizing low-velocity ion stopping in high-energy-density plasmas at the OMEGA laser facility. These measurements utilize a technique that leverages the close relationship between low-velocity ion stopping and ion-electron equilibration. Shock-driven implosions of capsules filled with $\mathrm{D}{}^3\mathrm{He}$ gas doped with a trace amount of argon are used to generate densities and temperatures in ranges from $1\times {10}^{23}$ to $2\times {10}^{24} {\mathrm{cm}}^{-3}$ and from 1.4 to 2.5 keV, respectively. The energy loss of 1-MeV DD tritons and 3.7-MeV $\mathrm{D}{}^3\mathrm{He}$ alphas that have velocities lower than the average velocity of the thermal electrons is measured. The energy loss of these ions is used to determine the ion-electron energy-transfer cross section, which is found to be in excellent agreement with quantum-mechanical calculations in the first Born approximation. This result provides an experimental constraint on ion-electron energy transfer in high-energy-density plasmas, which impacts the modeling of alpha heating in inertial confinement fusion implosions, magnetic-field advection in stellar atmospheres, and energy balance in supernova shocks.

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• Fusion products
• High-energy-density plasmas
• Inertial confinement fusion
• Plasma transport