# Effects of alpha stopping power modelling on the ignition threshold in a directly-driven Inertial Confinement Fusion capsule

## TL;DR

This study investigates how different alpha stopping power models affect ignition thresholds in direct-drive Inertial Confinement Fusion, revealing that the choice of model influences the energy required for ignition.

## Contribution

It introduces a Monte-Carlo based alpha energy transport calculation into hydrodynamic simulations and compares LP and BPS stopping power models near ignition conditions.

## Key findings

- BPS model requires about 10% more energy than LP model for same fusion output.
- The choice of stopping power model impacts the ignition threshold.
- Simulations map the transition between marginal ignition and high gain.

## Abstract

The alpha-particle energy deposition mechanism modifies the ignition conditions of the thermonuclear Deuterium-Tritium fusion reactions, and constitutes a key issue in achieving high gain in Inertial Confinement Fusion implosions. One-dimensional hydrodynamic calculations have been performed with the code Multi-IFE [R. Ramis and J. Meyer-ter-Vehn, Comp. Phys. Comm. 203, 226 (2016)] to simulate the implosion of a capsule directly irradiated by a laser beam. The diffusion approximation for the alpha energy deposition has been used to optimize three laser profiles corresponding to different implosion velocities. A Monte-Carlo package has been included in Multi-IFE to calculate the alpha energy transport, and in this case the energy deposition uses both the LP [C.K. Li and R.D. Petrasso, Phys. Rev. Lett. 70, 3059 (1993)] and the BPS [L.S. Brown, D.L. Preston, and R.L. Singleton Jr., Phys. Rep. 410, 237 (2005)] stopping power models. Homothetic transformations that maintain a constant implosion velocity have been used to map out the transition region between marginally-igniting and high-gain configurations. The results provided by the two models have been compared and it is found that - close to the ignition threshold - in order to produce the same fusion energy, the calculations performed with the BPS model require about 10% more invested energy with respect to the LP model.

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Source: https://tomesphere.com/paper/1702.07729