Self-absorption of H$_{\beta}$ line in pellet ablation clouds in devices with magnetic confinement of high-temperature plasma

We have determined the optical absorption depth for H$_{\beta}$ line in clouds of secondary plasma near pellets ablating in high-temperature plasma of devices with magnetic confinement. It is established that, for all values of the electron concentration (10$^{16}$–3 $\times$ 10$^{17}$ cm$^{-3}$) and electron temperature (2–5 eV) measured in typical impurity pellet clouds, the absorption is negligibly small. At the same time, it can be significant in clouds of higher density (10$^{17}$–5 $\times$ 10$^{17}$ cm$^{-3}$) with a temperature of 1–2 eV, which are typical of cryogenic fuel pellets.