Evaluation of Be fluxes into the ITER tokamak plasma due to sputtering of the first wall by D and T atoms leaving the plasma

Beryllium fluxes into the ITER tokamak plasma due to sputtering of the first wall by D and T atoms leaving the plasma were estimated. The energy spectra of deuterium and tritium atoms leaving the plasma were modeled using the DOUBLE-MC code. The flux of beryllium atoms entering the plasma was estimated to be 6.5 × 1017 atoms s−1 m−2. Azimuthal anisotropy of the fluxes of atoms leaving the plasma was taken into account, which increased the estimate of the beryllium flux by 15% compared to that in the isotropic case. With the typical ITER plasma confinement times of 3–5 s, this means that the concentration of beryllium impurities can be 2.5%–4.2% of the mean ion plasma density. Such a high content of beryllium ions in the region close to the separatrix can lead to significant sputtering of the divertor with multiply charged beryllium ions. The proposed model allows estimation of the flux of sputtered tungsten atoms into the near divertor plasma. By varying the density of the gas-plasma target and the electron temperature on the separatrix, one can reduce the tungsten impurities influx into the plasma.