Low-temperature helium release in nickel

Abstract

Measurements of 3He released by thermal desorption have been made in high‐purity annealed, cold‐worked, and single‐crystal nickel samples. The 3He was introduced by natural tritium decay to eliminate implantation produced defects. Release was observed in the temperature region from ∼100 to 300 K and above 800 K; no desorption occurred at intermediate temperatures. The low‐temperature release amounted to only ∼1% of the total 3He generated. Thus, even in the case of relatively defect‐free materials, helium becomes strongly trapped with a binding energy of ∼2 eV. The low‐temperature data can best be modeled with a bulk mobility of ∼0.35 eV and a pipe diffusion path of lower activation energy.