[en] High energy α-particles are used to deposit helium in nickel to various depths (10 to 100 μ) and at high temperatures (800 to 1250⁰C). The release of helium gas from the sample is monitored during the implantation by a mass-spectrometer. The diffusion constant of He can be estimated from the time dependence of the He-release after the α-particle beam is switched on. By varying the implantation temperature, the activation energy for He diffusion has been determined to be about 0.9 eV. Possible models for He diffusion at high temperatures will be discussed. Depending on the implantation depth up to 98% of the He remains in the sample. Electron microscopy shows that this He forms large bubbles (approximately 1 μm). (author)