3D-Hydrogen Analysis of Ferromagnetic Microstructures in Proton Irradiated Graphite

Recently, magnetic order in highly oriented pyrolytic graphite (HOPG) induced by proton broad- and microbeam irradiation was discovered. Theoretical models propose that hydrogen could play a major role in the magnetism mechanism. We analysed the hydrogen distribution of pristine as well as irradiated HOPG samples, which were implanted to micrometer-sized spots as well as extended areas with various doses of 2.25 MeV protons at the Leipzig microprobe LIPSION. For this we used the sensitive 3D hydrogen microscopy system at the Munich microprobe SNAKE. The background hydrogen level in pristine HOPG is determined to be less than 0.3 at-ppm. About 4.8e15 H-atoms/cm^2 are observed in the near-surface region (4 um depth resolution). The depth profiles of the implants show hydrogen located within a confined peak at the end of range, in agreement with SRIM Monte Carlo simulations, and no evidence of diffusion broadening along the c-axis. At sample with microspots, up to 40 at-% of the implanted hydrogen is not detected, providing support for lateral hydrogen diffusion.Comment: accepted for publication in Nucl. Instr. and Met

Deuterium retention in recrystallized tungsten irradiated with simultaneous deuterium-neon ion beams

Although neon has been considered for impurity seeding in the ITER tungsten divertor, there have been few studies on its effects on deuterium retention in tungsten. We investigate the effects of simultaneous (SIM) D-2.5% Ne ion beam irradiation on D retention in recrystallized W at 300–700K, with 500eV/D+ and 1keV/Ne+ ion energies, and compare to the effects of SIM D-3% He irradiation with 500eV/He+. Thermal desorption spectroscopy (TDS) up to 1473K, nuclear reaction analysis (NRA), and elastic recoil detection analysis (ERDA) are used to measure D, He, and Ne in the specimens. Ne is more effective than He at reducing D retention for higher exposure temperatures, even though less Ne is retained than He. He appears to modify the D TDS spectra peak shapes more than Ne, while He addition leads to increased D trapping within a few µm depth according to NRA. D retention may be reduced due to Ne sputtering, as well as a near surface interaction with Ne which blocks D diffusion past the implantation range and leads to higher surface re-emission. Keywords: Tungsten, Deuterium, Helium, Neon, Retentio