He ion irradiation effects on multiwalled carbon nanotubes structure Emad M. Elsehly, Nikolay G. Chechenin, Alexey V. Makunin, Andrey A. Shemukhin and Hussien A. Motaweh Eur. Phys. J. D, 71 4 (2017) 79 Published online: 04 April 2017 DOI: 10.1140/epjd/e2017-70658-0