**Acknowledgements**

This work has been supported by Ministerio de Ciencia, Innovación y Universidades Projects, ENE2015-70300-C3-1-RE, ENE2016-76755-R, NE2016- 76755-R, and MAT2012-384407-C03-01, and TechnoFusion Project (S2013/MAE-2745) of the Comunidad Autónoma Madrid (CAM) and partially by the European Communities within the European Fusion Technology Programme 2014–2018 under agreement No 633053. "The views and opinions expressed herein do not necessarily reflect those of the European Commission."

The authors wanted to thank the National Center for Electron Microscopy (CNME) staff and all the researchers and technician from CIEMAT, specially the researchers working on simulation: F. Mota, C. Ortiz, and F. Jiménez-Piñero. In addition, the authors wanted to extend their gratitude to all CMAM staff for their help, kindness, and contribution with this work. Finally, the authors do not want to miss the opportunity to express the appreciation to High Voltage Engineering Europa B.V. to allow and check this publication.
