COMSOL simulation for Electrical field distribution and enhancement

Background: I would like to study the electrical field distribution of CNT during a field emission process. CNT should have field enhancement effect as indicated in these 2 url link: [login to view URL] [login to view URL] However, I am a complete newbie in COMSOL. Tried multiple times but I can't get the field enhancement at the tip. What do I want: A COMSOL model that is able to change the CNT height, diameter, inter-CNT distance in a CNT ARRAY to study the effect of these changes field enhancement factor (or electrical field at CNT tips). Also kindly guide me on the usage (usage includes parameter change and data collection) and the basic concept of the model. I am just a graduate student and I am paying this amount from my savings. Apologies for the relatively low budget. Thank you!