1. The problem statement, all variables and given/known data You have a co-axial cylindrical capacitor placed in vacuum. The two co-axial cylinder tubes are made of copper. The outside tube radius a1 and inside tube radius a2, with overlapping length L; both tubes have a thickness of t. Say, the capacitor was designed to withstand 5 kV voltage at 10 kHz. Now you are applying 10 kV at same 10 kHz, and you see a breakdown. Assume a1, a2 and L are fixed. The question is: How can you make the capacitor work for 10 kV at 10 kHz? 2. Relevant equations C=epsilon*A/d 3. The attempt at a solution (1) dip the capacitor tubes in sodium hydroxide, then oven-heat it, to turn surface copper into a thin layer of copper oxide (CuO). CuO has larger dielectric strength, so it can withstand higher voltage. Issue: CuO has larger permittivity and will this affect the frequency transmission? (2) dip the capacitor tubes in nitric acid, to remove a thin layer of the copper, so the gap distance between two cylinders increased a little, affording a larger voltage. (3) coat the tubes with a thin layer of zinc. Similar idea as in attempt (1).