I have two plates with high voltage (+30KV) with a distance of 2mm. Inside of the vacuum, I did not see any discharge or arcing. After I insert the Rubidium vapor, I start seeing the corona discharge at the edge of the plate where the electric field is dense.
I think it is positive corona discharge, and from my understanding that positive corona, the electric field took the electron from the rubidium atom, and the electron accelerates toward the plate by the Coulomb force and ionizes other rubidium atoms with collisions. this starts to generate corona by an avalanche the process.
If I apply a negative voltage, it generates negative corona. The process is similar. The electrons are generated from the plate by photo-electric effect, and it accelerates outward to the plate by the Coulomb force, and discharge by an avalanche the process
My rubidium vapor ionization energy is ~4.1eV, and work function of my plate is ~4 eV. My vapor pressure is ~10^-4 torr (100C). Since their work function and ionization energy is similar, I cannot really tell which process will be more efficient. In order to suppress the corona, is negative voltage is better than positive voltage?
Instead of the significant change of the geometry of the plate, what method I can use the suppress the corona discharge?