High-speed electret charging using vacuum UV photoionization

We propose a high-speed charging method of electrets using vacuum ultraviolet irradiation. Due to a large amount of the ionization current at reduced pressure, it takes only a few seconds to charge 15-mu m-thick polymer electret film to the surface potential of -900 V. This charging rate is two orders of magnitudes larger than corona/soft-x-ray charging methods. The purity of N(2) gas depends on the charging rate since the O(2) quenching mechanisms of exited N2 molecule would exist. No charge decay is observed for 3000 h, which indicates charged electrets are as stable as those by other charging methods. (C) 2011 American Institute of Physics. [doi:10.1063/1.3548866]