Characterization and Efficacy Analysis of a Dielectric barrier discharge based Far UV-C 222 nm Excimer light Source

Far UV-C radiation (207-230 nm) has demonstrated potential as an antibacterial and antiviral agent. In addition, Far UV-C radiation is safe on skin and eye tissues. Together, these characteristics have the potential to fundamentally alter how and where UV-C radiation can be deployed for air and surface disinfection.

In this work, a co-axial dielectric barrier discharge (DBD) plasma based Far UV-C excimer light source has been characterized for the maximum absolute intensity by varying the different parameters such as gas pressure, applied voltage and frequency. A mixture of krypton with a very small fraction of chlorine gas has been used in the gas gap and pinched-off for bacterial inactivation efficiency analysis. When the high voltage was supplied to the DBD excimer source, then the excitation and ionization of both the gases (Kr and Cl 2 ) takes place. The cations of krypton and anions of chlorine gas get involved in a three-body recombination reaction with an atom or molecule of buffer gas (M) and form the excited complex (KrCl*) which decomposes rapidly and emits photons having wavelength of 222 nm. For the absolute intensity measurement, a photodetector has been used. A PMT based monochromator has been used for spectroscopic analysis. A very narrow band (FWHM ~ 1.7 nm) peaking at 222 nm has been obtained. Ultimately, the developed source has been tested for its bacterial efficiency on gram positive bacteria and a 7 log reduction has been achieved within 30 sec of Far UV-C treatment having an UV dose of ~300 µJ/cm 2 .