UV Sources





Contact RadTech

Medium Pressure Mercury Vapor

Medium pressure mercury vapor lamps are by far the most commonly used lamp in UV processing. They are divided into two categories, depending on their construction and method of energization. These are the arc, or electrode type of lamp and the microwave-powered, or electrodeless type.

“Medium pressure” is a general category of source in which the gas fill inside the transparent tube is the general range of one atmosphere of pressure. This pressure will typically be less than one atmosphere when the bulb is not operating, and 2-3 atmospheres when it is hot and operating. By comparison, “low pressure” lamps are only a fraction of an atmosphere in pressure, and produce much lower total power output, concentrated in relatively narrow emission. Well-known germicidal lamps are low-pressure mercury lamps, producing their strongest emission at around 254 nm, an effective bio-kill wavelength. High-pressure mercury lamps are broadband high energy sources – we may be familiar with these as they are often used in lighting applications.

Most medium-pressure UV lamps are mercury-based. In other words, they all contain some mercury. Mercury itself is rich in UV output in the 230 to 320 nm range, with some emission around 365 nm. By placing metal halide additives in the bulb with the mercury, additional spectral emissions are produced.