Longer Life UV Lamps !

Medium pressure UV lamps are basically gas discharge lamps. During operation the plasma inside the quartz glass tube generates the desired spectrum. In its centre the plasma has a temperature of approximately 5,000 to 7,000 K ! . This is created by the high current flowing through the electrodes. The surface of the lamp should be somewhere between 700 - 900 C.

Due to the small dimensions of the electrodes the current density is extremely high at their tips.

After hours of operation the inner surface of the quartz glass tube begins to blacken around the electrode area. This is normally called the "end blackening-effect" and comprises of the tiny particles of tungsten that leave the electrode, the good news is that this can be significantly reduced by the addition of halogen !

By adding halogen, a halogen "cycle" process is initiated which works as follows: The tungsten, when its sputtered from the electrode, deposits on the inside of the quartz glass tube ( or at the coldest place) and combines with the halogen. This combination breaks apart again near the electrode, depositing the tungsten back on it increasing the lamp life by 50% !