Hollow-cathode lamp Instrument Design
A HCL consists of an anode and a cathode inside of a glass tube. It is important that the gas is inert in order to minimize interferences in the output of the data. The anode is an electrode in which oxidation takes place. Oxidation is the loss of electrons. The cathode is an electrode in which reduction takes place. Reduction is the gain of electrons. The anode is typically constructed of some type of metal such as tungsten and is coated with a material the helps to prevent contamination from the sputtering process described below. The cathode is constructed of the pure metal of interest or a mixture of metals containing the metal of interest. This mixture of metals is referred to as an alloy. It is important that the cathode be stored under a vacuum to avoid any kind of contamination. Contamination of the cathode compensates the metal of interests purity and the data obtained for that metal.