A high intensity discharge light source includes an arc tube having a longitudinal axis and a main central discharge chamber formed therein. The arc tube includes first and second electrodes having inner terminal ends spaced from one another along the longitudinal axis. Each electrode extends at least partially into the main central discharge chamber or reaches the end portions of the main central discharge chamber. The arc tube includes first and second sub-chambers located at opposite ends of a main central discharge chamber. The sub-chambers are located entirely axially outward from the inner terminal ends of the electrodes to form cold spot locations for the dose pool outside the main central discharge chamber.