A phosphor for use with low speed electron beams is characterized by the following general composition formula. The hot water and cold water are supplied at a predetermined flow rate at a predetermined proportion, regardless of the pressure of the water supply. Each group of access points comprises one or more access points with at least one group of access points having at least two access points. The gas is vented to a separate flow path, while the fluid having a lower gas content is produced to a desired location.