As plasma increases in temperature, it becomes thicker. At a high enough temperature, plasma is thick enough to separate a vacuum from normal atmosphere. Plasma does not stop radiation, such as lasers, from moving through it. Because of this, scientists can use a plasma window to create an area of vacuum while still letting radiation to move through it. This is needed because certain types of radiation can only be created in a vacuum, but scientists need to use the radiation on things that are found in a normal atmosphere.