The mechanism is similar to that of a thermoluminescent dosimeter. They are now mostly superseded by electronic personal dosimeters and thermoluminescent dosimeters. Doped calcium fluoride, like natural fluorite, exhibits thermoluminescence and is used in thermoluminescent dosimeters. A wide range of ionization chamber, film badge, and thermoluminescent personal dosimeters are available. However, these are mostly superseded by such as thermoluminescent dosimetry (TLD) badges and electronic dosimeters.