The electronic personal dosimeter (EPD) is an electronic device that has a number of sophisticated functions, such as continual monitoring which allows alarm warnings at preset levels and live readout of dose accumulated. These are especially useful in high dose areas where residence time of the wearer is limited due to dose constraints. The dosimeter can be reset, usually after taking a reading for record purposes, and thereby re-used multiple times.
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PIN Dosimeter
PIN diodes are used to quantify the radiation dose for military and personnel applications.
MOSFET dosimeters
MOSFET dosimeters are now used as clinical dosimeters for radiotherapy radiation beams. The main advantages of MOSFET devices are:
1. The MOSFET dosimeter is direct reading with a very thin active area (less than 2 μm).
2. The physical size of the MOSFET when packaged is less than 4 mm.
3. The post radiation signal is permanently stored and is dose rate independent.
Gate oxide of MOSFET which is conventionally silicon dioxide is an active sensing material in MOSFET dosimeters. Radiation creates defects (acts like electron-hole pairs) in oxide, which in turn affects the threshold voltage of the MOSFET. This change in threshold voltage is proportional to radiation dose. Alternate high-k gate dielectrics like Hafnium oxide, Hafnium dioxide and Aluminum oxides are also proposed as a radiation dosimeters.