Dosimeter

Dosimeters are measuring instruments for the measurement of radiation dose - as absorbed dose or dose equivalent - in the context of radiation protection. In contrast to the dose rate meter, the dose rate, ie the radiation dose per unit of time measure, adds a dosimeter the dose over time to time.

Dosimeters are usually to be worn on the body, determined under circumstances particularly exposed to the radiation body parts ( finger ring ) and then hot personal dosimeter.

Personal dosimeter

• Füllhalterdosimeter (named after the housing shape and size): The electric charge and thus the voltage of a capacitor is reduced by incident ionizing radiation. The received since the charging dose is read at any time to the position of a metallic filament through a scale in the unit. The display can be erased by recharging, i.e., are reset to zero. Füllhalterdosimeter register X-rays and gamma radiation, and ( to a lesser extent, depending on the beta ray transmittance of the material) and beta radiation ( See also Sievert chamber).
• Film dosimeters: One in a plaque with different filter fields ( for spreading the range of sensitivity and differentiation by hard and soft radiation) befindlicher film is blackened by the irradiation. After the development can be measured by Schwärzungsvergleich defined with irradiated films, the dose received.

• Thermoluminescent (TLD ): in suitable crystals, the X-ray or gamma radiation produced microscopic changes, which emit in the evaluation of the absorbed radiant energy visible ( by heating the crystal) in the form of light. From the light yield results in the dose.
• Digital Dosimeter use electronic sensors and digital signal processing and show the current absorbed radiation dose to a digital display usually in mSv to. The units can be set so that it is reached by certain set limits a signal (eg, acoustic) Make (dose warning device).

Readabilities

Another distinction, which also determines the type of use is the readability.

• Direct reading devices are electronic devices which display on a display previously recorded dose since switching on the device. They are sometimes combined with dose rate meters because of the technical structure is very similar.
• Not direct reading dosimeter can be read only in retrospect with special facilities.

Use

The readable immediately and do not erasable dosimeter ( film badge, TLD, etc.) used as officially approved dosemeter for routine monitoring of occupationally exposed persons and usually evaluated monthly.

Direct reading dosimeters are often equipped with an additional alarm device that output a warning signal when a certain threshold. For this reason they are referred to as Alarmdosimeter. These thresholds are pre-programmed and can be adjusted depending on the application. In addition, they also often have devices in order to protect them from an erroneous off. This may for example consist of a necessary addition pin when off switch, or pressing the off switch is possible only in a specific sequence. They are mostly used for radiation protection units such as military or fire department and are used in uncontrolled radiation areas. Therefore, they are often referred to as tactical dosimeters.

Depending on the use of dosimeters are worn differently. Not to read can be worn under any protective clothing. They should record the dose which comes as close as possible to that of the body itself. Readable dosimeter must be worn hand over any protective clothing on the other. Personal dosimeter that will also detect alpha radiation, such as facilities for water production must be worn on the clothing due to the low penetration depth of alpha particles.