We are permanently exposed by ionizing radiation produced by radioactive matter in and on the ground and in the atmosphere. Further contributions are due to cosmic radiation, man-made radiation sources, contaminated food and contaminated commodities. Its damaging effects on biologic organisms depend on the nature of radiation (Alpha-, Beta-, Gamma-radiation) (see ). The dimension Sievert (Sv) has been introduced to describe its biologic effectiveness (siehe ). The mean annual exposure ("dose") applied to the population in Germany amounts to approx. 3.9 mSv (natural sources 2 mSv plus man-made sources 1.9 mSv). This corresponds to a continuous dose rate of 0.23 μSv/h and 0.216 μSv/h rsp., combined 0.446 μSv/h. These values are indicated in all time charts to provide a rough assessment of the actual situation.
The presently installed sensor stations register only the exposure of Gamma-radiation emanated from the atmosphere. We do not apply any weighting with respect to the biologic effectiveness vs the nature of radiation. (see ). Neither we compensate for the nonlinearity of the detector related to the Gamma spectrum. Nevertheless we apply the dimension Sievert (S) for the representation of the readings to facilitate a comparative estimation of the exposure situation. Hence the readings must only serve as an indicator for abnormalities and for the tracking of trends.
The presently installed sensor stations apply Geiger-Müller counter tubes for radiation detection. PIN-diode detectors are used in on-going experiments. By counting the impulses delivered by the detector a microcomputer (RaspberryPi) computes dose rate values. Mean values of a sliding window (15 minutes) are encrypted and transfered, via internet, to the server. Hardware and software are based on the open resource project PiGI.
Sensor station: Microcomputer and Geiger-Müller counter tube (l), outdoor installation with PoE splitter (r)
Sensor stations are rolled out in 4 by 6 by 8 inch boxes (10x15x20 cm) intended to be installed at an outdoor position which is protected against driving rain and direct solar radiation (e.g. mounted to a wall under a balcony or porch), preferably at 3 feet (1 m) above ground. They need a mains power supply for their operation and an internet access via DSL router. If an outdoor mains outlet is provided at the installation site data transfer can be facilitated via mains line. Alternatively data transfer and power supply can be merged on a single data cable (PoE). All options are descibed in detail in a downloadable installation guide.
Stations are installed at user sites on loan. They remain in the ownership of FIfF e.V.
dose rate readings transferred minute-by-minute by all sensor stations in the field are captured by an internet server. They are stored in a data base, processed and conditioned for graphic representations to be accessed by the user via internet, see time charts.