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New Measuring Instrument Identifies Radioactive Particles in the Air Optimal Radiation Protection

Radioactive decay is not a uniform process: Iodine and cesium emit their dangerous energy in different ways. In order to develop optimal radiation protection measures for humans and animals, scientists must first determine which radioactive materials are in the air. A new instrument developed at the University of Freiburg is capable of doing this—and is now being installed by the German Federal Authority for Radiation Protection.


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( © Alex White /


Radiation is dangerous and our senses cannot detect it until it is much too late. Radioactivity is created in complex processes of decay that must be measured very precisely. The recent events in Japan demonstrate how important it is to be able to differentiate between various radioactive materials in the air, isotopes such as iodine or cesium. Radioactive isotopes from Fukushima will be blown to Germany by the wind—albeit in much smaller concentrations than in Japan—and there are no generally accepted rules on how to protect humans and animals from these various types of materials in the long term: The radioactive energy released by iodine is stronger and thus more dangerous, but it exists only for a short period of time. Cesium, on the other hand, is less dangerous than iodine but emits dangerous energy for a longer period of time. Conventional measuring instruments only indicate whether there is radioactivity in the air over Germany at all, and if so in what intensity. It is not possible to use them to differentiate between different kinds of radioactive materials.

  • Measuring Instruments as Protection against Radioactive Materials

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The Bundesamt für Strahlenschutz publishes the radioactivity measured in Germany on a daily basis  (Grafik: Bundesamt für Strahlenschutz)
A research group at the University of Freiburg is now trying to find a way to better protect humans and animals against radiation: The Detector Technology Service Group at the Freiburg Materials Research Center (FMF), led by Michael Fiederle, is working on detector systems capable of making precisely this differentiation. In a joint research project with the German Federal Authority for Radiation Protection, the group is developing sensors and the electronics to run them, the Gamma Ray MultiChannelAnalyzer (GMCA). The efficient sensors and the GMCA can be built into compact systems and operated as self-contained units.
  • Nationwide Network of Measuring Sensors

The systems are to be deployed in the nationwide radiation monitoring network operated by the Federal Authority for Radiation Protection. The measuring sensors in this so-called local dose rate monitoring network identify the intensity of radiation at various points throughout Germany. In the current phase of the network, it is possible to view the current dose rate of gamma rays, a particular form of radioactivity with a very long range, on the Internet at However, although the current sensors at the measuring stations can measure the dose, they cannot not identify the radioactive products.

  • New Devices Being Put into Operation

The Federal Authority for Radiation Protection now plans to equip the measuring stations with sensors and electronics from the FMF in order to improve the performance of its local dose rate network and enable potential protective measures to be initiated immediately. The sensors have special characteristics that enable them to identify radioactive substances in combination with the GMCA. Not only do they measure radioactive decay in the manner of a Geiger counter, they also register the type of decay on the basis of its energy. Since each type of radioactive decay emits a characteristic form of energy, it is possible to identify the material emitting it, for instance radioactive iodine or cesium.

  • Development to Production

The detector systems developed by the research group are currently undergoing extensive tests on Schauinsland in the Black Forest, where the Federal Authority for Radiation Protection is determining how precisely they can detect and identify radiation. Following this test phase, the agency plans to install the systems at measuring stations throughout Germany. After all, radioactive isotopes can remain in the air for a long time—and it is important to develop optimal, individual protective measures for the long term. The systems are being produced by a start-up company of the FMF, X-Ray Imaging Europe XIE GmbH.



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Dr. Michael Fiederle

Michael Fiederle has served as director of the Material Characterization & Detector Technology Service Group at the Freiburg Materials Research Center (FMF) since 2002. His areas of scientific work include the production of semiconductor material and the development of radiation detectors on the basis of CdTe and CdZnTe. In 2006 Fiederle won the “Innovative Medical Technology” competition organized by the German Federal Ministry of Education and Research. In 2010 he received the “Room Temperature Semiconductor Detectors RTSD Scientist Award” at a conference in the USA.


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