Checking people at airports -- with terahertz...( This press release is available in...)

This press release is available in German.

Within the last few years the number of transport checks above all at airports has been increased considerably. A worthwhile effort as, after all, it concerns the protection of passengers. Possibilities for new and safe methods of transport checks are offered by terahertz radiation. Before this radiation can be used for this purpose, however, it has to be measured quantitatively, so that damage to health caused by radiation can be ruled out. The exact measurement of this type of radiation has now been successfully undertaken by the Physikalisch-Technische Bundesanstalt (PTB), the German national metrology institute, for the first time.

Radiation in the THz range (with wavelengths from 30 m to 3000 m and frequencies from 0.1 THz to 10 THz) penetrates clothing and many other organic materials and furthermore offers spectroscopic information on safety-relevant materials such as explosives and pharmacological substances. The broad spectrum of the possible applications extends from security check to the investigation of the spatial and/or time structure of the electron packages in the storage rings for synchrotron radiation production and in free-electron lasers, for which the receivers of the German Electron Synchrotron DESY characterized here are used.

The complete information on the THz spectra can only be determined with detectors of known spectral responsivity. Up to now, the integral responsivity of the respective detectors and their spectral distribution are still largely unknown. The PTB has now for the first time determined the spectral responsivities of two THz detectors in the wavelength range from 50 m to 600 m with the aid of cavity radiators.

In order to make available spectral radiation fluxes in the THz range, calculable according to Planck's radiation law, the PTB uses two THz
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