Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Checking people at airports – with terahertz radiation

18.09.2008
PTB succeeds in absolute measurement of terahertz radiation

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 checking people 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 µm to 3000 µm 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 µm to 600 µm 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 cavity radiators at different temperatures in connection with THz band and longwave-pass filters. The interior surfaces of the radiators are provided with a special coating which possesses a known and high emissivity also in the THz range and thus enables the calculability of the radiation incident on the detector. In order to obtain a sufficiently spectral purity of the THz radiation, a suppression of the infrared radiation of more than nine orders of magnitude is necessary.

By using an FT-IR spectrometer, the transmittance for all filter combinations used was accurately determined in the wavelength range from 0.8 µm to 1700 µm. Due to the calculable radiation of the cavity radiators and the known transmittance of the filters, it is possible to accurately determine the spectral radiation fluxes and thus determine the spectral absolute responsivities of THz receivers for the first time. Such absolutely characterized receivers will in future be utilized, e.g., both at the Metrology Light Source of the PTB to investigate the THz radiation produced there and in the investigation of the effect of THz radiation on the biological cell cycle.

PTB Contact:
Berndt Gutschwager,
E-Mail: berndt.gutschwager@ptb.de,
phone: +49 (30) 3481-7323

Imke Frischmuth | alfa
Further information:
http://www.ptb.de

More articles from Physics and Astronomy:

nachricht SF State astronomer searches for signs of life on Wolf 1061 exoplanet
20.01.2017 | San Francisco State University

nachricht Molecule flash mob
19.01.2017 | Technische Universität Wien

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>