IMTS: Real-time layer thickness measurement with terahertz

Fraunhofer HHI researchers have integrated the first continuous-wave terahertz spectrometer for real-time material testing into a compact housing.

Anne Rommel

https://idw-online.de/de/news701431

Terahertz is a key technology for non-destructive material testing. Major advantages are examinations without physical contact and the analysis of complex systems with a low contrast range, in which established methods like ultrasonic usually fail. The Fraunhofer Heinrich Hertz Institute HHI has successfully developed a cost-efficient and compact measurement system that conducts real-time measurements of the thickness of multi-layer systems for the first time, an essential technology e.g. for lacquering lines. The new terahertz measurement system T-Sweeper will be presented live at the IMTS from September 10th to 15th, 2018 (Fraunhofer booth 121815, East Building).

Terahertz radiation was already a major topic a good ten years ago, in connection with body scanners for inspecting passengers during airport security screening. Terahertz radiation was also to be used in measurement systems for material testing and inspec-tion of components. However, in spite of high expectations the breakthrough for te-rahertz technology took a long time. Compared to classical methods for non-destructive material testing today, such as X-ray radiation and ultrasonic, terahertz was long con-sidered simply too expensive. In recent years however, great progress has been made: An increasing number of systems has been introduced with designs based on standard components, making them significantly more economical to build. These developments are already raising the interest of potential users. System costs certainly will have to be cut further and the complexity of the systems will have to be reduced before terahertz technologies are established as an instrument in industrial process monitoring.
Cost-efficient and in real-time

Current developments at the Fraunhofer HHI could mean a considerable boost for the terahertz technology. A research team led by Björn Globisch, head of the terahertz re-search group at Fraunhofer HHI, has successfully developed a measuring device that replaces the previously used femtosecond pulse laser with compact continuous-wave laser technology. The fact that this continuous-wave measurement system is capable of eight measurements per second is key to allow real-time measurements without the use of a pulsed laser for the first time. The scientists will present this terahertz measurement system at the Hannover Messe trade fair and will give a live demonstration of non-contact layer thickness measurement for various multi-layer systems.

The principle employed by the Fraunhofer HHI to generate terahertz radiation is based on an optoelectronic process. Using a special semiconductor component, the beat of two continuous-wave lasers is converted into terahertz radiation, which corresponds exactly to the difference frequency of the two lasers.

The lack of significant success of terahertz technology in the past is largely due to the properties of the semiconductors used. These properties could initially only be achieved with materials that required illumination at a wavelength of 800 nanometers. This ra-ther exotic wavelength means both the lasers and the optical components of the te-rahertz system are much too expensive and not robust enough for industrial applica-tions.

Widespread wavelength Standard

"This is why we developed a semiconductor that can be excited by laser light at a wave-length of 1.5 micrometers," explains Globisch. "This matches the wavelength standard in optical telecommunications technologies, which means there are plenty of cost-effective and high-quality optical components and lasers available." On the way to a competitively viable terahertz system for material testing, however, another obstacle had to be overcome: The pulse laser, on which all conventional real-time capable te-rahertz systems are based, is a decisive cost factor in existing systems. Femtosecond lasers are not only technologically complicated and expensive on their own, terahertz spectrometers using pulsed lasers require additional optomechanical components that have to be precisely produced and adjusted in highly complex procedures.

One alternative is continuous-wave spectroscopy, in which continuous-wave radiation is generated instead of a terahertz pulse. Two continuous-wave laser sources are mixed and their beat signal is converted into terahertz radiation in a special semiconductor device. The wavelength of the terahertz radiation generated can be easily modified by changing the relationship of the laser wavelengths to one another. Continuous-wave systems have two decisive advantages compared to pulsed terahertz systems: First, the laser sources themselves are more compact and less expensive; second, no optome-chanical components are needed in order to operate the system.

Continuous-wave terahertz systems are already available, but they need periods ranging from several seconds to a matter of minutes to capture a measured signal. In contrast, industrial applications often operate like this: In the production, a robot arm moves over measurement points on painted/coated components and measures the coating thick-ness. Since the production cycle has to be maintained, there is only little time per meas-uring point. Until now, the measurement speed of continuous-wave terahertz systems was too slow to be viable in non-destructive testing applications.

Fraunhofer HHI has solved this problem using lasers that can be adjusted extremely fast (Finisar® WaveSource™) and by modifying electronics, data capture and algorithms to accommodate the high speeds required. This combination has increased measurement speeds by a factor of 160 compared to previous systems. This has made it possible for the first time to conduct material testing in real-time with continuous-wave terahertz systems. This system will be presented at the Hannover Messe trade fair in a live demonstration.

Application example: layer thickness measurement

Inspection of paints and coatings is an important application of non-contact terahertz measurement technologies. Here, layer thickness measurement makes up a significant part of quality assurance and production monitoring. Thus, for example, minimum thickness is ensured, consumption of resources is optimized by reducing the amount of excess material used and subsequent rectifications are avoided. Today, manual eddy current devices can be used with metallic substrates such as automotive sheet metal. This method however, fails on poorly conductive fiber-reinforced composites. Ultra-sound finds application in this context, but at the costs of mechanical contact. "There is a substantial need for a reliable measurement technique," says Globisch, "because the market for fiber-reinforced composites is growing in the automotive, aeronautics and wind power sectors." This is where the major advantage of the terahertz technology lies: Measurements are non-destructive and contactless, so that even coatings that are not completely dried can be measured as well. In addition, the quality of the results is not dependent on temperature and multi-layer systems can be directly resolved. Finally, terahertz radiation is non-ionizing and not harmful to humans due to its low power.

Although the new terahertz measurement system can be built using cost-effective standard optical components, it is currently even more expensive than for example ul-trasonic devices, which are manufactured in quantities of several hundreds of thou-sands. "However, the prices will become similar with future series production," Glo-bisch predicts. The advantages of the measurement technique and the current progress have convinced the researcher that the terahertz method will establish itself as a meas-urement technique for non-destructive material testing in the years to come.

Extending terahertz technology to obtain highly accurate thickness of automotive paint

http://phys.org/news/2016-07-terahertz-technology-highly-accurate-thickness.html

Now automotive body paint jobs get a major boost from the rapidly emerging field of terahertz (THz) technology used to improve the precision and quality control of layered paint coatings.

In a novel approach to industrial applications of THz technology, a team of German researchers began from the principle that thicknesses of multi-layered paint coatings can be measured using time-of-flight measurements of ultrashort THz pulses. The model they developed obtained a new level of precision in measuring individual coating layers. Their report appears in the current issue of Applied Physics Letters.

Developed by a team of investigators from the University of Kaiserslautern and Fraunhofer Institute for Physical Measurement Techniques in Kaiserslautern, the algorithm-informed computer model resolves individual paint layer thicknesses within multilayered paint samples well below ten microns—seven microns is typical—and down to four microns under certain constraints. A micron—also called a micrometer—is one thousand times smaller than a millimeter, many times smaller than the diameter of a human hair.

"By introducing an advanced regression procedure with a self-calibration model, our approach presents a framework that takes into consideration real industrial challenges such as the effect of wet-on-wet spray in the painting process. This is important because the multi-layer car coating process is complex, and a new approach is needed to improve vehicle paint quality control," explained René Beigang, the study's lead researcher.

THz technology uses non-ionizing radiation that occurs on the electromagnetic spectrum between microwave energy and infrared light waves, with frequency ranges from 0.3 THz to 10 THz. Invisible to the unaided eye, THz energy is considered non-destructive and non-invasive, and has many desirable analytical and industrial properties. It penetrates a variety of non-conducting materials and passes through common materials such as clothing, plastic, wood and paper. Excitement over its potential in a range of disciplines is rapidly building as teams race to harness it for uses as diverse as medical imaging to airport security checks.

The gist of their work is this: The time trace of a typical reflected pulse shows that there is a reflection from the front surface and substrate, as well as from each interface between different paint layers. From the time delay between consecutive reflected pulses the thickness of the layer can be deduced.

"By scanning the THz beam across the sample a 2-D image of the layer thicknesses of each individual layer can be obtained," Beigang explained.

He added that conventional approaches for automotive paint thickness measurements are limited due to the complexity of the multi-step painting process. Typically, five layers of thin coatings, including zinc phosphate, e-coat, primer or filler, basecoat and clearcoat, are deposited on the vehicle surface.

"New possibilities to overcome these restrictions have been shown by terahertz radiation," he said.

Results show this new approach is suitable to measure individual paint coatings on a variety of materials. These include metallic substrates, carbon-fiber-reinforced polymers, and on dielectric substrates—all with high accuracy.

"We believe our results with terahertz waves show we have successfully managed them to develop an extremely precise approach to help improve an industrial process involving multi-layered automotive paints," said Beigang.

Explore further: Broadband THz wave generation with metamaterials demonstrated

More information: Highly accurate thickness measurement of multi-layered automotive paints using terahertz technology, Applied Physics Letters, DOI: 10.1063/1.4955407

Terahertz technology reaches industrial maturity

http://www.fraunhofer.de/en/press/research-news/2016/april/terahertz-technology.html

Terahertz is a new technology in which nondestructive testing of components and surfaces is possible. Until now, these devices and, in particular, the sensor heads have been expensive and unwieldy. Researchers at Fraunhofer have now succeeded in making sensor heads more compact and, thus, cheaper, which facilitates their handling considerably. First prototypes are already being used for the production of plastic pipes. They are also very well suited for analyzing coatings of fiber composites. From April 25 to 29, 2016, these new sensor heads are being presented at the Hannover Messe (Hall 2, Stand C16/C22).

© Photo Fraunhofer HHI

The researchers at Fraunhofer have packaged the transmitting and receiving unit for terahertz radiation into a handy little sensor head with a diameter of only 25 and a length of 35 millimeters

The researchers at Fraunhofer have packaged the transmitting and receiving unit for terahertz radiation into a handy little sensor head with a diameter of only 25 and a length of 35 millimeters.

More than ten years ago, terahertz technology was the next big thing. Back then there was a lot of talk about ‚nude‘ body scanners. People thought that the devices that were being installed at airports were going to make revealing images of passengers. Moreover, scientists were hoping to develop measurement systems for material testing and inspection of components using terahertz radiation. Despite all these great expectations, the long-awaited breakthrough for terahertz technology did not come about. Compared to the conventional methods currently used for non-destructive testing, such as X-ray or ultrasound, terahertz technology is simply too expensive, unwieldy and overall impractical.

Measuring system with the innovative sensor head

The latest developments of the Fraunhofer Institute for Telecommunication, Heinrich Hertz Institut, HHI in Berlin, could now give terahertz technology a decisive boost. The research team of Thorsten Göbel, who heads the Terahertz Research Group at HHI, has succeeded in developing terahertz devices that for the first time are made from standard and therefore low-cost components and are also relatively easy to handle. At the Hannover Messe, the experts will be presenting a terahertz measuring system with an innovative sensor head, which allows easy testing of various components, such as plastic tubes. The principle employed by Fraunhofer HHI for generating terahertz radiation is based on an optoelectronic method. Using a special semiconductor, laser light pulses are converted into electrical terahertz pulses that are only one billionth of a second long.

The reason for the lack of success of the terahertz technology until now is mainly due to the required properties of the semiconductors being used. These could only be achieved with materials that required an illumination with a wavelength of 800 nanometers. Both the terahertz system‘s laser and optical components are too expensive and not robust enough for industrial use when using this rather exotic wavelength.

Commonly used wavelength standard

“Therefore, we have developed a semiconductor that can be stimulated with a laser light centered around a wavelength of 1.5 micrometers,” says Göbel. “In optical communications, this wavelength is standard, which is why there is large number of inexpensive and high-quality optical components and lasers on the market.”

However, one obstacle needed to be overcome on the way to creating an affordable and handy terahertz system for testing materials. Until now, the sensor head for scanning components was too big and heavy for easy handling. The reason: the terahertz transmitter and the receiver were two separate components that had to be mounted in a casing with great effort and precision. The main disadvantage of this arrangement was that samples can only be measured at an angle. Therefore, the object had to be exactly in focus of the transmitter and receiver so that the terahertz signal sent from the transmitter via the sample could be displayed on the receiver. If the distance between the sensor head and the sample changes, for example due to vibrations, it becomes more difficult to measure.

The Fraunhofer HHI experts have solved this problem by manufacturing an integrated chip that can transmit and receive simultaneously. Now it is possible to use a single optical lens that focuses on the object, which allows for a flexible operating distance. The researchers packed this transmitting and receiving unit, the transceiver, into a handy little sensor head with a diameter of only 25 and a length of 35 millimeter. The device will be presented at the Hannover trade fair.

Moreover, these terahertz sensor system prototypes have been in use by manufacturers of plastic pipes for some time now. These sensors are directly used in the production line to monitor the thickness of the pipe walls. If the walls are too thin, the pipe becomes unstable. If they are too thick, valuable plastic is wasted. Up to now, the production of plastic pipes has been monitored using an ultrasound system. Since ultrasound cannot measure correctly in the air, water is needed. Similarly to the ultrasound gel doctors use, the water works as a coupling medium between the ultrasound sensor head and the pipe. Therefore, the nearly 250-degree Celsius pipes must be dragged through a water tank. In addition, the ultrasound technology also fails with so-called intelligent pipes that are constructed from a wide-range of layers of different materials.

Another future application is the verification of paints and coatings on fiber reinforced composite materials. Today, it is possible to use handy eddy current equipment on metallic substrates, such as sheet metal for the automotive industry. However, this method fails on poorly conducting fiber composites. “The need for a reliable measurement process is enormous,” says Göbel, “because the market for composite materials is growing in the automotive, aircraft and wind energy industries.”

Although the new terahertz sensor system is constructed from inexpensive standard optical components, it is currently more expensive than, for example, ultrasonic devices, which are manufactured in quantities of many hundreds of thousands. “However, the price will drop in the future when volume production starts picking up,” Göbel predicts. Given the advantages of the measuring method and the current advances, Göbel believes that the terahertz method will be successfully established in the coming years

Inspecting letters with terahertz waves

The prize-winning team presents terahertz scanner for the secure identification: Professor René Beigang and Thorsten Sprenger (from left to right). Credit: Dirk Mahler/Fraunhofer

http://phys.org/news/2014-05-letters-terahertz.html#jCp

Is it a harmless parcel or a bomb, an innocent letter or a drug shipment? A new terahertz scanner is capable of detecting illicit drugs and explosives sent by post without having to open suspicious packages or envelopes

Alert at Schloss Bellevue. A suspicious letter addressed to German President Joachim Gauck has been detected, which might contain a bomb. Not willing to take any risks, the bomb squad is called out to destroy the package. Later investigations revealed that the envelope did not contain any explosives, but better safe than sorry. A year ago, this event created turmoil in the mail sorting office in Berlin, because at the time there was no safe and simple way of reliably detecting the presence of explosives or drugs in letters and small packets. A new solution is offered by the terahertz scanner developed by researchers at the Fraunhofer Institute for Physical Measurement Techniques IPM in Kaiserslautern in collaboration with Hübner GmbH & Co. KG in Kassel. Their T-COGNITION system is capable of detecting and identifying the hidden content of suspicious packages or envelopes without having to open them. One of this year's Joseph von Fraunhofer prizes was awarded to Prof. Dr. René Beigang of Fraunhofer IPM and Dipl.-Ing. Thorsten Sprenger, Head of Public Security and Photonics at Hübner, for their work on the terahertz scanner for the secure identification of hazardous materials and illicit drugs in postal consignments.

But why did the scientists choose to use terahertz waves for this application? Professor René Beigang explains: "The terahertz range lies midway between microwave and infrared in the electromagnetic spectrum, and thus combines the advantages of both." Like microwaves, these low-energy frequencies can easily penetrate paper, wood, lightweight fabrics, plastics, and ceramics. Moreover, terahertz waves generate characteristic spectra depending on the type of material they travel through, which can be analyzed quickly using intelligent software. A further significant advantage is that terahertz waves are non-ionizing and therefore safe to use in an unprotected environment, unlike X-rays. This makes the technology an interesting option for use in mail scanners.

Scaling up terahertz technology for industrial applications

Terahertz technology is still in its infancy, and until now it has found relatively few applications. The department of Material Characterization and Testing at the University of Kaiserslautern, sponsored jointly by Fraunhofer IPM and the Land of Rheinland-Pfalz, hopes to change this situation. "Our goal is to scale up terahertz technology and extend its range of use to include security applications," says Beigang. The engineers at Hübner were among the first to recognize the potential of the Fraunhofer researchers' work. The company's traditional line of business is manufacturing key components for the transportation industry (e.g. rail vehicles, buses, airport technology, automotive). A new division for public security was added in 2006, when the company first started to look for cooperation partners. The mail scanner project was launched four years later, based on previous joint development projects. In the meantime, the company has brought its T-COGNITION solution onto the market.

This is how the mail scanner works. Suspicious envelopes and packages are fed into the scanner on a retractable tray. They are then exposed to terahertz waves which are absorbed at different frequencies within the spectral range depending on the substance they travel through (characteristic absorption properties). Detectors at the output of the scanner record the transmitted wavelengths. "Within a few seconds, T-COGNITION produces a spectroscopic fingerprint that allows the detected hazardous material to be compared with database samples and definitively identified," says Thorsten Sprenger.

The system triggers an alarm if the consignment contains explosives or illicit drugs.The system is capable of examining the content of postal items up to C4 format with a thickness of up to two centimeters. Sprenger says: "It is the ideal mailroom solution for prisons, customs offices, government agencies, company headquarters, and embassies or consulates, because it helps to improve security and protect human lives."

T-COGNITION recently received the PrismAward, the equivalent of an Oscar in the photonics world, at the Photonics West 2014 international congress in San Francisco.

 Explore further: Nonlinear optical materials convert terahertz radiation into infrared light

Award-winning Letter Bomb Detector

FREIBURG and KASSEL, Germany, May 21, 2014 /NEWS.GNOM.ES/ –

http://news.gnom.es/pr/award-winning-letter-bomb-detector

- Thorsten Sprenger from Hübner GmbH and René Beigang from the Fraunhofer Institute for Physical Measurement Techniques receive the Joseph von Fraunhofer Prize 2014

Spotting letters and parcels containing explosives has just gotten easier thanks to the T-COGNITION system from Hübner GmbH, a global company headquartered in Kassel, Germany. The system uses terahertz technology to detect illegal substances without having to open the mail item. At today’s Fraunhofer-Gesellschaft Annual Meeting,Thorsten Sprenger and René Beigang were presented with this year’s Joseph von Fraunhofer Prize for their terahertz system for detecting dangerous substances such as explosives and narcotics.

Thorsten Sprenger heads Hübner’s Public Security and Photonics unit. The German company has been manufacturing components and systems for the transportation industry since 1946, adding security technologies to its portfolio in 2005. The collaboration with René Beigang from the Fraunhofer Institute for Physical Measurement Techniques in Kaiserslautern, Germany, was launched in 2006 with a feasibility study on the non-contact identification of hazardous materials using terahertz technology. Hübner has since developed a range of products for various applications

T-COGNITION is easy to operate. After being placed in the machine’s tray, the postal item is penetrated with terahertz waves of various frequencies, which are absorbed depending on the contents of the item. Every substance has its own unique absorption spectrum. This “fingerprint” is captured by the device and compared with referential spectrums in a database. An alarm sounds when a listed dangerous substance is identified. An important fact: terahertz waves are not harmful to humans.

The T-COGNITION system can enhance the work and safety in the police force, customs controls and prisons. It can also be used to protect prominent individuals. Hübner’s new product is designed to supplement, not replace, conventional x-ray scans. Postal items identified as potentially dangerous during a preliminary inspection by x-ray or by the Hübner Terahertz Imager T-SENSE can be examined by T-CONGNITION for a final check.  

The Oscar of the photonics industry

The Joseph von Fraunhofer Prize is not the first for Hübner’s innovation. Its T-COGNITION and the revolutionary C-WAVE – a technology for tunable laser light frequencies, were recognized at the Photonics West 2014 trade fair with the Prism Award, the Oscar of the photonics sector.

Contact:
Stefanie Schürmann
HÜBNER GmbH & Co. KG
Tel.:  +49-561-998-1930
Fax:  +49-561-998-1819
 stefanie.schuermann@hubner-germany.com

http://www.hubner-germany.com

http://www.publicsecurity.de

http://www.hubner-photonics.com

SOURCE HUEBNER GmbH & Co. KG

Terahertz Spectrometer Reliably Identifies Explosives and Narcotics in Mail Pieces

Published on January 2, 2014 at 6:12 AM

http://www.azooptics.com/News.aspx?newsID=18408

Does that incoming postal dispatch hold merely a harmless letter – or a bomb? Does it possibly contain drugs? T-COGNITION, the terahertz spectrometer helps to swiftly clear-up the question. This analytical device reliably identifies explosives and narcotics in mail pieces, and is primarily suited for use at embassies, public offices and correctional facilities.

Letters can be pushed through an input lid into the spectrometer. These are then exposed on the inside to terahertz waves. Detectors collect the reflected and transmitted waves, and compare the spectra with those on a database. Within a few seconds, the data points light up either red or green on the screen of the device – depending on whether any hazardous substances were detected or not. The use of the technology has multiple advantages: Terahertz waves that lie within the electromagnetic spectrum between infrared and microwave are not dangerous, penetrate packaging materials and produce – depen- ding on what kind of materials they hit – characteristic spectra that can be swiftly analyzed with the aid of intelligent software.

T-COGNITION is the result of a research collaboration between the Fraunhofer Institute for Physical Measurement Techniques IPM in Kaiserslautern and the Kassel-based Hübner GmbH Co. KG that has since brought the Terahertz spectrometer on the market. The antennas on the inside of the compact device (60 x 72 x 73 centimeters) were engineered jointly by researchers at IPM and the Carnot Institute IEMN (Institut d’Electronique, Microélectronique et de Nanotechnologies) in Lille.

Fraunhofer Institute for Physical Measurement Techniques IPM
Erwin-Schrödinger-Straße / Geb. 56 | 67663 Kaiserslautern | www.ipm.fraunhofer.de
Contact: Dr. Joachim Jonuscheit | Phone +49 631 205-5107 |joachim.jonuscheit@ipm.fraunhofer.de
Press: Holger Kock | Phone +49 761 8857-129 | holger.kock@ipm.fraunhofer.de

Source: http://www.fraunhofer.de/

Detective Work using Terahertz

http://www.fraunhofer.de/en/press/research-news/2012/november/detective-work-using-terahertz-radiation.html

It was a special moment for Michael Panzner of the Fraunhofer Institute for Material and Beam Technology IWS in Dresden, Germany and his partners: in the Dresden Hygiene Museum the scientists were examining a wall picture by Gerhard Richter that had been believed lost long ago. Shortly before leaving the German Democratic Republic the artist had left it behind as a journeyman's project. Then, in the 1960s, it was unceremoniously painted over. However, instead of being interested in the picture, Panzer was far more interested in the new detector which was being used for the first time here. Using it, the scientists gained important information about the layered structure of the wall and the structure of the picture area being examined. The joint project was sponsored by IWS, the Academy of Fine Arts Dresden [Hochschule für bildende Künste Dresden (HFBK)], the Research Institute for Monument Conservation and Archeometry [Forschungsinstitut für Denkmalpflege und Archäometrie (FIDA)] and the Technical University Dresden through the German Federal Ministry of Education and Research BMBF.

According to Panzer, the special thing about the terahertz (THz) scanner is that „In comparison with traditional processes, such as X-ray scanners, it works without causing any damage whatsoever. In addition, it does not require a special permit, as in the case of harmful X-rays. This is because the scanner only generates a radiated power of less than 1 µW. For comparison: under less than ideal conditions, cell phones emit up to 2 Watts. Furthermore the process, provides concrete data on the structure of the individual layers or of potential hollow areas. In this way the device also indicated in the Hygiene Museum that in one area the plaster on the wall had evidently been repaired - a valuable clue for the restorer.

The scientists used short electromagnetic pulses that penetrate the various materials almost without attenuation, whereby some materials display characteristic absorption lines, which can be used to identify them clearly. In previous tests, however, the system had reached its limits, for example with behind-the-wall paintings on uneven, very structured walls. For this reason the scientists at IWS continued to develop the detector head by modifying the THz optics together with the Fraunhofer Institute for Physical Measurement Techniques IPM. The application spectrum of the scanner was also expanded.

Caution, contaminated art

Currently, many museums cannot present valuable exhibits to the public because they are contaminated with biocides. The reason for this is that in the 1970s, with the best of intentions, antique textiles or wood sculptures were sprayed with pesticides to keep them from being destroyed. Today it is known that these agents are hazardous to health and a number of different measurement and decontamination processes are being tested. IWS, together with further partners, now wants to set up a project with the aim examining the possibilities and limits of the THz technology for organic biocides. „In contrast to the current X-ray fluorescence analysis which works on an element-selective basis, THz scanners recognize substances on the basis of the molecular bonding structure. Organic biocides, in particular, could be differentiated in such a manner," explains Michael Panzner.

To date, such expensive examinations are often only possible in well-equipped laboratories. In the future the tests are to be feasible on-site using a mobile scanner. However, a more research is still required until small, portable devices are available that are suitable for such purposes. Above all, close communication and cooperation with restorers and monument preservationists is required for the continued technological improvement of the THz measurement system. Panzner and his team are also hoping for a lively exchange at the European trade fair for monument preservation, restoration and refurbishment of old buildings, the denkmal, in Leipzig, Germany, where they will be exhibiting the new THz scanner generation in Hall 2, stand H30, from November 22 - 24, 2012.

Fraunhofer Institute Using Terahertz waves: small structures for high frequencies

http://www.mikroelektronik.fraunhofer.de/en/press-media/microelectronics-news/article/terahertz-wellen-kleinste-strukturen-fuer-hoechste-frequenzen.html

Ultrafast data transmission, detection of concealed weapons, or diagnosis of diseases – the range of potential applications for terahertz waves is enormous. Around the world, science and industry are working on developing electronic circuits for this previously largely unused spectral range. Fraunhofer IAF has set a European record by attaining a frequency of 0.66 THz.

Integrated circuit with ultrafast transistors: thanks to a gate length of only 20 nm, IAF was able to achieve a record frequency of 0.66 THz.
Photo: Fraunhofer IAF

Terahertz technology could make the search for people in a burning building much simpler. Photo: fotolia.de / Benjamin Nolte

Flames leap from the building and black smoke is rising. The fire department is already on the scene to fight the fire in the apartment building. Is anyone still inside? The heavy smoke makes it difficult to see and search for survivors. Terahertz technology, however, could make it much easier in the future for rescue teams to find people in burning buildings. Terahertz waves can penetrate smoke, dust, fog, and clothing – even from several hundred meters away. The electromagnetic waves are absorbed to different degrees by different materials, and do not damage the material. In combination with imaging techniques, an individual profile can be generated: a person can be detected reliably despite thick smoke.

Terahertz frequencies have great potential

The potential of the high-frequency range lies not only in rescue operations. Security personnel can discreetly detect persons carrying concealed weapons, even in a large crowd. Terahertz waves can be used to transmit large quantities of data over short ranges many times faster than is currently possible. Doctors can also see new possibilities in the diagnosis of diseases. The varied potential applications are one of the main reasons why science and industry are interested in opening up the high-frequency spectral range. The terahertz range – with frequencies of between 300 GHz and 3 THz and wavelengths of less than 1 mm and greater than 100 μm – lies on the electromagnetic spectrum between infrared and microwave. For a long time, terahertz waves were largely off-limits, because it was not technologically possible to manufacture electronic circuits that could use them. Transistors with high electron mobility and system architectures with many transmitting and receiving channels are needed to make use of the high-frequency range.

European record at Fraunhofer IAF

Researchers at the Fraunhofer Institute for Applied Solid State Physics IAF were the first in Europe to achieve a cutoff frequency of 0.66 THz. The record was attained using transistors made of III/V semiconductor structures (InGaAs/InAlAs) that give electrons an enormous drift speed. In conjunction with a transistor gate length of only 20 nm (approximately the length of a chain of 100 atoms), this made such high frequencies possible. Fraunhofer IAF in Freiburg is working closely in this field with the electronics company Sony Germany GmbH. “Over the next few years, we will work with our industrial partner to break the 1 THz barrier,” states Institute director Prof. Dr. Oliver Ambacher with confidence. In addition to the advantage of a high bandwidth, integrated circuits with fast transformers are of a very small size and have low energy consumption. Because they are also low-noise devices, they form the ideal technological basis for future terahertz systems. The technology is not yet mature enough to take advantage of the potential of high frequencies. The fire-fighter using a hand-held terahertz camera to find people in a burning house is still just a vision. But one that is moving closer.

Contact:

Sonja Kriependorf
Phone +49 761 5159-450
sonja.kriependorf(at)iaf.fraunhofer.de

Fraunhofer Institute for Applied Solid

On the safe side: Contact-free analysis of chemical substances

http://www.sciencecodex.com/on_the_safe_side_contactfree_analysis_of_chemical_substances-89720

December 2011: Security forces intercept a letter bomb addressed to Josef Ackermann, the head of Deutsche Bank. At almost the same moment, a letter bomb explodes in an office in Rome. The hand of the manager in charge of Equitalia, the tax-collection authority, was injured. Until now, police officers or security staff have had to conduct painstaking inspections of any suspicious parcels and letters by hand - an error-prone approach. At the end of 2011, though, the scanner T-Cognition 1.0 from Hübner company of Kassel, Germany, went on the market. The device, developed with the assistance of Fraunhofer researchers, detects, without contact, substances such as drugs or explosives contained in unopened letters or flat packages. The partners will be demonstrating the scanner at the Analytica trade fair in Munich (April 17-19) at the joint Fraunhofer stand (Stand 433/530 in Hall A1).

„You place the suspicious parcels or letters in a kind of drawer, and the device uses terahertz waves to determine whether it contains explosives. This protects confidentiality, and the mail can then be delivered safely," explains Dr. Joachim Jonuscheit, deputy division director at the Kaiserslautern facility of the Fraunhofer Institute for Physical Measurement Techniques IPM and the researcher in charge of terahertz analysis there. The attacks in Rome and Frankfurt fueled the security industry's interest in the analysis device.

„Most dielectric materials, such as plastics, clothing or paper, are transparent to microwaves and can also be penetrated by terahertz waves with comparatively low reduction. For non-destructive non-destructive testing, the terahertz range is extremely interesting," the expert adds. On the electromagnetic spectrum, terahertz waves can be found at the junction between microwaves and infrared radiation. The frequency range extends from 100 GHz to 10 THz; this corresponds to a wavelength from 3 mm to 30 µm. Terahertz waves combine the benefits of the adjoining spectral ranges: high penetration depth and low scatter, accompanied by good spatial resolution and the capability of spectral identification of unknown substances.

T-Cognition identifies chemicals, explosives or drugs, quickly and contact-free. A database comparison identifies any suspicious spectra and displays them on screen.

(Photo Credit: Huebner GmbH)

Like radiation in the infrared range, Terahertz waves reveal a substance's spectral signature. The measurement device features a database with the spectral „fingerprints" of hazardous materials and can be extended to include additional materials at any time. The device compares the spectral fingerprint of the substance to analyze with values in its database and returns a clear result. The scanner operates using transmission and reflection analysis. In safety checks, the terahertz wave offers low-loss penetration of envelopes made of paper or plastic to detect any chemical substances within. If a package contains, say, metal – as housing for an explosive device – the wave is reflected and measured by the receiver. This is how suspicious packages can be identified quickly.

Now the researchers also want to gain a foothold in the pharmaceuticals and chemicals industries. „Up until now, makers of pharmaceuticals had to prepare extra samples if they wanted to find out whether the mixture ratio in a particular drug was right, whether the chemical was in the desired crystalline structure, and whether quality was all right," Jonuscheit points out. „Depending on the substance and the material involved, our device clearly detects all of the chemicals found. It also provides basic analysis of the mixture ratio of multiple substances. Terahertz analysis also allows conclusions about the substances' crystalline structure. For instance, you can determine whether a potentially unwanted recrystallization has taken place. In the future, this can spare chemicals and pharmaceuticals manufacturers painstaking preliminary analysis and sample preparation," the expert points out.

Source: Fraunhofer-Gesellschaft