|
Sci Tech
T-rays
QUESTION: What are T-rays?
K. Chaitu, Madurai, T.N.
ANSWER 1: It is an innovative imaging system that uses optics and electronics to `see' the composition of objects — just as X-rays `see through' materials to reveal denser elements inside. They can show, for example, how much fat is in a slice of bacon, how much water is in a leaf, and whether a package holds a banana or a bomb — without touching it. The technique uses `T-rays' — terahertz (trillion-cycle-per-second) electromagnetic pulses — and differentiates between various materials, chemical compositions, or environments.
The technology has a variety of potential applications, from biomedical imaging of tissue to chemical-reaction analysis, environmental and pollution control, materials inspection, fault detection, profiling of doping and defects in semiconductors, and packaging inspection.
Researchers used laser pulses each lasting only 100 femtoseconds (one tenth of a trillionth of a second) to generate, detect, and measure electromagnetic pulses — T-rays — each lasting a picosecond (a trillionth of a second).
They transmitted the T-rays through various objects, using an imaging system of lenses and mirrors to focus the signals and to analyse changes in T-rays as they passed through objects.
They characterised the materials by measuring the amounts of distortion — from absorption, dispersion and reflection — of the T-rays passing through to a detector. Those going through the lean portions of a slice of bacon, for example, are distorted into a different waveform than are those passing through the fatty portions.
A digital signal processing unit processes the data and translates it into images that appear on a computer screen. The image of a slice of bacon shows different levels of T-ray transparency for lean and fatty areas. Since fat absorbs almost no T-rays, it looks white; meat absorbs roughly 25 times as many T-rays, so it looks dark. The digital signal processor was programmed to recognise characteristic shapes of transmitted waveforms and identify particular material at the spot illuminated by the T-ray beam. This information was obtained for each point on the object.
The technique is notable as it can distinguish between different chemical compositions inside a material even when the object looks uniform in visible light. Also, most plastics are transparent to T-rays,so it can `see' inside plastic packaging.
The Hindu S&T desk
ANSWER 2: Terahertz rays are electromagnetic pulses which has a frequency in the Terahertz range. Hence called as T-rays. One Terahertz (THz) has a frequency of 10{+1}{+2} (one thousand billion hertz), a frequency range which places T-rays between microwaves and infrared radiation in the electromagnetic family.
There are two main methods of producing T-rays, _ the Free Electron Laser and down conversion of pulses from visible lasers. Although worldwide study of T-rays is in its infancy, it has the potential for many applications not only to complement X-rays but also in certain circumstances, replace them.For ex, T-rays can detect different substances with great sensitivity (in ways X-rays, MRI and Infrared Lasers cannot), an ability that has strong significance for medical, agricultural, food and wine industries. They also are not cancerous, unlike X-rays. Plastics are transparent to T-rays, which gives many security applications. They are non-ionising, which means they do not cause cell damage like X-rays or even UV light.
S.Devashankar, Chennai
Printer friendly
page
Send this article to Friends by
E-Mail
Sci Tech
|
