Nano technology: how low can you go?

Forget the nano scale. DCU researchers developing free electron lasers measure the world on pico, femto and even atto scales

The measurement “pico” has an onomatopoeic ring to it. It sounds small. It is small. Not as small as its numerical subordinates though – femto, atto, zepto and yocto. These scales might be insignificant physically but in nano science, small is the new big.

It is reaching and identifying the world on these scales which makes all the difference in X-ray laser technology, an exciting branch of nanophysics where significant progress is being made in DCU. A “strategically focused collaboration” between researchers in Germany, Russia, the US and Ireland has led to the full characterisation of ultra short, ultra-intense X-ray pulses at free-electron lasers (FELs).

FELs bring together the benefits of X-ray and laser technology to create highly effective pulse measuring systems that offer exciting practical applications. “X-rays revolutionised many sectors over the last 100 years – medicine, industry and manufacturing techniques”, says DCU Professor John Costello. “Likewise lasers have radically improved many aspects of our lives.”

But, according to Costello, the technology behind X-rays has barely changed in terms of its design or use since being invented a century ago. “X-rays are produced in exactly the same way they were over 100 years ago by the guy who first made and used them – Wilhelm Conrad Röntgen ,” he says. “Basically you make an electron beam and fire it at a metal plate and the metal emits X-rays.”

Lasers were once described as a “tool looking for a solution”. Now you can’t get away from them: they’re used in TV and music systems, materials manufacture, welding, medicine, photodynamic therapy, etc.

But the “holy grail” has always been to make a usable X-ray laser system. The first attempts to build them began in the 1980s in big military labs in the US, UK and Japan, and while success was achieved, it came at a cost. “In terms of wall-plug efficiency, for every one watt of laser power generated from these original X ray lasers, over ten million watts had to go in,” says Costello. “They were terribly inefficient.”

X-ray lasers offer increased intensity thereby providing new uses and applications. “FELs generate pulsed X-ray beams where the pulses are literally millions of times shorter in duration and more intense than those in traditional X-ray beams,” says Costello.

Understanding the shape of a pulse is an important diagnostic tool. If we take an electrocardiogram (ECG) as an example: there are six different waves to be measured in the human heart, known as P, Q, R, S, T and U. The shape of these six different pulses tells you something different about heart function. Your measuring device, in this case an ECG, must be fast enough to process your heart pulse in real time.