New worlds open up – in billionths of a microsecond

New worlds open up – in billionths of a microsecond

The FemtoMAX beamline at MAX IV Laboratory will use extremely short light pulses to give researchers new insights into chemical reactions and the characteristics of solid materials. Researchers from a number of different fields are already queuing up to use the new tool. Project leader Jörgen Larsson hopes to gain wide-ranging knowledge, including the key to producing perfect diamonds from graphite.

It was far from self-evident that Jörgen Larsson would be a professor of atomic physics. In his teenage years he was actually more interested in the social sciences, but a mathematics teacher at his upper secondary school made him think again.

“Like many others I chose the natural sciences programme at upper secondary school, as it offered the best breadth with subjects in both the natural sciences and social sciences”, says Jörgen Larsson. “Mathematics had never really interested me that much before, but I had a fantastic teacher in the subject. She made me realise that mathematics could be both fun and highly useful. Moreover, as mathematics is fundamental for the other engineering sciences, the interest opened up considerable opportunities when it was time to choose a university education.”

Jörgen Larsson chose to study Engineering Physics at LTH, which according to him provides the broadest engineering education with an opportunity to specialise in a number of different fields.

“I chose courses simply on the basis of what I thought was most appealing and became interested in optics at an early stage. There were also many talented instructors at the university who awakened your desire to learn more, and from optics it’s not a very big step to atomic physics, which is based on optical measurement technology.”

His degree project was on resonance spectroscopy, an advanced measurement technology for measuring how the atom’s nucleus affects its electron-related state. It was 1987 and the Department of Physics was growing at a dramatic rate. Sune Svanberg had become professor of atomic physics seven years previously and this was the start of a staggering phase of development in which measurement techniques took great strides forward and generated spin-offs in a number of different areas, both within research and commercially through new innovation companies. Jörgen Larsson applied for, and was granted, a doctoral studentship focusing on spectroscopic measurements.

“I started my research during a very exciting period. The Department of Physics was still quite a small environment and there were no clear boundaries between the different divisions. During my time as a doctoral student I worked mostly on basic research. However, I also had the opportunity to learn from, and sometimes assist, colleagues who were working on the development of laser-based measurement methods for modes of combustion and photodynamic therapy against skin cancer. The doctoral studentship was for four years, but it took longer for me, as I could not resist the temptation to work for a couple of years at Lund’s high power laser facility on developing different types of laser light especially adapted for different measurement needs.”

After gaining a doctoral degree in 1994, he spent three years abroad as a postdoc. A spell at Imperial College in London was followed by a couple of years at Berkeley in California, where Jörgen Larsson had the opportunity to work with one of the leading materials researchers in the world, Professor Roger Falcone, and his research group.

“My stay there coincided with the completion of Berkeley’s own synchrotron radiation facility, Advanced Light Source (ALS), and Roger Falcone was asked if he could help to develop time resolved experiments using short light pulses. I got ‘the job’ together with a doctoral student, and that was my entry into the world of synchrotron light.”

In simple terms, a time resolved experiment can be explained as a film sequence, rather than a single photograph, of an extremely short time span, for example a chemical reaction that takes place within a time span of a few billionths of a microsecond (1 femtosecond = 1 billionth of a microsecond). Using this method, researchers can gain completely new insights into how different materials function and react to external effects at the atomic and molecular levels.

“Among other things, we took time resolved measurements of various semi-conductive materials that enabled us to study in detail exactly how they changed when heated ­– knowledge that could be used to develop even better and faster materials.”

The period in Silicon Valley provided a wealth of experience, both for his own research and on other levels. Proximity to many of the leading electronic companies in Silicon Valley created a very special atmosphere and a feeling of being at the centre of things. Jörgen Larsson also has a lot of good things to say about research funding in America, where there is a more long-term approach than in Sweden.

“In Sweden we have to expend a lot of energy on applying for grants every four years, whereas American senior researchers often have more long-term financing that is not directly linked to specific research projects. This means that they dare to take greater risks and it’s not unusual for them to switch areas of research, quite simply because they make new discoveries along the way. This financial security creates a dynamic that is often lacking in the Swedish research world.”

However, sunny California also had a darker side in the form of considerable social tensions and the gap between rich and poor. This gradually became more discernible and made Jörgen Larsson think about the kind of society he wanted to be a part of. He moved back to Lund in 1997.

“I got a research fellowship at the Department of Physics, financed by the Swedish Research Council. The assignment was to create conditions for time resolved experiments at MAX II, and eventually we gained grants to build a beamline for the extremely short light pulses that were required. This beamline, known as D611, has been in operation since 2001 and will be used for the last time on Saint Lucy’s Day – 13 December – this year after carrying out numerous advanced experiments that have helped to develop our knowledge. My first seven doctoral students used the beamline in their main research work.”

There is a clear thread that runs from the time that Jörgen Larsson and his colleagues began work on the D611 beamline in 1999 right through to the creation of FemtoMAX, the beamline in MAX IV Laboratory that will start operating soon and enable experiments at a completely new level.

Jörgen Larsson with his colleauge Henrik Enquist at the FemtoMAX beamline.

“Yes, we had a vision of building MAX IV even when we were building the first beamline, so you could say that we have been working with FemtoMAX in mind ever since then. After thousands of working hours and innumerable calculations and simulations we are now close to that goal. The 300-metre-long linear accelerator that generates an electron beam with sufficiently high energy has been in use since August (2015). The Short Pulse Facility (SPF), which generates the extremely short electron pulses we need, is essentially ready to go into operation. In the spring we were able to generate the first X-ray light and in late October we could, after obtaining authorisation from the Swedish Radiation Safety Authority, open the shutter for the first time and let X-ray photons into the beamline. There is still a lot of work to do on settings and fine-tuning for everything to work perfectly, but we estimate that we can take in the first users during 2016 and thereafter gradually increase the number of experiments.”

Jörgen Larsson has thus spent many years of his life putting his heart, soul and mind into developing an advanced machine. Even so, it is not the machine itself that interests him most, but rather the new worlds it could help to discover.

“The machine is like a carpenter’s hammer. It’s not the hammer itself that’s important, but what you can create with it. MAX IV and the FemtoMAX beamline will open up fantastic opportunities. Among other things we will be able to study ultrafast molecular movements in solid materials and gain new insights into how we can control chemical processes. Ultimately, this could lead to developments such as creating artificial photosynthesis that extracts energy from sunlight in an efficient and environmentally neutral way; boosting the packing density in ferroelectric memory to create enormous storage capacity; increasing the writing speed of a DVD disc by many times, or even producing diamonds from graphite.”

The last mentioned possibility is something that Jörgen Larsson finds particularly interesting. Diamonds are 100 per cent carbon atoms with very strong bonds. In previous experiments it has been possible to create diamonds on a microscale by firing laser beams at graphite – carbon with very loose bonds. Using the FemtoMAX beamline it will be possible to study the transformation process in real time and perhaps create the basis for an industrial process to produce large diamonds.

“However, these are just a few of the huge number of areas in which important questions can be answered by using the tool we have created. The tool will be used by researchers from all over the world in widely differing disciplines, and everything will be studied ­– from solid ‘dead’ materials to the molecules that build living cells. The task for our team will change, moving on from the build up phase to creating the best possible conditions for visiting researchers to conduct their experiments. MAX IV will be an extremely exciting workplace for many years to come.”

Physicists have often been criticised for being poor at describing the possible uses of their research. That is only natural, as much of physics concerns basic research, with opaque applications that are far ahead of their time. And even though Jörgen Larsson is enthusiastic in describing the applications of both atomic physics and materials research, it is basic research that is closest to his heart. This research is driven by pure curiosity and the determination to understand the world around us, and by its very nature it is not immediately ”useful” or readily applicable in new products and processes.

“Basic research is sometimes difficult to explain, but it‘s also completely essential. Take, for example, Sune Svanberg’s research and development work on lasers. Nobody could foresee 35 years ago the fantastic applications we have today in diverse areas such as measurement of air pollution and the treatment of skin cancer. The research has resulted in people being cured of life-threatening diseases, giving us cleaner air and the formation of a number of successful companies. But more than that, it has also shown the way for other researchers and generated new ideas and discoveries in other areas that are related in one way or another. And that’s why basic research is so important. We can’t say what today’s materials research will lead to in 35 years and that’s exactly why we can’t afford to neglect it. Good, broad and unrestricted basic research is an essential prerequisite for applied research with a more obvious eventual ‘usefulness’, but nobody can predict where the major breakthroughs will be made.”

Jörgen Larsson considers that there is a great interest in physics among the youth of today. There is a good flow of applicants to study physics and every doctoral studentship has between 40 and 100 applicants, of which five to ten are usually very highly qualified. Nowadays he divides his time between the Department of Atomic Physics and MAX IV Laboratory and has an office at both places. Despite the high workload he has time to supervise three doctoral students and is currently teaching two undergraduate courses in laser physics.

“Teaching is an important and stimulating assignment that has many rewards – I know, of course, from my own experience what a good instructor can mean for awakening interest. It is from among the students that we will find those who will continue to drive research onwards.”


Story by: Arne Berge
Photo: Madeleine Schoug