«We're making SLS fit for the future»

Mr. Braun, in December 2020 the Swiss Federal Assembly will be voting on financing for SLS 2.0 – that is, on whether the Swiss Light Source SLS can get an upgrade or not. How is it that work on the project is already under way?

Hans Braun: The official implementation phase of the project SLS 2.0 can only start in 2021 after the decision – positive, we hope – by the parliament. But naturally, we had to begin the planning phase long before that. This way we created a project plan the parliament can vote to finance.

Will the coronavirus pandemic cause the project to be delayed?

We all hope that, in spite of the coronavirus, we will get the green light for SLS 2.0 in December 2020.

What, specifically, are you already planning?

We are planning, for example, exactly what procurements are necessary so that we can start implementation immediately if we get the OK in December. We are now planning which experiment station should be set up where in the future. SLS is not getting any bigger, but the central electron storage ring, which supplies the X-ray light for the experiments, will be completely made over. Therefore, we have to look very carefully to see where which experiment can find its new place.

So it's a complex matter.

Absolutely. We have to fit the new electron storage ring into the existing building. We have to make sure, amongst others, that everything fits together with the existing infrastructure. This is a discussion and decision-making process that has been going on for many months, and which can only be mastered through cooperation among many colleagues with a wide range of competences. At PSI we have a lot of experience in this, and it is always amazing and gratifying to see the way so many people work together towards one major goal.

Are you referring to the project to build SwissFEL, another large research facility at PSI?

Exactly. I myself was previously project manager in the setting up of SwissFEL. It is now fully built and is being optimised. The experiences we gained with SwissFEL will now benefit the SLS 2.0 project.

Do you have a specific example in mind?

Yes: We have learned a lot in terms of data processing. With SwissFEL, we initially had the problem that we could not save and process the huge amounts of measurement data from the experiments quickly enough. Thanks to the great commitment of the specialist groups involved, this issue has now been resolved.

With the SLS 2.0 project, this aspect has now been assigned its own sub-project. We want to develop a tailor-made and sustainable concept for data processing right from the start.

Could you please explain again why the upgrade is necessary in the first place? Isn't SLS already one of the top facilities in the world among synchrotron light sources?

That's right – and it should stay that way. Science continues to develop. Yesterday's questions have been answered. And the questions of tomorrow either go into further detail or in a new direction. These are questions that cannot be answered using the previous facilities. We need to keep pace with the research – otherwise advances will eventually overtake us. So we're taking precautions and making SLS fit for the future.

What exactly will the SLS 2.0 project bring?

The current upgrade is about increasing the density of the X-rays. This will allow us to do more experiments in the same time or to get more data in the same amount of time. An experiment that previously would have taken 40 minutes will then take only one minute.

We will also be able to image larger areas of a sample than before. In other experiments, the resolution of our images will be higher, so we will be able to see and recognise even smaller structures.

This opens up many new possibilities, especially when it comes to examining complex systems. These might be biological samples, for example from the brain. We know its individual functional blocks, but we have only a rudimentary understanding of how they are interconnected at the lowest level.

How will SLS compare internationally after the upgrade?

Naturally, we do compare ourselves internationally. The Max IV project in Lund, Sweden, was a paradigm that influenced our thinking. It's the first synchrotron that was built with multibend achromat magnets – the same magnet system that SLS 2.0 will have. Max IV went into operation in 2016 and set a new standard internationally. Planning for SLS 2.0 began the following year.

Just recently, the ESRF facility in Grenoble, France, went back into operation after its upgrade, also with a similar technology. Many synchrotron light sources worldwide plan to further develop in this direction. Here at PSI we have the chance to join in the game very early, and very far ahead. At the same time, though, we can draw on the experience of Max IV and ESRF. That's the advantage if you come just a little bit later.

We are expected to be the third facility worldwide, after Max IV and ESRF, to make use of this technology.

What's your job as project leader?

There are many aspects to my work. I organise communication between all of the parties involved. With such a large project, this is crucial, because in the end it has to work as a whole.

Then, important decisions need to be made, and I coordinate this processes. For example, we recently decided that the new electron storage ring would operate at 2.7 gigaelectron volts instead of the previous 2.4. What consequences this has for planning and what advantages it will bring for the experiments must all be considered and reconciled.

Third, you have to stay attentive and understand which aspects have not yet been considered. We need to stay aware of technical developments that we shouldn't miss out on.

And finally, we can't forget that SLS will be used by researchers at Swiss universities and in industry, both now and in the future. We have to listen carefully: Who is expecting what from us? We must make sure that SLS 2.0 meets these expectations.

Interview: Paul Scherrer Institute/Laura Hennemann