Since the start of ARCNL in 2014, the University of Groningen (RUG) has been involved in ARCNL’s research program, because Hoekstra was part-time group member of the EUV Plasma Processes group. In Groningen, his research is embedded in the Zernike Institute for Advanced Materials. Scientific director Caspar van der Wal (RUG) recalls: “Although ARCNL was established by Amsterdam-based research organisations, it was clear from the start that Hoekstra’s expertise was crucial because he was and is the Dutch top-expert in ion physics relevant for extreme ultraviolet (EUV) light sources.”
The Zernike Institute houses the ZERNIKELEIF facility, a unique low-energy ion beam facility that can produce beams of (multiply) charged tin ions that generate EUV light in industrial sources for lithography.
“With ZERNIKELEIF we can produce ions that lack more than one electron, and select them on energy, charge state, and mass”, says Hoekstra. “We used to produce several kinds of ions that were relevant to fundamental research questions in astronomy and experimental physics. Our collaborations with ARCNL led us to specialize. Currently, we mainly produce beams of charged tin ions and study their interactions with matter. This shift in research topics also changed the population of graduate students we attract. We have a lot of students with an interest in applied physics.”
While Hoekstra’s work was the initial link between ARCNL and RUG, it gradually became clear that the Zernike Institute had more to offer. “ARCNL has developed into a mature research institute”, says Van der Wal, who has been a member of the ARCNL Governing Board until recently. “Many of the current scientific challenges are in the field of materials science. Think of hybrid materials or the contamination of surfaces. Even a contamination of only a few atoms can cause disturbed behaviour in such sensitive technology as EUV lithography. With the RUG as associated partner, ARCNL can profit from the knowledge on complex materials that the Zernike Institute has. The RUG and the Zernike Institute benefit as well. Being associate partners enhances closer collaborations between researchers and offers a stronger positioning in the scientific community and towards industrial partners. It also helps us opening up new horizons, getting to interesting new research questions.”
The associate partnership also took effect by officially integrating Hoekstra’s research group at the Zernike Institute in the Source Department at ARCNL. The Ion interactions group is physically situated in Groningen, but all members work in Amsterdam typically every Wednesday – and more often when running joint experiments.
“We had to get used to that at first, but despite the distance in kilometres, it feels natural for everyone now”, Hoekstra says. “Having two places to work has many advantages too. We now interact with a wider circle of experts. If we struggle at one location, the idea for a solution may come up at the other location.”
Being embedded in ARCNL and not just connected as a part-time employee, makes some aspects of his work a lot easier too, Hoekstra points out: “Because each location has its own strengths, experimentally, we are constantly considering what to do where. To really benefit from our complementary expertise and set-ups, we needed a vacuum suitcase to transport materials. Being partners makes it easier and more obvious to invest in this with our teams of technicians.”
Because ARCNL also had to get to know their new colleagues, the complete institute visited Groningen in spring 2022. Van der Wal: “This visit really helped to get to know each other better. After the visit I started hearing researchers from Groningen calling their Amsterdam colleagues with questions or collaboration ideas.”
“We have been sowing seeds that are starting to grow now”, Hoekstra agrees. “I am not surprised to work in Amsterdam on Wednesdays an find a colleague from another group in Groningen talking at the weekly ARCNL colloquium, as a result of newly established collaborations.”
Whether other partnerships are foreseen in the (near) future, is not yet possible to tell. “However, we are already picking the first fruits of this collaboration”, says Van der Wal. “As long as possible partners offer complementary expertise and can reinforce each other as is happening now, it is wise to investigate opportunities.” Van der Wal’s own role in the partnership stopped on January 1st 2023 when he was succeeded by Moniek Tromp.
Read also the interviews with