What problem was HIDRA originally created to solve, and how did the idea come about?

HIDRA is the former WEGA (Wendelstein Experiment in Greifswald Ausbildung) which was located at the Max Planck Institute for Plasma Physics in Greifswald, Germany. I did my postdoc there on WEGA back from 2006 – 2009. I arrived at UIUC in 2010, and in 2013 while at a conference and after discussions with my former colleagues, an opportunity was identified to bring WEGA to UIUC. This was be an ideal opportunity for the university and CPMI (Center for Plasma-material Interactions) to have their own device for doing lithium and PMI studies where we are not completely reliant on other machines and their schedules. HIDRA allows us to develop our liquid metal technology concepts that have been developed in other test-stands. This will allow us to get technologies to a TRL 4/5 level (TRL = Technology readiness level).

Who were the key people behind its founding, and what were those early days like?

Originally, it was discussions at the 2013 SOFE conference that I had with my former bosses and colleagues over dinner. I just made an off handed comment about what will happen to WEHA now that they have W7-X (Wendelstein 7-X) coming online. It was mentioned that they would be willing to give it to someone. It was at that point that I contacted CPMI director David Ruzic about who very quickly got approval from then NPRE head of department Jim Stubbins and then Dean of the GCoE Andreas Cangellaris. It took a year to raise funds, about $1 million at our end, and negotiations with Max-Planck and EU. In 2014 from late August to mid-October, I spent 8 weeks with some students and Prof. Davide Curreli in Greifswald disassembling WEGA and readying it for shipping to Illinois. Late October 2014, WEGA was packed up and shipped from Greifswald via Hamburg, Montreal, Chicago and finally Champaign. We were able to get all the main big components of the device installed in the first 10 days. It then took about 18 months of getting everything compatible for full operation and installation of all the smaller parts of the device. There were several custom power parts like a 12.4kV – 20kV transformer, a 25 kV sold state switch, and cooling tanks that needed to be manufactured. Finally, in late April 2016, we had our first plasma with many guests and dignitaries in attendance. We then had several months of commissioning various other components and before we started full operation of HIDRA in September 2016.

Can you share information about a project that wouldn't have been possible without HIDRA?

Well, the helium retention is really the big one. You not only need to be able to generate lithium ions but need the toroidal confinement to show that it can work in an actual fusion device. Often, it’s hard to convince other devices to run lithium in their machines to show something like this. But since we showed that this happens, especially as a stellarator, we have now been able to show retention in other devices, such as linear machines and tokamaks. This comes straight from the fact that we showed it originally on HIDRA. Now we are being asked to explore if other inert gases such as neon, argon, krypton and xenon will do the same thing. These are important as these gases are being explored as buffers to the wall surface to mitigate the heat fluxes coming to the surface from the plasma, however these gases need to be removed in in sufficient time before they themselves degrade the bulk plasma.

How has HIDRA fostered collaborations across different disciplines at Illinois?

HIDRA has fostered lots of collaborations not just within the university but also externally with other institutions and industry. Specifically, within NPRE we are working with Angela Di Fulvio and in MatSE with Trudy Kriven to explore new ceramics for extreme applications. We work with Tokamak Energy in developing liquid lithium technology as part of their Milestone program, also under our FIRE collaboration through PPPL we are working with ExoFusion to explore new liquid metal alloys for fusion applications. We have numerous collaborations through DOE and ARPA-E including national labs like PPPL, ORNL, LLNL and SRNL, and universities such as MIT, Penn State, Princeton, Virginia Commonwealth University and Colorado School of Mines. Working with our partners we have run experiments on other devices testing ideas including on MAGNUM_PSI at DIFFER in The Netherlands and EAST in Hefei, China.

What impact has HIDRA had on students and training the next generation of researchers?

HIDRA has been a major draw for students to the department and plasmas. The thought of fusion is exciting and is a growing field with over 60 companies worldwide now involved in the pursuit of fusion. Opportunities are offered not just for graduate students but also for undergrads to work on the machine in all aspects. We now have several grad students that worked on HIDRA graduate and are working in fusion at various institutions and companies including PPPL, Tokamak Energy and UCSD. The point of having a machine like HIDRA is that, aside from the research, you are training the next generation of fusioneers and HIDRA is designed to be operated and run by the students.

What have been the biggest challenges over the past decade, and what did you learn from them?

The biggest challenges are always making sure you have enough funding for students and to complete the work. The changing landscape these days means you always need to be looking at new opportunities.

Are there real-world applications or partnerships that highlight HIDRA's broader impact?

The helium retention that I have discussed previously has had the largest impact. It has got many people now looking more seriously at lithium as PFC material. We are now starting to build up a flowing lithium loop in HIDRA that will go towards solving many of the issues that flowing a liquid conductor through magnetic fields. We now are also looking at additive manufacturing of refractory metals such as Tungsten. Many of the components in future reactors will be 3D printed and so knowing how these will behave under constant plasma bombardment and exposure to lithium is crucial. The long pulse capabilities of HIDRA have allowed us to expose samples for up to 100,000 seconds and have seen some real interesting results such as tungsten-fuss formation..

Looking ahead, what's the vision for HIDRA for the next 5-10 years?

The next 5 - 10 years for HIDRA are looking very exciting. We will be really pushing forward the technology development of flowing liquid lithium systems, looking to solve a lot of the issues that come with operating a conducting fluid through a spatially varying magnetic field. We will be really getting a handle on how the plasma changes and why it seems to perform better with lithium, when a low recycling regime is achieved. Recycling in fusion means the atoms that come off the wall when operating. Lithium suppresses all this and so takes away one of the energy loss pathways. It’s why the sun works! Also, we are looking to develop the technology for the fusion blanket where electricity is produced, and fuel is bred to continue operation. We want to use HIDRA's unique steady state operating abilities to test designs of all these different concepts. Also with the new emerging world of AI, we are looking to develop an AI based digital twin of HIDRA to help with education and to do research into new PFC designs.