January 24, 2017

MDC Vacuum Products, LLC, recently had the opportunity to design and manufacture a 60” spherical ultra-high vacuum chamber for Professor Setthivoine You and his team of researchers at the University of Washington (www.aa.washington.edu/research/youlab). This was both an exciting and challenging manufacturing job that allowed MDC to contribute to new and important research. The goal of this research is to simulate an accretion disk and astrophysical jet in the ultra-high vacuum chamber in order to study the properties of plasma and magnetic fields. This will help advance the understanding of how astrophysical jets become so large, sometimes hundreds of thousands of light years long, while maintaining stability.

The research is being funded by the Department of Energy with the intention of progressing fusion energy science. Fusion energy is one of the most promising solutions to increasing energy demands and it is being studied in many different contexts. The experiments conducted by this research team are intended to contribute to cheaper and cleaner energy, more efficient and powerful jet propulsion, and advancements in laboratory astrophysics.

MDC was eager to support this research by manufacturing a unique spherical ultra-high vacuum chamber. This manufacturing job shows the commitment and attention that MDC gives to their customers and their ability to accomplish difficult projects.

“The chamber fabricated for the University of Washington posed a number of manufacturing challenges,” says Tony Casaray, MDC’s manufacturing manager.

The initial challenge was the chamber’s size. With a 60” outside diameter, it is a large chamber. Each of the hemispherical heads were manufactured from six formed segments, so the heads had to be pieced together. The segments were formed over-sized in their raw shape and had to be cut down to their exact size using a 5-axis laser to insure accurate fit-up. Fixturing was developed in order to jig the segments while they were carefully tacked in place.

Once each hemisphere was assembled the internal seams were fusion welded while skip welds were added to the exterior to insure structural integrity of the chamber. The hemispherical ends were precision bored on a large vertical turret lathe where one end was designed to accommodate a custom wire sealed flange used to mount a planar two-electrode plasma gun, which was a part of the University of Washington’s existing equipment.

On the other end, a hinged door with a double o-ring groove was incorporated. The door is designed to allow for easy access to the inside of the chamber. Differential pumping enables the vessel to reach the UHV pressures needed for fusion experiments. Port locations were bored into the perimeter of the chamber. Alignment was achieved using a helium neon laser, aimed at a focal point created inside the chamber, for each target location.

After welding and machining operations were completed port target locations were verified using a ferro-arm CMM. Lastly, the chamber was electropolished and vacuum leak tested before being assembled onto its frame. MDC was able to overcome these manufacturing challenges and deliver a high quality custom-made ultra-high vacuum chamber that exceeded expectations of functionality and cost.

The experiments conducted in this lab use high power plasma guns mounted onto the spherical ultra-high vacuum chamber manufactured by MDC. The chamber needs to be large so the plasma will not interact with the interior walls and spherical to provide unobstructed symmetrical views of the plasma for advanced diagnostics and experimental configurations. This unique chamber allows 3D tomographic reconstruction of the plasma’s internal shape and flows, and it is the heart of this experimental installation.

“The performance of the MDC vacuum chamber has proven to be better than our original design and in the end, was more cost effective than expected.” – Setthivoine You, Ph.D., Assistant Professor at the University of Washington