Developing a Spherical Ultra-High Vacuum System to Study Astrophysical Plasma Jets

60” spherical ultra-high vacuum chamber

Recently, MDC Vacuum Products, LLC, designed and manufactured a 60” spherical ultra-high vacuum chamber for Professor Setthivoine You  and his team at the University of Washington. This work was both interesting and challenging and it enabled MDC to contribute to new and important research.

The objective of this work is to investigate the properties of plasma and magnetic fields by simulating an astrophysical jet and accretion disk in the ultra-high vacuum chamber. This will help gain new insights into how astrophysical jets become very large, sometimes hundreds of thousands of light years long without any changes in stability.

A Unique Spherical Ultra-High Vacuum Chamber

The Department of Energy is funding this research work with the intention of advancing fusion energy science. Fusion energy is a potential solution to meet increasing energy demands and is being explored in many different contexts.

The experiments carried out by this research group are intended to contribute to more powerful and efficient jet propulsion, advancements in laboratory astrophysics and cheaper and cleaner energy.

MDC was eager to support this research work 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.

Tony Casaray, Manufacturing Manager, MDC

Manufacturing Challenges

60” spherical ultra-high vacuum chamber

The initial challenge was the size of the chamber. It is a large chamber with an outside diameter of 60”. Since each of the hemispherical heads were made from six formed segments, the heads had to be pieced together. The segments were created over-sized in their raw shape and were cut down to their correct size with a 5 axis laser to ensure accurate fit-up. Fixturing was developed in order to jig the segments while they were carefully tacked in place.

After assembling each hemisphere, the internal seams were fusion welded and skip welding was applied to the exterior to ensure structural integrity of the chamber. A large vertical turret lathe was used to precision bore the hemispherical ends and one of the ends was designed to house a custom wire sealed flange used to hold a planar two-electrode plasma gun, which was a part of the University of Washington’s existing equipment.

60” spherical ultra-high vacuum chamber

60” spherical ultra-high vacuum chamber

A hinged door with a double O-ring groove was added on the other end. The door is designed in such a way that the inside of the chamber can be easily accessed.

Differential pumping allows the vessel to attain the UHV pressures required 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.

60” spherical ultra-high vacuum chamber

After completing machining and welding operations, a ferro-arm CMM was used to verify port target locations. The final step was to electropolish the chamber, followed by vacuum leak testing before being assembled onto its frame.

MDC successfully overcame these manufacturing challenges and delivered a high quality custom-made ultra-high vacuum chamber that exceeded expectations in terms of cost and functionality.

60” spherical ultra-high vacuum chamber

60” spherical ultra-high vacuum chamber

The experiments carried out at this laboratory employ high power plasma guns installed onto the spherical ultra-high vacuum chamber fabricated by MDC. The chamber must be large enough to avoid the interaction of the plasma with the interior walls and have the spherical shape to deliver unobstructed symmetrical views of the plasma for advanced experimental configurations and diagnostics.

This unique chamber is the key component of this experimental installation, enabling 3D tomographic reconstruction of the shape and flows of the plasma.

60” spherical ultra-high vacuum chamber

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, University of Washington

 

60” spherical ultra-high vacuum chamber

This information has been sourced, reviewed and adapted from materials provided by MDC Vacuum Products, LLC.

For more information on this source, please visit MDC Vacuum Products, LLC.

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