To say that “building a particle accelerator is no easy task” is a ridiculous understatement designed to underscore the mind-bending complexity and amalgam of disciplines needed to accomplish such a feat of manufacturing.
There are over 30,000 particle accelerators in use today, according to the U.S. Department of Energy. Particle accelerators use charged particles to help nuclear physicists discover more about the physical laws of the subatomic world as described by quantum mechanics. By accelerating the particles that are the fundamental building blocks of our universe to high energies, scientists can engage in fixed target (linear accelerators and circular accelerators) and colliding beam experiments (circular accelerators).
Particle accelerators use electromagnetic fields to accelerate and increase the energy of a beam of particles from a particle source. The beam is controlled and focused by magnetic fields (electromagnets) and travels inside of a vacuum in a metal beam pipe.
There’s a lot more to the mechanics of particle accelerators, but in general, particles are directed at either a fixed target or two beams of particles are collided while particle detectors record the particles and radiation produced by experiments.
Given the need for such precision, traditional machining is the only method used to build components for particle accelerators. But scientists at SLAC National Accelerator Laboratory are attempting to develop methods of copper 3D printing to manufacture accelerator components.
Challenges
The researchers were able to additively manufacture part of a vacuum tube responsible for amplifying radiofrequency signals. The process of 3D printing the component made the klystron part transfer heat more efficiently. The researchers reported that the cost benefit of manufacturing particle accelerator components via 3D printing could save 70 percent in terms of manufacturing costs.
Balancing the trade-offs between electrical and thermal properties of copper-printed components was one set of challenges for the SLAC researchers to overcome. But attaining the high levels of material quality to avoid failure is the most critical obstacle to their success. If they fail, vacuum leaking and cracking would occur, putting expensive experiments entirely in jeopardy.
Moving layer by layer, the researchers studied the materials’ surface quality and used a finer grade of copper particulate and tweaked the printing method. Unfortunately, the by-product of using finer copper powder was too much oxide binding to each layer, degrading the overall purity of the metal.
To avoid too much oxide binding to each layer of copper, the scientists invented a method of using hydrogen to bind oxygen, forming water vapor and then removing it from the powder.
Bottom Line
SLAC researchers were able to 3D print a klystron output cavity component as a proof-of-concept part that could theoreticallybe used in a particle accelerator. But the potential applications extend beyond nuclear physics into satellite communication, defense systems, aerospace, and electrical grid systems.