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Building a Fusion Reactor (Part 2): Building a Vacuum System

After the preliminary research from the first article, we created our Vacuum Chamber 1.0 on December 15, 2023, at Walter Payton College Preparatory High School using the following method and parts:

Task 1. Vacuum chamber construction

  1. Attach 2 NPT 90 degree elbow to ¼” NPT dernord pipe fitting with two opening (female fittings)

  2. Attach Barbed hose fitting (1/4" specification) to elbow

  3. Attach Pressure gauge to second fitting

  4. Use 3-inch tri-clamp to attach to 316 inline sight glass (Body of the chamber)

  5. Connect Dual stage Rotary Vacuum Pump (maintenance requires Vacuum pump oil) to barbed hose fitting in vacuum chamber via (1/4" Diameter) High Vacuum tubing and Vacuum tubing clamps

  6. Close other end of 316 inline sight glass with (1/4" NPT Female with 3 inch Tri-clamp)

  7. Fill hole meant for high voltage feedthrough with 1/4" NPT Male 304 Stainless Steel Hex Head Screw Pipe Plug vacuum test

In crafting and buying supplies, it is important to keep a few things in mind: (1) that all fittings were the same, (2) the extent of quality in our first iteration, and (3) simplicity. For fittings, because of our usage of pipe system components, such as the 316 inline sight glass as our chamber body which is normally used in water or gaseous systems to transport the medium, many of the parts were by default NPT or National Pipe Tapered Thread. This shape is usually used for insulating liquid systems, but also works decently well in gaseous systems. We kept all specifications and connections to a 1/4" diameter. For (2), the quality of our first vacuum chamber iteration was not meant to be super high, and the one of the biggest takeaways that I got from our research, as mentioned before was safety first. Thus, our first test was just meant to achieve moderate pressures and be used to prove the function of all components. This ties into (3), as simple design design with minimal parts made the number of variables go down, making identifying problems easier.

Talking about safety first, this test was meant to prove the safety of our construction and also to provide insight and experience in the functions of each component, especially the vacuum. Before turning on the pump, we had to pour almost 2 complete jugs of high-performance vacuum oil into the tank for it reach desired levels, a surprisingly high amount of oil. For some reason, the oil level was not rising fast, and, even though the pump is marked to have a 330ml oil capacity, it seemed like much more than 330 ml, or 11.15 fl oz, was poured in. Once the pump was turned on, it took 10 seconds to reach a vacuum pressure of 27.5 inHg. One of the cornerstones for this test was to make sure that our stainless steel sight glass was structurally sound enough to withstand the pressure caused by vacuum pump. Thus, we kept our pump running at this pressure for 5 minutes, surrounding the chamber with upright textbooks to protect against possible glass implosion. Safety goggles are an important measure of safety, as well as electrician gloves, as the vacuum pump can potentially rip your skin off your hand if used dangerously. After 5 minutes, the pump turned off and it took 37 seconds pressure to reduce to 0. This means there an sizable leak that air flows into the chamber through, allowing the chamber pressure to stabilize to atmospheric once the pump is turned off.

Overall, the test was successful in proving the structural integrity and safety of the chamber and pump itself. 27.5 inHg vacuum pressure is a good place to start, but it is very far off our ultimate goal of ~29.92 inHg vacuum pressure or 15 microns

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