High Vacuum Engineering Design, Analysis, and Build of a Small-Scale Multipurpose System

Every fusor and fusion system seems to need a vacuum. This area is for detailed discussion of vacuum systems, materials, gauging, etc. related to fusor or fusion research.
Michael Bretti
Posts: 134
Joined: Tue Aug 01, 2017 4:58 pm
Real name: Michael Bretti

Re: High Vacuum Engineering Design, Analysis, and Build of a Small-Scale Multipurpose System

Post by Michael Bretti » Mon Jun 11, 2018 2:48 am

A few updates on the cooling system, control system, and overall direction of this project.

For the cooling system, the secondary tank capacity was increased a bit from the initial design. I had originally spec'd a 3"x10" pvc tank. However, since I was already using 4" pvc for the main tank and had some leftover, I decided to just increase the secondary tank capacity to a 4"x10" tank which takes up negligible extra space overall. Fill ports were also added to each of the tanks. Second, since I have purchased the main heat exchangers as sets of 2 for a great discount on eBay, I ended up with an extra leftover from my previous purchase. I will be adding this to the design to bring the primary cooling loop capacity up from 1200W to 1700W, which would allow me to run this cooling system now with either of my diffusion pumps. The contingency for this upgrade was already built in, so I figured I would add this now for minimal additional cost.

For the control system, as mentioned above, I will be going with an Arduino Mega microcontroller. Since I don't want to spend a massive amount of time creating my own fully custom GUI from scratch, I decided to look into several available solutions. The ones I initially researched and considered include the following:

1.) Azande - https://zeijlonsystems.se/products/azande/index.html
2.) MegunoLink - https://www.megunolink.com/?nabe=6011995085340672:1
3.) Instrumentino- http://www.chemie.unibas.ch/~hauser/ope ... index.html
4.) Makerplot- http://www.makerplot.com/

After a lot of looking into each of the options, researching their capabilities, evaluating my system requirements, and weighing their strengths and weaknesses, I have decided that I will most likely being going with MegunoLink. Azande and Instrumentino are both free, while MegunoLink and Makerplot go for about $40 each. I like both MegunoLink and Makerplot, and feel they both have a lot of powerful and robust capabilities to offer for monitoring, data logging, and control with the Arduino. However, based on my system, I feel that MegunoLink would be the best option for my needs. Now that I have the basic overview of the initial inputs and outputs for my control system, I will start coding up the controller, and probably download the free trial version first and experiment with it before I pull the trigger. The initial system inputs for monitoring and plotting will include the four thermocouple sensors for the cooling loop monitoring, the flow sensor, as well as a digital temp/humidity sensor for ambient monitoring, the roughing side thermocouple gauge, and the high-vacuum side wide range transducer. Outputs will need to control pwm for speed control of the three cooling pumps, as well as a 16-channel relay board for turning on and off the numerous heat exchanger cooling fans, water pumps, peltier modules, and interlocks for the diffusion pump main power, and other power and electronics needed for the system. Semi-automated to full automation of pumpdown is still expected, as well as real-time monitoring of all system and environmental parameters, in addition to data-logging system conditions each run and pumpdown to build up a log of run data to better control and understand the system.

In terms of the overall experimental direction for this build, I have decided on the first experiment and system that I will be concentrating on, and the main focus of my research going forward. This build will initially support a 300kV, 30MW peak-power nanosecond-pulsed electron gun for intense relativistic pulsed electron gun injector development, initially exploring scattering and transmission studies in open-air. The preliminary system cost analysis, gun design, Faraday cup, and extraction window are already in the initial design phase. This build will be used to support a much more high-power and ambitious system build in the future, and is a moderate stepping stone towards my ultimate goal. In addition to research into this rather unique and highly-specialized subset of the highest peak-power class of electron gun injectors in use for physics research (which usually reach in the many 10s of GW range for peak power), this build can also be used as the first starting point to support intense ion-beam development, which opens up the door for a lot of exciting, more high-energy experiments than normally done at the hobbyist level. However, electron beam work will be the primary focus, since I will not have to worry about the cost of gas handling subsystems for ion injectors.

Michael Bretti
Posts: 134
Joined: Tue Aug 01, 2017 4:58 pm
Real name: Michael Bretti

Re: High Vacuum Engineering Design, Analysis, and Build of a Small-Scale Multipurpose System

Post by Michael Bretti » Sun Jun 17, 2018 9:59 pm

Quick update on the cooling system build. The primary and secondary water tanks have been completed and assembled. Attached to the tanks are the thermocouple gauges, as well as fill ports at the top, and brass hose fittings for the cooling lines. A couple of additional ports were added as mentioned prior for future cooling capacity upgrades, which are currently capped off. No pvc glue was needed either for the pipe to end-cap fitting - it turns out that the standard 4" pvc to 4" clay pipe rubber adapters with hose clamps works perfectly between the pipe and cap interface, and provides a leak-tight seal that also allows me to completely disassemble the tanks if I ever need to get inside them in the future. Now that these are done, I can start mounting them to the MDF baseplate. Once these are on, then the rest of the cooling system mounting is pretty easy. The tanks have already gone through preliminary leak checking, and should be good to go.

Cooling Tank Pic 1.jpg

Cooling Tank Pic 3.jpg

Post Reply