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

Post by Michael Bretti » Tue May 08, 2018 6:02 pm

Richard Hull,

Yes, noise shielding is certainly a major issue with high peak-power pulsed systems. Fortunately I have directly worked with active shielding and noise suppression for electronics and instrumentation around these types of pulsers. It is a challenge, but I have dealt with it before very successfully. One of the systems I actually built for work was a 90kv Marx generator to simulate electron gun arcing faults specifically for EMP and noise shielding for sensitive electronics around the fault. My goal is to develop the pulsers to work successfully with my pulsed e-gun setup, then migrate it over towards pulsed neutron work later (the e-gun setup would be less costly due to the fact that no expensive gas or gas handling is needed.)

Activation analysis was actually the main method of detection I was planning on implementing for the high peak power fast-pulsed systems, and I look forward to the design challenges and getting to that stage of testing.

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

Post by Richard Hull » Wed May 09, 2018 3:45 am

The one thing about activation; it is the only warranted noiseless, absolute indication that thermal neutrons had been there. As you note, calibration can be tricky, but with good math and the knowledge to apply it, calibration can be very accurate. You will just need a good averaged flux over time. From this, based on the pulse peak voltage and current, the flux per pulse should be easily computed.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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

Post by Michael Bretti » Wed May 09, 2018 3:06 pm

Richard Hull,

Thank you for your advice. I also just finished reading that new PDF you posted on activation - really fantastic introductory paper on activation, I greatly enjoyed it and it was very helpful, especially the section at the end explaining different target materials for activation. I was planning on starting with silver, and seeing this list of additional elements to explore has given me some new ideas for experimental test stand development that I think would be very exciting to build and share with the fusor community. Although I won't get to activation for a long time, I can certainly start working on gathering the necessary information and designing the various detector systems.

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

Post by Richard Hull » Wed May 09, 2018 6:51 pm

Silver might have been #1 in my list and it certainly is the most common activated material here at fusor.net over the years.

Rhodium was #1 simply due to the raw data related to it, my own experience with it, and the fact that Enrico Fermi used it all through his work that lead to his Nobel Prize. He was forced to use made-up sources for his neutrons,(radium-beryllium), to calibrate and quantify them, he needed a fast activation element to 100%. Rhodium was ideal.

I had a friend who wisely purchased a 1 ounce bar of Rhodium, a short while back, when its price plunged to $700 per ounce. I contemplated it back then, but waited too long and the price soared again. As noted 1/10 ounce bars are available.

In my activation of my friend's bar, I was pleased that it exceeded silver in activation and that it took only 4 minutes to fully activate to 100% of its attainable radioactivity with a given flux!

As an ideal activation element it will forever remain #1 on any and all lists with only its crippling purchase price being its sole impediment.

Again........

100% of its atoms are ready to activate as it is a single isotope element. Its capture cross section is high and the finished radioactive product has a short half life, meaning weak and limited neutron sources can be rapidly checked out and quantified.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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

Post by Michael Bretti » Wed May 16, 2018 5:29 pm

New update on the V4 System build. After additional planning and design, I have settled on a table I will be using for the system. Below is a CAD model of the proposed design:

System V4 Dual Purpose Table Assembly - V4 Chamber.png

The experimental table consists of a 2'x2'x3' structure made from 80/20 10 series extrusion. The 80/20 was purchased off ebay for half its original price won during surplus lot auctions. I ended up getting both black anodized and silver 80/20 since that was what was available for cheapest in bidding lots, and arranged it to have at least a symmetric and pretty cool look color-wise. I was originally going to go with a 2'x2'x2' table, however after discussing this project and another vacuum system project with one of my friends, he suggested to save money by combining the infrastructure of the two systems to support both. After some careful planning and design, I have been able to come up with a low-cost solution to support both systems simultaneously. Only the 2.75" conflat based system is currently shown in the model. The roughing pump is in the center, laying on the floor to minimize vibrations transferred to the rest of the structure, but still keeping it within the build volume. There will be ample space for the power supplies, diffusion pump chiller, baffle chiller, and other control electronics. An additional 6" KF25 bellows line will be needed to connect the roughing pump to the main roughing line under the foreline trap.

The second system is based around a 6" conflat tee that I obtained for free. This system will be used for ion and plasma engine testing. Last year I had originally bought a very large 6" throat gate valve/butterfly valve combo for the 21 port custom conflat system I posted about a while ago, which after looking at the logistics to get operational, was recently sold. I also obtained an 8" water cooled baffle for the original system as well. Both the baffle and the valve were $100 each, and in excellent condition. Since I already have another Edwards EO4 diffusion pump, as well as the baffle, gate valve, chamber, and basic feedthroughs, all that is really needed are the two aluminum adapter plates to fit everything together. I was going to build a completely separate system for this setup, but since the diffusion pump is the same as the V4 system, it was decided to extend the table to accommodate this test chamber as well. I will end up splitting the roughing line symmetrically to feed into both diffusion pumps, as well as route cooling for both diffusion pumps and baffles to run off the same cooling system. I will only run one system at a time, never both simultaneously, so in my control architecture I will make accommodations to switch between pumping and cooling for both systems. Initially, this second system was planned for operation years down the road, however using this shared setup, I will be able to deploy it and start testing it in a much shorter time-span, since the infrastructure will already be built and shared from the first system. The cost savings implementing this shared topology is on the order of $2k or so. I will post an updated CAD render of both systems mounted with the proposed roughing line upgrade shortly.

In terms of the actual physical build, the 80/20 has already been ordered and arrived. The remaining hardware is coming in today. I have also already started modeling the chiller block subsystem of the diffusion pump cooling system. The main heat exchangers will be arriving within a week. Once this chiller is qualified, then I will proceed in building a second chiller for the baffles. I will also post design specs of the chiller as I progress further, but I have most of the parts already for the chiller block.

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

Post by Michael Bretti » Thu May 17, 2018 3:26 am

Bit of a sudden and unforeseen setback to the above plan. Upon completing the 80/20 table, I decided to open up one of the two hermetically sealed boxes that, when I received them along with the open diffusion pump, was told they were new, unopened pumps. The boxes were the same dimensional size and weight as the EO4 diffusion pump. However, it turns out that they were nothing more than very large circuit breaker boxes. They were such old pieces of equipment from decades ago it was forgotten what was in them and assumed to be pumps. Turns out I only have one instead of three diff pumps that I initially thought I had. Rather disappointing considering a large portion of future systems relied on the requirement of having multiple of the same diff pumps. However I am still quite happy that I have even one diff pump in new condition. I could still proceed to mounting the second chamber since I have most of the parts anyway, but running it will have to wait for now, since the small chamber is priority.

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

Post by Michael Bretti » Sun May 27, 2018 3:22 am

Quick build update. Most of the 80/20 table has been completed over a week ago. Still leaving some of the center support beams off until I actually start mounting equipment:

20180519_214150-1.jpg

The design of the chiller system has just about been finalized, and almost all of the remaining parts have been ordered. Many of the parts were ordered on eBay from overseas suppliers to save cost, so they will take over a month to get in, but that gives me plenty of time to work on other system designs. I am currently working on the cad model for the final design of the chiller subsection, which will be posted when completed. Its current specs are rated so far for around 1200W cooling capacity (1000W air-liquid heat exchanger capacity, and an additional 200W liquid-liquid heat peltier chiller capacity.) As described before, it is a triple-loop, closed loop peltier based chiller. The EO4 diffusion pump works optimally with cooling water at the inlet in the range 15C-25C (max), up to 850W of power. The entire chiller will be mounted to a 2'x2' MDF panel that will be mounted vertically to the back section of the table. The system will utilize 4 thermocouple gauges, mounted at the diff pump inlet, outlet, in the main water storage tank, and the secondary storage tank for the peltier heat exchanger subsection, in addition to a water flow meter. All three pumps used in the system will be PWM driven and modulated based on temperature readings to keep precise temperature control of the system, and controlled through an Arduino Mega.

I also have left space in the design for future upgrades to be able to double the entire cooling capacity of the chiller to around 2400W to be able to support my second larger high vacuum system for ion engine testing. Both of these systems will share the same cooling and roughing infrastructure to significantly reduce costs of having two operational systems. I have been able to secure an even larger diffusion pump in practically new and unused condition for free for the ion engine test stand, and as a result, this pump will require much more cooling capacity (with the temperature range at the inlet the same as the EO4). I will be posting details of this second build in a new post specifically for that system.

One final note. In addition to the new diffusion pump, I have recently acquired an incredible piece of physics equipment that will allow me to experiment with charged particle beams at energies and peak power levels unlike anything presented on these forums here so far. If I am successful with this new system design and rebuild, it will be, as far as I am aware, the highest energy and peak power charged particle beam system currently built and operated at the hobbyist level. In addition to this component, I also obtained supporting vacuum flanges and pumps to run it. I will post more details of this new, third system in a different forum topic, but its potential can bring about an exciting new level of physics research at the hobbyist level.

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

Post by Dennis P Brown » Sun May 27, 2018 5:04 pm

If your high energy charge particle device is so powerful, then you had better be aware of the x-ray hazard and be certain of your shielding.

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

Post by Michael Bretti » Sun May 27, 2018 6:14 pm

Yes, I am fully aware of the hazards, particularly with xrays. This device will not be operational for quite a while, so it will be a long term endeavor. I also work at a nuclear research facility so I have plenty of experience with radiation hazards and training. I also directly work with these devices regularly, and am well versed in their operation. I spent over a year almost exclusively working on various pulse power drivers for one, so this is by no means a typical amateur project.

I will be rebuilding it for a different mode of operation than its current configuration. It will only operate at very low repetition rates of a few hz at most, at only several nanoseconds in pulse widths. However I am looking at ultimately reaching the 1MeV barrier, with peak power levels of hundreds of MW at the nanosecond timescale. Not sure if I can drive 1MV across it yet, but I should be able to very readily achieve hundreds of kV without issue. I am already working on the preliminary specs for the pulse power driver for the rebuild. I will release more details later in a different post.

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

Post by Michael Bretti » Sun Jun 03, 2018 2:32 am

New update on the cooling system build. I have finally finalized the CAD designs and layout for the system. I have posted a full overview description as well as system specs, which can be found in the link below. I plan on eventually adding the engineering drawing sheets for all of the components, as well as datasheets for the parts used in the build:

http://appliedionsystems.com/portfolio/ ... p-cooling/

Just wanted to share a few of the CAD models for the proposed design. The first is the actual peltier chiller block. This is the second loop of the triple-loop system, where water is continuously flowed through the chiller from and to the tank. The cooled water mixes with the incoming water at the end of the first loop from the heat exchangers after the diffusion pump, which will help for better temperature control. The chiller block consists of five TEC1-12708 peltier modules sandwiched between two aluminum water cooling blocks - one for the hot side, and one for the cold side. The hot side features three solid copper heat sinks with integral cooling fans for initial heat extraction, where an additional 500W air-to-liquid heat sink removes the rest of the heat before entering the secondary storage tank:

Peltier Chiller Block - Resized.png

The next picture shows the full assembly of the chiller block. This includes 1" thick XPS insulation foam on the cold side, and HPDE plates to hold the assembly together. All thermal interfaces between heat sinks and peltier devices will use Arctic Silver 5:

Peltier Chiller Block Assembly - Resized.png

The next renders show the full assembly positioned on the 24" x 36" x 0.5" MDF board. Unfortunately a lot of the components have varying inlet sizes, so several different tube sizes and adapters were needed to mate everything together. The tubing consists of various sizes of opaque black EPDM, rated for -40F to 300F. This model took quite a while to finalize, as there were a significant number of hoses and connections to position and mate. However, it has let me fully plan out the system before the build. As mentioned above, the system has space and contingency built in for a future upgrade to double its heat handling capacity from 1200W to 2400W. Right now the estimated power consumption at nominal operation is expected to be around 450W:

Cooling System Assembly - Top View.png
Cooling System Assembly - Isometric View.png

Finally, the full cooling assembly is mounted to the 80/20 experimental stand with the V4 high vacuum system and roughing line:

System V4 Dual Purpose Table Assembly - V4 Chamber with Cooling System.png

So far, everything is falling into line well with the design. It should make for a compact but highly controlled and modular system. The cooling system has admittedly cost more than I had initially wanted, but it is best to plan and invest in a solid system now that can handle all of my needs for any vacuum projects in the foreseeable future. Since the roughing line and cooling system will work for both diffusion pumps I have, with a couple of aluminum adapter plates I can quickly and easily change between the three high vacuum chambers I have for testing, which saves a significant amount of money for the future, and provides me a robust experimental test stand design that will allow me to run all of my physics experiments for years to come. I have obtained all of the hardware to start the build, so I will be working on the actual cooling system in the next few weeks. I hope to actually do some test runs, as well as do thermal imaging to analyze the response and performance of the system. I will also be starting to work on the control software for the cooling system, which will be used to set several interlocks for the main diffusion pump power based on the system temperature and flow rates.

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