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Some Beefy Power Supplies

Posted: Wed Jun 19, 2019 1:36 am
by Robert Dwyer
Hello All,

I haven't been posting nearly as much as i want to, and that is, of course, because I have not been doing as much as I want to. Working two jobs and college turns to take up a lot of time.

I am however, slowly pinging away at the upgrade to my fusor. In fact, this will be an entirely new machine. I still plan on keeping it in a small chamber (upgrading to a 6-way flange for the extra two ports, for reasons you will see in a minute). Recently, two items I had been saving up for a long time have come in and I thought I would share them here:
These are two -6kv 725ma SA series power supplies. There are a variety of things I can think of to do with these, but the first item on my list would be to make an ion source of some kind. I have the idea of a DC magnetron ion source (like the one desrcibed in the paper by Takamatsu and that Carl Willis used). A coworker of mine, and Carl both suggested that it would make a very interesting (yet probably short lived) cavity magnetron from a microwave oven to act as an ion source. While intriguing, it also comes with all of the issues of a 4kw DC microwave source as well as these increadibly high currents at high voltage. I think the two extra ports will help accommidate two ions-guns. While ion sources, there design, and safety, are an interesting topic, I will leave any more discussion as to those sources from myself to the inevitable Ion Gun thread.

I do have a plan for the second supply. Since all of the high power switching and step-up is already done for me in the supply, I thought it may be a good project to replace the current multiplier, with a higher voltage output one. Perhaps 60-70kv? Of course, this would mean a drastic upgrade in radiation shield, HV safety, better ballasting, etc... but thats part of the fun as well!

I am very exciting about gettign things up and going. Many parts are just sitting in storage right now and it appears I may have a space to actually build something that produces neutrons soon (as long as those giving me the space are ok with the radiation). A nice luxury that I can afford now is time. I actually have time to take this slowly, being a lot more meticulous and careful (and safer) than my last fusor build, as then I was rushed with the thrill of achieving fusion before high school, and threatened with the exciting prospect of moving out to college. Now the goal is simply yield and activation experiments.

One of the first things on my list to do once I get setup is to better characterize these supplies (switching frequency, ripple, multiplier design). I will make sure to post those results here.

Re: Some Beefy Power Supplies

Posted: Thu Jun 20, 2019 1:41 pm
by Dennis P Brown
The use of one of those power supplies for a Ion Gun system(s) is useful. Agree that would be a great project to post in the appropriate forum.

As for the other being used for a voltage multiplier (VM) initial driver - the issue isn't the current capability of the power supply alone but also the output frequency is the most import criteria. The final caps in the VM will solely provide all the output current of the VM but its the driver frequency which has a huge impact on what that stack will output relative to current/power. If the unit you have is 60 Hz output, then it will very likely not be suitable for a VM. One requires more like a 20 - 50 kHz driver (which may be what your unit does provide - just don't know the units spec's.) The caps and diodes must also be suitable for operating with that freq. and those loads.

Microwave systems are extremely dangerous (shielding/leakage issues) and belong only for the near professional EE designer and expert builder. Of course, if you have expert advice, and confident of your own abilities in creating a truly microwave leak proof fusor/vacuum system, that could be a different issue.

Personally, I think the standard excitation method is more worth the effort - i.e. building your own a high frequency driver (if your current unit isn't suitable) for a VM. That is both a far more interesting (and considerably safer) and useful project to provide details here, in my opinion.

Good luck in school and building your systems!

Re: Some Beefy Power Supplies

Posted: Tue Jun 25, 2019 5:10 pm
by Robert Dwyer

I believe the unit supplkies 25kHz which should be enough to drive a multiplier. Of course, the multiplier would have to consist of many stages to step up to 60kv. When I get around to taking o-scope measurements of the driver, ill begin looking into the values of the diodes and capacitors to operate at those frequencies whilst keeping ripple low.

If I do use one of the units as a driver for a different multiplier, I will also have to heavily consider my options for ballasting, as the last thing I would want to do is arch and short circuit a multiplier stack that large.