Greetings from Oregon

[Mark Kimball]

Hello All,

As I write this it's raining .

I've been lurking around this site for some time & finally decided to join. My career has been in the field of semiconductor failure analysis (and the development/modification of FA tools). Both halves of that mean I lived and breathed the scientific method -- form a hypothesis, test it, evaluate, repeat. The work involved the use of semiconductor physics, chemistry, some structural analysis (think IC packaging problems), programming, you name it. It had the nicety of being tasked to take things apart in creative ways without having to put them back together again (maybe I was a grand torturer in a previous life).

I also have spent some time maintaining/troubleshooting the high vacuum systems on our focused ion beam and scanning electron microscopes, including replacing the tip seals on the scroll pumps. I have a small machine shop (lathe, mill, metal bandsaw, welder) so making a fusor sounds like an interesting and fun challenge. Since the vacuum required really isn't all that "hard", as part of that I may try making my own DP. A nice little vacuum system can be handy for all sorts of things beyond pumping a fusor chamber.

We have a low but detectable level of radon in our basement. According to the EPA, the level is "safe" but my wife likes to say that we have fission going on in our basement. If I get a fusor going we can round it up to "....and fusion, too".

Mark

[ian_krase]

Greetings!

I'd be very interested to hear about your DP project if you undertake it.

[Werner Engel]

Hi Mark!
Sounds like you have everything you need to start building a fusor.
So just start.

Do you allready know where to start?
Building the chamber?

Good luck and have fun!

Werner

[Mark Kimball]

I will start by haunting ebay for what I can find. And read every single FAQ on this site before I post any questions. Getting a good vacuum is important and useful for lots more than fusors so a backing pump, foreline trap, DP, fittings and instrumentation are high on the list. I already have a small spot welder (an ancient thing built by Tektronix for internal use) so I'm already ahead of the game when it comes to making grids.

Mark

[Jerry Biehler]

You're name sounds familiar. Do I know you?

[Jerry Biehler]

Oh, Surplus Gizmos has a bunch of nice rotary pumps for sale for a pretty good price. Newer units too.

[Dennis P Brown]

Welcome and if the radon gas is any bother (even if it is at "safe" levels), just use an active system to remove it - i.e. a fan to draw out the radon contaminated air in the basement to the outside and also an outside vent to allow clean air to replace this "contaminated" air (the fresh air vent will need to be opposite and well away from the exhaust vent for the radon removal to be effective. This method assumes you have acceptable levels - if not, use only a professional service to solve the problem.) Also, in cold climate's one had better insulate the floor if using this arrangement ... .

Besides the vacuum system, the power supply is a key and difficult issue for most and will need serious attention if you want to do real fusion. Read the FAQ's and definitely ask questions before buying a specific transformer (those things are costly and the wrong one is just a boat anchor ... .) The vacuum system is really a snap compared to that and neutron detection.

[Mark Kimball]

Hi Jerry,

I used to work very close to Surplus Gizmos. Picked up a few items over the years, but all the pumps I saw looked to be in pretty bad shape. I have a line on a Leybold D8 that looks pretty good, but if that falls thru I will renew my acquaintance with SG. Re: your question on having met before, I'm an engineer & therefore allowed to have a terrible memory when it comes to names . While I am now retired, I worked for Maxim Integrated for about 23 years in their semiconductor failure analysis lab. I did get several papers published in some FA-centric symposiums. The most recent was one held in Portland.

Mark

[Mark Kimball]

Hi Dennis,

Yes, we did go to an active system to drop the radon concentration. We initially tried an all-passive approach with perforated pipes under the basement slab but just couldn't get the level below 8 pC. An inline fan got the level to about 2.2 pC. Along the way I found the largest Rn source was the interface between the slab and walls. They are poured separately so the seam all around the perimeter of the basement was letting the radon in. I caulked the whole perimeter and dropped the level from 50 pC to 8. Our house is built on sediments brought in by the Missoula floods, and those silts are high in granite, which, in turn, has a relatively high concentration of uranium.....so we had a pretty good idea that we would have a radon problem. We did the mitigation up-front, and are glad we did.

Back to fusors, I agree that the vacuum system is the easy part. I have a 0-20KV Spellman I can use for preliminary work (picked it up at the Tektronix company store years back for a song). But the various FAQs I browsed suggest this won't be enough, unless ....maybe.... everything is perfect and I have a very good neutron detector.

Mark

[Jerry Biehler]

Stock always changes, they have been getting in a bunch of Axiden roughing pumps, look virtually brand new and they have been tested.

http://www.ebay.com/itm/Pfeiffer-Adixen ... 3f7df2c54f

[Dennis P Brown]

The issue is what power does that unit support? Yes, 20 kV can do it if the current at 18-20 kV is high enough (i.e. just because the unit is rated for 10 ma (power of 200 watts), that does not necessarily mean 10 ma at 20 kV but maybe 10 ma at 10 kV and 3 ma at 20 kV ...also,when working/running a fusor at lower range voltages like at 20 kV, higher power is needed than for one working at 30 kV. In the FAQ, Richard gives minimum power needed as well as viable voltages.)

For instance, I have a spare power supply; it is a 40 kV Glassman (negative voltage output, of course) but it is rated for only 5 ma (yes, could push it to 10 ma safely with the extra fan) but doubt it would give 10 ma above 30 kV. So, I don't bother with it but use my 32 kV, 30 ma x-former.

Do consider a small chamber with a high working pressure (30 microns; like a 4-way connector.) A recent poster got very high neutron counts with a similar 20 kV if I recall correctly.