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Greetings!

Posted: Tue Nov 14, 2017 1:14 am
by Samuel Berman
Hello everyone! I am a 15 year old high school student. I am interested in Chemistry, Engineering, etc, but only recently decided to tackle building a Fusor. This project will probably be a long term thing for me and it will take me a while to get all the materials. I did some searching online and decided to join this forum because it looks like the best place to be for this sort of stuff. Anyway, so far I have a vacuum pump (cheap 1 stage, so may need a different one), a glass jar, and a gasket (neoprene, so probably not suitable either :(). I have a decent amount of experience with this stuff as I have been tinkering in my garage for years. Wish me luck!

Re: Greetings!

Posted: Tue Nov 14, 2017 5:15 am
by Dennis P Brown
Hello, and welcome. Both a single stage pump and a 'glass jar' are only useful for a plasma demo; a fusor requires a steel chamber or steel vacuum connector like a four-way cross ( 2.75 inch or larger.) The other requirements are in the FAQ's so, you can research those items. Good luck in scrounging for items! Maybe request that group and post your results, from time to time. Hint: Keep a close eye on ebay or attend a 'ham radio gear' or similar electronics flea market for a two stage pump that is being offered for little money - ditto for a cheap micron range gauge/display combo.

Re: Greetings!

Posted: Tue Nov 14, 2017 9:45 am
by Samuel Berman
Thanks! I forgot to mention, I have a thermocouple gauge on the way that I got from eBay for $30. Hopefully it works.

Re: Greetings!

Posted: Wed Nov 15, 2017 9:39 am
by Nnnnnnn
Welcome Samuel, depending on your TC and pump you may or may not measure something. Some TCs will work in the 5 Torr (such as the DV-4), others only start giving you a useful reading below the 100 micron range. I don't know if a single stage pump can get down below 100 microns. In addition some TCs require DC Input, while others take AC. Both require an amplifier at the output and the AC TCs also require a filter (this is the kind I have. Will post about it soon). Just some things to consider before you hook up your gauge to the pump.

Re: Greetings!

Posted: Wed Nov 15, 2017 10:18 am
by Samuel Berman
Well, the pump is rated for 5 microns but I doubt it will get near that since it's a $40 pump. I bought the gauge with the controller so I don't have to worry about that. The gauge on the controller goes to 1000 microns, so does that mean it will measure at that pressure?

Re: Greetings!

Posted: Wed Nov 15, 2017 10:40 am
by Rich Feldman
Welcome, Samuel. Give it a go with what you got! If your path is typical, you will soon learn about leak detection and abatement. You're ahead of most noobs, in ability to measure vacuum before you light things up electrically.

Can we see some pictures? I bet your gauge mark for 1000 microns is near the high-pressure end of the scale. Is there an "atmospheric pressure" mark a little bit higher than that, where the pointer goes when powered up with no vacuum, or rests with no power?

You'll have a wide-range pressure gauge to complement your TC sensor, as soon as you can look at plasma configurations inside the jar.
Your NST, HV feedthrough, and internal electrode don't need to be fancy, or even DC to begin with.

Re. Niels's comment about vacuum sensors, RIchard Hull often mentions types where the heated thermocouple directly drives an analog meter movement. Nothing super-sensitive about the meter -- it just has a coil wound for low voltage instead of low current. (Gas safety valves for pilot lights are held open by a solenoid using voltage from a single TC junction -- tens of mV.)

Re: Greetings!

Posted: Wed Nov 15, 2017 10:41 am
by Dennis P Brown
This is the greetings section, so, best to move your questions to Chat section here after.

As to reading a 1000 microns accurately - well, depends but not really all that important. However, that range will tell you a lot about your $40 pump.

The key for any fusor gauge is the range from 3 to 20 microns since that is where most fusors operate. Likely your single stage pump will fail to get even to 100 microns. But, testing is your first step.

Re: Greetings!

Posted: Wed Nov 15, 2017 11:17 am
by Nnnnnnn
Great that simplifies things! Didn't expect it would come with a controller at such a low price. The fact that your meter starts at 1000 Microns is good, probably goes down to something like 10 microns? If you hook it up to your pump correctly, you will probably get some reading, which will tell you if your pump is any good.

Re: Greetings!

Posted: Wed Nov 15, 2017 12:45 pm
by Samuel Berman
Thanks for the info. Should I move this to the new user chat, or some other section?

Re: Greetings!

Posted: Wed Nov 15, 2017 7:08 pm
by Dennis P Brown
The chat area is better unless you have a non-elementary question; then use the correct section.

Re: Greetings!

Posted: Sat Nov 18, 2017 12:19 am
by Samuel Berman
How about for just discussing my pump/gauge and sharing details about my setup?

Re: Greetings!

Posted: Sat Nov 18, 2017 5:54 am
by Dennis P Brown
If you want to post a picture of the gauge and/or pump that you now have (unless it is a fully assembled, operating vacuum system - that could go under the "Images du Jour") or want some operational information on your pump and gauge system, or have a question on how best to test the pump those questions could would be appropriate for the 'Chat' section.

If you turn out to have an electronic question about the gauge controller or issues with the calibration, that would go in the vacuum system - ditto on, say, changing the pump oil.

If in doubt, just try the closest you feel is correct - not really a big concern unless it is an extremely elementary question addressed in the FAQ under the section appropriate for that device/knowledge area.

Re: Greetings!

Posted: Sun Nov 19, 2017 3:47 pm
by Joep Stuyfzand
Dennis P Brown wrote: Tue Nov 14, 2017 5:15 am Hello, and welcome. Both a single stage pump and a 'glass jar' are only useful for a plasma demo; a fusor requires a steel chamber or steel vacuum connector like a four-way cross ( 2.75 inch or larger.)
Is there any specific reason that you can not achieve D-D fusion in a glass jar fusor?
Or is it because a glass jar does not protect against x-rays so a glass jar is practically not useful for real fusion?

Re: Greetings!

Posted: Sun Nov 19, 2017 8:06 pm
by MatthewL
Joep,

One reason not to use a glass chamber is because an increased voltage above demo voltages will produce more powerful ion beams that can heat and weaken the glass causing an implosion. The glass will also allow most of the x-rays through as well. The FAQ's do answer this question in more depth so make sure to check there too.

Regards,
-Matthew

Re: Greetings!

Posted: Mon Nov 20, 2017 8:30 am
by Joep Stuyfzand
MatthewL wrote: Sun Nov 19, 2017 8:06 pm Joep,

One reason not to use a glass chamber is because an increased voltage above demo voltages will produce more powerful ion beams that can heat and weaken the glass causing an implosion. The glass will also allow most of the x-rays through as well. The FAQ's do answer this question in more depth so make sure to check there too.

Regards,
-Matthew
That cleared it up.
Thank you, Matthew.

Re: Greetings!

Posted: Mon Nov 20, 2017 8:55 am
by Dennis P Brown
This discussion really does need to be moved to the chat section since this section is meant to be used for Introductions only. Also, please read FAQ's a bit more on fusor design before posting specific questions. Saves time.