How do I build a Glow Discharge Tube?

[zheng89120]

Hello,

I'm an undergraduate student, doing an independent research project under a professor this summer. So the experiment I am working on involves using a glow discharge tube, with electrodes at two ends, to create and contain a plasma column. The purpose is to measure and analyze "wave modes" of plasma oscillations (a type of MHD wave) coming from the plasma. Unfortunately, my physics department does not have a glow discharge tube for me to use, so I have to either build it or order it. I have had no experience with glow discharge tubes, so I'm not sure what the best way (the fastest way) to obtain it is. Any ideas would be greatly appreciated.. need to at least finish experimenting before fall term. The specifications (roughly) of the tube should be:

38 cm long
5.5 cm outer diameter
5.15 cm inner diameter

with:
vacuum tubing (i guess for evacuating the tube) is: 3.8 cm diameter

also:
metal plate (allows the gas to flow thru, but defined the plane of the anode, instead of the vacuum tubing acting as the anode) is: 7.7 cm in diameter

How would I go about making this in the shop (with the help with shop technicians)? Or should I order it from an equipment maker (if so, how much)?

THANKS

[Drakkith]

Have you tried google? I typed in glow discharge tube suppliers and saw several links on the first page that looked promising.

[zheng89120]

Hello,

So it turns out the Glow Discharge was not the problem. The problem is that my department won't allow me to use their vacuum system this summer, because of liabilities. I was wondering is there any way I can order one of these systems for less than $5000? that would be awesome if I can get a "clearance deal" on one of these babies

THANKS

[jim hardy]

i get tired of insurance companies telling me what i can do.


how much vacuum do you need? More correctly what absolute pressure?

are you a tinkerer?

refrigeration vacuum pumps will pull a fairly decent vacuum like 0.1 inch mercury absolute.. Places like harbor freight sell them cheap. Or you can jury rig the compressor from one of those little dorm fridges you see in dumpsters.

if you need to make millitorr tell the professor he'll have to get more serious about helping you do the experiment.

[Drakkith]

Are you wanting a vacuum system for under 5k, or the whole thing vacuum and discharge tube and all for under 5k?

[zheng89120]

well, realistically I could pay for a vacuum system for under 2.5k, the department (shop) can provide the glow discharge tube

otherwise, I will have to finish this experiment as part of my 4th year thesis project, early next school year

[Drakkith]

So you want a vacuum system only then?

[zheng89120]

yes, is that obtainable?

[Drakkith]

I'm not sure. I guess it depends on how much of a vacuum you want. Do you know the required pressures you need to obtain?

[zheng89120]

roughly 1 milli to 1 micro Torrs

[Drakkith]

Alright. So you need just the pumps and connecting equipment? (Hoses, fittings, adapters, ETC?)

[zheng89120]

thanks so much for your guys' attention; you're awesome, Drakkith

the apparatus is uploaded here: http://s616.photobucket.com/albums/tt247/zheng89120/?action=view&current=Apparatus.jpg

I think the department probably has all the plumming, but need the "steel vacuum/pump system"

[Drakkith]

I'm actually not anywhere close to an expert on vacuum systems, so forgive me if these questions seem a little dumb lol.

What exactly is the "steel vacuum/pump system"?
I'm assuming you need the foreline and turbo pump at minimum. I've been trying to build a Fusor for about 9 months now, so I had to look into this stuff a little bit. I purchased a used turbo pump and controller from ebay, but I have no idea if any of it works yet. You can get a foreline pump for a few hundred dollars, more or less depending on the flow rate you need. A new turbo pump is REALLY expensive though, and you probably don't need a turbo pump exactly, but any type of pump that will reach your required pressure. I think there are a few types of pumps other than turbo's that will work

Since I don't know too much, all I can say is go to www.fusor.net, then go to the forums, to the Vacuum subforum, and look for some FAQ's on the vacuum systems. A search for "FAQ" in the vacuum forum would probably show them. A word of warning though, the forums over there REALLY suck with the layout and way it works lol.

[zheng89120]

thanks, I will keep you up to date on any new developements

[zheng89120]

So - would these component work for a vacuum system:

Turbo Pump: http://cgi.ebay.com/LEYBOLD-TURBOVAC-50-85401-1200-HZ-TURBO-VACCUME-PUMP_W0QQitemZ260761238541QQcategoryZ46548QQcmdZVi ewItemQQ_trksidZp5197.m7QQ_trkparmsZalgo%3DLVI%26i tu%3DUCI%26otn%3D5%26po%3DLVI%26ps%3D63%26clkid%3D 8401430470120031930#ht_2136wt_907

Controller: http://cgi.ebay.com/Leybold-Turbotronik-NT-450-turbo-pump-controller-/170613429049?pt=LH_DefaultDomain_0&hash=item27b95a5339

Foreline: http://cgi.ebay.com/Key-High-Vacuum-Products-Inc-MT-150-Foreline-Trap-/110654154709?pt=LH_DefaultDomain_0&hash=item19c38067d5

Vacuum pump?: http://cgi.ebay.com/VACUUM-PUMP-ROTARY-VANE-3-CFM-1-4HP-R134A-HVAC-TOOL-AIR-/150620509994?pt=LH_DefaultDomain_0&hash=item2311ae972a

[Drakkith]

I would think so, but you'd have to look at the numbers for everything. Sorry, I've bought a few items but I haven't even put them together yet lol