Demo Fusor close to first light

For posts specifically relating to fusor design, construction, and operation.
Larry Upjohn
Posts: 135
Joined: Wed Jan 03, 2007 8:06 pm
Real name: Larry Upjohn

Demo Fusor close to first light

Post by Larry Upjohn » Fri Sep 12, 2008 5:07 pm

Hi all;
just to assure everyone that I am not a transient lurker I am forwarding in the next posting several photo's of my first demo fusor effort. I am within hours of applying vacuum and power. This is my first attempt and my time is limited so I have taken almost a year to get this far. As per an earlier request I will place my photos in a second entry on this thread. More later, Larry Upjohn.
Larry Upjohn

Larry Upjohn
Posts: 135
Joined: Wed Jan 03, 2007 8:06 pm
Real name: Larry Upjohn

Re: Demo Fusor close to first light

Post by Larry Upjohn » Fri Sep 12, 2008 5:29 pm

Here are the photo's to document my progress. I am using a new Ford Model A sparkplug for my feedthrough at this stage and a 7500 Volt 60ma old NST wired per Richard's "The Farnsworth/Hirsh Fusor" paper found elsewhere in the Files section for my high voltage supply. Inner Grid is SS 3XX welding wire ( 0.030 inch?) and the outer grid is 2-0 guage copper ground wire. Base plate is a found piece of 7/8" 6061 aluminum and "bell Jar" is the 1/2 gallon fish bowl from Walmart (It is Anchor-Hocking made in USA glass no less) Will have pictures of first plasma shortly. Image 1 is the closeup of the innergrid and feedthrough, outer grid and has a flash reflection which I will learn to get rid of later. Image 2 is a more complete fusor photo sitting on my drill press table ( sorry for the visual clutter, again which will be reduced when operational).
Image 3 is a side on shot of my nearly complete HVDC power supply showing the NST and a home made HV capacitor filter somewhere around 0.5 mfd at 20KV. More later, Larry Upjohn.
Attachments
IMG_0304.JPG
IMG_0304.JPG (484.97 KiB) Viewed 1644 times
IMG_0302.JPG
IMG_0302.JPG (491.11 KiB) Viewed 1644 times
IMG_0299.JPG
IMG_0299.JPG (466.5 KiB) Viewed 1644 times
Larry Upjohn

User avatar
Chris Bradley
Posts: 2930
Joined: Fri May 02, 2008 11:05 am
Real name:

Re: Demo Fusor close to first light

Post by Chris Bradley » Fri Sep 12, 2008 6:02 pm

Ensure you have adequate protection around the kit like perspex sheeting, plus eye protection, to catch flying glass and other debris in the event of collapse and/or electron beam spot heating. Best to presume this will happen and to hope that it does not, rather than the inverse.

(if I need to say that! better safe..etc..)

good luck!

Larry Upjohn
Posts: 135
Joined: Wed Jan 03, 2007 8:06 pm
Real name: Larry Upjohn

Re: Demo Fusor close to first light

Post by Larry Upjohn » Fri Sep 12, 2008 6:10 pm

Chris;
forgot to add that I am using 10" concrete form tubing as a shield with porthole for photos during operation. This is has a 3/8" wall thickness and hopefully it will work for now. I will be replacing the glass "bell-bowl jar" with a unique SS chamber soon but I wanted to get some operational experience with this outfit first. Larry Upjohn
Larry Upjohn

User avatar
Chris Bradley
Posts: 2930
Joined: Fri May 02, 2008 11:05 am
Real name:

Re: Demo Fusor close to first light

Post by Chris Bradley » Fri Sep 12, 2008 6:36 pm

Glad to hear it! Safety first. All the best for a successful power-up. Are you running a variac, or is it straight on at nominal full voltage?

Larry Upjohn
Posts: 135
Joined: Wed Jan 03, 2007 8:06 pm
Real name: Larry Upjohn

Re: Demo Fusor close to first light

Post by Larry Upjohn » Fri Sep 12, 2008 7:16 pm

I have a 5 amp variac to ramp the NST up and down as per Richard's schematic. I have used the xformer before in a circuit to provide high frequency high voltage to an arc welder for TIG welding. This was since replaced by a commercial HF unit so the fusor HV power supply is a perfect home for this piece of electrical history. Larry Upjohn.
Larry Upjohn

User avatar
Carl Willis
Posts: 2841
Joined: Thu Jul 26, 2001 11:33 pm
Real name: Carl Willis
Location: Albuquerque, New Mexico, USA
Contact:

Re: Demo Fusor close to first light

Post by Carl Willis » Fri Sep 12, 2008 7:21 pm

Looking good, Larry. Should make a very pretty discharge. Your baseplate is sturdy and will support better chambers in the future when the glass fishbowl has "had enough."

I see you are using a lot of NPT / Teflon tape seals in the vacuum line. I have had endless problems with these in vacuum systems, to the point that I usually solder all pipe-thread fittings or epoxy them. At work, if I must make such a connection, I spray the Teflon tape with liquid "VacSeal" resin before wrapping it. That's the only way to guarantee a vacuum-tight joint. Otherwise it's a gamble--fine for small single joints like the 1/8" nipples on thermocouple gauges that are easily redone, but for manifolds with multiple fittings, a big headache in the making.

Good luck!

-Carl
Carl Willis
http://carlwillis.wordpress.com/
TEL: +1-505-412-3277

Dan Tibbets
Posts: 578
Joined: Thu Apr 17, 2008 5:29 am
Real name:

Re: Demo Fusor close to first light

Post by Dan Tibbets » Fri Sep 12, 2008 7:42 pm

A couple of 'possibly usefull' comments. I tried a old resistive spark plug as both a feedthrough and limiting resister, using a microwave oven transformer (MOT). It worked, sort of. With the modest vacuums I was obtaining (guessing ~100-200 microns) I had arching to the metal base of the spark plug where the ceramic met the metal. It was old so the surface of the ceramic may have had contaminates that was not as good an insulater as the ceramic itself. I made it work by coating the metal and metal ceramic juntion with several layers of liquid electrical 'tape'. It was ugly, but it worked- till the plug stoped conducting- assume the internal resister burned out.

Also, the tall metal extension may not be ideal as it will also 'glow'. Wraping multiple layers of plumbers teflon tape around it will insulate it some. The tape immediatly next to the glow will melt/fry but should work in a DEMO fuser where you are not concerned about contamination.

Good luck'

Dan Tibbets

Dan Tibbets
Posts: 578
Joined: Thu Apr 17, 2008 5:29 am
Real name:

Re: Demo Fusor close to first light

Post by Dan Tibbets » Fri Sep 12, 2008 7:56 pm

Additional, probably redundant note. In the picture of your NST I do not see a grounding wire attached . Make sure the NST case is well grounded!

And, is your capaciter bank wired is series to increase voltage tolorance of otherwise 'low voltage' capaciters, or are they in parellel to increase capacitance? I don't know the voltage of your NST. Make sure you do not have arching between your capaciter wireing. If the voltage is high enough to arc you may need to embed yor capaciter bank in oil or silicone glue, or hot glue, etc...

Dan Tibbets

User avatar
Richard Hull
Moderator
Posts: 12283
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: Demo Fusor close to first light

Post by Richard Hull » Fri Sep 12, 2008 8:25 pm

Good luck with first light.

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.

Post Reply