Tungsten Cathode, no Welding Required

For posts specifically relating to fusor design, construction, and operation.
Jon Rosenstiel
Posts: 1370
Joined: Thu Jun 28, 2001 5:30 am
Real name: Jon Rosenstiel
Location: Southern California

Tungsten Cathode, no Welding Required

Post by Jon Rosenstiel » Fri Sep 10, 2004 5:10 am

The photos below should give a pretty good idea of the process.

I used 0.026" diameter tungsten wire from Small Parts Inc. (Part# TW-026-60) This particular wire was amazingly ductile for tungsten wire. I also attempted to make a grid using 0.022" wire but it was much too brittle. As the saying goes, "your mileage may vary".

The tubing is 7 gauge thin wall 304 stainless steel hypodermic tubing from Small Parts also. (Part #HTX-07T) My HV feedthrough stalk has an OD of 0.156" and the 7 gauge tubing has an ID of 0.160". Produces a nice friction fit.

I cut the slots in the end of the ss tubing using a thin cutoff wheel in my Dremel tool.

There was no difference in performance (neutron count) compared to the more traditional 5 circle grids I had been using.

This grid will take some punishment. I've run my fusor at over 1kW input for 3 to 4 minutes at a time. And she ran exceptionally stable!

Jon Rosenstiel

Edit: As the photo here was lost, I have taken the liberty of substituting a diagram of the construction. If Jon has this image as a photo he can insert it to back up the diagram or contact me to edit it in.
I have done this to make the fine grid idea of Jon's retain a visual aspect for other to see how it is done.
Richard Hull 11/29/19

[attachment=0]Tungsten Cathode.jpg[/attachment]
Attachments
Tungsten Cathode.jpg
Tungsten Cathode.jpg (74.99 KiB) Viewed 16 times
Grid diagram.jpg

Q
Posts: 200
Joined: Mon Jan 12, 2004 10:45 pm
Real name:

Re: Tungsten Cathode, no Welding Required

Post by Q » Fri Sep 10, 2004 9:10 am

what a neat grid idea! and so simple too.

Q

Starfire
Posts: 1482
Joined: Wed Oct 24, 2001 6:14 pm
Real name:

Re: Tungsten Cathode, no Welding Required

Post by Starfire » Fri Sep 10, 2004 12:14 pm

Thanks & congrats. Jon - miniaturisation indeed, this must be the smallest grid ever made - and punches a Kilowatt. These photos should be archieved. ( what are you like at watchmaking? :)

User avatar
Adam Szendrey
Posts: 1333
Joined: Fri Mar 29, 2002 10:36 pm
Real name: Adam Szendrey
Location: Budapest, Hungary

Re: Tungsten Cathode, no Welding Required

Post by Adam Szendrey » Fri Sep 10, 2004 1:04 pm

A great idea! Thanks Jon!

Adam

User avatar
Richard Hull
Moderator
Posts: 11630
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: Tungsten Cathode, no Welding Required

Post by Richard Hull » Fri Sep 10, 2004 1:47 pm

This is how some of the grids were made by Miley's group. (they have built many systems, by many grad students, over the last 20 years.

Some were also assembled by bundling the long stems, as well, instead of the tube held method.

The other grids, (cross ways) can be attached by binding with 1mil or similarly fine W wire.

Good work Jon. Tungsten will have the same cleanup issues as Ta, but have the edge on the melting point.

I might try my hand at this method. at some point and it might just be NOW as my current grid system is faulty. I don't know if I will have time to implement a lot of stuff for fusor IV before the bash, but I am moving on some of them.

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.

Starfire
Posts: 1482
Joined: Wed Oct 24, 2001 6:14 pm
Real name:

Re: Tungsten Cathode, no Welding Required

Post by Starfire » Fri Sep 10, 2004 2:05 pm

I like the tie-down - photo 3

Jon Rosenstiel
Posts: 1370
Joined: Thu Jun 28, 2001 5:30 am
Real name: Jon Rosenstiel
Location: Southern California

Re: Tungsten Cathode, no Welding Required

Post by Jon Rosenstiel » Fri Sep 10, 2004 2:32 pm

John,

The grid isn't as small as it appears in the photos. I think what may have thrown you off are the 3, nested, alumina tubes in pic #5. The OD of the outermost tube is 3/4" (19mm).

The grid is about 1.3" in diameter. (33mm). That makes it about a 5:1 ratio to the 6" ID of the outer shell.

I should have included something in the photos to indicate perspective.

Jon Rosenstiel

User avatar
Brian McDermott
Posts: 682
Joined: Wed May 28, 2003 10:28 pm
Real name:

Re: Tungsten Cathode, no Welding Required

Post by Brian McDermott » Fri Sep 10, 2004 2:47 pm

Is that the same grid shown in your recent "supernova" post to Images du Jour?

Is there any advantage to having the crosswise rings on the grid as opposed to simply the setup shown in the photos?

User avatar
Richard Hull
Moderator
Posts: 11630
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: Tungsten Cathode, no Welding Required

Post by Richard Hull » Fri Sep 10, 2004 3:05 pm

I wouldn't image the cross links are critical provided enough vertical circles are used to fool the e-field into thinking it is a perfect sphere. It is sad that the better the transparency is, the worse the field uniformity is. There is a point, however, where the field is virtually perfect and yet the grid is still relatively, ion transparent.

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.

Jon Rosenstiel
Posts: 1370
Joined: Thu Jun 28, 2001 5:30 am
Real name: Jon Rosenstiel
Location: Southern California

Re: Tungsten Cathode, no Welding Required

Post by Jon Rosenstiel » Fri Sep 10, 2004 3:27 pm

Brian,
It's not the exact same grid as in the supernova photo, but is of the same construction and size.

Jon Rosenstiel

Post Reply