SC Magrid Feedthrough Simplification

31 08 2009

Doing more thinking on the superconducting magrid feedthrough. Rather than have a bend between the magrid and a centered feedthrough, it would probably be easier to make a custom conflat blank with an off center 2.75″ pass though welded on. Like this:

off_axis_feedthrough

The part would looks something like this (via MDC):

MDC_example





Donation

30 08 2009

Shout out to Anthony Clark from the UK for his donation of $10! Thanks Anthony!





FIRST PLASMA

29 08 2009

YES! Check this business:

IMG_4015

Here it is with the color levels adjusted so you can see more:

IMG_4013

This is really really exciting.

First thing I learned is you need some gas in that chamber to start a plasma. I started at pressures around  1 e-6 torr and got nothing. What you really need is pressures above 1 e-3 torr. My gauge doesn’t work in this range, so I was flying blind.

I had to install a valve to leak air into the chamber to keep the pressure where I needed it:

IMG_4018

Just playing with this device for 10 minutes gave me more of an intuition for plasma than most of the reading I’ve done on the topic.

I’m now one small step away from first fusion. FUCK YEA.





Grounding

29 08 2009

Spent the last two days throughly grounding the entire system.

We start by attaching a ground line directly to the overhead sprinkler system. First we scrape off the paint:

IMG_3987Then we attach this purpose made ground clip:

IMG_3986

Here it is installed:

IMG_3988

We are using 12 AWG insulated stranded copper. In addition to this pipe ground, we are also using outlet ground from two different circuits:

IMG_3992

Ground each piece of rack equipment, and the rack itself:

IMG_3989

Ground several points on the chamber, sled, and pump:

IMG_3990

Here is the high voltage connection point with high voltage divider inside glass insulation:

IMG_4000





Standoff for Superconducting Magrid

29 08 2009

I’ve been doing some brainstorming on the standoff for the superconducting magrid. This is a messy problem! You need a cryogenic feedthrough that is also a high voltage standoff. Then you need to pass in the YBCO superconducting cables, and wiring for the persistent switch.

Yesterday I realized that we can get most of the way there by welding together two off the shelf components:

standoff_feedthroughThis diagram refrences parts 9812107 and 9611005 from insulatorseal which is a subsidiary of MDC Vacuum. I’ve sent this drawing to insulatorseal for a quote. One problem is that part 9611005 is only rated up to 6kV so we will need a custom variant to get to the 10kV to 40kV range.

The idea with this setup is that the high voltage could come through a standard HV feedthrough and connect to the insulated tip of this feedthrough via a connecting wire:

SC_magrid_feedthrough





Inner Grid Standoff Redo

27 08 2009

So the approach I used to secure the inner grid just wasn’t cutting it: The inner grid was not tightly secured. So I took a page from Andrew Seltzman’s liquid cooled grid by using telescoping ceramic tubes:

IMG_3960

I had to file the OD 12.8mm tube with a diamond file to get it to fit inside the next larger tube.

Inside it’s wired together with wire nuts and teflon coated aircraft grade 24 AWG wire:

IMG_3961Note: we ended up using a shorter and thinner stretch of wire than pictured here, but this illustrates how it’s wired.

Here we see it all assembled:

IMG_3972





Outer Grid Fix

25 08 2009

During previous tests we noticed that the outer grid was not mechanically secure in the chamber. Today I added a support to the outer grid:
IMG_3951

Now it fits snugly in the chamber. Keeping the alignment correct was important.

Also we received the high voltage power supply back from Glassman. It’s been converted to a negative potential for use with a fusor. We got a nice shock mounted shipping rack:

IMG_3948

I’m getting everything ready for first plasma.








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