This is a challenge because the armature must be an excellent electrical insulator and have a  high heat tolerance. The ideal material is ceramic.

The problem with ceramic is that it we cannot machine it into the unique shapes required, but we can 3D print it! I’ve modeled the armature shape in OpenSCAD:

Here’s a link to the source code

The three curved “feet” have the same curvature as the inside of the reactor chamber, so it will fit nicely and sit still in the bottom of it.

the first column on the left holds the cathode, the middle column, the accelerator anode, and the last, the phosphor screen. the black line will be the path of the electrons to the center of the reactor. Everything here is pretty much how it’s going to be on the final armature, except the phosphor screen will have a different shape, and the distances between the columns will be different as well.

The MakerBot wouldn’t be able to print this all in one shot, so I printed it in sections, and glued them together to get a feel for the final one.

The accelerator cradle

Column for hot cathode

Base of the armature

Earlier version of the base

Assembled armature with cathode and accelerator

Hopefully when I send this file out to be printed in ceramic, they will be able to do it all in one piece. If not, I’l have to find some way of gluing pieces together

Domenick Bauer

Here’s a link to the OpenSCAD code.

By DOMENICK BAUER

See photos for measurements of hot cathode.

The next steps are modeling the hot cathode (plus clearance) and subtracting that from a cylinder in OpenSCAD:

ALWAYS BE KNOLLING (ABK)

1. Scan your environment for materials, tools, books, music, etc. which are not in use.
2. Put away everything not in use. If you aren’t sure, leave it out.
3. Group all ‘like’ objects.
4. Align or square all objects to either the surface they rest on, or the studio itself.

It’s a more deliberate version of “cleaning up”.

Today I’m taking some small steps toward building hot cathode electron gun v2.

Here is a physical diagram and schematic:

This is the hot cathode intended for  an electron beam welder. It has 34 mΩ resistance:

The parts of the electron gun will be arranged like this:

This is more simple than most electron guns. I don’t need a carefully focused beam, I just want to shoot a crude beam of electrons into the Polywell.

The next step is to design and build a simple armature to hold the pieces together.

Based on comments we may have one or more of these problems:

1) The hot cathode has been fouled by operation in normal atmosphere. I tried to avoid this, but who knows.

2) When I removed the CRTs glass casing, I may have removed a high voltage anode.

3) The phosphor screen may not be grounded well enough, causing deflection of the electron beam by charge accumulation.

4) The vacuum pressure is too high, scattering the electrons.

5) Something else.

My plan is to set aside the CRT based  electron gun, and try to build a simplified electron gun from scratch.

Previously I purchased a fresh hot cathode designed for electron beam welding.

The gun will consist of a hot cathode floating at -100V and a copper tube segment at +2000V for acceleration. A grounded phosphor screen will reveal any beam that forms.

Let me say a little about how I came to find Prometheus. I’ve done some fusor work in the past, and a few years ago, I built a Farnsworth-Hirsch fusor capable of star mode. Unfortunately I had to return to school before I could make a real attempt at fusion. Since then, I have been an avid follower of the fusion effort. Earlier this year, I came upon this blog, and found it very exciting.

I wanted to be a part of it, but knew that money was tight at Prometheus, so I applied for the Hodson Trust Internship Program, a fellowship offered by my school in which an applicant creates a proposal on something interesting he wants to do, and finds an organization where he can do it. If the Hodson committee likes the proposal and the organization, the applicant is awarded a stipend on which he can live while he does his internship.

Yesterday, I learned that I was awarded the internship!

It feels great to be here at Prometheus and I can’t wait to get started.

The light is made from aluminum milled right here in the shop we share.

The light is practically impossible to steal without removing the seat post. It senses your motion and turns on/off automatically. And the battery lasts longer than your typical bike light. It’s a tiny marvel of engineering.

Stuart is a master craftsman. I’ve seen him design and ship stunning robotics and dynamic sculptures over the years.

Stuart is a HUGE contributor to my fusion research. He taught me everything I know about prototyping.

So do yourself a favor and buy the last bike light you’ll ever buy.

Last week I was in Geneva doing a talk at LIFT 2012, which I will post when it goes online. As part of the conference I was invited to tour CERN and the Large Hardron Collider. Despite a hungover 7AM wakeup I managed to make the train to CERN. What an amazing experience!!

A cutaway showing how the beam line section are connected. The beam line tubes contract several centimeters as they are cooled with liquid helium, so bellows and sliding joins are used:

This is the main testing facility for beam line tubes:

This is a cavity resonator used in the Large Electron Positron Collider – the predecessor to the LHC:

Here we see the control room for the Large Hadron Collider. SO COOL.

James Bridle , who spoke at LIFT, wrote a nice post on our CERN visit.