I have Swiss TV journalist Yves Gerber in the lab today. I will try the electron gun again while he is here.

Previously in the comments, Olivier suggested the vacuum pressure is too high. Indeed, at 1.66 millitorr the pressure was higher than I wanted.

My first goal today is to check the empty vacuum chamber with blank flanges. A best case scenario.

With the initial pump down I only got down to ~3 millitorr…  about the same as last time. I used the stethoscope to listen for a leak but did not hear one.

I tried tightening the flanges one last time, and suddenly the pressure started dropping again.  I forget how much torque these conflat flanges need to fully seal.

Now I am seeing pressure in the range of 0.098 millitorr and dropping. Much better!

So now let’s install the electron gun, and see what we get.

UPDATE:

With the electron gun components in the chamber I am able to get down to 0.27 millitorr… not bad!

But when I turn on the electron gun… still no beam.

Exhausting!

Today I did another test of the CRT based electron gun in the vacuum chamber.

Spoiler alert: I didn’t see an electron beam.

This time I put a grounded piece of phosphor right in front of the beam path:

Here is a closeup of the grounding wire:

I printed the phosphor holder with 1% infill so it’s basically hollow, then I drilled it with holes to allow gas to escape:

The vacuum reached 1.66 millitorr which is not amazing, but good enough for this run.

I tested the wiring with the unbroken CRT, and it looked good:

Then I wired the power supply to the vacuum chamber feedthrough:

The I fired it up, you can see the hot cathode working:

But no beam.

:(

Previously I tested out the electron gun and I didn’t see a beam on the phosphor. I wanted to rule out the possibility that there WAS a beam, but it wasn’t hitting the phosphor screen. By moving the screen closer I can see the beam no matter where it is pointed.

So I designed and printed this sweet phosphor holder:

I have a small piece of broken phosphor glass from the CRT. I used the excellent OpenSCAD polygon editor to make a form fitting mount:

In real life:

That was easy!

I received the new SCR. It can handle 3000 amps peak current. It is much larger than the SCR I recently destroyed:

IRKT136-14 data sheet.

Here it is installed. Everything works:

I also added leads to the current sense resistor to avoid touching the back of the power supply:

The pressure necessary for plasma is still too high. I tried another tweak to the electron gun:

No joy. It requires about 24 millitorr for a stable plasma. UG.

Today I tweaked the electron gun.

My goal is to bring the electron gun closer to ground. This should reduce the pressure needed to strike a plasma.

I used Stuart’s DIY spot welder to make a hoop from welding wire:

I installed this hoop on the electron gun:

This arrangement brings ground potential closer to the electron gun.

And it worked somewhat.

With this hoop, I can strike a stable plasma at 18 millatorr. Better than yesterday’s 25 millatorr. Still needs work to get back to 8.5 millatorr.

When I went to fire the coils I discovered my SCR is shot:

Turns out the SCR’s peak current is 2,000 amps. At 2,300 amps we are well beyond that!

I have to order a new SCR tonight. Suggestions welcome.

Elsewhere… I drilled a hole in the langmuir probe holder to allow trapped gas to escape:

Also tested out the supercapacitors in my friend Arnie’s forklift:

They were able to lift Arnie twice!

Video of operation:

All photos.

I bought a second CRT; broke the vacuum by drilling an unused pin; scored it and smashed it!

Now we have an electron gun:

I installed it in the chamber and wired it up:

Here you can see down the beam line to the hot cathode.

I taped a piece of broken phosphor screen on the viewport so I can see the electron beam:

But something is not working, no beam.

Time to troubleshoot.

I finished the CRT power supply and got the CRT running with focus and grid:

As you can see we have an interference pattern. To the eye the beam looks much brighter in the center:

With the focus adjustment I can broaden the beam:

The CRT power supply:

Electron gun operational:

I got these high voltage supplies made for CRTs:

I still need to play around to get it focused, but a great start!

I will eventually break this tube (implosions! I know!) and use the electron gun and phosphor inside the vacuum chamber.

The idea is to run the sydney experiment with a pure electron beam. We are currently using an air or deuterium plasma.

Before I break the CRT I will operate it in tact. Here is the pinout for 3BP1.

This sweet CRT hack is a good start for the power supply needs.

Already got the hot cathode running:

On the 3D printing front I received the 3D printed ceramic coffee cup I ordered last month:

It looks really promising. Soon we’ll have a 3D printed ceramic magrid.

1 year,  7 months  and 8 days ago I learned of the copper coil Polywell that Joe Khachan and his team built.

I decided to repeat Joe’s experiment. Although challenging it seemed possible to achieve. I dubbed this endeavor the Sydney Experiment.

It took far longer than I expected to fabricate all the necessary parts for the experiment.

Today with great pleasure I ran the Sydney Experiment. Here we see what appears to be electron confinement:

This acquisition shows the floating potential of the langmuir probe.

This run was done with air plasma at 10 millitorr :

The electron gun was running  10KvDC @ 6.5mA:

The coil power supply was charged to ~ 400VDC:

This is just a first run. Now begins the actual experimentation and data gathering.

I do believe this is the WORLD’S FIRST AMATEUR POLYWELL!!!

The plasma during the run: