Fusor Forums

Hello fellow fusioneers- I’ve been working on my fusor intermittently for the last several months and have made reasonable headway leading to what I believe may be evidence sufficient to be admitted to the neutron club. Since I last checked in, I’ve built a new powersupply consisting of 4 MOTs in series under oil hooked to a 2 stage half-wave CW multiplier made of MO caps (also submerged). Unloaded, it can provide 50kV. In addition, I traded out my old chamber for a smaller unit originally used by Robert Tubbs. It was coated with the most horrific sputtering I have ever seen, and looked like an abused cast iron pan on the inside. Dave Housley was kind enough to lend me a media blaster, which was sufficient to remove the coating. Other than that and some lead sheet, the system remains very much the same as in my original post. Gas is provided by a D2 lecture bottle through a micro-metering valve, the feedthrough is a custom made unit ( download_thread.php?site=fusor&bn=fusor ... 1357713788 ) and the grid is a 3-wire stainless basket made using the Rosenstiel method.

First Neutrons

After replacing the inner grid and stem insulator and pumping the chamber down for about an hour, I brought up the reactor with a backfill of pure D2. As usual, I lit the poissor at 40microns. In this run I took special care to bring up the voltage and lower the pressure slowly. Counts began at 20kV/5ma with the poissor appearing as in the first picture. X rays were higher than normal, so I placed a lead cap on the second viewport and moved a lead sheet between the chamber and myself. As the voltage was raised, the detector indicated yet higher counts (above 500 per minute by the time I hit 30kV). I removed the tube from the moderator, and counts fell to near zero. Further, when the Ludlum’s voltage was dropped, the counts ceased. A further test using a toasty bit of pitchblende (acquired from Carl Willis) indicated the tube was not responding to gammas/x-rays. At this point I called Robert Tubbs to verify my results. When he arrived, he repeated the exact tests I had performed earlier, and videoed them.
As I am attempting to conform to the rules of the neutron club as established in the FAQ, I am aware that I do not meet the specification exactly. Namely, I do not have photographic evidence of the voltage and current during the run. In the video my body is blocking them, and the reactor is too finicky to take the pictures unaided. I don’t want to make Tubbs drive all the way to my house again before I post this, so feel free to delay my admission until I can meet that point.

VIDEO: Please excuse the language near the end. I was startled.
http://www.youtube.com/watch?v=qP9ddHgG7ms

Fusor CV:
~50kV MOC/MOT supply with 1.5Mohm ballast under oil
6” 7-port SS conflat chamber
250W CVC VMF21 Diffusion pump
Welch 1402 roughing pump
D2 lecture bottle
Single-stage regulator
SS-SS1 Micro metering valve
DIY glass-tubing feedthrough with pyrex insulator
Stainless grid (3-wire)

Detector CV:
Ludlum Model 12
12” x 1” Reuter Stokes He-3 tube
HDPE scraps and vac pump oil as moderator
1700 V

Run Information:
Average voltage 38kV (ranged from 36-42)
Current: 6ma (varied between 5-7)
Detector distance: 29cm
Detector NVTH: 26
Meter: Ludlum Mod. 12
Moderator: HDPE, pump oil
Time: 4:50 (video is the last 1:45 of that)
Average CPM during run: 900
Highest CPM (the next run): 3200 at 42kV
Background count (I have boring video if you’d like): one count per ~20 seconds

Photos

Fig.1: Fusor at 20kV, 5ma, 10 microns. This is when I began noticing significantly higher than background counts. Sorry for the off-kilter camera. This has been fixed.
Fig.2: Fusor at 38kV, 7ma, 8 microns showing x-ray speckling. This was taken near the peak of the neutron production I achieved. I would estimate I was seeing ~3000cpm when this was taken.
Fig. 3: The entire setup residing in the basement. Since the video was taken, I added some further lead shielding which can be seen in the photo. Please excuse the mess, as I'm temporarily living in the basement of my grandparents' home until I head off to MIT.

That's the business, Jake. Nicely done.

Jake
Well done
There may be a clue as to your success in picture two
The white dots in the pic are very similar to what I saw when I did the 12MeV proton beam into air a few years ago at work.
Neutrons and gammas/x-rays will affect the CCD in your camera causing the white spots.

admission to the neutron club is tantalisingly close keep at it

Jake,

Looks good, and if I got my figures right, you were producing some 20,000 neutrons per second isotropically.

Steven

Pulling the tube in the active video was the clincher and is all we needed to see. However, your writeup is superb and gives a good picture of what you have and did.

If that wasn't enough, any real fusioneer with limited controls, like myself, instantly reconized that only in a real fusor is there need for three or more pairs of hands in the mix and so clearly seen in the video as you claimed to have to devote full time and attention to "managing the gas", forcing Robert to pull the tube for you. You are very fortunate in having a 3He tube!

You are there. You've done it! Welcome to the neutron club.

Thanks for one of the fullest expositions on fusor success yet seen.

Richard Hull