Goodbye fusor IV 2004-2019...Hello Fusor V

[Richard Hull]

Fusor IV is working, as always, and will see its final demo at HEAS #30, Saturday Oct 5th. It has been a real trooper all these years in spite of a perpetual leak that I never spent the time and effort to fix. I did try on two occasions, but nothing came of it.

The record for Fusor IV was obtained during HEAS #27 in 2016 1.97 million n/s isotropic (42.7 kv @ 13.5 ma with 16 microns of D2) #@$%!#*&* just missed that 2mega mark @#*&^%^@!!

I will restructure the bench for fusor V and might temporarily check the Turbo, controller and related cables that I purchased at HEAS 27, flea market back in 2016. If the Turbo gives me a moments trouble, I will use the trusty old diff pump of fusorIV. I have been using the 5 cfm precision belt drive pump I bought at a hamfest for $25 back in 2001. It is still blasting down to about 8 microns in the fore line. I dare not change to one of my 5 nice Welch belt drives as the Precision is plumbed into the bench and is doing great. Don't fix it if it ain't broke. I hope to work up a 2.75 4-way cross and investigate all this small fusor hype.

As usual, I haven't run fusor IV for about 8 months. It takes the usual conditioning to bring it up to snuff. I started on Sept 20th with the usual dismal performance due to the perpetual 25 micron per minute leak.
Leak data: Take the chamber down to 5X10-4 torr and leave it there for 20 minutes. Close the manual 2.75 bellows valve to the fusor chamber. Time the leak....leaks at 25 microns per minute. This rate is read on my Baratron, capacitive, 0.1 torr rated, heated gauge. This can read 4 decades down.

The very best I obtained on the 20th was ~30,000 n/s isotropic. (29 kv @ 22 ma with 6.7 microns of D2)
Each day it has improved
21 Sept 32,690 n/s
22 Sept 80,220 n/s
23 Sept 215,860 n/s
24 Sept 453,740 n/s
25 Sept 635,460 n/s (37kv @ 19ma with 8 microns of D2).
26 Sept 1,203,900 n/s (41kv @19ma with 9.8 microns of D2)
27 Sept 1,194,300 n/s (39.8kv @ 18ma with 10 microns of D2)
28 Sept 1,201,560 n/s (41.3kv @16ma with 10.5 microns of D2)
29 Sept 1,601,118 n/s (41.2kv @ 18ma with 9.9 microns of D2) For the first time all 4 timed runs today went over 1 million n/s
30 Sept 1,839,968 n/s (40.5kv @ 19ma with 11 microns of D2) Almost broke fusor IVs record of 1.9 mega n/s
1 Oct 1,920,300 n/s (40kv @ 18ma with13 microns of D2) Tragedy!!! Grid fell from its silver soldered mounting. Drove the old boy too hard... Repairs undertaken.
2Oct 418,760 n/s (37.8kv @ 13ma with 7.6 microns of D2) Repairs made late 1 Oct. Ran every 12 hours since repairs. It's getting there.
3Oct 716,880 n/s (37kv @ 15.5ma with 8 microns of D2)

I hope to edit into this post, the daily top numbers over the next week.

Note: A very leaky fusor will fuse! All numbers given are for my bubble dosimeter calibrated 3He detector +/- 10% as is common in all neutron measurement work.

I will exercise it each day for my three consecutive runs to an elevated number via more pressure, voltage and current. It would be cool to exceed 1mega neutrons at HEAS. I do not see any impediment to that. I can usually, at most HEAS events, hit 1.5 million n/s. Bigger spherical fusors tend to not need the D2 pressures observed in very successful cross systems. The actual volumetric through-put (waste) may be the same....Interesting point?

I hope to see a number of you on The evening of October 4th and the entire day of the 5th for the last gasp of D2 in fusor IV.

Richard Hull

[Rex Allers]

One small question.

Re:
"...the 5 cfm precision belt drive pump I bought at a hamfest for $25 back in 2001."

I assume that is "Precision", as in the manufacturer, correct?

eBay has made things more accessible if you don't have a good flea market near by, but has also made that kind of bargain price more unlikely.

[Richard Hull]

Yes, the manufacturer is Precision. Their belt drive, slow winding pumps are every bit as good as Welch, but just like all pumps of good manufacture sold at e-bay, lab-X or hamfests, you are buying a "pig in a poke".

My purchase was no exception. The pump was very clean externally. I took off the shroud and found the large pulley frozen. I offered $15 noting it was frozen. I wanted it and had to pay a bit more. I lugged it home and with a few light taps of a hammer on the spokes of the large pulley in the direction of rotation freed the thing up. It had some old oil in it so I turned it rather easily by hand several times to wipe the pump body with oil internally.

I drained the oil and it did not look bad at all, no real sludge came out near the end when tilted as seen in horribly misused pumps. In went new oil and I ran the pump for about 2 hours, blanked off at the head with the ballast wide open the whole time. Another change of oil and a TC gauge at the head showed around 15 microns. I was stunned. The more it ran, it slowly cleaned itself up. I used it to replaced my good old trusty 5 cfm "Yellow Jacket" direct drive pump which I had used on demo fusors I and II. The Precision has had only 4 oil changes since 2003 as I went for real fusion in Fusor III and now fusor IV. Both pumps pulled into the 12 micron range, but the belt drive is always much quieter, soothing on the nerves, and I think, wears better.

Richard Hull

[Richard Hull]

Broke the mega mark today! See the original updated posting. On the 6th day of conditioning, I hit it. It was easy and very fast. Three runs took only 40 minutes from start up of the mechanical pump to shutting off the high voltage. The second best run of fusor IV today turned out 1.1mega n/s! Now I gotta' run it every day until the evening crowd arrives 8 days from now. I hope I don't blow a supply or something....

Richard Hull

[Jim Kovalchick]

Richard,
I consider that particular fusor of yours somewhat historic because of the inspiration it provided many of us who visited.

I wish I could be there to see it operate one more time, but alas, work obligations will keep me away.

On behalf of myself and my family, congratulations on Fusor IV's long run, and good luck with the next one.

Regards,

Jim Kovalchick

[Richard Hull]

Jim,

I am really sorry you couldn't make it this year. You will be missed. Thanks for the kind words and mentioning the role fusor IV has played in showing others a real working fusor, live and in person. Many who came here and saw it put through its paces, never built a working fusor. A few were inspired enough to make one of their own. Two Virginia colleges have made fusors after visiting fusor IV.

With all the interest in smaller systems, I just had to give them a spin. Fusor IV will sit in a place of honor on the top of the NIM rack much as an old race horse is put out to pasture.
It did over a million n/s again today. I updated the original post.

I hope to see you here maybe next year.

Richard Hull

[Richard Hull]

1 OCT.... in pushing the fusor IV, I actually dropped the tungsten grid from its mount. I have successfully pulled the entire fusor apart, replaced the grid. I cleaned it up a bit and reassembled in 5 hours. It went under vacuum and reached 17 microns with the mechanical pump only. I ion bombarded the freshly closed shell with 5kv @ 45ma. The 30 minute run under bombardment dropped the chamber pressure to 10.6 microns! This was about as good as it was before the incident.

The issue now is will the device need reconditioning? How will the diff pump operation and the first fusion run go? We will see.... I will be running the fusor well past midnight to do a first conditioning run.

So, we will have a fusor working at HEAS! Whew!

Richard Hull

[Richard Hull]

First fusor fusion run after the deadly grid falling from its silver soldered post. I noted around 8:30PM the usual grid sparkling occurred and electric burn off of little perturbations. This took about 1 hour to make me pleased with no sparking or minor flashes. Unfortunately, this meant fresh and very intense deposition on the view port window which was already heavily coated. The video image is extremely dim now, but can be made out for running and control purposes.

I began the fusion runs with a pressure of 7 microns of D2. I struggled for over 1/2 hour around 10:30 at night and finally got rather good and surprising results. Instead of being thrown back to day one, I managed to approach a quarter million n/s. Data follows.

102,100 25.4 kv @ 18ma with 6.4 microns of D2
249,200 34.6 kv @ 12ma with 6.1 microns of D2

After the runs with the chamber still on the mechanical and diff pumps, The chamber was down to 10e-4 torr and the TC gauge showed a fore line pressure of 8 microns. Pumps are doing great!!!

I have the first people arriving tomorrow and will continue to run hoping to approach the mega mark, again, by Saturday. I did not clean the 10 year deposition off the window when I had the fusor down today as it will be cleaned for fusor V. Fusor IV is living on borrowed time as it is, and It can run and function fine as witnessed above.

Richard Hull