Archived - Neutron from Thailand~!!!

[Jack Puntawong]

Yeahhhh!

Today, after I tweaked with my deuterium system, I have finally produced my first neutron while wearing my pajama listening to Beethoven's Symphony #9 (Very epic, I know). Here are the datas:

Background Count: 8978 counts over 30 minutes which equates to 299 cpm.

Fusion run:

28kV, 10mA at 5 micron
Counter: GE B-10 line neutron probe at 10cm from inner grid.
Moderator: 2 inches of paraffin
Counts: 511 cpm!!!


First of all, I would like thank my parent who support this project. When I first propose this idea, they simply said "yes, go for it". Secondly, I would like to thank William (Bill) Brinsmead who, despite know me as a stranger at first, provide me with every thing I lacked. Thanks Bill for helping out and for being a great friend! See you in Reno in 15 days.
Lastly, I would like to thank my friends (Class of 2013) and my school (Ruamrudee International School) for helping me fund the project.

cheers!

Kunakorn (Jack) Puntawong <---- If possible, can you please use this name in the Neutron Club list?

[Jim Kovalchick]

Jack,
I have a couple questions for you.

1. Your pressure seems very similar to what I thought you reported for air. Did you see a difference between the pressures for air and deuterium for the same voltage? This is important because if they are the same it could be a sign that you didn't get your line purged and are still making air plasma.
2. You really should do a negative check of your neutrons by taking a reading with and without your moderator. This would be good test to eliminate noise induced counts. I am pretty sure Mr. Hull will ask you to do this before entry to the neutron club.

I would also like to offer preliminary congratulations. I am pretty sure you have done it!

Jim K

[Jim Kovalchick]

Jack,
I just reviewed your data and see that your pressure at -28 kV did come up a little with deuterium. It is interesting that your first run with very few counts showed a lower pressure indicating air contamination. It is amazing how little gas flows so you always need to purge your gas line well before changing from one gas to another. It sounds like you have good D flowing now.

[Jack Puntawong]

Jim,

There was a slight difference between deuterium and air at the same parameters. The ideal pressure for air is between 2.7 to 3 micron. However, for deuterium, I was surprised that I could raised the pressure to about 5 microns with the limitation of my power supply. I think that if I keep producing more deuterium, the purity of the gas and neutron production are going to increase.

There might me a slight problem with the negative check that you proposed though. When I molded my paraffin, I place the B-10 probe inside it. After it had cooled down, the probe got stuck in the paraffin and I couldn't pull it off. However, I do have a large piece of borated polyethylene. If the number of neutron count reduces while I place it in front of the neutron probe, would this be a confirmation of neutron production ?

Kunakorn (Jack) Puntawong

[Jim Kovalchick]

Jack,
I believe that if you demonstrate that your count rate varies when you change the amount of moderator then you have reasonably demonstrated neutrons.

[Jack Puntawong]

Jim,

I'll try that today. However, I don't think that it's the noise induced count because when I turned on the HVPS using air, the count from the set-up is still between 280-320.

[Richard Hull]

I have some questions and have used the GE tube you have before and the bias voltage is absolutely critical and a normal back ground for the GE tube should be very, very low, maybe under 1 or 2 CPM, at most! I fear you might be operating this tube in a geiger mode and all your count data is due to x rays!!

The proper bias on these old tubes can have a wide range from 500 volts to 700 volts. The actual useful span, once the useful bias range is found, is very narrow, making this tube a bear to find its "gamma quiet zone". Much higher than 600 or 700 volts bias and the background goes up significantly due to NORM and other noise related issues. I see the meter reading in your image is about 900 volts! Way, way too high for the tube!! Even a superb GM counter will not normally exceed 50 CPM background. Something is very wrong with your numbers. It may be a bad tube, but the voltage is far too high to allow proper neutron counting. I suspect you are x-ray counting. Yes, you may be counting neutrons as well, but no way will the GE tube count that high a background with correct bias.

I am rather shocked no one else caught this. Perhaps no one here who has used the GE tube has seen this posting. You are up against folks who know this tube and its normal characteristics. No gas counter tube in the world will have a background of over 50-70 CPM when setup correctly. Correctly adjusted, normal neutron counters of the BF3 and 3He types never have a background of over 5-10 CPM which are mostly huge cosmic particle star sprays and ground based neutrons. The GE tube is far less sensitive and 1-3 CPM would be a norm.

Not nearly enough data to be included in the neutron club. Make sure you review the neutron club rules.

Reset your bias to a 2 or 3 CPM background level and then re-run your tests You may find that at your operational level the count might increase by only 15-20 additonal CPM over background, maybe more. The big test, once the tube is set properly, is to get the increased count, (making neutrons), then with the machine still running, remove the moderator far from the tube and the count should go back to background levels as it it is not now seeing neutrons anymore. If the count does not go down or goes up, you are still just seeing x-rays and no neutrons are present, you are not doing fusion. It is important to get the tube out of the moderator. tubes should be very loose in any moderator. A 1 inch diameter tube will work just fine in a 2" hole in the moderator. having a moderator hug the tube tightly is just not needed at all and gains nothing, in the end.

Again these tubes can be a bear to set up, but once setup correctly, they are fine tubes and are moderately sensitive to neutrons in a good moderator placed close to the fusor chamber.

Richard Hull

[Jack Puntawong]

Richard,

The bias is 860 volt. The technical spec of this particular tube said 600-800 volt. However, when we did a "plateau" graph to find the optimal voltage, we found that the optimal voltage for this neutron tube is between 850-900 volts. At the range over a 1000 volt, the counts shoot up rapidly to around 70,000 cpm so I stopped there. The professor was also surprised that the background count is this high. We thought that there might be something wrong with my counter so we tested the tube with the his Ludlum too and the result is the same.

I'll try running the fusor again today with air and turn on the detector again to confirm whether there is any x-ray. Also, I'm returning to the university tomorrow so I will be able to use the neutron source again! =) Please ask question if you have doubts. I'll do another run and will keep you guys update as soon as possible.

This is the data point of the "plateau" plot:



And this is the source we use. It is wrapped around a metal tube and surrounded by mountains of polyethylene + lead.



Also, removing the neutron tube is a bit problematic. When I molded the paraffin, I place the tube inside the liquid paraffin over night. The next morning it got so hard that I couldn't pull the tube off. I do have another B-10 tube I bought from Brian for Back-up though. I'll place that in a 6" pvc water tube.

[Richard Hull]

Again set the tube's bias for under 10 cpm background. Your bias is way too high and the background count is insane by any nuclear standard. PMT's with large scintillators can have large backgrounds as they are designed to count gammas and pick up even 10 and 20kev gamma and x-rays. They are not gas tubes, but photon counters. There are a ton of low energy photons around. You are counting these at such a high bias. You have got to get rid of any and all photons up through 3mev and that means a much lower bias. try 500 volts and work up until you just get a count or two a minute. Then and only then will you have a pure neutron counter and not a gamma counter.

You do not need a neutron source for this.

The thing to have done would have been to adjust the bias for a background of 2-5 CPM and then expose the probe in moderator to the neutron source and not struggle for some sort of plateau. The GE tube is good, but tricky of adjustment.

Before making the neutron club we need realistic counts. The GE tube will not roar to life if you are doing fusion at 30kv voltage and only 5 microns...Believe me, it will not. The increased count over background will be obvious, but you will not see a monsterous difference.

example: Background 4 cpm with fusor off and in place at the fusor..... run as you noted above in the original run post and you might see a ten fold increase to 40 CPM...While still running, remove your tube. Background is now 6 cpm.........You are a winner and doing fusion! Your tube is working just fine.

Richard Hull

[Jack Puntawong]

Richard,

After I saw your response, I went right to the hardware store to purchase the end cap for the 6" pvc. I put the two end cap together, drilled a hole, filled it with water and placed the tube into it. There really is a point where the background count is between 2-4 cpm as you said but I had to spend at least 20 minutes finding it. I took the background over the period of 10 minutes before and after the experiment and the average is 3.9 cpm and 4.1 cpm respectively.

During the operation, I measured the neutron and it was 18 cpm. I did not see any star mode though. I think I might need to add another circle to the inner grid to get the geometry right. However, you can see the plasma during operation on picture 4. Then I took out the tube from the water tube and measure again. The count is 6 cpm.

1. My set-up:



2. Background count before the operation:



3. During the operation (4.5 micron, 10mA,27-30kV) :



4. Took off the neutron probe from the water: