Proton Accelerator - Part II Gamma Radiation

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Jason C Wells
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Proton Accelerator - Part II Gamma Radiation

Post by Jason C Wells » Thu Jun 11, 2015 12:40 am

Today I did produced about .2mr/hr beta. My geiger counter has a beta window. I didn't get any gamma, but when I flipped open the beta window, my geiger counter started ticking away. When I held the geiger tube away from the target chamber, the counts dropped. I'm definitely making radiation now.

This particular experiment is part of my ongoing proton-boron fusion project. This test run did not include the boron target. Vacuum was right at 10-e4 which is the lower limit of my baratrons. It puts on quite a light show.

I haven't figured how to manipulate/scale video yet. Private message me and I will send the video to you direct or make some other arrangement. It's really pretty cool. You'll want to see.

Regards,
Jason C. Wells
IMG_20150610_171658932_HDR-sm.png
This is a well lit photo of the video that documents my accelerator column producing beta radiation.
Last edited by Jason C Wells on Thu Jun 11, 2015 12:46 am, edited 1 time in total.

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Jason C Wells
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Re: Proton Accelerator - Part II Gamma Radiation

Post by Jason C Wells » Thu Jun 11, 2015 12:43 am

While I was putting the finishing touches on the last message, I went back out to the garage to check on something. The chamber pressure had fallen low out of range, so 10e-5. I fired up the VDG to do another quick run. This time I got .3 mr/hr with the beta window closed.

I making gamma!

Regards,
Jason C. Wells

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Dennis P Brown
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Re: Proton Accelerator - Part II Gamma Radiation

Post by Dennis P Brown » Thu Jun 11, 2015 10:46 am

Your measuring Gamma rays but from where? An accelerator itself only produces X-rays - a target getting hit with protons can, in some cases, produce nuclear transmutations that could lead to Gamma rays but your post does not mention any such target/beam.
By the way, Beta radiation is composed of electrons. Not sure what that has to do with Gamma rays.
An accelerator can produce a dangerous level of X-rays when operating due to electron acceleration from the target and following the huge potential field from the VDG. These electrons hitting the glass walls and any metal at the end of the tube can generate these X-rays. These electrons can be produced when the target is being irradiated by high energy protons (and also by protons hitting the side walls.) As such, shielding may be required and certainly it is important to measure the radiation threat near the accelerator - as you appear to be doing.
You might want to consider wearing dose badges during accelerator operation.
An anti-electron back streaming bias voltage at the target is a good idea as well. This can strongly help to suppress this effect.
Glad you are posting your progress - a very interesting project! I too have built an accelerator but with my refusal, at least so far, to dis-assemble my turbo pump to get a piece of glass out of it (read this as inability to get the darn thing apart), my fully complete accelerator has just been collecting dust (lol). My VDG has given me constant issues but your "dry box" could work. I am concerned by the plywood, however. Plywood is conductive at those voltages and may rob your VDG of most its current/voltage. Consider plexiglass for the box. Using rope to support the accelerator tube may also create a severe current/voltage drain.

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Richard Hull
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Re: Proton Accelerator - Part II Gamma Radiation

Post by Richard Hull » Thu Jun 11, 2015 11:11 pm

The assumption is they are X-rays. With zero data like the voltage and current actually impressed and realized, we and you know nothing about what is going on, but can make generalized assumptions. Again, no data loses the day. It is still just plasma play time.

Voltage actually measured across operating the device.......Super important to know
Current actually measured through the operating device......Very important to know
Pressure actually measured.......Not very important, but good to know.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Jason C Wells
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Re: Proton Accelerator - Part II Gamma Radiation

Post by Jason C Wells » Mon Jun 15, 2015 3:52 pm

Plasma play time is fun.

To Dennis and Richard. I do agree with all of your comments. I'm working my way through things bit by bit. I think of something. I try it. I see the shortcomings. I improve it. It's not very engineer-y of me, but I'm very happy with my progress just the same. If I had my former employer's budget, I would not have done the first 90% of the work I've done and I would have an instrumentation engineer dealing with all the sparky stuff.

Everything I am doing is with a proton beam. That info is not in the paragraphs. It's in the subject header.

My comments about beta were showing the difference between the higher pressure performance and the lower pressure performance. At first during high pressure (10e-4) I didn't get gamma. I only got beta. As you asked, from where? Probably just various secondary collisions of lower energy photons knocking electrons out of their orbits. But when pressure dropped to less than 10-e4 (low off the scale), I started seeing the gammas. It makes sense. There would be less thermalization of the incoming protons and so I would get higher energies. The geiger counter is a crude instrument, but it is fun to hear it tick. And it keeps me safe-ish.

I'm working on acquiring a detector that can read energy plus something called a kick sorter which can supposedly produce a spectrum of all energies of particles incident upon the detector. That spectrum is the brass ring. One spike will stand out over all the others.

I couldn't attach the video. But here is a still photo from the radiation producing test run. Compare to the well lit photo above for perspective.

Regards,
Jason C. Wells
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Proton Beam VDG.PNG
The proton beam incident upon a zinc-sulfide target.
Proton Beam VDG.PNG (36.84 KiB) Viewed 2246 times

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Jason C Wells
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Re: Proton Accelerator - Part II Gamma Radiation

Post by Jason C Wells » Tue Jun 23, 2015 9:41 pm

I added a current meter to the beam line circuit today. I record 8-10 microamps beam current at <10-e4 Torr with my Van De Graaff running. The VDG belt drive delivers 10-12 microamps to the upper terminal. My current losses are pretty low so thats good news.

Near future work will be to measure the delivered energy of the proton beam.

Since a few days ago, I've lost the juice to produce gamma. I don't know why. I did observe some glowing "debris" inside my accelerator column which is probably diff pump oil.

Regards,
Jason C. Wells

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Re: Proton Accelerator - Part II Gamma Radiation

Post by Bruce Meagher » Wed Jun 24, 2015 7:25 am

I think you might discover you are simply producing x-rays by accelerating charged particles into different materials. What are the possible nuclear reactions you believe are creating the beta and gamma radiation? Is your target Zinc-Sulfide as mentioned in the picture above?

Could it be opening the “beta” window on your geiger counter allowed you to measure lower energy x-rays compared to when the window was closed? Beta particles don’t travel very far through matter. A 1 MeV beta particle is stopped by ~2.3mm of Pyrex glass (if I did my math correctly) . How energetic would a beta particle need to be to escape your accelerator’s target chamber?

Also, wouldn’t you expect a drop in pressure from 10-4 Torr to 10-5 Torr to actually increased the terminal voltage in a weak VG supply? Increasing the terminal voltage would therefore raise the average x-ray energies produced explaining your observations.

As Richard mentioned, measuring the terminal voltage would provide valuable information.

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Dennis P Brown
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Re: Proton Accelerator - Part II Gamma Radiation

Post by Dennis P Brown » Fri Jun 26, 2015 10:35 am

Your VDG current appears ok if you are measuring the current off the VDG dome - not sure if that is what you are doing. If you are measuring the current from the "target" that may not be advisable since you are just picking up some free ions in the plasma. Not the same as the VDG current.
More of a concern is the vacuum, if your values are being given in the torr or Bar, MPa scale range (if just Pa, then you are fine.) You need a min of bottom 10-5 torr to not create a vast cascade of ions in the tube that will disrupt most of your beam (the mean free path of a proton at 10-4 torr is rather short (if memory serves, a few cm in the high end of that range and a few tens of cm in the bottom end of that range - either 10-4 torr range range is not sufficient for a nigh energy charged proton in a tube filled with other charged particles (the accelerator tube isn't an environment filled with mostly neutral particles)).) Even a small untrapped DP should get your device to 10-5 torr in a properly sealed system so it appears you have leak(s). The good news is that 10-4 torr one can then use either alcohol or a can of keyboard "dust off' aerosol to detect/locate the leak(s). Until then, you are wasting your time. By the way, your tube diameter appears large enough to internally install Einzel lens. These would vastly improve your beam focus once you get your vacuum to the bottom of the 10-5 torr or better still, 10-6 torr.
Aside: often, alcohol alone will reseal a leaky gasket after it is sprayed on the bad seal. Also, there are liquids sold that can be used to seal high vacuum joints to stop a small leak.

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