FAQ - How to avoid being killed or irradiated by your viewport

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Richard Hull
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FAQ - How to avoid being killed or irradiated by your viewport

Post by Richard Hull »

You will not and cannot be killed by your view port!!"

You can be irradiated and needlessly suffer major eye damage looking into the viewport with the naked eye
If you are near the viewport with over 40kv applied you can suffer radiation burns to the skin
All of this can be easily avoided with proper care and attention in using your viewport in a safe manner


My 1-ich diameter viewport at 45kv using a calibrated ion chamber meter puts out a steady 0.12 Roentgens/hr of x-radiation plus fast neutrons. As I refuse to look directly into the eye of the gorgon, I heavily shield my view port. I also position it so it will not point in the direction of nearby people. I view by jamming a small wide angle video camera up against the glass and running a video cable directly to a video monitor.

Yes, over time, the X-radiation and the fast neutrons will destroy the odd pixel leaving a white dot in the image. The important thing is that I retain my eyesight and get a ghostly beautiful image of the entire grid and all the space outside and around it with rays and the works. Nice!

Another method is to use relay mirror setups and view off axis with a small telescope. A monocular would be good if it can focus as close as 4 feet. This is less desirable due to nearly zero field about the grid. A sharp optical guy could easily setup a custom relay lens system. One might even project the image via a suitable lens into a dark box onto a frosted screen for viewing.

Part of any good safe fusor system design is to keep the viewport pointed in a direction away from nearby people and remote view live while operating. Also, remember to lead shield around the viewport to stop scattered x-radiation. The viewport will act to visually alert you to runaway of conditions that threaten the operation as well as assist in getting the system working perfectly. Using the video method, the video monitor is placed close to the operating controls to allow for instant feedback to operational changes in pressure, voltage and current during experiment and startup.

Never look into your view port directly with the naked eye over about 5kv in a demo system for protracted periods
In fusor systems working over 20kv devise some method of averted or remote viewing as noted above and shield the viewport with suitable lead shielding
Design your fusor such that the viewport is not pointing at you or an audience nearby

I picked up on this back in 1999 with my early fusor III work. I attach a couple of images.
Attachments
1999 FIII.camera anno.jpg
1999 13pt.star anno.jpg
416-1.JPG
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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Finn Hammer
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Re: FAQ - How to avoid being killed or irradiated by your viewport

Post by Finn Hammer »

If it is considered bad form to reply in a FAQ, please delete this.
I like to view the grid, as well as the surrounding void, to judge the level of water vapour in the fusor, during the conditioning phase, and to monitor the colour of the grid during fusion.
To meet this desire, I purchased a Lesker VPZL-275XLG viewport, and with the equivalence of about 2mm lead in it, the radiation level has so far been kept below 1mR/hour at 1 meter distance.
This is measured by a freshly calibrated Ludlum model 9 ion chamber meter.
Since I intend to increase voltage and currents to "insane" levels, I have aquired a 200mm by 300mm slab of 25mm thick lead glass, equivalent to 8mm lead.
I will have this glass cut in circular blanks, and one fitted into a 8mm lead sheet, to place in front of the fusor.
Am I wrong in assuming that such an arrangement should void most concerns related to a radiation hazard from the viewport?
Edit: Combined by a remote operating station 5 meters from the fusor....

Cheers, Finn Hammer
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Richard Hull
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Re: FAQ - How to avoid being killed or irradiated by your viewport

Post by Richard Hull »

Your post is highly relevant to this FAQ. Thanks for posting. Finn notes the only reason to have a viewport at all on a fusor is to observe the goings-on in the device. Without a rather constant view of the interior and especially the grid assembly, one cannot expect to fine tune or control the fusor to any useful degree.

Any form of lead glass with a known equivalent lead content rating is quite satisfactory, of course. The fact that you operate remotely at 5 meters means you are absolutely safe with zero shielding.

I work at about 1.7 meters with zero shielding on the fusor, but with more than adequate lead shielding around the camera and viewport assembly. At 45 KV , 1.7 meters distant, with a calibrated Victoreen ion chamber meter placed in my lap, I read about 1mr/hr. A 100mr pen dosimeter in my shirt pocket zero'd just before any fusor work will, after the average startup-run-shutdown of the fusor, will not really even be off zero.

Were I to go above 60kv, new concerns about shielding would become significant. The fusor shell does a great job of filtering out 100% of the burning x-rays. (15kv to 30kv) X-rays that are above 35kv will not burn you, but are more of a concern related to internal organs.

Note: with 35-40kv applied to a fusor almost no x-rays of those energies are seen exiting the fusor compared to x-rays trapped into the fusor. The reason is that x-rays like beta rays are a continuum their Peak energy is no where near the voltage applied.

The view port, however, remains a possible injurious source of x-radiation in any fusor. Thus, the importance of this post.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: FAQ - How to avoid being killed or irradiated by your viewport

Post by Andrew Seltzman »

Shielding matters, and it doesn't take a lot to stop the x-rays since a majority of the dose rate is the soft x-ray bremsstrahlung continuum. With a thin glass viewport the x-ray dose rate measured on an ion chamber in contact with the viewport surface was in the 30-50R/h range, after a 0.3mm thick lead shield (made out of a conflat cap with 3 layers of 0.1mm thick lead tape) the dose rate is so low it can barely be picked up on a 44-9 pancake probe. It's also impressive to see how fast the dose rate falls off with distance when measured with an ion chamber. It's MUCH faster than inverse square as the soft x-rays are rapidly attenuated by the air. The SiO2 viewport will cut off anything below about 10keV, but the 10-20keV range is strongly absorbed by any air between the viewport and detector.

A dosimeter sticker pressed up against the glass inside the 0.3mm lead shield cap on the other hand was reading about 1000rem after several years of intermittent operation (not exceeding a few hours total time).
cap outside.png
cap inside.png
The x-ray dose rate when running at 40kV, 18mA outside a Lesker VPZL-275XLG viewport (and 1/8" stainless fusor shell) is about 125uR/h. This takes the dose rate from a face-burning 60R/h of soft x-rays to less than the federal dose rate limit (0.5mR/h) for exposure to the general public from a consumer device. I would highly recommend the Lesker VPZL-275XLG viewport, it's a convenient, effective shielding system.
SAM_7062a.jpg
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Re: FAQ - How to avoid being killed or irradiated by your viewport

Post by Frank Sanns »

Using the work Killed, is drawing attention that we may not want when it comes to radiation on the site. I don't believe that anybody is getting enough x-rays from their viewport to kill them.

While we should shield and keep things as low as possible, death by x-rays from a viewport is probably not a thing at all.

Running at voltages at 45KV and up, when the entire chamber becomes transparent to x-rays is where the risk is. We have to believe that anybody running at those conditions will clearly understand the real risks including even backscatter at those voltages.
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
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Richard Hull
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Re: FAQ - How to avoid being killed or irradiated by your viewport

Post by Richard Hull »

Death would be nearly impossible with a fusor via any radiation under 40kv applied. Your noting that folks running well above 50kv"should have the sense and have earned the "chops" to significantly shield their system is well taken. Still, we never know when some newbie with money behind him will come in and get his hands on 100kv supply by luck or money and go into the effort without a learning period.

The electrical and electrocution issues coupled with x-rays are always a prime concern and x-rays out of a view port can easily injure the eye of a newbie with only 20kv applied if they spend a lot of time looking into the viewport while learning to operate their fusor. The viewport remains the only easy way out of the fusor for x-rays. The "killed" notation in the title was for attention grabbing purposes. I went back and edited my first post accordingly to note that death by x-rays is just not possible.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: FAQ - How to avoid being killed or irradiated by your viewport

Post by Mark Rowley »

I too was hesitant to respond to an FAQ, but here's my 2 cents worth...

After getting a system dialed in, the use of the viewport can be totally abandoned and sealed up. If instrumentation is good, the viewport has almost no practical use. When neutrons start clicking away its just a matter of making fine adjustments to the gas flow and voltage to ramp up the count rate. None of those adjustments require any view of the plasma.

In my case, the only time the port came in handy was after the system was shut down to inspect grid condition, and that was rare. Otherwise the entire fusor was encased in a lead box.

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Re: FAQ - How to avoid being killed or irradiated by your viewport

Post by Richard Hull »

Many are the reasons for a view port. All of the foregoing replies attest to it. I have many visitors to see my system. Lead covers only the viewport/camera system. The fusor is in full view all the time, for the sake of the visitors as is all the instrumentation and nothing amuses the down at heel like the star image on a video screen, the senseless and annoying roar from the 3He detection system where individual clicks are no longer heard as when the machine was being brought up. The image and roar tells them what was once merely shiny, dead, yet impressive kit, is now alive and doing fusion. In addition, the giant, 6 LED digits in the large counter are just a blur, save for the slow counting of the 4th,5th, and in end, the 6th digit. Wrapping it all up with making what was just demonstrated as a dead silver dollar, now radioactive. I have great fun with the Plebeians. Oh, I keep them safe as houses, keeping them at safe distances and shielding that which must be shielded. I would never want to hurt them or see them come to harm as I do not consider them Helots.

If one has an audience of the unanointed, there has to be a dinner and a show. I often have pizza and swill for the masses, for like so many, they want bread and circus. The more intrigued and inquisitive may ask questions. I give them what they are used to.... half-truths and gobbledygook. They smile and are sated. The very rare smart one calls me out, and I take him aside and invite him to the next monthly HEAS meeting to see if he fits.

Not only is the viewport dangerous, but for most, it is the way to watch the gorgon being brought forth and is forever useful in controlling the beast. It can be as good as any instrument in the hands of the fusor's owner/operator. I would hate to see a new user with all the instrumentation in the world and yet not have a viewport. A live picture is always worth a thousand words. Just acquire the image safely. Real fusioneers are rare and it is important to keep them safe and sighted.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: FAQ - How to avoid being killed or irradiated by your viewport

Post by Dennis P Brown »

A mirror was how even the ancient Greek's handled the Gorgon; it enables real time viewing, is cheap, simple, and close to fool proof. Further and lucky for the ancient Greek's, requires no electronics!
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