New (improved!) fusor design

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Liam David
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Re: New (improved!) fusor design

Post by Liam David »

Was that the dose rate including the lead shielding?
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Anze A Ursic
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Re: New (improved!) fusor design

Post by Anze A Ursic »

Sorry I should have specified something; the meter measuring exposure right infront of the viewport was one of those devices you set to record data and it records exposure as a function of time, no person needed. So nobody was even near the chamber when this was happening. But no, that dose rate was without shielding. The only thing between the meter and the viewport was a mirror although the meter itself was slightly off-center so it was perhaps not in the "direct beam" of X-rays that gets shielded, but atleast that shows even inside the room there aren't many hotspots.

In fact we were all outside the room remote controlling and monitoring everything. The radiation levels outside didn't even rise from background. The person said based on our setup (shielding + remote control + 20ft of distance) would probably allow us to run 40-50kV. It's overkill but it appeases the regulators. But he never measured inside the room next to the shielding or anything like that.
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Liam David
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Re: New (improved!) fusor design

Post by Liam David »

Those measurement conditions seem a little disingenuous... The 2 mrem/hr NRC requirement for accelerator dose rate is for any areas that are publicly accessible (no geofence interlock + some other requirements). Even that requirement is an average over a specified amount of time and occupancy factor--a temporary maximum can be higher. Most important for your case is that the measured dose rate should include any shielding. I'm not saying that you should argue with the safety staff given your goals and deadline, but they seem to be taking the rules a little too far. I can stand corrected should the laws in Pennsylvania be more restrictive.
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Richard Hull
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Re: New (improved!) fusor design

Post by Richard Hull »

I agree with Liam. Measurements must be taken with any and all shielding in place right at the outside of the shielding to see if it is protecting personnel in the room with the device. Another test should be made away from the shielded area in the same room to test for scattered radiation that is not directly, "line-of-sight shielded from the source. Line of sight, (shadow cone), shielding is usually all that is needed at low levels or radiation.

I have given many discussions and diagrams of "shadow cone shielding" for fusors in the forums in the past. Try this FAQ...

viewtopic.php?p=34227&hilit=shadow+cone#p34227

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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Anze A Ursic
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Re: New (improved!) fusor design

Post by Anze A Ursic »

I did get a clarification today after they discussed yesterday's results. I will be able to go higher, because we are in a different room - on the hallway outside the room with 4.5m of air separation, several inches of lead, steel chamber, etc...

The 2.0mR/hr issue was actually simply because this is a publicly accessible lab and they view this device as a POTENTIAL X-ray generator. Their fear is that somewhere down the line, after this project is discontinued and shielding is removed, people who don't know what they're doing are playing with it, getting plasmas or whatever while in the same room, exceed the 2.0mR/hr at the viewport and hurt someone. In that case they would be responsible since this is now classified as an X-ray producing machine, which falls under their jurisdiction.

For the actual test they don't care about the exposure at the viewport behind the shielding. They will be measuring exposure outside all 4 walls of the room to ensure it never exceed 5.0mR/hr. This, of course, will not happen with several inches of lead and 6" of steel reinforced concrete. They will also measure around the only door going into the lab which is left just slightly ajar for passing cables through. Since the viewport is shielded and turned 90 degrees away, it should also not be an issue.

Like I said, yesterday several measurement devices didn't even show higher than background radiation at 22kV (at least in terms of X-rays.) at our operator table, so I am certain we are good and I will be able to go up to 25-30kV easily with no issue.

I've gotten to know them - they are great people, but they do have to somewhat work within very restrictive rules. So I understand their need to be pedantic.
Matt_Gibson
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Re: New (improved!) fusor design

Post by Matt_Gibson »

Can you suggest removing a key part of the fusor so that no asshat could possibly x ray themselves without it?

-Matt
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Anze A Ursic
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Re: New (improved!) fusor design

Post by Anze A Ursic »

Good point Matt, and I actually said this will be disassembled (the power supply will be taken to storage, any gas accelerant removed, etc...) but it's already registered with the state as an X-ray producing device, and on friday it may fall under neutron producing device too. So to your question; no. I think once it's registered, it'll always be viewed as a radiation source. It is what it is. This may sound silly, but I just want to get fusion, do a few runs and compare data and then go home. I'm living on some guy's couch eating Walmart sandwiches since I'm in town for the sole purpose of building this fusor. It'll be great when I achieve fusion - but I just also wanna get it done lol.
Matt_Gibson
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Re: New (improved!) fusor design

Post by Matt_Gibson »

I hear ya…It can be hard working around people that don’t know much about what we do.

Glad to see that you have so much drive to get this done! You’ll go far in life with that sort of perseverance. It’ll pay off, trust me.

-Matt
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Anze A Ursic
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Re: New (improved!) fusor design

Post by Anze A Ursic »

Yeah last week I clocked in around 95 hours of lab time in 7 days hahahaha. I rebuilt part of that massive chamber, pumped down several times after any flange was removed / replaced, built the new device and everything in that time and other people were coming down to the lab just to check on my sanity. It's in the basement of our building with no windows so you're always on the brink of going crazy. Especially the noisy pumps running for hours and heating up the room. But yeah even the current results make it worth it. It's cool to see how close I am, it'll be a hard wait till Friday...
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Anze A Ursic
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Re: New (improved!) fusor design

Post by Anze A Ursic »

Well I suppose it was worth it.

I got fusion today! Several runs were done, the highest of which was at 28.0kV and around 10mA if I am not mistaken (all recorded so I will double check)/ Both the BD-PND bubble detector and a neutron detector brought in by the safety people detected neutrons. I figured a quick update of this magnitude was needed. I will obviously collect all my findings in and post an official neutron club application!

Anze
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