BGO gemstone

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Andrew Robinson
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BGO gemstone

Post by Andrew Robinson »

Hope everyone is doing well out there. I've been in hiding lately from Fusor.net haha, but I just got something back that I know many of you on here will be able to appreciate so I figured I would pop in for a moment and post.

Ok this is a pretty long story so I will do my best to keep it short. This all started a couple years ago right before HEAS 2019 I believe. Some time earlier in the year I met a new contact via a mutual friend named Arya Akhavan. Arya is a plastic surgeon at UNC and lives here in Raleigh. Little did I know, Arya is also a world famous lapidarist that has done some absolutely stunning work! Do some Google searches and you will see some of the stones he has cut over the years. This all came about as I had recently come up with the idea to build a nuclear themed ring for myself and it just so happened that Arya was also interested in some BGO. So we setup a time to meet and did a little collaboration/trade. I provided him some rough BGO in exchange for a couple of cut stones, one of which is very unique. The ultimate goal was to machine in house a Zirconium ring with a tension set BGO stone. After quite a bit of discussion and a little bit of CAD, we finally settled on a stone design that would be suitable for a tension set ring keeping in mind the brittleness of the BGO. At the end of the day after a little bit of research, we knew there was the possibility that the stone would be too brittle, but we decided to press ahead anyways. If all else failed, the stone can still exist separate for viewing purposes only and a stronger more suitable albeit less cool stone could be used functionally for the ring. Here are a few examples of the goal.
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Now for the BGO, we had considered another potentially interesting property that we wanted to explore. We were curious, and someone on here may know better than I so I welcome the input, if over time in high fields if BGO discolors. This is where Tim Koeth comes in. Tim and I collaborated and just as soon as the idea got started some BGO samples were heading back with him to Maryland. Now, despite the unfortunate BGO outcome seen below, the results were still fantastic! I am still waiting to see Tim again in person to discuss the results more, but these pictures should suffice to explain what happened hahaha...
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So clearly that did not work out haha. BGO is actually far more brittle than we anticipated. Even cutting it according to Arya was quite an adventure. It is apparently a VERY gummy material to cut and required an excessive amount of flushing. As far as we know, this is the first instance of BGO ever being faceted. Whats even cooler is the gemstone design is unique, so no other stone exists like it in the world!!! Here is a gif of final design we settled on.
BGO.gif
Looks like Fusor.net wont allow animated gif so here is an external link if you want to see the stone move: https://host.atomiklan.com/forums/Fusor/BGO/BGO.gif
and finally, here is the final product! Well, at least here is the cut stone. I have yet to machine the ring and honestly I most likely will not be doing the tension set with this stone anyways. I believe it is just far too brittle. Best kept in its box at this point. Also, I am still working out the CAD/CAM details to cut the ring. Cutting zirconium is turning into an adventure all by itself! Makes for a pretty impressive fireworks display inside the machine on occasion! I will try to capture some video next time I do a test.
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I can wire anything directly into anything! I'm the professor!
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Rich Feldman
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Re: BGO gemstone

Post by Rich Feldman »

Very cool, Andrew. Thanks for sharing. Picture of real thing is worth 100 simulated renderings.

Speaking of faceted gems, at some point I was visiting someone's office & got to handle a big crystal of some kind of magneto-optical garnet.
It had a strong yellow or orange color, IIRC.
It was amazingly dense for a transparent body, maybe in a class with your BGO.

Zirconium is one of the metals I started cutting for my own ringmaking project in 2013. Why did you choose Zr?
Somewhere I have a sawed-off block big enough to machine into a plain cylindrical ring.
Just found 8-year-old pictures, reminding me that the chunk would not meet dimensional requirement before some "working".
zrblock.jpg
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Richard Hull
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Re: BGO gemstone

Post by Richard Hull »

A number of years back I scored a 3X3 BGO scintillator xtal attached to a 3" PMT ready for use. I obtained it from the great old O.E Technologies in Madera, NM. Don Orie, the owner, and I did a lot of business together back in the 90's. I obtained 3 of my 6 large 3He Reuter and stokes P4 neutron tubes and a 24" X 2" BF3 and this BGO Harshaw combo from him among many other goodies. Those days of such surplus goodies are pretty much gone now. The BGO xtal is incredibly heavy, like a chunk of lead in a can with a PMT attached. Terribly inefficient compared to NaI:tl but will easily stop and indicate 3 MeV gammas which the Sodium Iodide doesn't capture well. It just has very wide collection peaks, and will not see any close by lesser peaks. NaI is bad enough, but BGO is worse by a factor of 2. Still, it does reach out into gamma energies just not found in NaI.

Richard Hull
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