Hehe. Yeah, 50 pages and counting. I wonder what the record is? Not that's a particularly laudable accomplishment, perhaps a testament to prolix conversations!
-
Welcome back Guest! Did you know you can mentor other members here at H-M? If not, please check out our Relaunch of Hobby Machinist Mentoring Program!
Needing more than a spark test?
- Thread starter graham-xrf
- Start date
Pi and dead bug construction happening as a matrix proto board "hat". I have some LQFP "universal" little PCB coming (£1.86 for two on eBay).
I might just stand on on my GPIO "hat", or maybe hold it on with a dob of hot-melt.
This part is only for the ADC. The amplified, buffered, relatively bomb-proof TIA signal is not MHz, so can be brought to the ADC.
OK on the 50 posts. All that reflects is that we are talking about the design, letting it all hang out - but yes, it is an unusual thread. When we get our first plots, we can drop a short posting in the forum under an new title, teasing the curious.
An off-the-wall question.. I have no idea (yet) whether anything unusual is happening, but would we expect some increased counts just because the Am241 sources that have been pulled out of their metal smoke chambers, are in the same jar as about 10 Thorium gas mantles?
I might just stand on on my GPIO "hat", or maybe hold it on with a dob of hot-melt.
This part is only for the ADC. The amplified, buffered, relatively bomb-proof TIA signal is not MHz, so can be brought to the ADC.
OK on the 50 posts. All that reflects is that we are talking about the design, letting it all hang out - but yes, it is an unusual thread. When we get our first plots, we can drop a short posting in the forum under an new title, teasing the curious.
An off-the-wall question.. I have no idea (yet) whether anything unusual is happening, but would we expect some increased counts just because the Am241 sources that have been pulled out of their metal smoke chambers, are in the same jar as about 10 Thorium gas mantles?
"An off-the-wall question.. I have no idea (yet) whether anything unusual is happening, but would we expect some increased counts just because the Am241 sources that have been pulled out of their metal smoke chambers, are in the same jar as about 10 Thorium gas mantles? "
What is the theory behind that?
Robert
What is the theory behind that?
Robert
The decay product of Thorium is Radium (I think). Anyway, when you put a gamma source (Like Am241) together with Thorium, I think it possible the interaction can breed stuff one does not want - but I don't know. The infamous David Hahn put smoke detector sources, thorium, luminous clock dial paint, and various other stuff rolled up together in foil in a potting shed, which did begin radiating about 1000x background, and was steadily increasing. He tried to separate it, leaving the Am241 in the shed with the dial paint. and packed the rest into his car trunk. At that stage, he got nabbed by the police. The radiation which had started out from smoke detectors was measurable outside the house and along the street. There was a whole cleanup incident. Hahn died young, and there are lots of articles about it.
Of course, he had put together everything radioactive he could get hold of, all in a foil ball held together with duck tape. Nothing like the small amounts of stuff I have in the jar, which is basically 8 radioactive sources of Am241 and 10 thorium mantles. The Am241 is mostly an alpha radiation source, but it also does gamma, which is the radiation we use to get the XRF gadget to work.
https://unbelievable-facts.com/2018/12/david-hahn.html
https://harpers.org/archive/1998/11/the-radioactive-boy-scout/
Last edited:
This is going to a bit of a challenge!
Couple things. First, unless any of the radioactives emit neutrons, there will be no radio-activation. Gammas irradiating nuclei won't do it.
I confess to some confusion here because, according to Wikipedia, in sufficient quantities Am241 could make a bomb but I haven't seen anything to suggest any of its decay routes emit a neutron so I don't understand how that is possible. Perhaps an Americium fission weapon needs a "primer" of some other fissile to make it go bang?? That said, the quantities we're talking about for XRF are far below what's needed for neutron activation anyway. Fugetaboudit.
Second, regarding the blue/pink dots, that's not an issue unless you are going to heat the entire IC package to solder-melt temperature (dead-bug assembly isn't there). And if you are, just bake the part at some temperature below 100C awhile, pull it out of your oven and immediately solder it down. 2 hours' baking time at 80C will do just fine. The conversion of absorbed moisture into steam is an issue with larger packages, especially if they have an exposed paddle (typically used for heat sinking) so that's why the monitor cards are packaged with this kind of device.
BTW, if you're reflowing multi-layer PCBs I strongly suggest baking them out beforehand, too. I've seen problems that suggested they had delaminated internally, causing through-hole vias to become open or intermittent. Debugging something like that can be a real PITA so don't go there.
I have direct experience on what can happen to large IC packages if they're not baked before solder reflow. It caused havoc on a Tektronix production line and initiated a huge investigation into all kinds of possible mechanisms, all but one of which turned out to be a waste of time and money. THAT episode is the reason I advocate baking IC's out before reflowing them. It became part of the standard procedure we used for re-mounting customer returns on eval boards. Some in the lab didn't bother baking out the eval boards, but I always did. Why court disaster if you can avoid it?
I confess to some confusion here because, according to Wikipedia, in sufficient quantities Am241 could make a bomb but I haven't seen anything to suggest any of its decay routes emit a neutron so I don't understand how that is possible. Perhaps an Americium fission weapon needs a "primer" of some other fissile to make it go bang?? That said, the quantities we're talking about for XRF are far below what's needed for neutron activation anyway. Fugetaboudit.
Second, regarding the blue/pink dots, that's not an issue unless you are going to heat the entire IC package to solder-melt temperature (dead-bug assembly isn't there). And if you are, just bake the part at some temperature below 100C awhile, pull it out of your oven and immediately solder it down. 2 hours' baking time at 80C will do just fine. The conversion of absorbed moisture into steam is an issue with larger packages, especially if they have an exposed paddle (typically used for heat sinking) so that's why the monitor cards are packaged with this kind of device.
BTW, if you're reflowing multi-layer PCBs I strongly suggest baking them out beforehand, too. I've seen problems that suggested they had delaminated internally, causing through-hole vias to become open or intermittent. Debugging something like that can be a real PITA so don't go there.
I have direct experience on what can happen to large IC packages if they're not baked before solder reflow. It caused havoc on a Tektronix production line and initiated a huge investigation into all kinds of possible mechanisms, all but one of which turned out to be a waste of time and money. THAT episode is the reason I advocate baking IC's out before reflowing them. It became part of the standard procedure we used for re-mounting customer returns on eval boards. Some in the lab didn't bother baking out the eval boards, but I always did. Why court disaster if you can avoid it?
Last edited:
While I still have some way to go on nuclear engineering, and I do get it that neutrons can just waltz into the middle of an atom without a big force to overcome, I can figure we don't have many to worry about. It's just that, when I don't know, I ask.
I find out that the name "Americium" was dreamed up partly motivated by being in the same group right after Europium. Discovered at the same time as Curium, which is right next to it in the Table Periodic, it was supposed to be an improvement on the provisional names "Pandemonium" and "Delirium". I have to say, I would have been perfectly OK with the provisional names!
I hear you about baking the chips. Here that would involve a sneak into the kitchen. I don't have a little "oven". My only recent thoughts in that direction was thinking to bring together some 1mm Molybdenum wire, a PID controller and some N-Type thermocouples together with a earthenware pipe and some insulation. I was thinking up to 1250C, but I suppose such could be persuaded to sit at 80C.
I had thought perhaps using solder paste, as if for re-flow, but not doing the re-flow. Instead, just gently heat the pins from the top with a soldering iron bit. It sounds as if one should bake out the chip anyway.
Re: Messing with the Pi. Getting it to read and write to the pins is now done and working OK. This not using any of the usual libraries, and definitely not anyone's Python code. The chip can run at 2Ms/sec in turbo mode, but we are thinking to use "normal" mode at up to 1.5Ms/sec, because there is no minimum time to a next sample. I have to wait a day or two for the LQFP experimenter boards to mount the expensive little thing. They were clearly invented in response to the basic need to connect something made exceptionally small to a fault, to end up with terminals us mortals can see, and solder a wire to.
I find out that the name "Americium" was dreamed up partly motivated by being in the same group right after Europium. Discovered at the same time as Curium, which is right next to it in the Table Periodic, it was supposed to be an improvement on the provisional names "Pandemonium" and "Delirium". I have to say, I would have been perfectly OK with the provisional names!
I hear you about baking the chips. Here that would involve a sneak into the kitchen. I don't have a little "oven". My only recent thoughts in that direction was thinking to bring together some 1mm Molybdenum wire, a PID controller and some N-Type thermocouples together with a earthenware pipe and some insulation. I was thinking up to 1250C, but I suppose such could be persuaded to sit at 80C.
I had thought perhaps using solder paste, as if for re-flow, but not doing the re-flow. Instead, just gently heat the pins from the top with a soldering iron bit. It sounds as if one should bake out the chip anyway.
Re: Messing with the Pi. Getting it to read and write to the pins is now done and working OK. This not using any of the usual libraries, and definitely not anyone's Python code. The chip can run at 2Ms/sec in turbo mode, but we are thinking to use "normal" mode at up to 1.5Ms/sec, because there is no minimum time to a next sample. I have to wait a day or two for the LQFP experimenter boards to mount the expensive little thing. They were clearly invented in response to the basic need to connect something made exceptionally small to a fault, to end up with terminals us mortals can see, and solder a wire to.
One of those little, cheap toaster ovens may be in my future, if I do more circuit boards. Thermocouples and controllers are pretty cheap these days.
Alpha particle bombardment can cause fission and proton number changes.
Apparently Thorium is fissionable under alpha particle bombardment. This would produce some dangerous byproducts. I suspect the conversion rate would be quite low but I guess this is the perceived risk.
Robert
Apparently Thorium is fissionable under alpha particle bombardment. This would produce some dangerous byproducts. I suspect the conversion rate would be quite low but I guess this is the perceived risk.
Robert
The only reference I found regarding alphas causing fission on Thorium indicated it took ~30+MEV alphas to do it. The alphas emitted by Americium are about 1/6th that energy. So for most elements the risk is low from that particular route. However, if Am241 is combined with Beryllium it CAN generate neutrons via alpha capture in the Be neucleus. Apparently because Be has a large capture cross section for alphas.
The Wikipedia article on Americium indicated that Am214 will spontaneously fission with the release of a neutron, at 1.2 atoms/second-gram. Since we're talking about micro-curies here, that particular route isn't very risky, either. However, this does explain why Am241 could be used to make a bomb, if you've got a whole bunch of it. And I mean a whole lot: without any neutron reflectors you'd need a sphere 50+ Kg to reach critcal mass, 19+ cm in diameter. No secrets here, I got all that off the 'net.
I think the most significant danger is the alpha particles themselves if the Am241 is ingested. So it's necessary to be very careful when extracting the little disks from smoke detector sources.