fusordoug wrote:Well, tritium has some serious disadvantages other than being expensive, hard to obtain (legally) and radioactive. Yes, DT has 100x the cross section of DD, roughly. In a gas mix, though, it drops because there will be collisions between DD and TT as well, so that 100x gets trimmed down quite a bit - lets call it to around 30 or so. Being different weights makes the huge (factor of ~2800 improvement) bunching breakthrough I'm pursuing a bit more difficult if not impossible (more on that when I replicate, it's why I'm doing so much boring work with shielding).
The real issue, and one that has ITER shut down at present, is how energetic the resulting neutrons are - ~16 Mev vs 2.5. This is enough more to knock iron or other heavy atoms out of their lattice, which has kind of a bad effect on structural integrity, superconducting magnets (thank heavens this approach doesn't need them - but it still needs a vacuum vessel). I almost can't believe that supposedly the best scientists on the planet didn't figure this out till more than a decade after they started taking funds...and I didn't think of it till they reported it either, but it's why they shut down for "materials research", which is smoke, since no atomic structure can withstand 16 mev neutrons, period. Chemical bonds etc are so strong and no stronger at least so far observed, and people have looked really hard - and not just for this, but for a lot of potential applications if you could do better than a normal covalent bond can do.
BTW, though our thing looks like, and was originally inspired by Farnsworth, the whole IEC thing is BS and not what's happening in there at all. There is zero confinement and no effective recirculation at all. I've checked, hard. What we have here is a multi-way beam collider, which has other important considerations to make efficient (and which is why Farnsworth/Hirsch/Meeks fusors have been stuck in a rut so long - they had the wrong idea about what's going on and tried the wrong stuff to make it better by following incorrect conclusions the data doesn't back up).
Having come over 8 orders magnitude since we started a few years ago, the remaining few don't seem too daunting, and frankly, another factor 30 both doesn't get us there - and probably won't be needed anyway once bunching (old tech for accelerators in general) is properly tuned - I only had it going around 20 seconds - and got a dose, behind the lead we had then - of 5x the yearly limit for a pro in that time, which is why I'm doing much more on shielding (boring but I want to live). I'm absolutely chomping at the bit to get real replication on this effect - it fits the math and the standard model fine and works everywhere else it is used - but dying for it is not in the plan.
I've only replicated it so far for about a 3 second run, which is all I've tried because I don't like rad sickness (it truly sucks, honest).
It had taken me the 20 or so seconds to realize that all my sensitive gear had shut down due to too much output, not the fusor simply not working...that's fixed now, with less sensitive backups and better data aq. Now to finish the job of letting the operator stay alive to see it. Hopefully, some other lab will be able to replicate this too, once I publish the details, though the above is enough of a hint to the accomplished worker.
Oh, I completely believe you about rad sickness. I've read about Daghlian and Slotin and their fatal doses from their demon core accidents. That is not a nice way to go, or even to spend time getting better from, in lesser magnitude doses.
If you're running into shielding issues, and your basement cannot withstand the area of lead required to keep you alive, is it time to seek better foundations for what is, in essence, life support? If nothing else, make yourself a sub-bunker in an annex that you can duck behind? I know you want to witness the thing, but there are points where that becomes futile and you have to leave the room.
I've stood atop the 50MW test reactor at a university (while it wasn't running unfortunately, I really wanted to see Cherenkov radiation), and I've seen the stacks of lead that they have to use to shield themselves from the neutron sources from the core, not to mention the layers of cement behind them for gamma attenuation.
Either way, thank you for entertaining and answering my question. I appreciate the thorough response and cannot wait to see you fire the bad boy up again.