Hopefully, we won't need those things. The charcoal would quickly "fill" with other things (it's not very picky about what it absorbs), or results from previous runs -- Or so I'd guess. I am a little worried about the pulsations from a normal pumpdown from air/STP messing up the diaphragm, and adding any extra resistance would make that worse -- and the pump output would easily just blow out any oil in a small trap when it had to do actual work, like after any time the tank has been at STP -- it really blows out of there then (1Hp forepump), noisily. The way I plan to do this, any hydrogen would have to go downhill against air to get out anyway,
'we'll just have to try it! I did the plumbing to outdoors sloping down the entire way, to handle any condensation, so hydrogen won't just leap out of the system, it would have to diffuse. No point fixing what we don't know is broken yet.
This does remind me I need to put a tight mesh screen on the outdoors end to keep bugs from building nests in the pipe, though. It's that time of year, and I'd hate to anger any wasps building in there...
Lessee -- 10 liter tank (gross estimate). 10k cc. Total equivalent gas in there at 2e-2 mbar (.02 x 1/1000) would be 10 * .02, or .2 cc at STP, more or less? That pipe cap holds maybe 50 cc or so, and the light gas would float up to the detector face, or so I'd assume. It would take 10 fills and flushes to even make 2cc of output gas, probably enough to just get the T into the cup. Obviously, this will have to be glued on (silicone so it can be removed) so putting things like charcoal in there that need to be changed every time wouldn't work out operationally. And of course, the charcoal would stop the very low energy (18.6 kev) betas cold, not what we want -- that's why the detector window had to be so doggone thin and fragile. It looks very much like this detector was optimized for T (we got it from a nuclear (fission) plant) -- nothing else would need such a super thin window. (I'm guessing it's a lot thinner than a mil).
Of course, if you wanted to grind up some of that palladium you have in your "end of the world" PM stash, we could catalyze any hydrogen into very heavy water in the cup....probably only need an ounce or so (!). Just kidding
Ok, let's have a little back of envelope fun here. People who really know this math will understand how grossly oversimplified I'm doing this, but I'm making the estimates conservative by the incorrect assumptions I'll make (bear with me a minute). As Robert Heinlein said, anyone who can't get to order of magnitude quick this way doesn't deserve to call themselves an engineer. Those words and that idea have served me quite well over my career, you just gotta have perspective!
Lets assume we're making 1e6 T's per second -- not far off, we probably make more on a good run (lots more). We'll assume we catch most all of them (not conservative, but see below).
In a five minute run (300 seconds), that's 3e8 or so T's we make. T has a half life of 12.32 years, or 17740 minutes (neglecting leap years etc). So half of those will decay in one half life, making our number 1.5e8/17740 per minute for decays. Divide through: 8.455467869e+3 counts per minute if we get them all counted. Now that should be very solidly out of background!
Edit: My numbers were wrong. The real number of minutes in 12.3 years is: 6464880 (12.3x365x24x60) so dividing through again with the right number of minutes gives 2.320228682e+1 decays per minute. The question now becomes accounting for the somewhat larger number I actually did measure. This might not be rocket science, since my math that assumes constant decays for 12.3 years is clearly wrong -- decay is faster at the start of the interval (at least twice that, as 100% of the isotope is still there).
In truth, since they are all there at the beginning, the initial count rate is going to be faster yet -- the count rate per 12 years is an average (which isn't right for exponential decay, but close enough for hand grenades), higher at the start, lower at the end. But since we don't probably catch them all, and won't count them all either, it kinda still gets us into the ballpark, no?
I'd expect at least a k count/minute after a good run, given all the losses and errors. Probably more. We'll have to see what the background is on this detector to see if that's going to be good enough to declare victory or not, but I suspect it will be if my other experience with phototubes and scintillators in our background means anything. This particular scintillator is a lot smaller than the one I'm basing my guesstimate on after all, so the background shouldn't be as high as henny (about 10 times the size) or my other 1" cube (about 3 times the size). Henny gets to 6000 cpm on background, the other one about half that, and this one should be less than half that, or about 600 cpm, I'd guess (but no need to guess, this I can measure and might get that done tonight). So our signal should be well out of the noise...Cool, if true. This one's worth it.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.