How can Carbon-11 be created in a Cyclotron?

[Sebastiaan]

Question: How to create the Isotope Carbon-11?

We all know it becomes Boron11 after decay which is very usefull, but how to create the Isotope in a Cyclotron to begin with? Specificly what is the source material and it available and what it the exact Nuclear Formula?

 

[e.bar.goum]

Question: How to create the Isotope Carbon-11?

We all know it becomes Boron11 after decay which is very usefull, but how to create the Isotope in a Cyclotron to begin with? Specificly what is the source material and it available and what it the exact Nuclear Formula?

According to the IAEA, the common methods are 14N(p,$\alpha$) at a beam energy of 11-19 MeV and 11B(p,n) at 10 MeV http://www-pub.iaea.org/MTCD/publications/PDF/trs465_web.pdf -- See page 17, table 2.4

 

[Sebastiaan]

Alright but how to interper this? it requires Nitrogen-14 and a proton produces an alfa particle + Carbon-11?

so the nuclear forumula would be N14 + p => He4 + C11 ?

Also, is this an endothermic or exothermic reaction?

 

[e.bar.goum]

Alright but how to interper this? it requires Nitrogen-14 and a proton produces an alfa particle + Carbon-11?

so the nuclear forumula would be N14 + p => He4 + C11 ?

Also, is this an endothermic or exothermic reaction?

That's what that notation means, yes. 14N(p,$\alpha$) is shorthand for 14N + p-> 11C + $\alpha$ . It also tells you that the proton is the beam.

You find out whether or not the reaction is "endothermic" or "exothermic" (although those terms aren't really used very much) by calculating the Q-value - that's the difference between the entrance and exit channel masses. There's a handy calculator http://www.nndc.bnl.gov/qcalc/ telling us that the reaction has a negative Q-value: -2.992 MeV, thus "endothermic"

 

[Sebastiaan]

Damn, that's a lot of energy. I was hoping conversion from atmosheric Nitrogen into B11 it wasn't that expansive, as I wanted to use for (hypothetical) aneutronic p-B fusion, which only creates 8.7 MeV from which 63.7% is released into bremsungstralung :-(

Thanks for helping me understand

 

[Sebastiaan]

Oh, Btw, I tried the Calculator myself, and it gives me an different result:

Reaction for 14N + 1H => 11C+4He
Q-value: -2922.82, 0.95 keV,
Threshold :3133.12, 1.02 keV

I guess I'm doing something wrong here.

 

[e.bar.goum]

That's exactly the same result, except for my typo! I meant -2.922 MeV, sorry!

 

[e.bar.goum]

In any case, 11B is naturally occurring, and it has 80.1% abundance. I don't see why you've got to use a cyclotron to produce micrograms of the stuff (expensively!) when you can just mine it by the tonne, then enrich it.

 

[Sebastiaan]

Yes but Boran-11 is rare in the universe but on earth, we have the luxury of concentrated Boron deposits at specific locations. But what if your landed on alien world without access to this and you have to create everything ISRU? Of course we can find Deuterium in the sea but when fusing it with itself creates a lot of Neutrons. The only remaining Aneutronic fusion which doesn't require complex mining operations would be p-N15 from nitrogen in the Atmosphere. But this seems quite hard to achieve

 

[QuantumPion]

I think if you had the technological capability to make a working aneutronic P-B power reactor, you could figure out how to run it on D-T or whatever instead in the unlikely event of a boron shortage.

 

[Sebastiaan]

Well, D-D would create a lot of neutrons , which could be used convert atmospheric N-14 into Tritium and B11 which can both be used for fusion

 

[e.bar.goum]

In this absurd hypothetical, it'd still be better/faster/easier to find whatever boron was on the hypothetical planet, and mine it.