Neutron production inside cyclotrons?

[Sven Andersson]

There tend to occur in accelerators and ion sources, when they are "run" on deuterons, fusion reactions with neutron production, due to collisions with residual gas in the chamber. Now, I wonder if the same phenomenon has been observed with cyclotrons when they are "run" with deuterons? Or perhaps Li3+?

Knowledge about this could exist among engineers who work on radiation protection rather than among physicists.

S.A.

 

[mfb]

All accelerators with sufficient energy for nuclear reactions (a few MeV) produce free neutrons when particles hit something. Using deuterons makes it worse as they are easily split into proton and neutron, but spallation can happen with every target (apart from hydrogen, but you cannot built an accelerator out of hydrogen).

 

[e.bar.goum]

Further to mfb's comments that you always get neutrons if you're performing nuclear reactions, whether or not you're using a deuterium beam: In fact, it's usually the most significant background (away from big bending magnets where you get plenty of bremsstrahlung, but people and detectors are unlikely to be hanging around) in terms of both radiation protection and detector damage. Those big heavy doors in accelerator facilities aren't made for stopping photons, but are actually typically filled with a boronated plastic/wax or water of some form -- anything with a large probability of neutron scattering.

(As an aside, the largest room background I've ever seen in person was actually from a proton beam - not just due to bremsstrahlung, but also due to the huge flux of neutrons whenever they hit anything that wasn't a proton.)

 

[Sven Andersson]

Further to mfb's comments that you always get neutrons if you're performing nuclear reactions, whether or not you're using a deuterium beam: In fact, it's usually the most significant background (away from big bending magnets where you get plenty of bremsstrahlung, but people and detectors are unlikely to be hanging around) in terms of both radiation protection and detector damage. Those big heavy doors in accelerator facilities aren't made for stopping photons, but are actually typically filled with a boronated plastic/wax or water of some form -- anything with a large probability of neutron scattering.

(As an aside, the largest room background I've ever seen in person was actually from a proton beam - not just due to bremsstrahlung, but also due to the huge flux of neutrons whenever they hit anything that wasn't a proton.)

To mfb and e.bar.goum; have you ever seen or heard of neutron production in a bending magnet, without the beam hitting something, apart perhaps from residual gas?

 

[e.bar.goum]

To mfb and e.bar.goum; have you ever seen or heard of neutron production in a bending magnet, without the beam hitting something, apart perhaps from residual gas?

You've got to have some kind of nuclear reaction for neutron production. I'd think it is possible, but you'd hope to hell that you don't have enough gas in your accelerator for that to have any measurable impact on room background, otherwise, well, you don't gave much of an accelerator.

Not what you asked, but if you're using said bending magnet as a charge selecting magnet (e.g after electron stripping) you'd of course get neutron flux, but that's because the charge states you don't pick will be hitting things.

 

[mfb]

To mfb and e.bar.goum; have you ever seen or heard of neutron production in a bending magnet, without the beam hitting something, apart perhaps from residual gas?

You can have radioactive isotopes in the beam (including neutron emitters), but I guess that's not what you are looking for.
If the beam hits nothing, no neutrons are produced. It is possible to make up hypothetical scenarios where high-energetic photons hit deuterium and split it, but ...

I get the impression your actual question is something else, something you didn't ask yet.