Free Neutrons - What interacts with them?

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Discussion Overview

The discussion centers around the interactions of free neutrons, particularly whether they can interact with photons before undergoing decay, and explores various experimental observations and theoretical implications of such interactions. The scope includes theoretical considerations, experimental evidence, and applications in nuclear reactors.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants note that free neutrons can interact with photons, but only at high energies due to the neutron's neutral charge.
  • Others mention that the neutron's magnetic moment allows for interaction through magnetic mechanisms, and neutron scattering can be used to measure magnetization transitions.
  • It is suggested that the main interactions of slow free neutrons before decay are with certain nuclei through the strong interaction, including capture and scattering processes.
  • One participant emphasizes that free neutrons are involved in initiating fission in nuclear reactors, which raises questions about the relevance of photon interactions in that context.
  • There is a clarification that the original question specifically asks about photon interactions, separate from the context of nuclear reactions involving uranium nuclei.
  • A later reply acknowledges a misunderstanding in framing the question and reiterates the focus on photon interactions with free neutrons.

Areas of Agreement / Disagreement

Participants express differing views on the relevance of photon interactions with free neutrons, particularly in the context of nuclear reactors. While some agree that photons can interact with neutrons under certain conditions, others emphasize that the primary interactions in reactors involve neutrons and nuclei, not photons. The discussion remains unresolved regarding the specific nature and conditions of photon-neutron interactions.

Contextual Notes

Participants highlight the complexity of neutron interactions, noting that the conditions under which photons might interact with free neutrons are not fully established. There are also references to specific experimental contexts, such as neutron detectors, which may influence the discussion.

Who May Find This Useful

This discussion may be of interest to those studying nuclear physics, particle interactions, and experimental methods in detecting neutron behavior.

Chaos' lil bro Order
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Hey, I was wondering about possible interaction with free neutrons and if any have been seen experimentally. Here is a quote from hyperphysics:

'A free neutron will decay with a half-life of about 10.3 minutes but it is stable if combined into a nucleus.'

Can a photon interact with the free neutron before it undergoes its weak interaction decay?
 
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Hi order, it is possible for a photon and a neutron to interact. The neutron is electrically neutral and so low energy photons would not do the job. However, when the photons have high enough energy they can "see" the quarks that the neutron is composed of. Quarks do have electric charge and so interact with photons.
 
The neutron also has a magnetic moment, weak though it is, so it will also interact through that mechanism. In fact, you can measure magnetization transitions using neutron scattering in this way.
 
Chaos' lil bro Order said:
Hey, I was wondering about possible interaction with free neutrons and if any have been seen experimentally. Here is a quote from hyperphysics:

The main interaction of (slow) free neutrons before decay is with certain nucleae, often through the strong interaction. This can be capture, (in)elastic scattering or genuine nuclear reactions. For instance, there is a big interaction cross section with Boron-10, Helium-3, lithium-6,gadolinium-157,-uranium-235, and these reactions are often used in a thermal neutron detector, because the reaction products are electrically charged and quite energetic, so easily detected by an ionisation-sensitive detector (charge collection, scintillation...).
 
Er... free neutrons are the ones that intract with uranium nuclei to initiate fission in our nuclear reactors. So yes, they can interact.

Zz.
 
Doesn't the neutron react with the uranium nuclei, and not a photon in nuclear reactors?
 
Who is addressing "photon" in nuclear reactors?

Zz.
 
Can a photon interact with the free neutron before it undergoes its weak interaction decay?
The thread starter?

He doesn't ask if the neutron interpheres with the nucleus, he asks if the neutron can interact with a photon.
 
Yeah, but in a nuclear reactor? I was the one who brought up the example in a nuclear reactor. The OP only wanted to know if neutrons interact with anything, and brought up a question of neutron interacting with a photon.

Zz.
 
  • #10
ZapperZ said:
Yeah, but in a nuclear reactor? I was the one who brought up the example in a nuclear reactor. The OP only wanted to know if neutrons interact with anything, and brought up a question of neutron interacting with a photon.

Zz.

Yes, you are both right. I first asked whether the free neutron could interact with anything, but then specifically asked whether a photon would interact with it. I should have wrote the fission example into my question as one example, since its the easy obvious one.

My question was flawed, not your responses. I guess I really just wanted to know if a photon interacts with a free neutron, so then?
 
  • #11
vanesch said:
The main interaction of (slow) free neutrons before decay is with certain nucleae, often through the strong interaction. This can be capture, (in)elastic scattering or genuine nuclear reactions. For instance, there is a big interaction cross section with Boron-10, Helium-3, lithium-6,gadolinium-157,-uranium-235, and these reactions are often used in a thermal neutron detector, because the reaction products are electrically charged and quite energetic, so easily detected by an ionisation-sensitive detector (charge collection, scintillation...).

Great answer Varn, ty.

Maybe you can help me understand why Cadmium is such a good neutron absorber (ie. cadmium control rods in nuclear reactors)...
 

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