Gamma rays

This area is for discussions involving any fusion related radiation metrology issues. Neutrons are the key signature of fusion, but other radiations are of interest to the amateur fusioneer as well.
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Sam Flint
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Gamma rays

Post by Sam Flint »

Are gamma rays emitted in one specific direction or are they spherical ie emmitted as a wave three dimensionally from atom?
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Steven Sesselmann
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Re: Gamma rays

Post by Steven Sesselmann »

Sam,

Gamma rays are emitted isotropically from the nucleus unless they are attenuated by something surrounding the nucleus. The atomic nucleus doesnt stand still it spins or jiggles and it's impossible to determine where a proton or a neutron is at any one moment in time, therefore also the gamma. There could be cases where radioactive isotopes are homogenously mixed with led, in which case the lead being a strong attenuator will shield the gamma, so the gamma rays will appear to be coming from the surface only.

Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG
Sam Flint
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Re: Gamma rays

Post by Sam Flint »

I dont think that really answers my question. Im not asking if it can originate from anywhere in the nucleus, im asking if when a gamma ray is emmited, is it a thin "ray" that goes off in one specific random direction, or is it like a ripple on a 3D pond spreading out as a spherical wave so to speak?
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Steven Sesselmann
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Re: Gamma rays

Post by Steven Sesselmann »

Sam,

A gamma ray is a photon, only with a much shorter wavelength, and energy in the keV or MeV region, while a light photon is in the eV region. So yes unless you are looking at an extremely small region of space, a gamma ray behaves like a particle not like a wave.

Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG
Sam Flint
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Re: Gamma rays

Post by Sam Flint »

Thanks for the reply. Seems your answer could still be interprited a few ways (particle wave duality). Can you just simplify your answer. Let me pose a very basic very hypothetical experiment to ask my question one final time. Assume you have a single atom of some hypothetical type. The atom is between two planes of detectors of infinite length. Now, the hypothetical atom emits a SINGLE gamma ray. Assuming the gamma ray is not emmited perfectly parallel to the planes one of two things will happen. Either A, a single detector will register the gamma ray if it really acts like a ray, or B, both detectors will detect the gamma ray (wave) at same time. Which is true?
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Dennis P Brown
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Re: Gamma rays

Post by Dennis P Brown »

Gamma rays are singular events but that does not mean that they are not or do not also behave as waves. They cannot be localized anymore, or less then any singular photon - that is, one can do experiments that demonstrate one type of nature or another. It is incorrect to view visible light only as a wave either. Yet, to us, it appears as a pure wave in many common experiments, but in reality, it is a wave-packet called a photon.

There is a MAJOR problem with your thought experiment - that one can know if a single gamma ray was emitted. That isn't really possible (like getting just one atom isn't really possible.) But it is possible to, on average, get one photon (a probability calculation) to appear and get a single count on a specific detector. In that, the gamma ray acts like a particle but one can do experiments where it acts as a wave. For instance, for large numbers of emitted particles, they as a group will very much look like a classical wave. Again, how one does the experiment matters.

Since your detectors are so large, of course the gamma appears as a pure particle. But if one uses very small detectors, that is, high resolution, the wave nature will become dominate.

Refine your question if this answer isn't clear.
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Steven Sesselmann
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Re: Gamma rays

Post by Steven Sesselmann »

Sam,

You are beginning to speculate on theoretical physics, don't get me started, in any case this is the wrong forum.

Your second diagram is false, the photon can only be detected in one detector, if you want to understand why, you have to crawl a lot further down the rabbit hole. Once you get right down there you probably end up scratching your head like everyone else. I have my own views about this but this is not the place to discuss it.

I encourage you to get to the bottom of the problem, but don't let it take control of your life :)

Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG
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Rich Feldman
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Re: Gamma rays

Post by Rich Feldman »

OK, another couple cents worth on the topic.

At the scale of everyday objects, gamma "rays" behave like energetic, uncharged particles, as Dennis and Steven have said. In your example of two infinite parallel-plane detectors, a gamma ray originating between them (e.g. from certain radioactive decay events) will register on one detector or the other. If a three-dimensional track detector (e.g. cloud chamber, bubble chamber) responded to a gamma ray, there would be a straight trail.

Some events, such as positron-electron annihilation, generate two gamma "rays" that depart in nearly opposite directions. The particle model fits so well, people routinely measure the angular correlation of those pairs with milliradian resolution. Each departure from exact-oppositeness of direction, as with Doppler broadening of the 511 kV spectral line, is a data point about electron momentums in the material being probed. See "ACAR".
All models are wrong; some models are useful. -- George Box
Frank Sanns
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Re: Gamma rays

Post by Frank Sanns »

It is a gamma RAY not a gamma wave.

All electromagnetic waves including very energetic ones like gamma rays are photons. As such, each INDIVIDUAL one has momentum. Momentum is a vector so it has magnitude and direction. The direction means each INDIVIDUAL photon goes out in a single (random) direction. (Your picture #1 (true/false))

A group of photons all going out in their random direction gives the appearance of going out in all directions but it is really just the composite of individual photons (gamma rays) going out in their individual unique directions.
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We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
Sam Flint
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Re: Gamma rays

Post by Sam Flint »

Thank you all for finally clearly answering this hypothetical question.
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