How far do gamma rays extend from an accelerator?

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Discussion Overview

The discussion revolves around the extent of gamma rays emitted from accelerators, specifically focusing on the area affected by gamma radiation and the implications of distance and shielding. Participants explore the conversion of area measurements and the nature of gamma radiation in comparison to other forms of radiation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant references the HERMES III accelerator's output, questioning the significance of the area of 1000 cm2 in terms of safety and distance from gamma rays.
  • Another participant clarifies that area and radius are different measurements, providing a calculation for the radius of a circle with that area, likening it to the size of a pizza.
  • There is a discussion about the safe distance from gamma rays, with one participant suggesting that safety is achieved when behind shielding.
  • Some participants compare gamma radiation to light, noting that it travels in straight lines and spreads out, becoming dimmer with distance.
  • One participant expresses uncertainty about the interpretation of what constitutes a "large area" in the context of gamma rays, suggesting that context matters significantly.
  • There is a request for clarification on converting cm2 to radius in inches, indicating a lack of confidence in online conversion tools.

Areas of Agreement / Disagreement

Participants express varying degrees of understanding regarding the implications of area measurements and the nature of gamma radiation. There is no consensus on what constitutes a "large area" in this context, and the discussion remains unresolved regarding the specifics of distance and safety measures.

Contextual Notes

Limitations include potential misunderstandings about the measurements being discussed (area vs. radius) and the varying interpretations of safety distances in relation to gamma radiation.

Rev. Cheeseman
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According to https://www.osti.gov/servlets/purl/7234564, the HERMES III which stand for High Energy Radiation Megavolt Electron Source accelerator is "capable of delivering a peak dose of ~100 krad (CaF2) over a useful area of ~1000cm2 (area where dose is greater than 50% of the peak dose) in a pulse on the order of 20ns".

I'm bad at math but I'm curious, is area of 1000cm2 after we convert to radius in feet is indeed a large area? How do we convert 1000cm2 to feet?
 
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wonderingchicken said:
How do we convert 1000cm2 to feet?

You don't. One is an area, the other is a length.

The radius of a circle with area 1000 cm2 is 7 inches. About the size of a pizza.

wonderingchicken said:
What is the safe distance from gamma rays

That's a completely different question, and the answer is "once you're behind the shielding".
 
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Vanadium 50 said:
You don't. One is an area, the other is a length.

The radius of a circle with area 1000 cm2 is 7 inches. About the size of a pizza.
That's a completely different question, and the answer is "once you're behind the shielding".
So it is considered as a "large area" only when we are talking about gamma rays then. Correct?

So in a nuclear explosion, the gamma radiation keeps extending as long as there is no barrier, shield, etc.?
 
wonderingchicken said:
So it is considered as a "large area" only when we are talking about gamma rays then. Correct?
I don't know if you are understanding what is being measured. If I'm understanding correctly, the device behaves a bit like a laser pointer, but emitting very powerful gamma rays instead of light. The 1000cm2 is the size of the spot it makes on the wall.
wonderingchicken said:
So in a nuclear explosion, the gamma radiation keeps extending as long as there is no barrier, shield, etc.?
Gamma radiation is just like light only higher frequency. It'll keep going in a straight line until stopped. But (like the visible flash from an explosion) the radiation spreads out, so is dimmer the further away you are. So the further away you are from an explosion the better. With something emitting a beam, like the HERMES device you cited, the radiation spreads much less - so you either need to be begind a shield or not in the line of fire.
 
wonderingchicken said:
So it is considered as a "large area" only when we are talking about gamma rays then. Correct?

I don't know. How long is a piece of string? 14" diameter is huge if you're talking about silicon wafers, and not so huge if you're talking about buildings. For pizza, 14" is large, 16" is extra large.
 
Vanadium 50 said:
I don't know. How long is a piece of string? 14" diameter is huge if you're talking about silicon wafers, and not so huge if you're talking about buildings. For pizza, 14" is large, 16" is extra large.

Gotcha. How do we convert cm^2 to radius in inches? I tried some online converters but I'm not sure if they are correct.
 
wonderingchicken said:
Gotcha. How do we convert cm^2 to radius in inches? I tried some online converters but I'm not sure if they are correct.
Have you tried searching "cm^2 to square inches" then "radius from circle area"?
 
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