Number of ionizations by heavy ion beam

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Discussion Overview

The discussion revolves around the number of ion-pairs produced by a heavy ion beam depositing energy in a volume of matter, specifically focusing on the case of liquid water and the Bragg peak. Participants explore the relationship between deposited energy and ionization, as well as the potential for atomic excitations and other energy loss mechanisms.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant suggests that the number of ion-pairs produced can be estimated by dividing the deposited energy by the average energy of ionization, while acknowledging that some energy may cause atomic excitations instead of ionizations.
  • Another participant notes that the fraction of energy lost to excitations will depend on the target material, beam type, and beam energy, and mentions additional processes such as phonons and lattice displacements.
  • A participant expresses interest in the specific case of liquid water and the Bragg peak, seeking information on simulation programs.
  • Geant 4 is recommended as a standard simulation tool for high-energy physics, with a suggestion that it may also be suitable for the Bragg peak scenario.
  • TRIM/SRIM is mentioned as another effective tool, noted for being easier and quicker to use for simpler problems compared to Geant 4.

Areas of Agreement / Disagreement

Participants generally agree on the need to consider various factors affecting ionization, such as the target material and beam characteristics. However, there is no consensus on the exact fraction of energy that contributes to ionizations versus excitations, and the discussion remains unresolved regarding the specifics of these processes.

Contextual Notes

The discussion highlights limitations in understanding the fraction of energy lost to different processes, as well as the dependence on specific definitions and conditions related to the target material and beam energy.

Who May Find This Useful

This discussion may be useful for researchers and students interested in the effects of heavy ion beams in materials, particularly in the context of radiation physics and simulation techniques.

ORF
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Hello

If a heavy ion beam deposits a certain energy E in a volume V, how many ion-pairs will it produce in matter?

I think that the number of ion-pairs will be the energy divided by the (average) energy of ionization. A friend told me that a part of the deposited energy will cause also atomic excitations without ionizations, but we don’t know the fraction of energy for each process. I suppose that the fraction of excitations will be negligible compared to ionizations, but I’m not sure of that.

Thank for your time (with a reference to a book will be enough).

Greetings!
 
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The fraction will depend on the target, the beam type and beam energy. You also get phonons and lattice displacements. There are programs that can simulate it.
 
Hello

Thank you for answering :)

I'm interested in the case of matter=liquid water and E=Bragg's peak.

On the other hand, you have aroused my curiosity: how can I find that programs?

Greetings!
 
Geant 4 is standard in high-energy physics, but I guess it works well for the Bragg peak, too.

No lattice displacements for liquids of course.
 
TRIM/SRIM will work well for this problem too, and is a little easier/quicker to run than Geant 4 for this kind of simple problem. http://www.srim.org/
Don't let the terrible website fool you, it's good stuff, and is pretty standard in medium/lowish energy beam physics.
 
Hello

I've taken a look to Geant4 and SRIM, and SRIM seems easier :)

Thank you for your help!

Greetings!
 

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