The fractional energy loss of charged particle per radiation length

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CzTee96
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The figure usually has a caption that goes like this: "Fractional energy loss per radiation length as a function of electron or positron energy in lead," but I do not fathom is at (1/E)dE/dx =1, it seems like the particle is losing all of its energy at ~7MeV by ionisation. Therefore, I would not expect the other contributions will happen. However, the diagram seems to suggest that even at very low energy we still have losses through other processes and most bizarrely the "fractional loss" through ionisation even went greater than 1 at very low energy. For example, it seems like at 5MeV we have the "fractional energy loss per radiation length" is 1.2E! What does this even mean? Is it trying to say that the ionisation is "relatively higher" than the other processes, and the fraction of all the processes is not normalised to 1?
Also, I would expect at such a low energy the electron will lose all its energy via ionisation, but why there is still a contribution from the Bremsstrahlung at 1MeV, which is around 0.6?Source: https://cds.cern.ch/record/2315747/
 
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  • #2
Look at the units. It's per radiation length - if one loses 6% of the energy in 0.05X0, where is that on your plot?
 
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FAQ: The fractional energy loss of charged particle per radiation length

What is the fractional energy loss of a charged particle per radiation length?

The fractional energy loss of a charged particle per radiation length is the fraction of its energy that a charged particle loses when it travels a distance equal to one radiation length in a material. This is primarily due to the emission of bremsstrahlung radiation.

How is the radiation length defined?

The radiation length is defined as the mean distance over which a high-energy electron loses all but 1/e of its energy by bremsstrahlung, or equivalently, the mean free path for pair production by a high-energy photon.

What factors influence the fractional energy loss per radiation length?

The fractional energy loss per radiation length depends on the type of charged particle, its energy, and the atomic number (Z) of the material it is passing through. Higher Z materials generally result in greater energy loss per radiation length.

Why is bremsstrahlung significant for high-energy charged particles?

Bremsstrahlung, or braking radiation, is significant for high-energy charged particles because it becomes the dominant mechanism of energy loss as the particle's energy increases, especially for electrons and positrons. This is due to the fact that the probability of bremsstrahlung increases with the energy of the particle.

How can the fractional energy loss per radiation length be calculated?

The fractional energy loss per radiation length can be calculated using empirical formulas or detailed simulations that take into account the particle's energy, the material's properties, and the interaction mechanisms. The Bethe-Heitler formula is commonly used for high-energy electrons and positrons.

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