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M. Brugger et al.
5.1 The Interactions of High Energy Particles with Matter
Modern accelerators use leptons or hadrons (including ions) and have beam energies
spanning the MeV to TeV range. Therefore, the capability of modelling particle
interactions and showers from these energy ranges down to thermal energies is
essential during all stages of the lifetime cycle of an accelerator, from the accelerator
design through operation to its final decommissioning.
Before briefly discussing general aspects of hadronic and electromagnetic showers, a short overview is given of important ingredients for accelerator applications:
• energy deposition for the design of accelerator components and elements (e.g.,
collimators, magnets);
• particle fluences as a function of energy, angle and position (e.g., detector or
radiation damage and radiation to electronics studies);
• distribution of particle interactions, inelastic interaction density (e.g., for tracking
and loss pattern studies);
• residual nuclei production and generation of radioactive isotopes by beam
interactions (e.g., radiation protection aspects like air activation or equipment
handling).
To allow for calculations of related quantities, the underlying physical processes
must not only be well understood and described in models, but also included in
calculation codes able to yield allow reliable estimates within a reasonable time.
5.1.1 Basic Physical Processes in Radiation Transport
Through Matter
Hadron and electromagnetic showers are very complex phenomena, whose description in terms of basic physical interactions requires a detailed and complex
modelling.
As soon as the energy of a primary hadron beam exceeds a few tens of MeV,
inelastic interactions start playing a major role and generate secondary particles
that will have enough energy to trigger further interactions giving rise to hadronic
showers. Furthermore, whenever the beam energy is high enough that significant
pion production can occur, an increasing fraction of the energy will be transferred
from the hadronic to the electromagnetic part due to meson decay (e.g., π 0 decaying
into a gamma pair). The pion production threshold for nucleons interacting with
stationary nucleons is around 290 MeV.
Therefore, energetic hadronic showers are always accompanied by significant
electromagnetic showers, where the latter ones tend to develop independently
without further hadronic particle production (with the exception of electro- and
photo-nuclear interactions of lower importance for hadron accelerators, which
however have to be considered for lepton accelerators).
M. Brugger et al.
5.1 The Interactions of High Energy Particles with Matter
Modern accelerators use leptons or hadrons (including ions) and have beam energies
spanning the MeV to TeV range. Therefore, the capability of modelling particle
interactions and showers from these energy ranges down to thermal energies is
essential during all stages of the lifetime cycle of an accelerator, from the accelerator
design through operation to its final decommissioning.
Before briefly discussing general aspects of hadronic and electromagnetic showers, a short overview is given of important ingredients for accelerator applications:
• energy deposition for the design of accelerator components and elements (e.g.,
collimators, magnets);
• particle fluences as a function of energy, angle and position (e.g., detector or
radiation damage and radiation to electronics studies);
• distribution of particle interactions, inelastic interaction density (e.g., for tracking
and loss pattern studies);
• residual nuclei production and generation of radioactive isotopes by beam
interactions (e.g., radiation protection aspects like air activation or equipment
handling).
To allow for calculations of related quantities, the underlying physical processes
must not only be well understood and described in models, but also included in
calculation codes able to yield allow reliable estimates within a reasonable time.
5.1.1 Basic Physical Processes in Radiation Transport
Through Matter
Hadron and electromagnetic showers are very complex phenomena, whose description in terms of basic physical interactions requires a detailed and complex
modelling.
As soon as the energy of a primary hadron beam exceeds a few tens of MeV,
inelastic interactions start playing a major role and generate secondary particles
that will have enough energy to trigger further interactions giving rise to hadronic
showers. Furthermore, whenever the beam energy is high enough that significant
pion production can occur, an increasing fraction of the energy will be transferred
from the hadronic to the electromagnetic part due to meson decay (e.g., π 0 decaying
into a gamma pair). The pion production threshold for nucleons interacting with
stationary nucleons is around 290 MeV.
Therefore, energetic hadronic showers are always accompanied by significant
electromagnetic showers, where the latter ones tend to develop independently
without further hadronic particle production (with the exception of electro- and
photo-nuclear interactions of lower importance for hadron accelerators, which
however have to be considered for lepton accelerators).