Interactions of Radiation with Mattercosmicraysschool.ufabc.edu.br/pres/Pietro.pdf · Interactions...

transcript

Interactions of Radiation with Matter

Pietro Chimenti25/08/2010

Layout of the presentation:●Introduction

●Interaction of Muons●Of Electrons and Photons

●Of Hadrons

A few referencesTextbooks:●G.F.Knoll, “Radiation Detection and Measurements”, John Wiley and Sons●W.R.Leo, “Techniques for Nuclear and Particle Physics Experiments: A How-to Approach”, Springer

Particle Data Group (many pictures from this):●http://pdg.lbl.gov/2010/reviews/rpp2010-rev-passage-particles-matter.pdf

Interactions of Radiation with Matter - Pietro Chimenti - 25/08/2010

On the subject of this presentationRadiation--> Particles!“Low” intensity: no collective effects!We analyze the interaction of a single particle crossing a material:

Particles to be considered●Photon: mass-less, no charge, stable●Electron: M~0.511MeV/c^2, charged, not strongly interacting, stable●Muon: M~106MeV/c^2, charged, not strongly interacting, T~2.2X10^-6 s●Proton: M~938MeV/c^2, charged, strongly interacting, stable●Neutrons, pions, kaons, other nuclei

An example of interaction(Bubble chamber)

The simplest case: muons

If the muon energy is not too high the interaction is dominated by the transfer of

energy to electrons of the material.

The interaction of a fast muon with an atom

Differential energy transfer cross section (Rutherford - corrections due to atomic physics

however are needed).

The interaction of a fast muon with an homogeneous material

We have to sum (integrate) over the interaction with all the surrounding atoms.

M: momentum of order J of the distribution of released energy. Order 0: total number of

interactions.Order 1: mean released energy

Example: stopping power in Copper

Important features: low and high energy behaviour, minimum, Bethe approximation.

Radiative Energy Loss (1)

The range is the typical length traveled by a particle of a given energy in a certain material.

Bragg Peak

The Bragg Peak is an increase in energy deposition close to the end of the particle path.

Multiple Coulomb scattering

Incoherent scattering of the particle from nuclei.

Stopping power of mixtures

A simple weighted sum of the stopping power of the single compounds (Bragg Additivity).

An electromagnetic shower

The interaction of electrons, positrons and photons in materials is tightly connected.

The interaction of electrons

Important feature: the critical energy.

The critical energy

The development of the shower depends on the atomic number Z.

The interaction of photons with materials

Three important effects: photoelectric, Compton and pair production.

The dominant process in photon interaction

The photon absorption length

High Z material (e.g. Lead) are particularly effective in shielding against E.M. radiation.

An eletromagnetic shower in Icarus

An hadronic shower in Icarus

Basic features of hadronic showers

Hadrons produced abundantly, but also muons. E.M. Component much reduced.

How to detect particle interactions

●photons from: fluorescence, scintillation, Cherenckov effect, transition radiation●electrons and/or ions from ionization●Phase transition in material (e.g. cloud chamber)●Phonons (crystal lattice vibrations)

A Water Cherenkov Example (Super-Kamiokande)

Conclusions

I hope you enjoyed the lecture.

Have fun at the school!

Interactions of Radiation with Mattercosmicraysschool.ufabc.edu.br/pres/Pietro.pdf · Interactions...

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