Principles of Radiation Interaction in Matter and Detection

The following sections are included:

• Dedication
• Preface to the Fourth Edition
• Preface to the Third Edition
• Preface to the Second Edition
• Preface to the First Edition
• Contents

The phenomena associated with the interaction of radiation in matter are commonly understood to include a wide variety of physical effects. Moreover, the nature of the interaction in matter depends on the incoming type of radiation and energy. The incoming radiation may also inflict temporary or permanent damage to the detectors material and readout electronics. In most cases - for moderate exposure to irradiation fields -, detectors are not prevented from operating normally, but - in presence of large irradiation fields and/or as a result of exposure to large accumulated fluences - induced radiation effects may degrade devices performance…

The study of radiation detection requires a deep understanding of the interaction of particles and photons with matter, where they deposit energy via electromagnetic or nuclear processes. As a result of such processes, a fraction of the incoming particle energy is released inside the medium. However, there are detectors, like the so-called calorimeter detectors, in which the whole particle energy is almost degraded and deposited via a series of successive electromagnetic and/or nuclear processes…

In this chapter, we will discuss the various electromagnetic processes which take place when passing photons interact in a medium.

Photons can be fully absorbed by matter in a single scattering or by a few subsequent interactions. Emerging electrons will mainly experience collision losses at sufficiently low energy (i.e., below the critical energy) or will radiate other photons. The most relevant processes for photon absorption in matter are the photoelectric, Compton and pair production of electrons and positrons…

In previous chapters, we discussed the electromagnetic interactions of electrons, positrons, photons and heavy charged-particles with matter. These interactions manifest themselves in many ways, like ionization or excitation of atoms or molecules; they can also result in i) emission of photons or electrons, ii) emission of radiation due to a collective effect in the dielectric medium, iii) electron and positron pair generation and, finally, iv) bremsstrahlung…

Semiconductors are a group of materials having conductivities between those of metals - which are good conductors with conductivities as large as 10⁶ [Ωcm]⁻¹ in the case of aluminum deposited metal-strips in integrated circuits - and insulators, like silicon dioxide, used to isolate portions of integrated circuits, with a conductivity of (or lower than) ≈ 10⁻¹⁵ [Ωcm]⁻¹; hence the name…

In a semiconductor, currents are generated by net flows of carriers due to phenomena resulting in the variation of their thermal velocities. The physical process responsible for the motion of these carriers is known as transport.

In this chapter, we consider various phenomena affecting or arising from the transport of carriers in semiconductors, like those determining the mobility of electrons and holes - thus, their drift velocities - and the Hall effect, i.e., the motion of carriers when a magnetic field is applied to a semiconductor. The present treatment covers the dependencies of the drift motion on temperature, dopant concentration and strength of the electric field…

Silicon is the most widely employed active material for radiation detectors and the realization of electronic devices used in the fabrication and development of electronic circuits. The present technology evolves toward the creation of faster and less power consuming devices of increasingly small sensitive volume and higher density circuits, achieving, now, sub-micron technology with an increase of the number of memory elements. These devices are then used for applications of large to very large scale integration (VLSI) in several fields including particle physics experiments, reactor physics, nuclear medicine and space. Many fields of application present adverse radiation environments that may affect the operation of the devices…

Nowadays, silicon devices are the main components of any electronic system based on very large scale integrated semiconductor technologies. Similarly, since decades, silicon detectors have become the most common semiconductor radiation detector for position and energy measurements. Other devices, for instance solar cells for spacecrafts, are currently more often based on various semiconductor materials, realizing single (e.g., GaAs) or multiple (e.g., GaInP/GaAs/Ge) junctions…

The conversion of the energy deposited by incoming particles or radiation into photons can lead to particle detection, energy determination and discrimination between particles of different masses. Therefore, the use of scintillating materials, or the construction of detectors enhancing the Čerenkov or the transition radiation effects, can be of great use in many application fields, such as high-energy physics or medical imaging. The photons emitted in such detectors must be transported, by light guides or wavelength shifting (WLS) fibers, to photosensitive devices, e.g., photomultipliers, in order to be collected. In this chapter, the organic and inorganic scintillators will be reviewed, as well as the Čerenkov and transition radiation detectors, with many examples. A section will also be devoted to the description of the light transport and detection techniques…

Solid state detectors - referred to as semiconductor detectors - are made from semiconductor materials. These detectors benefit from a small energy gap between the semiconductor valence- and conduction-bands. Therefore, a small energy deposition can move electrons from the valence band to the conduction band, leaving holes behind. When an electric field is applied, the two charge carriers (electron and hole) drift toward their respective electrodes and produce a signal. Therefore, the passage of an ionizing particle in the sensitive part of a solid state detector can be detected by collecting the charge carriers liberated by energy deposition in the semiconductor. In this chapter, the basic principles of operation and main features of semiconductor detectors will be explained in details. The specific example of the microstrip detector will also be discussed. Silicon is widely used as sensitive (sometimes referred to as active) part in these semiconductor detectors…

The results reviewed in Chapters 7 (on Radiation Effects and Displacement Damage in Semiconductors) and 8 (on Radiation Environments and Damage in Semiconductors) and their interpretation show a progressive understanding of the physics phenomena underlying the displacement damage effects resulting from the radiation interaction in semiconductors. Although there is no general model supporting a comprehensive interpretation of the characteristics after irradiation, the generation of complex defects is certainly among the fundamental mechanisms responsible for the degradation of the semiconductor properties. These deep defects are mostly created by non-ionizing energy-loss (NIEL) processes, which generate primary defects by the initial particle interaction and by the cascade generation due to nucleus recoil, and secondary defects caused by the diffusion of the primary point defects (interstitials and vacancies). The different extension of the cascade and concentrations of impurities may favor a slight dependence of the damage effects on the type and energy of the incoming particle, as well as, on the type and resistivity of the semiconductor. It is worth to be remarked that a review of particle interaction and displacement damage in silicon devices operated in radiation environments was already provided by Leroy and Rancoita (2007)…

There exist several types of gas filled chambers, each type is characterized with a specific mode of operation. Ionization chambers are detectors filled with a gas or a noble liquid in which the ionizing particle creates ion-electron pairs. The ions and electrons then drift under the applied electric field to the cathode and anode, respectively, where they are collected. If the electric field is increased, the electrons have enough energy to ionize the gas themselves and one reaches a region of gas multiplication. The detectors using this mode of operation are called proportional counters. If the electric field is further increased, for example in a Geiger-Mueller counter, the electrons are so energetic that UV photons are emitted, when they reach the anode. The principle of operation of the ionization chamber will be explained in detail in this chapter. To demonstrate the usefulness of this type of detector, the study of pollution in liquid argon using an α-cell will be discussed extensively. The chapter will conclude with the principles behind proportional and Geiger-Mueller counter modes of operation.

Collisions between two particle beams (collider experiments) or by a beam interacting with a fixed-target (fixed-target experiments) or the interaction of cosmic rays with space matter or the Earth's atmosphere (astrophysics, gamma-ray astronomy, cosmic-ray studies) frequently produce a variety of particles through very complicated configurations of events covering a large solid angle…

A large fraction of matter in the Universe is non-luminous and non-baryonic. The most recent evidence is provided by the WMAP measurement of the cosmic radiative background [WMAP (2014)]. WMAP provides a picture where the Universe is consisting of ~ 4% of baryonic matter, 23% of cold dark matter and 73% of dark energy. Dark matter cannot be accommodated in the Standard Model of particles. Supersymmetry (SUSY) provides a candidate for dark matter. The lightest supersymmetric particle (LSP), the neutralino, predicted in SUSY emerges as the most promising candidate for cold dark matter (CDM). The neutralino is seen, then, as a weakly interacting massive particle [WIMP (see page 46)]. There are many experiments dedicated today to the search for dark matter. They can be classified into two types: direct and indirect searches for dark matter. The direct searches are looking for dark matter through the direct detection of WIMPs via their spin-dependent or spin-independent interactions with nuclei. These experiments are done through the measurement of the elastic scattering of WIMP on nuclei. Recoil nuclei are detected via ionization or via scintillation or through heat measurement (phonons) or their combinations. Indirect searches for dark matter are done through the detection of products of annihilations or decays of dark matter yielding photons, electrons, neutrinos, protons and their antiparticles with energy spectra characteristic of the dark matter state. Part of the research program of experiments in space is devoted to the indirect search of dark matter…

The knowledge about the physics governing the interactions of particles with matter and particle detection finds applications in the field of nuclear medicine imaging technique. This technique uses the injection into the patient of radionuclides directly emitting photons, or of radiopharmaceuticals, labeled with a positron emitting isotope. Photons directly produced by the radionuclide or produced by the annihilation with electrons in the body of positrons emitted by the radiopharmaceutical are detected by radiation detectors to reconstruct three dimensional images representing the distribution of radioactivity inside the patient's body and measure metabolic, biochemical and functional activity in tissue. Magnetic Resonance Imaging (MRI) is another imaging technique, which does not require the use of any radioactive material and uses instead the non-zero nuclear spin, an intrinsic property found in nuclei (see page 308). MRI uses magnetic fields varying from 0.2 to 2T and radio-frequency (RF) waves to observe the magnetization change of the non-zero spin nuclei. The hydrogen isotope ¹H, which has a nuclear spin of , is a major component of the human body and is used as the main source of information…

The following sections are included:

• General Properties and Constants
• Mathematics and Statistics

The following sections are included:

• Bibliography
• Index