#research/radiography/electron-clouds See also: [[20230424 Electron Clouds at Energies above 2 MeV have 2 Characteristic Shapes]] and [[Fast electrons carry the energy imparted from a photon]]. # Electron Clouds Motivation: definition of electron clouds The term "electron cloud" refers to the distribution of electrons that are generated from a fast electron when a photon interacts with a detector material, such as CdZnTe. During a given interaction, the photon ionizes valence electrons, creating electron-hole pairs. The resulting electron cloud is essentially a collection of these ionized electrons. Depending on the energy of the incident photon, the size and shape of the electron cloud can vary. For instance, larger deposited energies result in larger electron clouds, which can significantly affect the induced signal on each pixel and, consequently, the position resolution of the detector. Zhang ([[@zhangEVENTSRECONSTRUCTION3D2005]]), Zhu ([[@zhuDigitalSignalProcessing2012]]), Xia ([[@xiaInteractionReconstructionDigital]]), and Shy ([[@shyArtifactsHighEnergyCompton2020]]) have all studied electron clouds in great depth. Where my work expands is studying these electron clouds for high energy depositions. ## Electron Cloud Geometry - At lower energies, electron clouds take on a spherical, or perhaps ellipsoid-like shape. At higher energies, this shape takes on a more complicated shape. - This is because of the way electrons scatter and deposit their energy, as characterized by the [[Bethe Formula for Stopping Power]] and by electron cloud scattering mechanics due to electrostatic forces. - From the collisional and radiative loses a higher energies, it is possible to determine relevant geometrical information about the electron cloud by using electronic information provided by the detector readout. ## Related Thoughts: - How do we characterize electron cloud geometry? - Why do we even case about electron cloud geometry? - knowing this can improve the position resolution in the the system [WRITE THIS]