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Stochastic Radiation Transport Methods
Published in Jerry J. Battista, Introduction to Megavoltage X-Ray Dose Computation Algorithms, 2019
where: hv’ ≡ scatter photon energy (MeV)hv ≡ incident photon energy (MeV)X0 ≡ radiation length (cm)n ≡ electron density (electron/cm3)r0 ≡ classical electron radius (cm)c ≡ speed of lightm0 ≡ electron rest massm0c2 ≡ electron rest energy (MeV)ϵ ≡ hv′/hvα ≡ hv/m0c2
Particle Detection
Published in Walter Fox Smith, Experimental Physics, 2020
where Lrad is the radiation length, the mean length for a given material to decrease the number of particles passing through by 1/e. Multiplying both sides by the count rate R gives the differential change in count rate, which is negative since electrons are absorbed and the count rate decreases: −dR=RdP=RdxLrad
Basic Physics of X-ray Interactions in Matter
Published in Paolo Russo, Handbook of X-ray Imaging, 2017
This process, however, is less probable than the pair production in the Coulomb field of the nucleus. If the photon energy is substantially greater than the rest mass of the electron, Eγ ≫ m · c2, then the cross-section is given by (Heitler 1954): σpair=4⋅Z2⋅α⋅r02⋅(79⋅ln(183Z13)−154)≈79⋅(4⋅Z2⋅α⋅r02⋅ln(183Z13))=79⋅ANA⋅x0, where x0 is the radiation length of the electron, defined in Section A.3.
Application of Accelerator Beam Dumps for Dark Matter Searches
Published in Nuclear Science and Engineering, 2023
Patrick Achenbach, Mirco Christmann
For a beam dump with a total radiation length of T and Ne and primary beam electrons of energy E0, the dark Bremsstrahlung process leads to a yield N of dark photons with , where NA is Avogadro’s number, A is the atomic mass, and X0 is the radiation length of the beam dump material. The dark photon decay into χ particles is also handled by the event generator. For each kinematic setting, a list of four vectors was obtained and used for the particle gun in the Geant4 simulation. Then, the particles were projected to the detector position. Figure 3 shows their distribution at the entrance to the DarkMESA room. The detection probabilities were calculated using , in which the minimum detectable recoil energy xmin plays a crucial role in the detector efficiency. The recoil energy spectrum dσ/dEr and the maximum transferable energy xmax follow from the elastic scattering kinematics off electrons.
Measuring time with high precision in particle physics
Published in Radiation Effects and Defects in Solids, 2022
B. Kaynak, S. Ozkorucuklu, A. Penzo
The beam profile depends on energy: for the T24 beam line the beam spot was approximately 15 mm wide at 5 GeV and increases to 25 mm at 2 GeV. The experimental areas are equipped with high-resolution tracker systems (MIMOSA). For electron beams, the experimental setup must be optimized in view of keeping both the radiation length X0 and the ionization energy loss dE/dx of all the setup components as low as possible; particularly X0 controls the multiple scattering and the showering probability of electrons in the apparatus.