A Cloud-Chamber Study of Cosmic-Ray Air Showers at Sea Level

Relf, Kenneth E.

doi:10.1103/physrev.97.172

Phys. Rev.

1955

DOI: 10.1103/physrev.97.172

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A Cloud-Chamber Study of Cosmic-Ray Air Showers at Sea Level

Kenneth E. Relf

Abstract: A diffusion-type cloud chamber eight feet long, four feet wide, and five inches deep has been used to study the lateral structure of cosmic-ray air showers in a region near the core. Three showers were recorded in which the core lay within sixty to ninety centimeters from some point on the periphery of the chamber. The results show that the lateral distribution of the shower particles in all but one photograph follow exceedingly well the Moliere distribution. The deviations from the Moliere distribution are al… Show more

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Cited by 4 publications

References 41 publications

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Two‐Photon Absorption in an Indirect‐Gap Semiconductor Quantum Well System. I. Interband Transitions

Hassan

1994

Physica Status Solidi (b)

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Phonon-assisted two-photon interband transitions in an indirect-band-gap semiconductor layered quantum well (QW) and quantum well wire (QWW) are theoretically studied. The spectral dependence of the two-photon absorption (TPA) coefficients dl), a'", d 3 ) in one-dimensional (lD), 2D, and also 3D (bulk) systems, respectively, are found to vary according to (2hw hQ -EG)p, where hw(hQ) is the photon (phonon) energy and E , is the effective indirect gap. p takes the values 0, 1,2, and 3 depending on the dimension of the system and the form of momentum matrix elements. The analytical expressions of the electron-photon and electron-phonon matrix elements in QW systems are given.The numerical calculation of the TPA coefficients dl), dzl, and d 3 ) in Si,,,Ge,,, shows that:for polarization parallel to the confinement directions, is four (two) orders of magnitude bigger than d3' for allowed -allowed transitions. Furthermore, dl) is two orders of magnitude larger than d2), for both photon polarizations with respect to the confinement directions in QW systems. This enhancement of dl) over a('' and d 3 ) is interpreted as due to the additional lateral quantum confinement of the carriers in QWW and also due to the intra-subband momentum matrix elements.

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Two‐Photon Absorption in an Indirect‐Gap Semiconductor Quantum Well System. I. Interband Transitions

Hassan

1994

Physica Status Solidi (b)

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Two‐Photon Absorption in an Indirect‐Gap Semiconductor Quantum Well System. II. Excitonic Transitions

Hassan

1994

Physica Status Solidi (b)

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A theory of phonon-assisted two-photon exciton transitions in indirect-band-gap semiconductor layered quantum wells (QW) and quantum well wires (QWW) is developed. The expressions for the two-photon absorption coefficients in one-dimensional (lD), a::', 2D, @, and 3D (bulk), a::), respectively, are calculated. The spectral dependence of these expressions, the vicinity of the band edge, are found to obey the law (2ho hS2 -E , + E&)O, where hw(hQ) is the photon (phonon) energy, E , the effective indirect gap, and Ek: the exciton binding energy. The values of /? vary from -f up to $ depending on the dimension of the system and the type of the coupling matrix element involved in each transition process. Before the edge, the final exciton states are of s-or p-symmetry according to the photon polarizations with respect to the confinement directions in the QWs and to the selection rules allowed by the momentum matrix elements. A numerical estimation for the case Si,.,Ge,,, shows that a::) for both photon polarizations (parallel and perpendicular to the confinement direction of the QWs) is enhanced over the values of u!:' and EL: ) (allowed and forbidden transitions). Furthermore ukl) is also enhanced over the u!:) values of bulk materials. This behaviour of the a,,' s is interpreted as due to (i) the additional confinement of the carriers which occur going from 3D + 2D -+ 1D systems, (ii) the photon polarization configurations with respect to the confinement directions, and (5) the coupling matrix elements.

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Neuro-explicit semantic segmentation of the diffusion cloud chamber

Müller,

Porawski,

Wilde

et al. 2023

Review of Scientific Instruments

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For decades, in diffusion cloud chambers, different types of subatomic particle tracks from radioactive sources or cosmic radiation had to be identified with the naked eye which limited the amount of data that could be processed. In order to allow these classical particle detectors to enter the digital era, we successfully developed a neuro-explicit artificial intelligence model that, given an image from the cloud chamber, automatically annotates most of the particle tracks visible in the image according to the type of particle or process that created it. To achieve this goal, we combined the attention U-Net neural network architecture with methods that model the shape of the detected particle tracks. Our experiments show that the model effectively detects particle tracks and that the neuro-explicit approach decreases the misclassification rate of rare particles by 73% compared with solely using the attention U-Net.

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A Cloud-Chamber Study of Cosmic-Ray Air Showers at Sea Level

Cited by 4 publications

References 41 publications

Two‐Photon Absorption in an Indirect‐Gap Semiconductor Quantum Well System. I. Interband Transitions

Two‐Photon Absorption in an Indirect‐Gap Semiconductor Quantum Well System. I. Interband Transitions

Two‐Photon Absorption in an Indirect‐Gap Semiconductor Quantum Well System. II. Excitonic Transitions

Neuro-explicit semantic segmentation of the diffusion cloud chamber

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