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Origins
Published in Douglas S. McGregor, J. Kenneth Shultis, Radiation Detection, 2020
Douglas S. McGregor, J. Kenneth Shultis
There are six types of quarks, with the fanciful names of up, down, top, bottom, charm and strange, in what is now known as the standard model. Hadrons are subcategorized as mesons and baryons, where mesons are composed of two quarks and baryons are composed of three quarks. The two most well-known and stable baryons are protons and neutrons. Protons are composed of two up-quarks (each with charge of +2/3 qe) and one down-quark (charge of −1/3 qe), yielding a total charge of +qe. Neutrons are composed of one up-quark and two down-quarks, yielding a total neutral charge. Neutrons not bound in an atomic nucleus are radioactively unstable with a half-life of 10.23 minutes. When a neutron is free from an atomic nucleus, one of the down-quarks decays into an up-quark, causing the neutron to decay into a proton, an electron, and an antineutrino.
Discovery, science and progress
Published in Mário S. Ming Kong, Maria do Rosário Monteiro, Maria João Pereira Neto, Progress(es) – Theories and Practices, 2018
Underlying all the Standard Model structure described so far lays the ethereal Higgs field introduced in the 1960s by Peter Higgs, Robert Brout and François Englert and further exploited by Carl Hagen, Gerald Guralnik and Thomas Kibble (KIBBLE 2009). The Higgs field quantum, also called Higgs boson, is the only known fundamental particle with a spin consistent with zero (hence a boson). The precise nature of this particle is not yet fully clear. Recently discovered at the Large Hadron Collider at CERN (HIGGS 2012), the Higgs boson has been since then at the centre of an intense experimental and theoretical research effort. Up to this moment, it is unclear whether this particle is nothing but the keystone of the known subnuclear structure, or whether it is the herald of a new, yet to be discovered, the realm of new Physics beyond the Standard Model.
Understanding the Atom and the Nucleus
Published in Robert E. Masterson, Nuclear Engineering Fundamentals, 2017
There is one final distinction that we would like to make when it comes to the study of nuclear particles (like protons and neutrons) that we may encounter in our study of nuclear reactors. A hadron is a very heavy composite particle that is made out of two or three quarks in a bound state. Hadrons themselves come in two classes. The first class is called baryons (which consist of three quarks) and the second class is called mesons (which are made up of one quark and one antiquark). The best well-known examples of hadrons are protons and neutrons, which are also known as baryons. The best-known examples of mesons are the gluons, which carry the nuclear force field. Mesons are force particles that have integer spins (0, 1, −1, etc.), and baryons are matter particles that have fractional spins (multiples of 1/2 like 1/2, 3/2, and 5/2). Figure 1.23 shows how these two particle families compare. Hence, a nuclear accelerator is able to collide both baryons and mesons. However, from a practical point of view,
Novel LHC collimator materials: High-energy Hadron beam impact tests and nondestructive postirradiation examination
Published in Mechanics of Advanced Materials and Structures, 2020
Giorgia Gobbi, Alessandro Bertarelli, Federico Carra, Jorge Guardia-Valenzuela, Stefano Redaelli
The CERN Large Hadron Collider (LHC) [1] is the largest and most energetic particle accelerator in the world, with two counter rotating proton beams, having a design stored energy of 360 MJ each, circulating in a ring installed in a 27-km long underground tunnel. Superconductive magnets producing an 8.3 T magnetic field, cooled in a bath of superfluid helium, guide the particles over their circular orbit. The two beams are accelerated inside the ring with a radiofrequency system and then brought into collision inside four detectors—ALICE, ATLAS, CMS, and LHCb. The energy stored in the beams will be almost doubled in the next years with the High Luminosity LHC (HL-LHC) upgrade [2], aimed at increasing the machine performances. In such operational conditions, the unavoidable beam losses could compromise the functioning of other components, e.g. magnets. Therefore, the LHC is endowed with a collimation system [3], whose main functions are removing stray particles, which would induce quenches in the superconductive magnets, and shielding the other machine components in case of accidental beam impacts. The complete LHC collimation system comprises about 50 collimators per beam. A scheme of an HL-LHC collimator is showed in Figure 1.
Influence of Doppler broadening model accuracy in Compton camera list-mode MLEM reconstruction
Published in Inverse Problems in Science and Engineering, 2021
Yuemeng Feng, Jean Michel Létang, David Sarrut, Voichia Maxim
Using the Compton camera to detect γ rays was proposed during 1970s simultaneously for astronomical [1] and nuclear medicine [2] imaging applications. Its advantage over other devices such as the widely employed collimated cameras and the coded aperture is the large angle acceptance. To identify the direction of an incoming γ ray, the camera makes use of a coincidence mechanism based on Compton scattering. More recently, its application to ion-range monitoring in proton and hadron-therapy through prompt-gamma detection was proposed. The energies of the prompt-γ rays are in this case too large to cope with parallel-hole acquisition, unless hard collimation is employed [3,4], and this complicates three-dimensional imaging and reduces the resolution.
Characterization of three GEM chambers for the SBS front tracker at JLab Hall A
Published in Radiation Effects and Defects in Solids, 2018
L. Re, V. Bellini, V. Brio, E. Cisbani, S. Colilli, F. Giuliani, A. Grimaldi, F. Librizzi, M. Lucentini, F. Mammoliti, P. Musico, F. Noto, R. Perrino, C. Petta, M. Russo, M. Salemi, F. Santavenere, G. Sava, D. Sciliberto, A. Spurio, M.C. Sutera, F. Tortorici
In its full configuration, the new spectrometer will consist of a dipole magnet with integral field up to 3 T, three charged particle trackers (front, second and third trackers), two identical proton polarimeters (two wall analyzers followed by the second and third trackers respectively), and an hadron calorimeter, as shown in Figure 1 (2). The SBS will be complemented by the existing, refurbished BigBite spectrometer (3), used as electron arm.