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Low Energy Particle Accelerators and Laboratories
Published in Vlado Valković, Low Energy Particle Accelerator-Based Technologies and Their Applications, 2022
In their article, Craddock and Symon (2008) described particle accelerators using magnets whose field strengths are fixed in time to steer and focus ion beams in a spiral orbit so that they pass between and can be accelerated by, the same electrodes many times. The first example of such a device, Lawrence's cyclotron, revolutionized nuclear physics in the 1930s, but was limited in energy by relativistic effects. To overcome these limits two approaches were taken, enabling energies of many hundreds of MeV/u to be reached: either frequency-modulating the rf accelerating field (the synchrocyclotron) or introducing an azimuthal variation in the magnetic field (the isochronous or sector-focused cyclotron). Both techniques are applied in fixed-field alternating-gradient accelerators (FFAGs), which were intensively studied in the 1950s and 1960s with electron models. Technological advances have made possible the construction of several proton FFAGs, and a wide variety of designs is being studied for diverse applications with electrons, muons, protons and heavier ions. All fixed-field accelerators offer high beam intensity, in some cases deliver beams of 2 mA. Synchrocyclotrons and most FFAGs operate in pulsed mode, but are capable of much higher pulse repetition rates (≤kHz) than synchrotrons (Craddock and Symon 2008).
Area and Individual Radiation Monitoring
Published in Arash Darafsheh, Radiation Therapy Dosimetry: A Practical Handbook, 2021
Radiation exposure can be external or internal. However, since sealed radioactive sources and particle accelerators are typically used in radiotherapy, all exposures can be considered external. External radiation doses to an individual result from exposure to external sources of ionizing radiation, that is, radiation sources outside the body [1]. Gamma rays, x-rays, high-energy beta particles, protons, and neutrons are considered “penetrating radiation” and present an external exposure hazard. Conversely, low-energy beta particles and alpha particles are relatively “non-penetrating” and present less of an external radiation exposure hazard. Neutrons are produced in particle therapy facilities, therapy linear accelerators (linacs), fast neutron therapy facilities, and boron neutron capture therapy (BNCT) facilities. Particle therapy facilities (heavy ions) produce neutrons with maximum energies in the GeV range [2]. Proton therapy facilities produce neutrons with energies as high as the primary proton beam energy (∼250 MeV). Typically, either cyclotrons or synchrotrons are used in these facilities. Fast neutron therapy facilities produce neutrons with energies between 50 MeV and 70 MeV. These neutron therapy beams are produced by reactors, cyclotrons, and linear accelerators. BNCT uses epithermal neutrons for therapy. The neutron source for epithermal radiation is generated from nuclear reactors and accelerator-based neutron sources (ABNS).
An Invitation: Acceleration!
Published in Rob Appleby, Graeme Burt, James Clarke, Hywel Owen, The Science and Technology of Particle Accelerators, 2020
Rob Appleby, Graeme Burt, James Clarke, Hywel Owen
We may define a particle accelerator as a device – often called a ‘machine’ – that endows subatomic particles with large and variable amounts of kinetic energy. ‘Large’ here is in comparison with the sorts of energies one obtains from a particle source such as a simpler electron gun or ion source that might produce particles of tens of thousands of electron-volts (eV).∗ Particle accelerators differ from other sources of energetic particles – such as radioactive decay – in that an accelerator allows us (more or less) to freely choose the particle energy; for example, alpha particles from a given radionuclide – say, americium-241∗ – are emitted with only a single energy (of several MeV). We will see in the next chapter that electric fields are the predominant method of providing a particle with kinetic energy, and this demands that the particles we accelerate are charged so as to experience an acceleration from that field; the beams of particles that travel through an accelerator are therefore often described in terms of the equivalent current they carry. However, there are also so-called secondary sources of particles, some of which may be electrically neutral; three important examples are the photon, the neutron and the neutrino, all commonly produced by accelerators and used extensively in science and engineering for quite different things.
Design and dosimetry of a facility to study health effects following exposures to fission neutrons at low dose rates for long durations
Published in International Journal of Radiation Biology, 2021
Thomas B. Borak, Laurence H. Heilbronn, Nathan Krumland, Michael M. Weil
We have developed a capability to continuously expose large cohorts of mice and rats to high LET radiations for up to 400 d at dose rates on the order of 1 mGy/d. The impetus was to provide an infrastructure necessary to generate empirical data on the health effects of exposures to radiation at dose rates and total doses similar those that will be encountered by astronauts during extended missions in deep space. Previous investigations have reported a large RBE for the induction of solid tumors following acute exposures to HZE particles produced at particle accelerators. Our goal was to enable life span duration experiments using rodents to determine if this large RBE observed for accelerator produced HZE particles persists for chronic exposures to high LET radiation at low dose rate, or if there is sparing or enhancement of tumorigenesis.
A new class of weighted bimodal distribution with application to gamma-ray burst duration data
Published in Journal of Applied Statistics, 2020
Najme Sharifipanah, Rahim Chinipardaz, Gholam Ali Parham
The Universe is home to numerous exotic and beautiful phenomena, some of which can generate almost inconceivable amounts of energy. Supermassive black holes, merging neutron stars, streams of hot gas moving close to the speed of light, these are but a few of the marvels that generate gamma-ray radiation, the most energetic form of radiation, billions of times more energetic than the type of light visible to our eyes. The data from the Fermi gamma-ray space telescope are opening this high-energy world to exploration and discovery. With GRBs data, astronomers at long last have a superior tool to study how black holes, notorious for pulling matter in, can accelerate jets of gas outward at fantastic speeds. Physicists are able to study subatomic particles at energies far greater than those seen in ground-based particle accelerators; and cosmologists are gaining valuable information about the birth and early evolution of the Universe.
Dosimetry study on Auger electron-emitting nuclear medicine radioisotopes in micrometer and nanometer scales using Geant4-DNA simulation
Published in International Journal of Radiation Biology, 2020
Seifi Moradi Mahdi, Shirani Bidabadi Babak
The results show that on a single-cell scale, each radioisotope transmits more dose than 131I (the exception is only in three configurations N ← Cy, N → CS and C → CS for 99Tc) and, on the other hand, they transmit small amounts of dose to healthy cells adjacent to the cancerous cell (up to 2.5%). These diagnostic radioisotopes have a good half-life and easier access to them. For example, access to therapeutic 211At radioisotope is limited due to the need for an alpha particle accelerator with moderate energy to produce it. Another 211At problem, its daughter, is 110Po, which emits alpha particles with a half-life of 138.4 days. Also, due to the proper energy of the Auger electrons and the internal conversion electrons of these diagnostic radioisotopes, they can also be used in cluster irradiation of cancer cells.