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Significance of TL Radiation Dosimetry of Carbon Ion Beam in Radiotherapy
Published in Vikas Dubey, Sudipta Som, Vijay Kumar, Luminescent Materials in Display and Biomedical Applications, 2020
Karan Kumar Gupta, N.S. Dhoble, Vijay Singh, S.J. Dhoble
The depth dose distribution of HCP beams, when the HCP beam incident on any medium is very low in the entrance region, shows a straight trajectory, and prominent dose (as a peak) in the stopping region, also called Bragg peak, which results in the irradiation of very small confined tumors or other malignant cells within the patient’s body. HCP passing through any medium loses its maximum energy due to interaction with atomic electrons of the medium (Tobias et al. 1952). It also undergoes elastic or inelastic collisions with the nucleus. The main difference of the electron beam and heavy charged particle beam is due to the rest mass of the electron which is less than the HCP mass. Thus, the electron beam loses its maximum energy during its first interaction with the matter but the scattering angle of HCP is very low, resulting in a sharper lateral dose distribution and traversing a long distance through the medium along with producing secondary electron and higher order electron.
Planar Active-Edge Sensors
Published in Cinzia Da Vià, Gian-Franco Dalla Betta, Sherwood Parker, Radiation Sensors with Three-Dimensional Electrodes, 2019
Cinzia Da Vià, Gian-Franco Dalla Betta, Sherwood Parker
As previously mentioned, planar detectors with active edges were successfully developed at VTT/Advacam, Finland, several years ago [42–53]. Devices were made on SOI substrates of different active thicknesses, ranging from 50 µm to 675 µm. Most studies have been performed using pixel sensors compatible with readout chips of the Medipix/Timepix family. Besides investigating the electrical properties for different edge designs, which were generally very good with low leakage currents and high enough breakdown voltages, the response of the edge pixels has been thoroughly studied in order to quantify the impact of the trench electrode on the distortion of the electric field configuration. To this purpose, different experimental setups have been used, such as position-resolved laser systems, synchrotron beam scans, and charged particle beam tests. Depending on the detector structure (e.g., n-on-p, p-on-n, n-on-n, p-on-p), the electric field distortion was found to lead to either enhancement or reduction of the charge collected by the edge pixels. However, for imaging applications, this effect can be quantified and corrected during data acquisition or in the postprocessing phase.
Introduction: The optical nature of a charged particle beam
Published in Timothy R. Groves, Charged Particle Optics Theory, 2017
Since this works for any point in the object plane zO, we deduce that all object points are imaged simultaneously, each to a unique point in the image plane. This is the mechanism by which a magnified image of an extended object is formed. The negative of the ratio of rI to rO is called the magnification of the image relative to the object. By convention, the magnification is negative in this case, because the image is inverted relative to the object. By performing the construction in Figure 1.4 for multiple object points rO, it is easy to convince oneself that this magnification is the same for all object points. The magnification depends only on the relative positions of the object plane zO and the lens plane zL, and on the focal length f. The smaller the focal length f, the more the rays are deflected, and the stronger is the lens. The focal length is the same for all object points rO. For a charged particle beam, the focal length also depends on the particle energy. The higher the particle energy, the longer is the focal length. This is a direct result of the fact that a faster particle spends less time in the lens field, and is therefore deflected less than a slower particle.
Impact of neutron irradiation on electronic carrier transport properties in Ga2O3 and comparison with proton irradiation effects
Published in Radiation Effects and Defects in Solids, 2023
Jonathan Lee, Andrew C. Silverman, Elena Flitsiyan, Minghan Xian, Fan Ren, S. J. Pearton
Proton irradiation is performed using a high-energy charged particle beam generated by cyclotron. A cyclotron is a particle accelerator which uses the Lorentz force to accelerate charged particles to high speeds. In the absence of an electric field component, electrons moving perpendicular to magnetic fields will exhibit uniform circular motion. The magnetic field is omitted from a slab which lies parallel to the magnetic field. In this region, after exiting the magnetic field, an electric field is applied to accelerate the charged particles before entering another magnetic field region. The circular motion radius enlarges each time an acceleration is applied in the magnetically blank region, consistent with its higher velocity. Using this relatively simple method, high energies can be imparted to charged particles. Charged particles can be accelerated to relativistic speeds and a beam can be sustained. This method is used here for proton irradiation using a MC-50 Cyclotron at the Korea Institute of Radiological and Medical Science with the proton energy 10-MeV. The proton beam was injected into a low-vacuum chamber, where the β-Ga2O3-based devices were loaded, facing the proton beam. The average beam-current, measured by Faraday-cup, was 100 nA during the proton irradiation process. Proton fluence was fixed at 1014 cm−2. The room scattering or temperature value of L was ∼340 nm for the nonirradiated sample and decreased with increasing temperature due to increased recombination. After proton irradiation, the room temperature diffusion length was reduced to ∼315 nm. The values of the activation energy according to equation (4) were 41.8 and 16.2 meV and the asymptotic L0 values were 145 and 228 nm for the nonirradiated and proton irradiated samples, respectively. The main defect created in Ga2O3 by proton irradiation has been identified as a Ga vacancy with two hydrogens attached [76].