1,720,977 research outputs found
Magnetic quadrupole simulations for focusing the electron beams emitted by a plasma focus device
No full textA Plasma Focus (PF) device allows for production of electron beams that, through a suitable target interaction, can be converted in X-ray pulses that have been considered for radiobiology or medical applications such as imaging or radiotherapy, in dependence from the working parameters and setup. The Plasma Focus Device for Medical Applications #3 (PFMA-3), hosted at the Montecuccolino Laboratory of the University of Bologna, has been designed for these purposes. In the device, electron pulses are generated during the pinch phase in the order of 1.0 E+15 particles in few tens of ns. One of the main advantages in dealing with the beams emitted by a PF is their self-collimated behavior at the emission time. Unfortunately, during the traveling distance from pinch to target, that collimation can be partially lost due to the repulsive interactions. One solution is to implement a magnetic device based on a quadrupoles triplet able to confine the beam in spots with a few mm diameter. This kind of focusing allows for using the PF as a source for generating extremely short X-ray pulses that could be more easily further managed for specific applications. A computational model of the PFMA-3 has been set using COMSOL© Multiphysics and the Monte Carlo MCNP6 code. The electron spectra used as source for simulations were acquired experimentally using a magnetic spectrometer, while the beam shape entering the magnetic system to be designed has been detected using Gafchromic© HDV2 film dosimeters and used as a benchmark for the numerical models. The magnetic field generated by the quadrupoles has been carefully designed through a parametric study with COMSOL© Multiphysics and the focusing effectiveness verified. The designed geometry has been then modeled in MCNP6 to perform coupled electron-photon transport simulations for estimating electron fluxes, spectra and X-ray doses as modified by the quadrupoles triplet application
Digital twins in dosimetry and radiotherapy, a survey and some applications
No full textDigital Twins (DTs) are emerging as a powerful tool in several applications, including Dosimetry and Radiotherapy (RT). Indeed, DTs have increased their effectiveness, up to the point that can be considered as virtual replicas of physical objects, processes, or systems. Through predictive modeling, DTs can determine optimal doses in radiation therapy, assist in defining personalized treatment schedules for individual patients, and monitor treatment responses. Moreover, DTs play a pivotal role in designing radioisotope production processes in the field of nuclear medicine. This can help to ensure the most effective treatment possible while minimizing the risk of side effects. As a frontier case example, DTs can be employed in the analysis of a possible new source for flash radiotherapy worth with respect to their effectiveness parameters like Radio-Biological Effectiveness (RBE) or cell Surviving Fraction (SF). Flash techniques involve the delivery of a high dose of radiation in a short time, reducing damage to surrounding healthy tissue while possibly increasing damage to malignant cells. DTs could be used to simulate and collect data about particle interactions with the treated tissues, optimizing the treatment and leading to improved outcomes. The most powerful tools that can be applied in DTs development are the Monte Carlo (MC) codes, particularly those with the highest capability of a detailed material/geometry description through an automatized spatial discretization approach like the one based on Unstructured Mesh (UM), allowing a common mathematical domain for both particle/radiation transport and thermal, fluid-dynamics and mechanical simulations. What comes out from various kind of applications is a common ground in terms of data management, phase space identification, simulation tools, that can be easily recognized even if spanning from cell response to technological devices, making realistic the perspective of the setup of general optimization procedures
A Plasma Focus device as ultra-high dose rate pulsed radiation source. Part II: X-ray pulses characterization
No full textA PF device has been setup, studied and evaluated as a fast pulsed self-collimated electron beam source for X-ray generation for radiotherapy applications. The worth of this source stands on the extremely short generation time (50 ns as reference delivery time) and on its intensity, being able to produce X-ray pulses able to transfer a dose in the order of 1 Gy each. The electron-X-ray conversion process for several metal targets is here analyzed using Monte Carlo simulations based on measured electron spectra discussed in Part I; some results have been benchmarked with experimental data. The perspectives of the development of a medical source based on this technology are finally evaluated
A Plasma Focus device as ultra-high dose rate pulsed radiation source. Part I: Primary electron beam characterization
No full textA Plasma Focus is a device able to generate in the pinch phase several kinds of radiation fields. One of them are the backward emitted electron's beams that can be used as source for X-ray pulses generation through the interaction with a suitable target. The worth of this source stands on two elements: first, being connected to the lifetime of the pinch phase, the electron current lasts a few tens of nanoseconds, we can say 50 ns as reference; second, the electron bunches carry a charge of the order of 0.1 mC. These two aspects grant the generation of X-ray pulses of extremely short duration, while the quite strong charge bunches allow a potential dose transfer by the X-rays in the order of 1 Gy per pulse. These characteristics have made this source of interest with respect to possible medical applications, in particular for radiotherapy of superficial tumors, given also that the extremely high dose rate could be of help in winning radio-resistance of specific cancer cells as in the case of melanoma. In this first part of the work, after a brief outline of the PF working principles, the experimental techniques used for the detection and the analysis of the characteristics of the primary electron source have been described. The results showing their correlation with the capacitor's bank energy and the possible scaling laws that could drive the setup of specific X-ray generation devices for radiotherapy treatments have been thoroughly discussed
Preliminary Neutronic characterization of a MW class and HALEU space nuclear reactor
No full textA preliminary design of a space nuclear reactor, with a power in the range of one MW and based on a High Assay Low Enriched Uranium (HALEU) fuel and a cooling system relying on Heat Pipes with sodium as coolant, has been carried out and analysed thanks to a full Monte Carlo model. Reactivity control system worth, biuiiup and shielding and some sensitivity analysis, have been modelled with the MCNP6 code. The reactor should be able to provide approximately 2 MW of thermal energy for ten years. The outcomes emerging from this work have highlighted the potentialities and the neutronic feasibility of the chosen material and technological solutions in terms of system masses, volumes and broad performances. The results of this study will be used to inform the subsequent design steps targeting an optimal configuration satisfying the established requirements
Sensitivity analysis via adjoint Monte Carlo calculations of plasma focus irradiation of micro-silica beads in phantoms
No full textOne of the main issues in the analysis of the performances of radiation detectors via Monte Carlo methods is their sensitivity with respect to the various irradiation parameters: source intensity and position, detector effectiveness and sensitivity, etc. In the present work, the capability of a quite new Trueinvivo© micro-silica beads TLD has been analyzed from the point of view of the Monte Carlo modeling of the irradiation process and the possibility of a speed up of the calculations using accurate bias techniques based on the adjoint solution of the transport process. The source considered is a Plasma Focus device explicitly designed for cell cultures or “in vivo” tests. The experimental data and the pure analogic Monte Carlo simulation previously obtained results coming from dosimeters at different depth and positions in a PMMA phantom composed by slabs and built for hosting the TLDs, have been benchmarked with respect to the adjoint bias approach. The results obtained through different biasing techniques, backward particle transport analysis, Weight Windows and a discrete ordinate model solution, show how it is possible to optimize the Monte Carlo calculations with great effectiveness
Status of JADE, an open-source software for nuclear data libraries V&V
No full textIn the last couple of years, a combined effort between NIER, Universit`a di Bologna and Fusion For Energy led to the development of JADE, a python-based open-source software for the Verification and Validation of nuclear data libraries. Nuclear data is fundamental for particle and radiation transport simulations which, in turn, are responsible for the evaluation of key quantities for fusion-related machines design such as nuclear heating, DPA, particles production and dose rates. The aim for the project is to offer standardization and automation to the V&V process of data libraries in order to speed up their release cycles and, at the same time, improve the quality of the data. JADE takes advantage of MCNP for the particles and radiation transport simulations and, even if it is potentially applicable to the whole nuclear industry, a particular focus on fusion applications is obtained through the selections of the default benchmarks that have been implemented. The code was recently made publicly available to the community and the status of its development is summarized in this work. The more important features and benchmarks (both computational and experimental) are described, together with a brief discussion on the major case studies where JADE has been used. Lastly, the current strength and limitations of the tool are evaluated and the foreseen future developments for the project are outlined
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dosimetric analysis and experimental setup design for in-vivo irradiation with a Plasma Focus device
No full textLooking at possible clinical applications of the Plasma Focus (PF) technology as medium-low energy extremely fast radiation source, aiming at the treatment of skin cancer pathologies, in vivo experiments on mice are a due step. To properly design the experiments, a dosimetric analysis on a PMMA mouse phantom has been devised and carried out. The dose delivered to the phantom has been evaluated in experiments using Gafchromic films, standard TLD chips and TL glass beads to be able to optimally reconstruct the radiation field produced by the PF at various depths in the phantom. The whole setup has also been analysed with a Monte Carlo model using the MCNP6 code to produce a correlation between the results obtained from the various dosimetric technologies
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