Effect of short- and long-range correlations on neutron skins of various neutron-rich doubly magic nuclei

We study the effects of correlations beyond the independent particle model in the evaluation of neutron skins of various neutron-rich doubly magic nuclei.We consider short- and long-range correlations to take into account the presence of the strongly repulsive core of the bare nucleon-nucleon interaction and collective nuclear phenomena, respectively. Despite the strong sensitivity on the structure of the nucleus considered, our results indicate that, in general, correlations increase the values of the neutron skins.Junta de Andalucia FQM387Spanish Government PID2019-104888GB-I00European Commissio

Evaluation of the overdiagnosis in breast screening programmes using a Monte Carlo simulation tool: a study of the influence of the parameters defining the programme configuration

Objectives To build up and test a Monte Carlo simulation procedure for the investigation of overdiagnosis in breast screening programmes (BSPs). Design A Monte Carlo tool previously developed has been adapted for obtaining the quantities of interest in order to determine the overdiagnosis: the annual and cumulative number of cancers detected by screening, plus interval cancers, for a population following the BSP, and detected clinically for the same population in the absence of screening. Overdiagnosis is obtained by comparing these results in a direct way. Results Overdiagnosis between 7% and 20%, depending on the specific configuration of the programme, have been found. These range of values is in agreement with some of the results available for actual BSPs. In the cases analysed, a reduction of 11% at most has been found in the number of invasive tumours detected by screening in comparison to those clinically detected in the control population. It has been possible to establish that overdiagnosis is almost entirely linked to ductal carcinoma in situ tumours. Conclusions The use of Monte Carlo tools may facilitate the analysis of overdiagnosis in actual BSPs, permitting to address the role played by various quantities of relevance for them.Work partially supported by the Biomedical Research Networking Center- CIBER de Epidemiología y Salud Pública (CIBERESP), the Spanish Ministerio de Ciencia y Competitividad (FPA2015-67694), the European Regional Development Fund (ERDF) and the Junta de Andalucía (FQM0387)

ECCPA: Calculation of classical and quantum cross sections for elastic collisions of charged particles with atoms

Financial support from the Spanish Ministerio de Ciencia, Innovación y Universidades / Agencia Estatal de Investigación / European Regional Development Fund, European Union (projects no. RTI2018-098117-B-C22 and PID2019-104888GB-I00 ) and from Junta de Andalucía (projects no. FQM387 and P18-RT-3237 ) is gratefully acknowledged.Program summary Program Title: eccpa CPC Library link to program files: https://doi.org/10.17632/c3tn9hyfvb.1 Licensing provisions: CC by NC 3.0 Programming language: Fortran 90/95 Nature of problem: The program computes differential cross sections (DCSs) for elastic collisions of charged particles (electrons, positrons, muons, antimuons, protons, antiprotons, and alphas) with neutral atoms. Calculations are performed within the static-field approximation with screened Coulomb potentials expressed as a sum of Yukawa terms with their parameters fitted to approximate the atomic electrostatic potentials resulting from the Thomas–Fermi model and from self-consistent Dirac–Hartree–Fock–Slater calculations. The program eccpa provides DCSs computed with four different approaches: the classical trajectory method, the Born approximation, the partial-wave expansion method with approximate phase shifts, and the eikonal approximation. The user is allowed to select the atomic number of the target atom, the potential model, the kind of projectile and its kinetic energy. Calculation results are written in a number of output files with formats suited for visualization with a plotting program. A Java graphical user interface allows running the program and visualizing the results interactively. Solution method: A relativistic extension of the classical trajectory method is formulated on the assumption that the interaction in the center-of-mass frame is central, which is a fundamental requirement of the adopted calculation schemes; the DCS in the laboratory frame is then obtained from the relativistic (Lorentz) transform of the DCS calculated in the center-of-mass frame. This scheme qualifies as semi-relativistic, because it accounts for relativistic kinematics in a rigorous way, but disregards the differences between the interactions observed from the laboratory and the center-of-mass frames. We consider the elementary quantum formulation based on the relativistic Schrödinger (or Klein–Gordon) wave equation obtained from the correspondence principle. Accurate DCSs for potential scattering can be computed by using the partial-wave expansion method, at the expense of considerable numerical work. To avoid the difficult calculation of phase shifts from the numerical solution of the radial wave equation, we adopt a simplified strategy that combines the (first) Born approximation, for both the scattering amplitude and the phase shifts, and the Wentzel–Kramers–Brillouin (WKB) approximation for the phase shifts. We also describe the semi-classical eikonal approximation, which is known to yield reliable DCSs for collisions with small scattering angles. The case of collisions of electrons and positrons is considered on similar grounds, with the scattering amplitudes obtained from the Dirac equation. The numerical work is simplified by approximating the interaction potential as a sum of Yukawa terms, which allows performing a good part of the calculations analytically. Integrals of functions given by analytical formulas are calculated by means of an adaptive algorithm that combines the 20-point Gauss-Legendre quadrature formula with a bisection scheme; this algorithm allows strict control of numerical errors and gives results with a relative accuracy better than about for well-behaved integrands. The whole calculation for a given energy of the projectile takes no longer than a few seconds on a modern personal computer, quite irrespectively of the energy and of the atomic number of the target atom. Additional comments including restrictions and unusual features: The adopted interaction potentials correspond to atoms with point nuclei. The use of a parameterization instead of numerical tables of the potential (obtained, e.g., from atomic structure calculations) has a minor effect on the calculated DCSs. This effect is limited to large scattering angles, where the actual DCS does differ from calculations with screened Coulomb potentials due to the effect of the finite size and structure of the atomic nucleus, which is disregarded here. DCSs obtained from the partial-wave expansion method and with the eikonal approximation provide a fairly accurate description of collisions with small and moderate deflection angles. They can be used, e.g., in Monte Carlo simulations of the transport of fast charged particles in matter. The information generated by the program allows assessing the accuracy of calculations with the various approaches, and permits identifying the ranges of validity of the classical trajectory method and the Born approximation.The Fortran program eccpa calculates differential and integrated cross sections for elastic collisions of charged particles with atoms by using the classical-trajectory method and several quantum methods and approximations. The collisions are described within the framework of the static-field approximation, with the interaction between the projectile and the target atom represented by the Coulomb potential of the atomic nucleus screened by the atomic electrons. To allow the use of fast and robust calculation methods, the interaction is assumed to be the same in the center-of-mass frame and in the laboratory frame. Although this assumption neglects the effect of relativity on the interaction, it allows using strict relativistic kinematics. The equation of the relative motion in the center-of-mass frame is shown to have the same form as in the non-relativistic theory, with a relativistic reduced mass and an effective potential. The wave equation for the relative motion, as obtained from the correspondence principle, is formally identical to the non-relativistic Schrödinger equation with the reduced mass and the effective potential, and it reduces to the familiar Klein-Gordon equation when the mass of the target atom is much larger than that of the projectile. Collisions of spin 1/2 projectiles are also described by solving the Dirac wave equation. Various approximate solution methods are described and applied to a generic potential represented as a sum of Yukawa terms, which allows a good part of the calculations to be performed analytically. The program eccpa is useful for assessing the validity and the relative accuracy of the various approximations, and as a pedagogical tool.Ministerio de Ciencia, Innovación y UniversidadesEuropean Commission PID2019-104888GB-I00, RTI2018-098117-B-C22European Regional Development FundJunta de Andalucía FQM387, P18-RT-3237Agencia Estatal de Investigació

Radiation sensitive MOSFETs irradiated with various positive gate biases

This work was supported in part by the European Union's Horizon 2020 research and innovation programme under grant agreement No. 857558, and the Ministry of Education, Science and Technological Development of the Republic of Serbia, under the project No. 43011.The RADiation sensitive metal-oxide-semiconductor field-effect-transistors (RADFETs) were irradiated with gamma rays up to absorbed dose of 110 Gy(H2O). The results of threshold voltage, V-T , during irradiation with various positive gate biases showed the increase in V-T with gate bias. The threshold voltage shift, Delta V-T , during irradiation was fitted very well. The contributions of both the fixed traps (FTs) and switching traps (STs) during radiation on Delta V-T were analyzed. The results show the significantly higher contribution of FTs than STs. A function that describes the dependence of threshold voltage shift and its components on gate bias was proposed, which fitted the experimental values very well. The annealing at the room temperature without gate bias of irradiated RADFETs was investigated. The recovery of threshold voltage, known as fading, slightly increase with the gate bias applied during radiation. The Delta V-T shows the same changes as the threshold voltage component due to fixed states, Delta V-ft , while there is no change in the threshold voltage component due to switching traps, Delta V-st .European Union's Horizon 2020 research and innovation programme 857558Ministry of Education, Science & Technological Development, Serbia 4301

Multiple scattering calculations for proton beams: Comparison of results from the general-purpose Monte Carlo codes penh, fluka and topas

This work has been partially supported by the Spanish Ministerio de Ciencia y Competitividad ( PID2019-104888GB-I00 ), the European Regional Development Fund (ERDF) and the Junta de Andalucía, Spain ( FQM387 , P18-RT-3237 ). One of us (M.A.) thanks J. Schuemann and H. Paganetti for useful discussions. Funding for open access charge by Universidad de Granada / CBUA is also acknowledged.Purpose: To test the multiple Coulomb scattering theories implemented in the Monte Carlo simulation codes PENH, FLUKA and TOPAS. Methods: Simulations with the three codes of proton beams with initial energies between 100 and 220 MeV impinging normally on slabs of 14 different compositions and various thicknesses were performed. The simulated angular distributions of transmitted protons are very approximately Gaussian with a characteristic angle θ0, which measures the spread of the distribution. The characteristic angles resulting from the simulations are compared to experimental data available from two experiments. The degree of agreement is quantified by the χ2 statistic. The 151 cases considered are analyzed by grouping the data in various ways (all together, by experiment, according to the energy of the proton beam or the slab material). Results: In general, PENH produced the better description of the experimental data. If all data are included, the χ2 values were 3.7±0.6 for PENH, 18.7±0.4 for FLUKA and 7.4±1.5 for TOPAS. The ranges in the values of χ2 obtained for the various data groups are [0.1±0.2;10.7±4.1] for PENH, [0.10±0.03;221.1±7.8] for FLUKA, and [0.2±0.3;46.2±26.4] for TOPAS. The minimum and maximum values in these ranges occur, in the three codes, for the Zn and the brass slabs, respectively, with 158.6MeV protons. Conclusions: The three codes provide a reasonably accurate description of multiple scattering distributions of protons transmitted through material slabs. Brass is the material whose experimental data are worst described by the three codes analyzed.Spanish Ministerio de Ciencia y Competitividad PID2019-104888GB-I00European Regional Development Fund ERDFJunta de Andalucía FQM387, P18-RT-3237Universidad de Granada / CBU

Dosimetric response of radiochromic films to protons of low energies in the Bragg peak region

One of the major advantages of proton or ion beams, applied in cancer treatment, is their excellent depth-dose profile exhibiting a low dose in the entrance channel and a distinct dose maximum (Bragg peak) near the end of range in tissue. In the region of the Bragg peak, where the protons or ions are almost stopped, experimental studies with low-energy particle beams and thin biological samples may contribute valuable information on the biological effectiveness in the stopping region. Such experiments, however, require beam optimization and special dosimetry techniques for determining the absolute dose and dose homogeneity for very thin biological samples. At the National Centre of Accelerators in Seville, one of the beam lines at the 3 MV Tandem Accelerator was equipped with a scattering device, a special parallel-plate ionization chamber with very thin electrode foils and target holders for cell cultures. In this work, we present the calibration in absolute dose of EBT3 films [Gafchromic radiotherapy films, http://www.ashland.com/products/gafchromic-radiotherapy-films] for proton energies in the region of the Bragg peak, where the linear energy transfer increases and becomes more significant for radiobiology studies, as well as the response of the EBT3 films for different proton energy values. To irradiate the films in the Bragg peak region, the energy of the beam was degraded passively, by interposing Mylar foils of variable thickness to place the Bragg peak inside the active layer of the film. The results obtained for the beam degraded in Mylar foils are compared with the dose calculated by means of the measurement of the beam fluence with an ionization chamber and the energy loss predicted by srim2008 code.EU Initial Training Marie Curie Network FP7-PEOPLE-2011-ITN-289485Spanish Research Projects No. FPA2014-53290-C2-2-PSpanish Research Projects No. FPA2013-47327-C2-1-RAndalusian Research Project No. P12-FQM-160

A radiobiological study of the schemes with a low number of fractions in high-dose-rate brachytherapy as monotherapy for prostate cancer

Purpose Schemes with high doses per fraction and small number of fractions are commonly used in high-dose-rate brachytherapy (HDR-BT) for prostate cancer. Our aim was to analyze the differences between published clinical results and the predictions of radiobiological models for absorbed dose required in a single fraction monotherapy HDR-BT. Material and methods Published HDR-BT clinical results for low- and intermediate-risk patients with prostate cancer were revised. For 13 clinical studies with 16 fractionation schedules between 1 and 9 fractions, a dose-response relation in terms of the biochemical control probability (BC) was established using Monte Carlo-based statistical methods. Results We obtained a value of α/β = 22.8 Gy (15.1-60.2 Gy) (95% CI) much larger than the values in the range 1.5-3.0 Gy that are usually considered to compare the results of different fractionation schemes in prostate cancer radiotherapy using doses per fraction below 6 Gy. The doses in a single fraction producing BC = 90% and 95% were 22.3 Gy (21.5-24.2 Gy) and 24.3 Gy (23.0-27.9 Gy), respectively. Conclusions The α/β obtained in our analysis of 22.8 Gy for a range of dose per fraction between 6 and 20.5 Gy was much greater than the one currently estimated for prostate cancer using low doses per fraction. This high value of α/β explains reasonably well the data available in the region of high doses per fraction considered.Spanish Ministerio de Ciencia y Competitividad FPA2015-67694-PEuropean Union (EU)Junta de Andalucía FQM038

Measurement of the Li8 half-life

We report a new measurement of the Li8 half-life using a plastic scintillator and an ultrafast waveform digitizing module. The result, T1/2=(838.40±0.36)ms, improves by a factor of 2.5 the most precise result obtained so far and is furthermore deduced with negligible corrections due to dead time.Ministerio de Ciencia e Innovación FPA2008-0468

Influencia de las corrientes mesónicas de intercambio en la difusión magnética de electrones por núcleos de capa cerrada

Reducción altaUniv. de Granada, Departamento de Física Atómica y Nuclear. Leída el 28-09-8