Search

In this work a complete description of the 7Li(p, n)7Be reaction near threshold is given using center-of-mass and relative coordinates. It is shown that this standard approach, not used before in this context, leads to a simple mathematical representation which gives easy access to all relevant quantities in the reaction and allows a precise numerical implementation. It also allows in a simple way to include proton beam-energy spread affects. The method, implemented as a C++ code, was validated both with numerical and experimental data finding a good agreement. This tool is also used here to analyze scattered published measurements such as (p, n) cross sections, differential and total neutron yields for thick targets. Using these data we derive a consistent set of parameters to evaluate neutron production near threshold. Sensitivity of the results to data uncertainty and the possibility of incorporating new measurements are also discussed. Fil: Herrera, Maria Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina Fil: Moreno, Gustavo Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. YPF - Tecnología; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina Fil: Kreiner, Andres Juan. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; Argentina

In this work we review all the available experimental neutron data for the 7Li(p,n) reaction near threshold which is necessary to obtain an accurate source model for Monte Carlo simulations in Boron Neutron Capture Therapy. Scattered published experimental results such as cross sections, differential neutron yields and total yields were collected and analyzed, exploring the sensitivity of the fitting parameters to the different possible variables and deriving a consistent working set of parameters to evaluate the neutron source near threshold. Fil: Herrera, Maria Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; Argentina. Universidad Nacional de San Martín; Argentina Fil: Moreno, Gustavo Ariel. YPF - Tecnología; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina Fil: Kreiner, Andres Juan. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; Argentina. Universidad Nacional de San Martín; Argentina

Within the frame of an ongoing project to develop a folded Tandem-Electrostatic-Quadrupole accelerator facility for Accelerator-Based Boron Neutron Capture Therapy (AB-BNCT) a theoretical study was performed to assess the treatment planning capability of different configurations of an optimized beam shaping assembly for such a facility. In particular this study aims at evaluating treatment plans for a clinical case of Glioblastoma.

In the frame of the construction of a Tandem Electrostatic Quadrupole Accelerator facility devoted to the Accelerator‐Based Boron Neutron Capture Therapy, a Beam Shaping Assembly has been characterized by means of Monte‐Carlo simulations and measurements. The neutrons were generated via the 7Li(p, n)7Be reaction by irradiating a thick LiF target with a 2.3 MeV proton beam delivered by the TANDAR accelerator at CNEA. The emerging neutron flux was measured by means of activation foils while the beam quality and directionality was evaluated by means of Monte Carlo simulations. The parameters show compliance with those suggested by IAEA. Finally, an improvement adding a beam collimator has been evaluated.

Glioblastoma multiforme and metastatic melanoma are frequent brain tumors in adults and presently still incurable diseases. Boron Neutron Capture Therapy (BNCT) is a promising alternative for this kind of pathologies. Accelerators have been proposed for BNCT as a way to circumvent the problem of siting reactors in hospitals and for their relative simplicity and lower cost among other advantages. Considerable effort is going into the development of accelerator‐based BNCT neutron sources in Argentina. Epithermal neutron beams will be produced through appropriate proton‐induced nuclear reactions and optimized beam shaping assemblies. Using these sources, computational dose distributions were evaluated in a real patient with diagnosed glioblastoma treated with BNCT. The simulated irradiation was delivered in order to optimize dose to the tumors within the normal tissue constraints. Using Monte Carlo radiation transport calculations, dose distributions were generated for brain, skin and tumor. Also, the dosimetry was studied by computing cumulative dose‐volume histograms for volumes of interest. The results suggest acceptable skin average dose and a significant dose delivered to tumor with low average whole brain dose for irradiation times less than 60 minutes, indicating a good performance of an accelerator‐based BNCT treatment.

The study of doubly odd nuclei has become a subfield of nuclear structure in its own right. A large body of data has been accumulated and we shall attempt in this work an approximation to a review. This however has to be qualified, otherwise the scope of the subject would be unmanageably extensive. We shall concentrate ourselves on near-yrast states of deformed and transitional nuclei and hence to studies carried out predominantly, though not exclusively, through the (HI, xnypzα) reaction. Some nice examples of how high-spin and low-spin work complement each other will also be given.

When decoupled proton and neutron orbitals combine in doubly-odd nuclei, one obtains a special type of collective structure called a “doubly-decoupled” band. A particle-plus-rotor and cranking model analysis provide a qualitative understanding of all the special features of these bands, showing that strong coriolis effects dictate their main behavior, while the p-n residual force seems to be much less important. They display additivity of striking accuracy for alignments and inertia parameters. Several of these bands have been followed beyond the first band crossing, showing again additivity for the shift in crossing frequency. These properties may raise questions concerning the deformation-driving tendency of the πh 9/2, orbital and on the exclusive vi 13/2 origin of the first backbend.