Characteristics of proton beams and secondary neutrons arising from two different beam nozzles

Abstract

Tandem or Van de Graaff accelerator with an energy of 3-MeV is typically used for PIXE analysis. In this study, the beam line design used in PIXE analysis was used to increase the production of isotopes instead of the typical low-energy accelerator from a 13-MeV cyclotron.For PIXE analysis, the proton beam should be focused at the target through the use of a nozzle after degrading the proton beam energy from 13-MeV to 3-MeV using an energy degrader. Previous studies have been conducted to determine the most appropriate material and thickness of the energy degrader. Based on the energy distribution of the degraded proton beam and the neutron occurrence rate at the degrader an aluminum nozzle of X thickness was determined to be the most appropriate nozzle construction. Neutrons are created by the collision of 3-MeV protons into the nozzle after passage through energy degrader. In addition, a sufficient intensity of proton beam is required for non-destructive analysis of PIXE. Therefore, in order to optimize nozzle design, it is necessary to consider the number of neutrons which arise from the collision of protons inside the nozzle, as well as the track direction of the generated secondary neutrons, with the primary aim of ensuring a sufficient number of protons passing through the nozzle as a direct beam. A number of laboratories are currently conducting research related to the design of nozzles used in accelerator fields, mostly relating to medical fields. In this paper, a comparative analysis was carried out for two typical nozzle shapes in order to minimize losses of protons and generation of secondary neutrons. The neutron occurrence rate and the number of protons after passing through the nozzle were analyzed using a Particle and Heavy Ion Transport code System (PHITS) program, in order to identify the nozzle which generated the strongest proton beam.

MCNPX’S Water Equivalent Thickness Simulation of Material with Different Density via Proton Beam Irradiation

“…The radiological thickness of materials and beam penetration range is often referred as the water equivalent thickness (WET). In the clinical application of radiotherapy, it is mandatory to obtain a WET calculation with high accuracies to ensure the beam that penetrated the human tissues is capable to deliver high dose of radiation into the deep-rooted tumours and kill the malignant cancerous cell without any major damages to the healthy tissues [17]. However, within a critical range of cumulative doses of 40-100 Gy when given with "conventional" fractionation of 1.8-2.0 Gy/fraction, small increases in dose may result in large increases in clinical impact.…”

A novel method involving Matlab coding to determine the distribution of a collimated ionizing radiation beam

“…In the case of the production of radionuclides used in nuclear medicine, knowing the geometric parameters of the beam involved is very important from the point of view of the economic efficiency, meaning a minimization of the losses by better estimations of the obtained activities and by a better management of the expensive target materials used. In present there are various methods to determine the distribution and the dimension of an ionizing radiation collimated beam [6].…”