A New Simulation of Track Structure of Low-Energy Electrons in Liquid Water:Considering the Condensed-Phase Effect on Electron Elastic Scattering

A new Monte Carlo simulation of the track structure of low-energy electrons （〈10keV） in liquid water is presented. The feature of the simulation is taken into consideration of the condensed-phase effect of liquid water on electron elastic scattering with the use of the Champion model, while the dielectric response formalism incorporating the optical-data model developed by Emfietzoglou et al. is applied for calculating the electron inelastic scattering. The spatial distributions of energy deposition and inelastic scattering events of low-energy electrons with different primary energies in liquid water are calculated and compared with other theoretical evaluations. The present work shows that the condensed-phase effect of liquid water on electron elastic scattering may be of the influence on the fraction of absorbed energy and distribution of inelastic scattering events at lower primary energies, which also indicate potential effects on the DNA damage induced by low-energy electrons.

Optimization and numerical simulation for the extraction system of the H^- multicusp ion source

A new ion source has been designed and manufactured for the CYCLONE30 accelerator, which has a much advanced performance compared with the original. It is expected that the newly designed ion source extraction system will transport a very large percentage of the beam without deteriorating the beam optics, which is designed to deliver an H- beam at 30 keV. The accelerator assembly consists of three circular aperture electrodes made of copper. The simulation study was focused on finding parameter sets that raise the beam perveance as large as possible and which reduce the beam divergence as low as possible. Ion beams of the highest quality are extracted whenever the half-angular divergence is minimum, for which the perveance current intensity and the extraction gap have optimum values. The triode extraction system is designed and optimized by using CST software （for Particle Beam Simulations）. The physical design of the extraction system is given in this paper. From the simulation results, it is concluded that it is possible to achieve this goal by decreasing the thickness of the plasma electrode, shortening the first gap, and adjusting the acceleration electrode voltage.

Development of H− multicusp ion source

Introduction The ion source is one of the key devices for the high-intensity cyclotron,which exerts influence on the beam intensity and applications of the machine.This paper will provide an introduction to current measures and present relevant experimental study as well as the beam test results.Purpose The existing ion source of the accelerator has a 2-mA output current.Our aim is to increase the current to roughly 5 mA to decrease the reaction time of cyclotron.Therefore,a new ion source was developed.To this end,some simulations were performed,and the simulated ion source was constructed,and then some measurements were noted.Methods and materials The CST code is used to simulate the chamber and extraction system.For construction,some materials such as copper and stainless steel are used.Tungsten wire of 2.1 mm diameter was developed to reach high beam current.Turbo and rotary pump is chosen for system evacuation.Faraday cup can be used for readout.The magnets for plasma confinement are made of Nd–Fe–B material.Results The source assembly consists of a tubular plasma chamber(inner diameter:100 mm;length:150 mm)with 12 columns of permanent magnets(Nd–Fe–B material)to provide a stronger multicusp field,a three-electrode extraction system,and a top cover with a confinement magnet inside.Now,5 mA H−beam can be extracted from the ion source with a plasma electrode aperture of 13 mm under an arc power of 6 kW.The optimum H2 gas flow rate and the change of pressure found during the tuning process of the ion source are presented.