Xing Chen, Ph.D. - US grants

Science Research Laboratory (SRL) is developing new, compact linear induction accelerator (LIA) technology which offers many advantages for bulk sterilization of medical products. These accelerators are reliable and significantly less expensive than electrostatic or rf accelerators. In addition, SRL induction accelerator are scalable to average electron beam powers of more than 800 kW at beam energies ranging from 5-10 MeV, providing an average of 100 kW of repetitively pulsed, high dose rate x-ray flux. An experimental research program and concurrent design study will be carried out for Phase I. An experiment to demonstrate efficient sterilization of medical product using high dose rate radiation from an existing LIA is planned. In addition, a study will explore electron beam transport and x- ray target designs for production of a uniform x-ray radiation field for a definitive sterilization experiment to be performed in Phase II.

This is an award to support research on the feasibility of using an electron beam to remove hydrocarbon pollutants from exhaust gases emerging from combustion processes to reduce or eliminate their potential for polluting air into which they are discharged. The experiments will be conducted using an existing, pulsed induction accelerator to irradiate controlled gas mixtures containing aromatic and chlorinated aromatic organic compounds such as benzene and chlorobenzene. The work plan includes analyses to identify the byproducts produced during radiation, their concentrations and the dose of radiation required to reduce their concentration to environmentally acceptable levels.. Results of this project are expected to provide the basis for engineering design of an optimal, all-solid-state induction accelerator system for the reduction to acceptable levels of the concentration of hydrocarbons in exhaust gases from combustion processes that are subjected to electron beam radiation. The proposal leading to this award was submitted in response to NSF 92-30, Small Business Innovation Research under Topic No. 25d, Environmental Systems.

The objective of this program is to develop high intensity, large area, directed atomic nitrogen beam sources for molecular beam epitaxy (MBE). The nitrogen beam source will be based on an inductively-driven plasma accelerator that efficiently ionizes and accelerates plasma to energies between 1 and 100 eV. The plasma beam will have densities between 1015 and 1017 cm-3. At these high plasma densities, molecular ions such as N2 or NH3 decompose rapidly, generating a high intensity, high energy atomic plasma beam. When operated at high pulse rates, average beam current densities of 1-10 A/cm2 can be delivered. This beam current density is a factor of 100 to 1000 times higher than achievable with existing rf or ECR plasma sources. Moreover, the nitrogen source may be configured with beam cross sections from 0.1 to 1 m2 and with an average beam power scaleable to tens of kilowatts or higher, allowing for broad area, high rate growth of GaN, AlN and other nitrides. In Phase I, the feasibility of this electrodeless atomic/plasma beam accelerator technology will be experimentally analyzed as a high power nitrogen source for MBE. An optimized atomic nitrogen beam source will be designed for fabrication in Phase II. The Phase II program is structured to experimentally characterize and optimize this nitrogen beam source for MBE.