Electron Beam Stabilization Research Articles

High‐Performance Carbon Fibers Prepared by Continuous Stabilization and Carbonization of Electron Beam‐Irradiated Textile Grade Polyacrylonitrile Fibers

AbstractThe manufacturing of high‐performance carbon fibers (CFs) from low‐cost textile grade poly(acrylonitrile) (PAN) homo‐ and copolymers using continuous electron beam (EB) irradiation, stabilization, and carbonization on a kilogram scale is reported. The resulting CFs have tensile strengths of up to 3.1 ± 0.6 GPa and Young's moduli of up to 212 ± 9 GPa, exceeding standard grade CFs such as Toray T300. Additionally, the Weibull strength and modulus, the microstructure, and the morphology of these CFs are determined.

Cellulose-based carbon fibers prepared using electron-beam stabilization

Abstract Cellulose fibers were stabilized by treatment with an electron-beam (E-beam). The proper-ties of the stabilized fibers were analyzed by scanning electron microscopy, Fourier trans-form infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric anal-ysis. The E-beam-stabilized cellulose fibers were carbonized in N 2 gas at 800°C for 1 h, and their carbonization yields were measured. The structure of the cellulose fibers was deter-mined to have changed to hemicellulose and cross-linked cellulose as a result of the E-beam stabilization. The hemicellulose decreased the initial decomposition temperature, and the cross-linked bonds increased the carbonization yield of the cellulose fibers. Increasing the absorbed E-beam dose to 1500 kGy increased the carbonization yield of the cellulose-based carbon fiber by 27.5% upon exposure compared to untreated cellulose fibers. Key words: electron-beam stabilization, carbonization yield, cellulose fiber, cross-linked bond 1. Introduction

Characterization of Polyacrylonitrile Based Carbon Nanofiber Mats via Electron Beam Processing

The aim of this study was to evaluate the ability of electron beam irradiation to drive stabilization reactions within PAN nanofiber mats to obtain carbon nanofiber mats. PAN nanofiber mats with fiber diameters of 300-400 nm were prepared via an electrospinning method. Electrospun PAN nanofiber mats were stabilized by electron beam irradiation with various doses up to 5,000 kGy. Using the irradiation-stabilized PAN nanofiber mats, carbon nanofibers were obtained by pyrolysis in a tube furnace for 1 h at 1,000 degrees C under an N2 atmosphere. FT-IR analysis indicated that the transformation of C[triple bond]N groups to C==N groups was accelerated by electron beam stabilization. The thermal behavior of the PAN nanofiber mats was studied using DSC and TGA. DSC thermograms showed that the peak temperatures of the exothermic reactions were found to decrease with increasing electron beam irradiation doses. Irradiation-stabilized PAN nanofiber mats were not observed to dramatically decrease in weight between 290 degrees C and 320 degrees C, an observation presumed to be related to cyclization. The char yields of PAN were found to increase with increasing irradiation doses.

Magnetic field generation and relativistic electron dynamics in circularly polarized intense laser interaction with dense plasma

The generation of both axial and azimuthal magnetic field components by the intense laser-dense plasma interaction and relativistic electron dynamics are studied in theoretical analysis and three-dimensional particle-in-cell simulations. For a circularly polarized laser, the cylindrical symmetry can be applied. Interacting with this laser, both axial and the azimuthally magnetic fields are generated and play an essential role in hot electron beam collimation, stabilization, and shaping. It is significantly different from the linearly polarized case, where the azimuthal current and the axial magnetic field are absent, therefore the axial current density gets filamentary early in the ramp plasma and is focused into a single channel in the dense (with a density larger than the critical density nc) plasma later, and the electron and ion density distributions as well as the azimuthally magnetic field profile are broadened in the polarized direction to form an ellipse-like structure in the transverse plane. Instead, the results for the circularly polarized laser analytically and numerically show a much better collimation of the relativistic electron beams than in the case of the linearly polarized laser, due to the axial field component generated by azimuthal electron dynamics.

Electron beam pumped krypton fluoride lasers for fusion energy

High-energy electron beam pumped krypton fluoride (KrF) gas lasers are an attractive choice for inertial fusion energy (IFE). Their short wavelength and demonstrated high beam uniformity optimizes the laser-target physics, and their pulsed power technology scales to a large system. This paper presents the principals of this type of laser and the progress toward developing technologies that can meet the IFE requirements for repetition rate (5 Hz), efficiency (>6%), and durability (>3/spl times/10/sup 8/ shots). The Electra laser at the Naval Research Laboratory (NRL) has produced >500 J of laser light in short 5-Hz bursts. Research on Electra and the NRL Nike laser (3000 J, single shot) has shown that the overall efficiency should be greater than 7%. This is based on recent advances in electron beam stabilization and transport, electron beam deposition, KrF laser physics, and pulsed power. The latter includes the development of a new solid-state laser triggered switch that will be the basis for a pulsed power system that can meet the IFE requirements for efficiency, durability, and cost. The major remaining challenge is to develop long-lived hibachi foils (e-beam transmission windows). Based on recent experiments, this may be achievable by periodically deflecting the laser gas.

Improved CD Accuracy by Electron Beam Stabilization in KrF Lithography.

Improved CD Accuracy by Electron Beam Stabilization in KrF Lithography.

A Comparative Study of Deep-UV Thin Resist by Electron Beam Stabilization.

The method of electron beam stabilization has been applied for improving the etch selectivity of resist patterns having an aspect ratio of less than 3:1. With the application of electron beam stabilization, the Deep-UV photoresists based on the chemical structures of Acetal and ESCAP have been evaluated with respect to etch selectivity as a function of electron beam dose and etch condition. A resist etch rate reduction of 20 percent and 26 percent in a metal etch process, have been observed for the two types of resists, Acetal and ESCAP respectively, at 2000μC/cm2. The thermal and chemical properties were characterized before and after electron beam stabilization using DSC, TGA, and FT-IR. The cross-sectional views of resist patterns after electron beam processing were also investigated to understand the chemical stability of resist during the electron beam process. Based on the experimental results, the application of electron beam stabilization for real device fabrication below 0.14μm has been presented.

Electron beam stabilization and dissolution behaviors of advanced deep UV photoresist for sub 0.3 μm microelectronics fabrication

Through the years, 248-nm deep-UV (DUV) photolithography technologies have been used in sub 0.3 μm microelectronics fabrication. In order to fundamentally understand the development behaviors of DUV photoresist and optimize the lithographic process accordingly, the dissolution kinetics of an advanced 248-nm DUV photoresist OCG ARCH2 was studied by varying the concentrations of photo-acid-generator (PAG) and the cooling rate after post exposure bake (PEB). As popularly known, DUV photoresists are very sensitive to airborne contaminations from N-methylpyrrolidone (NMP) or ammonia, etc. As an alternative method for thermal annealing, electron beam (E-beam) was employed to stabilize the DUV Photoresists in order to improve critical dimension (CD) control and post exposure delay (PED) stability. It was observed that E-beam stabilization of DUV photoresist could result in a comparable PED and CD control reported on thermal annealing.

Stabilized electron beams: An auroral thermal wave

The behaviour of the ionosperic plasma of the high‐latitude F2 region is investigated when it is in collective interaction with auroral electron beams. It is shown that the usual increase in plasma density from the electron beam formation region to the ionospheric F2 region maximum is the cause of the electron beam stabilization relative to the upper hybrid waves generation at the Cherenkov resonance. The collective dissipation of the beam energy at the Cherenkov resonance is possible only in the region of small plasma density gradients, which always takes place near the F2 region maximum. The auroral thermal wave is a region of high‐frequency plasma turbulence traveling upward to meet the electron beam. The plasma wave dissipation due to large collision frequencies with ions and neutrals must result in anomalously large electron temperatures and their transverse gradients, repeatedly registered in auroral discrete arcs. The plasma wave conversion (E ∼ 0.5 V/m are measured) into electromagnetic waves at 2fp in the auroral thermal wave and the plasma turbulence region upward motion must result in a fast decrease of the radiation frequency at 2fp, what was also registered. Results of a numerical simulation of the auroral thermal wave are in good agreement with experiment. The influence of the ion inertia, the altitude of the F2 region maximum, plasma density, energy, density, and the degree of energy homogeneity of the auroral electron beam on the formation and development dynamics of the thermal wave are investigated.