Determination of Electron Swarm Parameters in Pure CHF_3 and CF_4 by a Time-Resolved Method

The density-normalized effective ionization coefficient （α - η）/N （α and η are the ionization and attachment coefficients respectively）, the electron drift velocity Ve and density- normalized longitudinal diffusion coefficient NDL in trifluoromethane （CHF3） and carbon tetraflu- oride （CF4） were measured using a pulsed Townsend technique over a wide E/N range. From the plots of （α- η）/N, we have derived the limiting field strength, （E/N）nm, which is valid for the analysis of insulation characteristics and applications to power equipment. Comparisons of the electron swarms parameters between CHF3 and CFa have been performed, and the global warming potential （GWP） is also taken into account.

Investigation of the performance of CF3I/c-C4F8/N2 and CF3I/c-C4F8/CO2 gas mixtures from electron transport parameters

CF3I gas mixtures have attracted considerable attention as potential environmentally-friendly alternatives to SF6 gas,owing to their excellent insulating performance.This paper attempts to study the CF3I ternary gas mixtures with c-C4F8 and buffer gases N2 and CO2 by considering dielectric strength from electron transport parameters based on the Boltzmann method and synergistic effect analysis,compared with SF6 gas mixtures.The results confirm that the critical electric field strength of CF3I/c-C4F8/70%CO2 is greater than that of 30%SF6/70%CO2 when the CF3I content is greater than 17%.Moreover,a higher content of c-C4F8 decreases the sensitivity of gas mixtures to an electric field,and this phenomenon is more obvious in CF3I/c-C4F8/CO2 gas mixtures.The synergistic effects for CF3I/c-C4F8/70%N2 were most obvious when the c-C4F8 content was approximately 20%,and for CF3I/c-C4F8/70%CO2 when the c-C4F8 content was approximately 10%.On the basis of this research,CF3I/c-C4F8/70%N2 shows better insulation performance when the c-C4F8 content is in the15%–20%range.For CF3I/c-C4F8/70%CO2,when the c-C4F8 content is in the 10%–15%range,the gas mixtures have excellent performance.Hence,these gas systems might be used as alternative gas mixtures to SF6 in high-voltage equipment.

CHRONOABSORPTOMETRY FOR THE DETERMINATION OF KINETIC PARAMETERS OF ELECTRON TRANSFER REACTIONS USING LONG-OPTICAL-PATH ELECTROCHEMICAL CELL

A single potential step chronoabsorptometric method for the determination of ki- netic parameters of simple quasi-reversible reactions is described.It is verified by determining the kinetic parameters for the electroreduction of ferricyanide.A long-optical-path electro- chemical cell with a plug-in electrode is used.The thickness of solution layer is 0.55 mm

Noise behaviors of a closed-loop micro-electromechanical system capacitive accelerometer

The noise of closed loop micro-electromechanical systems(MEMS) capacitive accelerometer is treated as one of the significant performance specifications.Traditional optimization of noise performance often focuses on designing large capacitive sensitivity accelerometer and applying closed loop structure to shape total noise,but different noise sources in closed loop and their behaviors at low frequencies are seldom carefully studied,especially their behaviors with different electronic parameters.In this work,a thorough noise analysis is established focusing on the four noise sources transfer functions near 0 Hz with simplified electronic parameters in closed loop,and it is found that the total electronic noise equivalent acceleration varies differently at different frequency points,such that the noise spectrum shape at low frequencies can be altered from 1/f noise-like shape to flat spectrum shape.The bias instability changes as a consequence.With appropriate parameters settings,the 670 Hz resonant frequency accelerometer can reach resolution of 2.6 μg/(Hz)1/2 at 2 Hz and 6 μg bias instability,and 1300 Hz accelerometer can achieve 5μg/(Hz)1/2 at 2 Hz and 31 μg bias instability.Both accelerometers have flat spectrum profile from 2 Hz to 15 Hz.

Breakdown Electric Field of Hot 30% CF_3I/CO_2 Mixtures at Temperature of 300–3500 K During Arc Extinction Process

We calculated the uniform dielectric breakdown field strength of residual 30% CF3I/CO2 gas mixtures during the arc extinction process over the temperature range 300-3500 K at 0.1 MPa. The limiting reduced field strengths are decided by a balance of electron generation and loss based on chemical reactions estimated by the electron energy distribution function （EEDF）, which employs the Boltzmann equation method with two-term expanding approximation in the steady-state Townsend （SST） condition. During the insulation recovery phase, the hot CF3I/CO2 gas mixtures have maximum dielectric strength at a temperature of about 1500 K. At room temperature 300 K, the electric strength after arc extinction （90.3 Td, 1 Td=10-21 V.m2） is only 38% of the original value before arc （234.9 Td）. The adverse insulation recovery ability of CF3I/CO2 gas mixtures in arc extinction hinders its application in electric circuit breakers and other switchgears as an arc quenching and insulating medium.

Differential nonlinear photocarrier radiometry for characterizing ultra-low energy boron implantation in silicon

The measuring of the depth profile and electrical activity of implantation impurity in the top nanometer range of silicon encounters various difficulties and limitations, though it is known to be critical in fabrication of silicon complementary metal–oxide–semiconductor(CMOS) devices. In the present work, SRIM program and photocarrier radiometry(PCR)are employed to monitor the boron implantation in industrial-grade silicon in an ultra-low implantation energy range from 0.5 keV to 5 keV. The differential PCR technique, which is improved by greatly shortening the measurement time through the simplification of reference sample, is used to investigate the effects of implantation energy on the frequency behavior of the PCR signal for ultra-shallow junction. The transport parameters and thickness of shallow junction, extracted via multi-parameter fitting the dependence of differential PCR signal on modulation frequency to the corresponding theoretical model, well explain the energy dependence of PCR signal and further quantitatively characterize the recovery degree of structure damage induced by ion implantation and the electrical activation degree of impurities. The monitoring of nmlevel thickness and electronic properties exhibits high sensitivity and apparent monotonicity over the industrially relevant implantation energy range. The depth profiles of implantation boron in silicon with the typical electrical damage threshold(YED) of 5.3×10^(15)cm^(-3) are evaluated by the SRIM program, and the determined thickness values are consistent well with those extracted by the differential PCR. It is demonstrated that the SRIM and the PCR are both effective tools to characterize ultra-low energy ion implantation in silicon.

Equilibrium electron beam parameters of the High Energy Photon Source

Purpose The physics design of the High Energy Photon Source(HEPS)was finished after many times of iteration.Hereby,the typical equilibrium electron beam parameters corresponding to the proposed two baseline operation modes in the baseline design of HEPS are presented.Methods To compute the equilibrium parameters of the electron beam,the lattice parameters,RF parameters,and the parameters of the insertion devices(IDs)were determined first.Furthermore,it is more precise to use the full-current electron beam parameters in the estimations of the performance of the synchrotron light.Therefore,not only the single-particle dynamics but also the current-dependent collective effects need to be considered in the computations of the full-current,equilibrium parameters of the electron beam.Both analytic computations and multi-particle tracking simulations were carried out.Results The full-current,equilibrium parameters of the electron beams in the HEPS storage ring are presented in this paper.Moreover,the main beam parameters in the injector(the booster and the LINAC),corresponding to the two baseline operation modes of the storage ring,are also presented.Conclusion The typical electron beam parameters corresponding to the two baseline operation modes are given in detail in this paper.

Time of the Energy Emission in the Hydrogen Atom and Its Electrodynamical Background

The time of the energy emission between two neighbouring electron levels in the hydrogen atom has been calculated first on the basis of the quantum aspects of the Joule-Lenz law, next this time is approached with the aid of the electrodynamical parameters characteristic for the electron motion in the atom. Both methods indicate a similar result, namely that the time of emission is close to the time period of the electromagnetic wave produced in course of the emission. As a by-product of calculations, the formula representing the radius of the electron microparticle is obtained from a simple combination of the expressions for the Bohr magnetic moment and a quantum of the magnetic flux.

Monte Carlo Simulation of Electron Swarms Parameters in c-C_4F_8/CF_4 Gas Mixtures

The swarm parametes for c-C4F8/CF4 mixtures, including the density-normalized effective ion- ization coefficient, drift velocity and mean energy were calculated using Monte-Carlo method with the null collision technique. The overall density-reduced electric field strength could be varied between 150 and 500 Td, while the c-C4F8 content in gas mixtures is varied in the range of 0-100%. The value of the density-normalized effective ionization coefficient shows a strong dependence on the c-C4F8 content, becoming more electronegative as the content of c-C4F8 is increased. The drift velocity of c-C4F8/CF4 mixtures is more affected by CF4. The calculated limiting field strength for c-C4F8/CF4 mixtures is higher than that of SF6/CF4.

Performance Enhancement in Dye-Sensitized Solar Cells with Composite Mixtures of TiO_2 Nanoparticles and TiO_2 Nanotubes

In the present investigation,a new composite nanostructured photoanodes were prepared using TiO_2 nanotubes（TNTs） with TiO_2 nanoparticles（TNPs）.TNPs were synthesized by sol-gel method,and TNTs were prepared through alkali hydrothermal method.Dye-sensitized solar cells（DSSCs） were fabricated with different photoanodes comprising of various ratios of TNTs ＋ TNPs,synthetic indigo dye as photosensitizer,PMII（l-propyl-3-methylimidazolium iodide） as ionic liquid electrolyte and cobalt sulfide as counter electrode.The structures and morphologies of TNPs and TNTs were analyzed through X-ray diffractometer,transmission electron microscope and scanning electron microscopes.The results of the investigation showed that the DSSC-4 made with composite photoanode structure（TNTs/TNPs）（90% of TNPs ＋ 10% of TNTs） had improved photocurrent efficiency（2.11%） than pure TNPs（1.00%） and TNT film（0.78%）.Electrochemical impedance spectra revealed that the composite TNTs/TNPs film-based DSSCs possessed the lowest charge-transfer resistances and longest electron lifetime.Hence,it could be concluded that the composite TNTs/TNPs photoanode facilitates the charge transport rate and enhances the efficiencies of DSSCs.