Electron beam modeling and analyses of the electric field distribution and space charge effect

In electron beam technology, one of the critical focuses of research and development efforts is on improving the measurement of electron beam parameters. The parameters are closely related to the generation, emission, operation environment, and role of the electron beam and the corresponding medium. In this study, a field calculation method is proposed, and the electric field intensity distribution on the electron beam’s cross-section is analyzed. The characteristics of beam diffusion caused by the space charge effect are investigated in simulation, and the obtained data are compared with the experiment. The simulation demonstrated that the cross-sectional electric field distribution is primarily affected by the electron beam current, current density distribution, and electron beam propagation speed.

Understanding surface charge effects in electrocatalysis.Part 2:Hydrogen peroxide reactions at platinum

Electrocatalytic activity is influenced by the surface charge on the solid catalyst.Conventionally,our attention has been focused on how the surface charge shapes the electric potential and concentration of ionic reactant(s)in the local reaction zone.Taking H_(2)O_(2)redox reactions at Pt(111)as a model system,we reveal a peculiar surface charge effect using ab initio molecular dynamics simulations of electrified Pt(111)-water interfaces.In this scenario,the negative surface charge on Pt(111)repels the O-O bond of the reactant(H_(2)O_(2))farther away from the electrode surface.This leads to a higher activation barrier for breaking the O-O bond.Incorporating this microscopic mechanism into a microkinetic-double-layer model,we are able to semi-quantitatively interpret the pH-dependent activity of H_(2)O_(2)redox reactions at Pt(111),especially the anomalously suppressed activity of H_(2)O_(2)reduction with decreasing electrode potential.The relevance of the present surface charge effect is also examined in wider scenarios with different electrolyte cations,solution pHs,crystal facets of the catalyst,and model parameters.In contrast with previous mechanisms focusing on how surface charge influences the local reaction condition at a fixed reaction plane,the present work gives an example in which the location of the reaction plane is adjusted by the surface charge.

Quantitative evaluation of space charge effects of laser-cooled three-dimensional ion system on a secular motion period scale

In this paper,we introduce a method of quantitatively evaluating and controlling the space charge effect of a lasercooled three-dimensional（3 D） ion system in a linear Paul trap.The relationship among cooling efficiency,ion quantity,and trapping strength is analyzed quantitatively,and the dynamic space distribution and temporal evolution of the 3 D ion system on a secular motion period time scale in the cooling process are obtained.The ion number influences the eigen-micromotion feature of the ion system.When trapping parameter q is ～ 0.3,relatively ideal cooling efficiency and equilibrium temperature can be obtained.The decrease of axial electrostatic potential is helpful in reducing the micromotion heating effect and the degradation in the total energy.Within a single secular motion period under different cooling conditions,ions transform from the cloud state（each ion disperses throughout the envelope of the ion system） to the liquid state（each ion is concentrated at a specific location in the ion system） and then to the crystal state（each ion is subjected to a fixed motion track）.These results are conducive to long-term storage and precise control,motion effect suppression,high-efficiency cooling,and increasing the precision of spectroscopy for a 3 D ion system.

Space Charge Effects in CSL Gauge——with previously assumed charge distribution

The "cascade static lens （CSL） gauge" has a high sensitivity（S） because the emitted electrons repeat the go and back oscillation before they are received by the electrodes. (S=18.6 Pa-1 (2480 Torr-1 in a

Examining Adsorbent Charge Effect on Metal Removal from Contaminated Water

Heavy metal contaminated water sources can cause serious health problems for humans,animals,and plants.Heavy metals can lead to the decrease or loss of liver,kidney,and brain function.Objective:The aim of this research is to examine the effect of charge on adsorbents in the removal of metal cations.Study Design&Methods:Standard solutions of Ca,Cu,Pb,and Zn with concentrations of 1,000 ppm were treated with sodium carbonate and sodium phosphate with various charges.Then,the solutions were placed on a shaker for 24 h,centrifuged,and the supernatant was analyzed using ICP-AES(Inductively Coupled Plasma-Atomic Emission Spectrometry).Results:The order of average metal removal by sodium phosphates is:dibasic(99.3%)>monobasic(96.5%)>tribasic(95.4%).The average metal removal by sodium carbonate and bicarbonate is 98.5% and 96.4% respectively.Conclusion:The adsorbent removability depends on the relationship between the charge present on the metal and the charge on the adsorbent.Thus,metal cations in this study with a+2 charge had a greater affinity for the adsorbent with-2 charged ligands,dibasic sodium phosphate and sodium carbonate.

Interfacial charge effects of supported-metal-cluster heterostructures on azo hydrogenation catalyzation

The impact of interfacial charge on catalytic performance of supported-metal-cluster(SMC)heterostructures remains unclear,hindering efforts to develop high-performance SMC catalysts.Herein we systematically investigated interfacial charge effects of SMCs using a model system of graphene-supported gold-nanoclusters(AuNCs/rGO)for azo hydrogenation.Three types of SMCs with different interfacial charges were synthesized by anchoring electropositive 2-aminoethanethiol(CSH),amphoteric cysteine(Cys),and electronegative 3-mercaptopropionic-acid(MPA)onto AuNCs/rGO,respectively.All three SMCs exhibited high and selective catalytic activity to azo-hydrogenation in four representative azo dyes.The catalytic activity of Cys@AuNCs/rGO was lower than that of CSH@AuNCs/rGO but higher than that of MPA@AuNCs/rGO.However,the cyclic stability of Cys@AuNCs/rGO was inferior to that of both CSH@AuNCs/rGO and MPA@AuNCs/rGO.Further mechanistic studies revealed that amino ligands modified CSH@AuNCs and Cys@AuNCs agglomerated into large-size gold nanoparticles on rGO surface during catalytic reaction under NaBH_(4) action,leading to reduced efficiency and cyclic stability.Conversely,non-amino ligand modified MPA@AuNCs only partially detached from rGO surface without agglomeration,resulting in better cyclic stability.Protection of amino groups in ligands such as modifying-NH_(3)^(+)group in Cys into imine to form N-isobutyryl-L-cysteine(NIBC)substantially improved the cyclic stability while maintaining the high activity in the NIBC@AuNCs/rGO catalyst system.Our work provides an approach for developing a highly-active and stable SMC heterostructure catalyst via manipulating interfacial charges in SMC.

Space Charges Effect of Static Induction Transistor

The space charge effect (SCE) of static induction transistor (SIT) that occurs in high current region is systematically studied.The I V equations are deduced and well agree with experimental results.Two kinds of barriers are presented in SIT,corresponding to channel voltage barrier control (CVBC) mechanism and space charge limited control (SCLC) mechanism respectively.With the increase of drain voltage,the gradual transferring of operational mechanism from CVBC to SCLC is demonstrated.It points out that CVBC mechanism and its contest relationship with space charge barrier makes the SIT distinctly differentiated from JFET and triode devices,etc.The contest relationship of the two potential barriers also results in three different working regions,which are distinctly marked and analyzed.Furthermore,the extreme importance of grid voltage on SCE is illustrated.

Tailoring the microstructure and properties of PES/SPSf loose nanofiltration membranes using SPES as a hydrophilic polymer for the effective removal of dyes via steric hindrance and charge effect

Herein,polyethersulfone(PES)and sulfonated polysulfone(SPSf)blend membranes were prepared with addition of sulfonated polyethersulfone(SPES)as a hydrophilic polymer and adipic acid as a porogen via non-solvent induced phase separation method for effective fractionation of dyes based on the influence of steric hindrance and charge effect.Raman spectroscopy and molecular dynamic simulation modeling confirmed that hydrogen bonds between PES,SPSf,SPES,and adipic acid were crucial to membrane formation and spatial arrangement.Further addition of hydrophilic SPES resulted in a membrane with reduced pore size and molecular weight cut-off as well as amplified negative charge and pure water permeance.During separation,the blend membranes exhibited higher rejection rates for nine types of small molecular weight(269.3–800 Da)dyes than for neutral polyethylene glycol molecules(200–1000 Da).This was attributed to the size effect and the synergistic effect between steric hindrance and charge repulsion.Notably,the synergistic impact decreased with dye molecular weight,while greater membrane negative charge enhanced small molecular dye rejection.Ideal operational stability and anti-fouling performance were best observed in M2(PES/SPSf/SPES,3.1 wt%).Summarily,this study demonstrates that SPES with–SO3‒functional groups can be applied to control the microstructure and separation of membranes.

Study on time-dependent lattice to alleviate space charge effects in CSNS/RCS

Purpose Tune shift and spread due to the space charge effects and collective instabilities in intense proton synchrotrons,such as the CSNS/RCS,a rapid cycling synchrotron at China Spallation Neutron Source,are the main causes of beam loss.Tune shift/spread is large when the beam kinetic energy is low and will cause particles to cross dangerous resonances,while they will gradually decay with the increase of kinetic energy.Methods An efficient way,which was verified in operational accelerators,is to tune the working point during different acceleration periods:injection,acceleration and extraction.With the newly added function of time-dependent lattice in the ORBIT code,one can simulate the physical performance with different tune patterns to find the best way to reduce beam loss.Results The method to tune the working point by time-dependent lattice to weaken the crossing of dangerous resonances has been exploited,and implemented in the ORBIT code.It is the first of such try to apply the method in CSNS/RCS.Conclusions The results presented in this paper show that the time-dependent lattice method does help reduce beam loss in the injection and early acceleration.

Total Ionization Dose Effects on Charge Storage Capability of Al2O3/HfO2/Al2O3-Based Charge Trapping Memory Cell

Because of the discrete charge storage mechanism, charge trapping memory（CTM） technique is a good candidate for aerospace and military missions. The total ionization dose（TID） effects on CTM cells with Al2O3/HfO2/Al2O3（AHA） high-k gate stack structure under in-situ 10 keV x-rays are studied. The C-V characteristics at different radiation doses demonstrate that charge stored in the device continues to be leaked away during the irradiation,thereby inducing the shift of flat band voltage（V（fb））. The dc memory window shows insignificant changes, suggesting the existence of good P/E ability. Furthermore, the physical mechanisms of TID induced radiation damages in AHA-based CTM are analyzed.

Charge state effect on the K-shell ionization of iron by xenon ions near the Bohr velocity

Fe K-shell ionization cross sections induced by 2.4-6.0 MeV Xe^20＋ are measured and compared with different binary- encounter-approximation （BEA） models. The results indicate that the BEA model corrected both by the Coulomb repulsion and by the effective nuclear charge （Zeff） agrees well with the experimental data. Comparison of Fe K-shell X-ray emission induced by 5 MeV xenon ions with different initial charge states （20＋, 22＋, 26＋, 30＋） verifies the applicability of the effective nuclear charge （Zeff） correction for the BEA model. It is found that Zeff correction is reasonable to describe direct ionization induced by xenon ions with no initial M-shell vacancies. However, when the M shell is opened, the Zeff corrected BEA model is unable to explain the inner-shell ionization, and the electron transfer by molecular-orbital promotion should be considered.

Effect of Residual Charge Carrier on the Performance of a Graphene Field Effect Transistor

The temperature-dependent effect of residual charge carrier （no）, at the Dirac point, on mobility is studied. We fabricate and characterize a graphene field effect transistor （GFET） using 7nm TiO2 as the top-gate dielectric. The temperature-dependent gate voltage-drain current and room temperature gate capacitance are measured to extract the carrier mobility and to estimate the quantum capacitance of the GFET. The device shows the mobility value of gOO cm^2 /V.s at room temperature and it decreases to 45 cm^2 /V.s for 20 K due to the increase of n0. These results indicate that the phonon scattering is not the dominant process for the unevenness dielectric layer while the coulomb scattering by charged impurities degrades the device characteristically at low temperature.

Microscopic Effective Charges and the B(E2) Values of Terminating States in Mirror Nuclei (51)～Mn and (51)～Fe

The microscopic effective charges in mirror nuclei 51Mn and 51Fe are investigated with the particle-vibration coupling model based on the self-consistent Skyrme-Hartree-Fock and continuum random-phase-approximation approaches. The isovector parts are predicted to be around 0.15, and the proton effective charges are around 1.25 e, which is less than the empirical value of epff p = 1.5 e. The microscopic effective charges in neutron rich 51Mn are about 10% less than its proton rich mirror. These effective charges are combined with the shell model to calculate the reduced electric quadrupole transition probability B（E2） values in 51Mn and 51Fe. It turns out that the microscopic effective charges have well reproduced the B（E2） values and its ratio in the terminating states.

Charge Exchange Effect on Space-Charge-Limited Current Densities in Ion Diode

The article theoretically studied the charge-exchange effects on space charge limitedelectron and ion current densities of non-relativistic one-dimensional slab ion diode, and comparedwith those of without charge exchange.

Measurement and analyses of the mean effective ion charge in the centre of tokamak discharges

There are two different definitions for specifying the mean effective ion charge Zeff in plasmas： a） from the Spizer electrical resistivity of the plasma and b） from bremsstrahlung radiation losses of the plasma. In this paper Zeff in the centre of tokamak ohmic discharges has been determined from information on sawtooth-relaxations of the steady state plasma, based on the analysis for the power balance of the plasma electrons in the plasma centre during the period of recovery after the sawtooth crashes. This method is found to supply reliable results for tokamak parameters. While its application requires some efforts in data analysis, it can provide a reliable determination of Zeff, independent of the information from bremsstrahlung radiation losses of the plasma.

The electronic structures, Born effective charge tensors,and phonon properties of cubic, tetragonal,orthorhombic, and rhombohedral K_(0.5)Na_(0.5)NbO_3: A first-principles comparative study

The electronic structures, Born effective charges（BECs）, and full phonon dispersions of cubic, tetragonal, orthorhombic, and rhombohedral K0.5Na0.5Nb O3 are investigated by the first principles method based on density functional theory.The hybridized states of Nb 4d and O 2p states are observed in the valence band, showing the formation of a strong Nb–O covalent bond which should be responsible for the displacement of Nb and O atoms. The abnormally large BECs of Nb and O indicate the possibility of phase instability induced by the off-center displacement of Nb and O atoms. The phonon dispersions reveal that the ferroelectric instability of K0.5Na0.5Nb O3 is dominated by Nb and O displacements with significant Na characteristics. In addition to the ferroelectric instability, there is also rotational instability coming from the oxygen octahedra rotation around one axis. Moreover, the Γ phonon properties of orthorhombic KNb O3, Na Nb O3, and K0.5Na0.5Nb O3 are also studied in detail.

Pressure Effects on the Charge Carrier Transportation of BaF_2 Nanocrystals

The charge transport behavior of barium fluoride nanocrystals is investigated by in situ impedance measurement up to 35 GPa. It is found that the parameters change discontinuously at about 6.9 GPa, corresponding to the phase transition of BaF2 nanocrystals under high pressure. The charge carriers in BaF2 nanocrystals include both Fions and electrons. Pressure makes the electronic transport more difficult. The defects at grains dominate the electronic transport process. Pressure could make the charge-discharge processes in the Fm3m phase more difficult.

Effects of Thickness on the Electrical Conductivity of Sputtered YSZ Film with Nanocrystalline Columnar Microstructure

In order to investigate the effect of the thickness on the electrical conductivity of yttriastabilized zirconia(YSZ) film, the nanocrystalline columnar-structured YSZ film with thickness of 0.67-2.52 μm was prepared by magnetron sputtering through controlling the deposition time. All the sputtered films with different thicknesses consist of the main phase of cubic YSZ as well as a small amount of monoclinic YSZ. The thicker films exhibit a typical columnar grain structure based on the fractured cross-sectional SEM observations. The average diameters of columnar grains increase from about 40 nm to 100 nm with the film thickness from 0.67 μm to 2.52 μm according to TEM analysis. The thinnest YSZ film with 0.67 μm thickness shows the highest apparent electrical conductivity in the four films in 400-800 ℃ due to the contribution from the highly conductive film/substrate interfacial region. On the other hand, the real electrical conductivities of YSZ films increase with film thickness from 0.67 μm to 2.52 μm after eliminating the contribution of the film/substrate interface. The increasing film thickness leads to the grain growth as well as the decrement in the volumetric fraction of the resistive columnar grain boundary and a consequent higher real electrical conductivity.

Enhanced removal of ultra fi ne particles from kerosene combustion using a dielectric barrier discharge reactor packed with porous alumina balls

Ultrafine particles(UFPs)are harmful to human beings,and their effective removal from the environment is an urgent necessity.In this study,a dielectric barrier discharge(DBD)reactor packed with porous alumina(PA)balls driven by a pulse power supply was developed to remove the UFPs(ranging from 20 to 100 nm)from the exhaust gases of kerosene combustion.Five types of DBD reactors were established to evaluate the effect of plasma catalysis on the removal efficiency of UFPs.The influences of gasflow rate,peak voltage and pulse frequency of different reactors on UFPs removal were investigated.It was found that a high total UFP removal of 91.4%can be achieved in the DBD reactor entirely packed with PA balls.The results can be attributed to the enhanced charge effect of the UFPs with PA balls in the discharge space.The UFP removals by diffusion deposition and electrostatic attraction were further calculated,indicating that particle charging is vital to achieve high removal efficiency for UFPs.

Oxygen Functionalization-Induced Charging Effect on Boron Active Sites for High-Yield Electrocatalytic NH_(3) Production

Ammonia has been recognized as the future renewable energy fuel because of its wide-ranging applications in H_(2) storage and transportation sector.In order to avoid the environmentally hazardous Haber-Bosch process,recently,the third-generation ambient ammonia synthesis has drawn phenom-enal attention and thus tremendous efforts are devoted to developing efficient electrocatalysts that would circumvent the bottlenecks of the electrochemical nitrogen reduction reaction(NRR)like competitive hydrogen evolution reac-tion,poor selectivity of N_(2) on catalyst surface.Herein,we report the synthesis of an oxygen-functionalized boron carbonitride matrix via a two-step pyrolysis technique.The conductive BNCO(1000)architecture,the compatibility of B-2p_(z) orbital with the N-2p_(z) orbital and the charging effect over B due to the C and O edge-atoms in a pentagon altogether facilitate N_(2) adsorption on the B edge-active sites.The optimum electrolyte acidity with 0.1 M HCl and the lowered anion crowding effect aid the protonation steps of NRR via an associative alternating pathway,which gives a sufficiently high yield of ammonia(211.5μg h^(−1) mg_(cat)^(−1))on the optimized BNCO(1000)catalyst with a Faradaic efficiency of 34.7%at−0.1 V vs RHE.This work thus offers a cost-effective electrode material and provides a contemporary idea about reinforcing the charging effect over the secured active sites for NRR by selectively choosing the electrolyte anions and functionalizing the active edges of the BNCO(1000)catalyst.