Ionizing Radiation Effects in Inversion Layer Silicon Solar Cells

Ionizing irradiation experiments on a new inversion layer solar cell have been carried out to determine its potential for space applications. A scanning electron microscope was used as a source of low energy (2-12 keV) electrons in doses up to 1014 e/cm2. Phototopographic scanning and C-V analysis were used to determine the effects of the radiation on the Si02-Si system. The electron irradiation results are validated by comparison with those of a conventional X-ray experiment. The operation, fabrication and electrical characteristics of the cell are also discussed. Large increases in both the oxide charge and surface state density were observed, but little change occurred in the cells' output characteristics below 105 rads (Si). A drop-off in power at higher doses is explained in terms of surface recombination and series resistance increases. The results of isochronal and UV annealing experiments on these effects are also presented. The cells are concluded to have potential for use in space.     

Simulation study of the influence of leak electrons on the discharge characteristics of a cusped field thruster

Previous studies have shown that leak electrons in cusped field thrusters can move along the channel axis to the anode after crossing the magnetic cusp on the exit. In this paper, a one- dimensional fluid model is built along two typical electron paths to study the influence of leak electrons on the discharge characteristics of a cusped field thruster, considering the electron temperature equation. It is found that the frequencies of low-frequency oscillations increase with a decrease in the proportion of leak electrons, which is related to an increase in the ion speed in the channel. Simulation results show that the position of the peak electron temperature is near the magnetic cusp on the exit and the position of the peak electron density is located downstream from the middle magnetic tip. With a decrease in the proportion of the leak electrons, the peak electron temperature and peak electron density decrease and the position of the peak electron density moves away from the exit, which is related to a decrease in the potential fall on the exit and an increase in confinement of electrons to the middle magnetic cusp.     

Study of possibilities for a spin flip in high energy electron ring HERA

In a high energy electron ring the spins of electrons become spontaneously polarized via the emission of spin-flip synchrotron radiation. By employing a radio frequency radial dipole field kicker, particle spin directions can be rotated slowly over many turns. A model which couples three dimensional spin motion and longitudinal particle motion was constructed to describe nonequilibrium spin dynamics in high energy electron storage rings. The effects of a stochastic synchrotron radiation on the orbital motion in the accelerator synchrotron plane and its influence on the spin motion are studied. The main contributions to the spin motion, the synchrotron oscillations and the stochastic synchrotron radiation, have different influence on the spin polarization reversal in different regions of the parameter space. The results indicate that polarization reversal might be obtained in high energy electron storage rings with a significant noise even with relatively small strengths of a perturbing magnetic field. The only experimental datum available agrees with the model prediction, however further experimental data would be necessary to validate the model.     

Terahertz Plasma Waves in Two Dimensional Quantum Electron Gas with Electron Scattering

We investigate the Terahertz(THz) plasma waves in a two-dimensional(2D) electron gas in a nanometer field effect transistor(FET) with quantum effects, the electron scattering,the thermal motion of electrons and electron exchange-correlation. We find that, while the electron scattering, the wave number along y direction and the electron exchange-correlation suppress the radiation power, but the thermal motion of electrons and the quantum effects can amplify the radiation power. The radiation frequency decreases with electron exchange-correlation contributions, but increases with quantum effects, the wave number along y direction and thermal motion of electrons. It is worth mentioning that the electron scattering has scarce influence on the radiation frequency. These properties could be of great help to the realization of practical THz plasma oscillations in nanometer FET.     

Runaway Electron Suppression by ECRH and RMP in KSTAR

We have observed reduction of the runaway electron synchrotron radiation, hard X-ray (HXR) intensity, and HXR energy after applying 110 GHz 2nd harmonic electron cyclotron resonant heating (ECRH) during runaway electron (RE) discharges at low density with startup runaway electrons. However, we did not see a significant reduction of X-rays from 170 GHz 2nd harmonic ECRH at a higher field. A recently installed IR TV camera was used to observe the forward cone of synchrotron radiation from high energy REs in KSTAR. We have observed changes to the synchrotron images and reduction of the HXR by application of resonant magnetic perturbations (RMP) from in-vessel control coils (IVCC) installed inside KSTAR in the n = 1 configuration.     

低能注量X射线辐照下圆柱腔内辐射环境及IEMP的模拟研究

通过MCNP程序模拟计算了低能注量X射线辐照圆柱腔外端面并透射进入腔体时,腔内各作用面的综合辐照环境及电子发射参数。结合3维粒子模拟（PIC）程序,对多发射面作用下圆柱腔内电磁场和粒子分布进行了模拟计算,并与仅存在上端面电子发射时的电磁场结果进行对比。结果表明,在实际情况下,圆柱侧壁和下端面会发射大量电子,能将上端面中心处的轴向电场强度增大至仅上端面发射电子时的2倍,而由于此时腔内多发射面作用下电流方向的复杂化,磁场强度则略微减小。同时,比较了由MCNP计算得到的前向散射电子能谱和部分文献采用的近似能谱,分别提供电子发射速度时内电磁脉冲（IEMP）的电场强度波形。结果表明,能谱的改变会对电磁场带来极大的改变,故建议通过相关蒙特卡罗（MC）程序计算IEMP电子发射能谱。     

The interaction of high-current pulse beams with plasma in a magnetic field

We have studied the interaction of an electron beam with currents up to 8.5 A and energies up to 15 keV with a plasma in a magnetic field, the intensity of which varied between 36O and 1320 Oe. We studied the energy distribution of electrons after passage of the electron beam through the plasma as a function of the beam current, residual gas pressure (air), and the intensity of the longitudinal magnetic field. We measured the intensities of the transverse and longitudinal highfrequency fields excited by the beam in the plasma; these reach about 100 V/cm and 1–2 kV/cm respectively. This proves that the high energy losses of the beam due to its passage through the plasma are caused by excitation of high-frequency vibrations.Translated from Atomnaya Énergiya, Vol. 14, No. 3, pp. 249–256, March, 1963     

High-Energy Radiation Damage in Silicon Transistors

An experimental investigation of electron and gamma ray damage in silicon transistors is presented. At low values of fluence (?e < 1014 electrons/cm2), loss in common-emitter dc current gain of medium frequency n-p-n planar transistors at collector currents of one to 10 milliamperes is attributed to changes in the surface recombination velocity. Displacement-induced recombination centers in the base region cause a reduction in gain when ?e is greater than 1014 electrons/cm2. A technique of saturating the surface damage with low energy electrons (E = 125 kev) so as to permit a separation of surface and bulk damage is demonstrated. The minority-carrier lifetime-damage constant, K?, has been estimated from the separated bulk-damage curve. It agrees with the value determined from electron irradiation of a low frequency (f?b = 1.25 Mc/sec) mesa n-p-n transistor which is shown to suffer degradation in gain only from bulk recombination current losses within the base region. Surface damage from both electrons and gamma rays is annealed at 250°C or by injecting emitter currents of 200 milliamperes which generate a high internal temperature. In contrast to this behavior, electron irradiation of p-n-p transistors caused loss in gain which is attributed to bulk damage. Damage constants, K?, determined from the data show that p-n-p transistors suffer bulk radiation damage about five times greater than n-p-n transistors.     

对改性晶圆上制备的PDSOI NMOS器件热载流子效应的全面认识

通过与常规器件的对比,本文详细研究了在硅离子注入改性晶圆上制备的PDSOI NMOS的热载流子诱导退化现象。理论分析和TCAD模拟结果表明,硅离子注入在埋氧层中引入的电子陷阱能够捕获注入的电子,并通过改变电场来影响氧化层的热载流子退化。在不同的应力条件下,其效果也有所不同。对改性器件施加热载流子应力时,改性器件的前栅和背栅之间存在着更明显的相互作用。同时,探讨了总剂量辐照对改性器件热载流子退化的影响。在改性器件中存在辐照增强的热载流子退化,高温退火只能部分消除这一影响。     

A New Collective Effect, High Flux Ion Accelerator

A new type of accelerator capable of producing a large flux of medium energy ions is discussed. The accelerator contains a charge neutral plasma in a magnetic field. Electron currents parallel to B? heat the plasma electrons to an average energy kTe by the Joule process. The electrons try to escape from the plasma into an adjacent vacuum region along the magnetic field lines. In doing so they create a charge separation electric field which collectively accelerates the ions to energies ?10 kTe . The large resistivity necessary to obtain both the rapid heating and impedance matching to high power sources results from electron streaming instabilities in the plasma. Feasibility is investigated using a one dimensional, time dependent fluid model. In this model a realistic circuit is coupled to the plasma electrons. The resultant plasma heating and expansion are numerically followed in time and space. These calculations seem to imply that present day technology utilizing high voltage Blumlein transmission lines (Z ? 1?) seem capable of creating a 10 MeV proton stream with energy >10 kJ, and equivalent current density >10 kA/cm2     

紫外激光烧蚀Cu诱导发光羽外观特征动力学研究

通过测定脉冲紫外激光在氦气中烧蚀金属Cu诱导发光羽的发射光谱及其强度随时间的分布,拍摄了发光羽的照片。实验结果表明：在低压下,发光羽的中心区与中间层均为混合色,外围层为黄绿色;中压下,发光羽的中心区和中间层均为白色,外围层为淡绿色;高压下,发光羽的中心区和中间层均为白色,外围层为微绿色。发光羽区域随着环境气压的增大而减小,其颜色随环境气压的增大而变淡。结合实验结果,对发光羽的发光机理进行了探讨。中压及低压下以电子与原子、离子的碰撞传能激发以及原子与原子、离子的碰撞传能激发为主要机理;高压下以电子韧致辐射及电子与离子的复合激发为主要机理。并用此机理定性地解释了所观察到的实验现象。     

Wake effect in interactions of fast ions with supported two-dimensional electron gas

We study the interactions of fast charged particles with a two-dimensional electron gas supported by an insulating substrate, describing its high-frequency plasmon excitations by a two-fluid hydrodynamic model with the parameters characteristic of graphene. The induced number density per unit area of electrons in the two-dimensional electron gas and the total electric potential in its plane are derived as functions of the projectile velocity and the particle position. We show that, when the speed of the particle moving parallel to the two-dimensional electron gas exceeds a threshold value for the collective excitations of σ and π electrons, the oscillatory wake effect develops both in the induced number density and in the total electric potential trailing the particle. When the particle speed matches the phase velocity of the quasiacoustic π plasmon, the induced number density shows usual wake oscillations, in contrast to the single-walled carbon nanotubes where oscillations precede the position of the particle.     

Leakage Current Phenomena in Irradiated SOS Devices

A detailed study of ionizing radiation effects on SOS devices has been performed with emphasis placed on determining the mechanisms of back-channel leakage current phenomena. Behavior for n-channel transistors fabricated with both wet and dry gate oxides is compared and differences in radiation response are attributed to a larger density of hole traps in the sapphire for dry-oxide devices. It is observed that reduction of radiation-induced leakage current to very near its preirradiation value can be readily accomplished by continuing to irradiate a device under a condition of zero drain bias. Studies with low-energy electrons (6 - 45 keV) from a scanning electron microscope reveal that energy must be deposited in the sapphire in order to increase the leakage current and that energy deposition in the sapphire bulk is unimportant in terms of leakage current production. For the present devices, the region which is effective in producing such current extends into the sapphire a distance on the order of 2 ?m from the Si-Al2O3 interface. If hole traps are spatially distributed, then the dominant mechanism for reducing leakage current is shown to be injection of electrons from Si into Al2O3 where they neutralize trapped holes. A model for radiation-induced production and reduction of leakage current in SOS devices is described.     

Sem Micro-Irradiation Techniques in Semiconductor Devices

This paper extends the application of the Scanning Electron Microscope (SEM) to the irradiation of several small areas on a single device with independent energies and doses of electrons. Specifically the SEM is used to irradiate several areas on 2 cm × 2 cm inversion layer silicon solar cells. To diagnose the radiations' effects in these areas, a technique is employed which involves phototopographic laser scanning to assess the changes in the photocurrent response. Mercury probe C-V measurements are used to determine the changes in the oxide-silicon system. The results obtained are shown to compare favourably with other low energy electron data and with x-ray irradiation experiments.     

Fast Electrons Behavior in Presence of External Radial Electric Field in IR-T1 Tokamak

The fact that the mean free path of an electron in plasma is a strongly increasing function of its velocity gives rise to the phenomenon of fast (high energy) electron production. In an electric field, electrons which exceed a critical velocity, for which the collisional drag balances the acceleration by the field, are accelerated freely and can reach very high energies. In low density tokamak discharges a considerable amount of these high energy electrons with energies up to tens of keV to MeV can thus be created. As these energetic electrons are effectively collision-less, they follow the magnetic field lines and can therefore been used to probe the magnetic turbulence in the core of the plasma. In this research, external electric field effects on the discharges which lead to this phenomenon were investigated. Tokamak limiter biasing is one of the methods for controlling the radial electric field and can induce a transition to an improved confinement state.     

Generation of Oxide Charge and Interface States by Ionizing Radiation and by Tunnel Injection Experiments

Results of irradiation and high field tunnel injection experiments on MOS capacitors are discussed. The midgap voltage shift as a function of dose is caused by hole trapping only. In the case of tunnel injection, the generation of electron-hole pairs by impact ionization requires a much larger electron density and high fields. Thus a model of charge build-up is established which takes into account the hole trapping in neutral oxide states, the subsequent electron trapping in now positively charged states and detrapping of captured electrons. By means of this model, the prediction of the radiation hardness of MOS devices is feasible, provided that the impact ionization coefficient a is known accurately. If this is not the case, the combined techniques of ionizing irradiation and tunnel injection can be utilized to determine ? = ?o exp(-H?/F) as a function of the electrical field F. Electron capture and detrapping crosssections ?n and ?n, resp., can be deduced by fitting the model to the experimental results. An F-3 dependency for ?n and an exp(-H?/F) dependency for ?n are found. Only a weak dependence on different processing parameters is observed. The proposed model is verified by a sequence of irradiation and injection steps. The generation of oxide charge is accompanied by an increase in interface state density Dit with a distribution, which peaks at about 0.15 eV above midgap, in both experiments. The results indicate that the generation of interface states is proportional to the amount of trapped holes.     

Enhanced field emission from nano-graphite coated carbon nanotubes

An effective method by low energy carbonhydrogen ion treatment to enhance field emission of the carbon nanotubes (CNTs) is demonstrated. Comparing with control, field emission (FE) currents of the CNTs by carbonhydrogen ion irradiation increased, and the turn-on field and the threshold field decreased significantly. The structure characteristic revealed by transmission electron microscopy demonstrates that CNTs are coated by nano-graphite particles after being treated with low energy carbonhydrogen ion and that there are large quantities of defects and grain boundaries in the coated layer. It is considered that the coating layer can decrease the effective surface work function of CNTs and correspondingly increase field emission. In addition, the defects, the grain boundaries and the C-H dipoles forming in the process of the low energy ions irradiation can effectively enhance the field emission.     

In-situ observation of the effect of the precipitate/matrix interface on the evolution of dislocation structures in CLAM steel during irradiation

The key factor that affects the irradiation resistance of a material is its structure such as grain size and precipitates. Two types of China Low Activation Martensitic (CLAM) steels with a different number density of MC phase were pre-ion implanted and subsequently irradiated by electrons using ultra-high voltage electron microscope (HVEM). The effect of MC phase on the growth behavior of dislocation loops and the stability of pre-existing precipitates were investigated in situ and this may give some hints on the way to increase the ability against irradiation damage. The results show that a high number density of the fine MC phase improves the strength of the material and also helps to inhibit the fast growth of dislocation loops. The interface between the precipitate and the matrix acts as an effective sink to trap radiation induced point defects, which can possibly result in an improvement of irradiation resistance to some extent. However, the coarsening of precipitates because of radiation enhanced diffusion is another issue that needs to be seriously considered when developing a nuclear material.     

On the transformation of ß-particle energies to electric energy in germanium crystals with p-n junctions

We present the results of an investigation performed in 1955 on the transformation of the energy of fast electrons into electric energy by germanium crystals with p-n junctions, as well as data on the efficiency of this transformation and its dependonce on the absorbed radiation flux and total dose. It is found that the basic factor reducing the efficiency of transformation is the increase of the recombination rate of electrons and holes on recombination levels of structural defects arising as a result of the irradiation. Changes in the equilibrium electric conductivity and carrier mobilities play a secondary role. A method is indicated for reestablishing the initial properties of crystals by heating them. Ionization curves are given for monoencrgetic electron beams in germanium.The authors express their sincere gratitude to P.Ia. Glazunov who took part in the experiments with the artificially accelerated electrons, and to P.N. Kodochigov for his valuable help in the preparation and examination of the Sr⁹⁰–Y⁹⁰ samples.     

Observation of low-frequency oscillation in argon helicon discharge

We present here a kind of low-frequency oscillation in argon helicon discharge with a half helical antenna. This time-dependent instability shows a global quasi-periodic oscillation of plasma density and electron temperature, with a typical frequency of a few tens of Hz which increases with external magnetic field as well as radiofrequency(RF) power. The relative oscillation amplitude decreases with magnetic field and RF power, but the rising time and pulse width do not change significantly unde...