Modeling Errors in Microwave Plasma Diagnostics Employing the Reflection Coefficient

The use of the complex reflection coefficient, R, at microwave frequencies as a plasma diagnostic tool in the high electron density range (1012 electrons/cm3) has been reported by several authors. A common assumption is that at microwave frequencies the boundary between free space and a stationary plasma is best described as a step function in electron density. Actually, many practical boundaries consist of a finite-width region wherein the electron density has a finite gradient. The complex reflection coefficient is derived for the finite width boundary and comparisons are made with an assumed sharp boundary. It is shown that improper modeling of the plasma boundary can result in significant error in electron density measurements when R is used as a diagnostic tool.     

9 MeV行波电子直线加速器加速管微波测试及调整

介绍了海关大型集装箱在线检测用加速器的核心部件９ＭｅＶ行波电子直线加速器加速管的微波测试及调整,并详细描述了加速管微波调谐、加速管与矩形波匹配以及加速管整管场分布及总衰减量的测量,给出了加速管微波测试及调整的结果,结果表明微波调度满足物理设计的要求。     

Diagnosis of Unmagnetized Plasma Electron Number Density and Electron-neutral Collision Frequency by Using Microwave

The plasma diagnostic method using the transmission attenuation of microwaves at double frequencies （PDMUTAMDF） indicates that the frequency and the electron-neutral collision frequency of the plasma can be deduced by utilizing the transmission attenuation of microwaves at two neighboring frequencies in a non-magnetized plasma. Then the electron density can be obtained from the plasma frequency. The PDMUTAMDF is a simple method to diagnose the plasma indirectly. In this paper, the interaction of electromagnetic waves and the plasma is analyzed. Then, based on the attenuation and the phase shift of a microwave in the plasma, the principle of the PDMUTAMDF is presented. With the diagnostic method, the spatially mean electron density and electron collision frequency of the plasma can be obtained. This method is suitable for the elementary diagnosis of the atmospheric-pressure plasma.     

Pyrolytic Graphite Irradiated with 4 keV Hydrogen Ions Using Reflection High-Energy Electron Diffraction

Separation of barium isotopes with a selective two-step photoionization process was accomplished using a continuous wave dye laser and ultra-high pressure mercury lamp. Narrow line-width laser light was tuned to the 6s^{2 1}S₀--6s6p ¹P₁ resonance line (553.6 nm), and only a single isotopic component in an atomic beam was excited through the isotope shift. The excited atoms were successively ionized by uv radiation and deflected by a static electric field.

The spectrum of the ion current separated isotopically agreed well with spectroscopic data within the system resolution of 65 MHz. The isotopic enrichment of ¹³⁸Ba was 97%, which corresponded to the selectivity of 1.36. The ionization rate defined as what portion of the incident atoms was ionized was approximately 4x10^?5%. The photoionization cross section was estimated from the experimental results by using the least squares method. The resultant value was (4±1)x10^?23m².     

Direct Measurements of the Electron Energy Flux versus Electron Temperature Gradient in Tokamak Discharges

Electron thermal transport is one of the most complex processes in fusion plasmas.It is generally described by a simple thermal diffusivity in transport analyses of discharges,but there is evidence of critical gradient effects with moderate stiffness.By analyzing periodic perturbations to an equilibrium,one can measure the variations in electron energy flux and electron temperature gradient over the perturbation cycle,obtaining the flux as a function of gradient over the range of parameters generated by the perturbation.Although time-dependent transport analysis is very sensitive to noise in the input data,averaging over many cycles of a periodic perturbation can provide data of sufficient quality.The analyses presented here are based on the ECE temperature data with high spatial and temporal resolution and full profile coverage on DIII-D for sawteeth and modulated ECH heating.     

医用电子直线加速器的测量

本文概要介绍了加速器的一般知识和测量准备工作，较详细地介绍了对加速器吸收量，百分深度剂量，射线能量，射野离轴比，射野均坦度等几个主要项目的测量和计算方法，并重点强调了对加速器进行正确可靠的剂量，是放射治疗质量保证和质量控制的重要环节。     

放射性气溶胶测量中能量补偿系数时间特性研究

为进一步提高能量甄别法测定放射性气溶胶测量结果的准确性,开展了能量补偿系数的时间依赖特性研究。根据核素在滤膜上的衰变规律对补偿系数的时间特性进行了全面分析,研究了取样时间、等待时间和测量时间对其的影响,并进行了测量验证,获取在实验条件下最佳的时间分配组合,可为放射性气溶胶快速测量工作提供参考。     

Effects of Electron-Ion Collisions on Stimulated Raman Backward Scattering Under Different Electron Densities

Effect of electron-ion collision on stimulated Raman backward scattering (SRBS) spectrum are investigated by numerical simulations. In the given parameters and plasma condition, the growth rates of SRBS are found to strongly depend on the electron density, and the gap in the SRBS spectrum corresponding to the high electron density could be explained by the collisional damping. In the low density region, a much higher Landau damping estimated by the linear theory makes the collisional damping negligible. However, the present results show that, collisions play a even more important role than known in the linear theory.     

电子磁谱仪法测量超热电子温度

利用超热电子磁谱仪测量了紫外超短脉冲激光与固体等离子体相互作用产生超热电子的能谱,在无预脉冲、激光强度为1017 W/cm2 条件下,紫外超短脉冲激光与固体(Cu)等离子体相互作用产生超热电子的能谱呈双温麦克斯韦分布,超热电子温度为81 keV,激光吸收的主导机制为真空吸收。     

Present Status of the Electron Cyclotron Emission Measurements on HT-7 and EAST

Present status of the diagnostics for electron cyclotron emission measurements on both HT-7 and EAST is reported. A 16-channel heterodyne radiometer system and a 20-channel grating polychromator, have been installed on HT-7 and EAST. A 32-channel heterodyne ra- diometer system, with a wider frequency coverage and better spatial resolution, is being built. In order to provide a reliable electron temperature profi, an in-situ absolute calibration system is currently being built. With the ECE measurements, study on the electron heat transport and the anomalous Doppler resonance is conducted.     

Study of SiO_2 Films Prepared by Electron CyclotronResonant Microwave Plasma

1.IntroductionInoptIcaltelecommunlcatlons,ltisnecessarytodevelopoptlcalfibresystemswithhighertransmls-sionefficlencyandnetworkflexlblllty.Todate,hott'-ever,theyhavebeenfarfromreallzation,baslcallybecauseofdifficultiesinprocessesoffabricatingpla-naropticalwaveguidesanddeviceswithlowbendandtransmlsslonlosses[l1.Whicharedirectlyre-liedonopticalwaveguidefilmperformancesuchashighrefractiveindexandlowsurfaceroughness.Assilicafilmsarecapabletobedepositedoncrystallinesiliconsllbstrateandfurtherformac…     

Development of Synchronous Circuit between Microwave Pulse and Electron Gun Pulse

正Irradiation processing is a kind of high-tech green machining technology.Through the biological,chemical and physical effects of highenergy radiation on substances,a lot of functions were fully implemented,such as disinfection,     

Improvement of the Harmonic Technique of Probe for Measurements of Electron Temperature and Ion Density

Conventional Langmuir probe techniques usually face the difficulty of being used in processing plasmas where dielectric compounds form,due to rapid failure by surface insulation.A solution to the problem,the so-called harmonic probe technique,had been proposed and shown effectiveness.In this study,the technique was investigated in detail by changing bias signal amplitudes Vo,and evaluated its accuracy by comparing with the conventional Langmuir probe.It was found that the measured electron temperature Te increased with Vo,but showing a relatively stable region when Vo ＞ Te/e in which it was close to the true Te value.This is contrary to the general consideration that Vo should be smaller than Te/e for accurate measurement of Te.The phenomenon is interpreted by the non-negligible change of the ion current with Vo at low Vo values.On the other hand,the measured ni also increased with Vo due to the sheath expansion,and to improve the accuracy of ni it needs to linearly extrapolate the ni-Yo trend to Vo=0.The results were applied to a diagnosis of the plasmas for chemical vapor deposition of diamond-like carbon thin films and the relationship between plasma parameters and films deposition rates was obtained.     

Electron Capture to the Continuum at Asymptotically High Velocities

The velocity distrubutions of electrons ejected from gaseous He targets into the forward direction by 15-18 au velocity bare O, Ne and Ar nuclei are measured. The shape of the resulting ECC (electron capture to the continuum) cusps is studied in detail by three fitting methods and compared to theory. The results favor theoretical treatments which include higher-order ejected electron partial waves to describe the observed asymmetry.     

S波段高功率微波测试台架的研制

S波段高功率微波测试台架主要由磁控管、调制器、微波传输元件及高功率测试装置和保护装置组成。该台架采用量热法利用水负载吸收微波功率,通过工频校准测量微波部件的承受功率能力。利用水负载高功率测量装置对小功率计测量系统校准,测量微波部件在高功率状态下的插入损耗、隔离度、输入电压驻波比等性能指标,从而实现微波部件的高功率考验与测试。此外,采用高功率环行器和微波反射快速保护装置,确保测试台架的高功率稳定运行。