Surface plasma source with saddle antenna radio frequency plasma generator

A prototype RF H(-) surface plasma source (SPS) with saddle (SA) RF antenna is developed which will provide better power efficiency for high pulsed and average current, higher brightness with longer lifetime and higher reliability. Several versions of new plasma generators with small AlN discharge chambers and different antennas and magnetic field configurations were tested in the plasma source test stand. A prototype SA SPS was installed in the Spallation Neutron Source (SNS) ion source test stand with a larger, normal-sized SNS AlN chamber that achieved unanalyzed peak currents of up to 67 mA with an apparent efficiency up to 1.6 mA∕kW. Control experiments with H(-) beam produced by SNS SPS with internal and external antennas were conducted. A new version of the RF triggering plasma gun has been designed. A saddle antenna SPS with water cooling is fabricated for high duty factor testing.     

介质透镜操控光电导天线辐射太赫兹波的研究

飞秒激光驱动的太赫兹 (terahertz, THz) 光电导天线是THz时域谱系统中常用的THz源,受全向辐射模式的影响,该光电导天线的天线主瓣小,方向性差。对波束的有效操控将有助于提高光电导天线的发射效率。以低温生长的砷化镓 (LT-GaAs) 作为天线基底材料,通过电磁仿真软件CST对蝶形天线辐射THz波的电磁分布特性进行仿真,研究了介质透镜对蝶形天线辐射出的THz波的操控。通过对透镜扩展厚度的理论与数值分析,得出一定频率下的最佳透镜扩展厚度值。仿真结果表明：随着频率的提高,蝶形天线在加载更小扩展厚度的硅透镜时可获得更好的方向性。     

A cryogenic source of slow monochromatic positrons

A cryogenic source of slow monochromatic positrons based on ²²Na radioactive isotope has been developed and produced at the Joint Institute for Nuclear Research. A monochromatic beam is formed from a continuous β⁺ spectrum with energies of 0–0.5 MeV using a solid neon moderator frozen onto a copper substrate that is cooled to temperatures of 5–7 K. The efficiency of condensation of neon onto the substrate is >99.8%. A slow positron beam with an intensity of 5.8 × 10³ particles/s and a mean energy of 1.2 eV at a spectrum width of 1 eV has been extracted from a ²²Na-based test source. The fraction of decelerated positrons is 1% of the total flux.     

Fast plasma discharge capillary design as a high power throughput soft x-ray emission source

We present the experimental details and results from a low energy but high repetition rate compact plasma capillary source for extreme ultraviolet and soft x-ray research and applications. Two lengths of capillary are mounted in two versions of a closely related design. The discharge operates in 1.6 and 3.2 mm inner diameter alumina capillaries of lengths 21 and 36 mm. The use of water both as dielectric and as coolant simplifies the compact low inductance design with nanosecond discharge periods. The stored electrical energy of the discharge is approximately 0.5 J and is provided by directly charging the capacitor plates from an inexpensive insulated-gate bipolar transistor in 1?μs or less. We present characteristic argon spectra from plasma between 30 and 300 A? as well as temporally resolved x-ray energy fluence in discrete bands on axis. The spectra also allow the level of ablated wall material to be gauged and associated with useful capillary lifetime according to the chosen configuration and energy storage. The connection between the electron beams associated with the transient hollow cathode mechanism, soft x-ray output, capillary geometry, and capillary lifetime is reported. The role of these e-beams and the plasma as measured on-axis is discussed. The relation of the electron temperature and the ionization stages observed is discussed in the context of some model results of ionization in a non-Maxwellian plasma.     

圆锥滚子直动从动件圆锥凸轮的数控加工

应用单参数曲面族包络面理论分析和研究圆锥滚子直动从动件圆锥凸轮机构,导出了圆锥凸轮廓面的数学表达式。以此为基础,建立了采用尺寸等于或小于圆锥滚子尺寸刀具加工圆锥凸轮时的刀具刀尖轨迹方程。     

Electron cyclotron resonance ion source plasma chamber studies using a network analyzer as a loaded cavity probe

A method and first results utilizing a network analyzer as a loaded cavity probe to study the resonance properties of a plasma filled electron cyclotron resonance ion source (ECRIS) plasma chamber are presented. The loaded cavity measurements have been performed using a dual port technique, in which two separate waveguides were used simultaneously. One port was used to ignite and sustain the plasma with a microwave source operating around 11 GHz and the other was used to probe the cavity properties with the network analyzer using a frequency range around 14 GHz. The first results obtained with the JYFL 14 GHz ECRIS demonstrate that the presence of plasma has significant effects on the resonance properties of the cavity. With plasma the frequency dependent behavior is strongly damped and this trend strengthens with increasing microwave power.     

A source of a wide-aperture gas-discharge plasma flow

The described generator produces a wide-aperture flow of charged plasma particles (electrons, positive and negative ions) with a cross-sectional diameter of at least 120 cm, which propagates to a distance of 50 cm or more (depending on the operating mode and the geometric dimensions of the vacuum chamber). The uniform distribution of charged particles in the cross section of the plasma flow is at least 98%. The discharge current reaches 1 A or more at an accelerating voltage of 0.3–6 kV. The energy of particles in the plasma flow under such conditions was 10–6000 eV at current densities of up to 10 mA/cm². The generator structure contains coaxially positioned meshes of the anode grid and the cathode grid. The latter closes the cavity inside the cathode volume at a depth of 3–5 mean free paths of electrons in the gas-discharge plasma flow. The cathode is manufactured so that the cavity diameter exceeds the diameter of the through cavity in the cathode insulation, the latter being determined by the size of the plasma-flow cross section. The distance between the grid anode and the cathode grid is equal to the Aston dark space of a glow discharge, thus permitting the cathode lifetime to be increased to 3 years. It is shown that the duration of the cathode continuous operation is determined by the chosen values of its cavity depth and accelerating voltage.     

A starting device for a metal plasma source

An explosion of a thin self-renewable carbon film is used for initiating an arc in a vacuum-arc metal plasma source, which makes operation of the device independent of the operating mode of the plasma source and allows the circuit of the setup to be simplified, since there is no need for generating high-voltage triggering pulses. The service life of this device in vacuum is more than 10⁵ triggering pulses.     

Characteristic of a triple-cathode vacuum arc plasma source

In order to generate a better ion beam, a triple-cathode vacuum arc plasma source has been developed. Three plasma generators in the vacuum arc plasma source are equally located on a circle. Each generator initiated by means of a high-voltage breakdown between the cathode and the anode could be operated separately or simultaneously. The arc plasma expands from the cathode spot region in vacuum. In order to study the behaviors of expanding plasma plume generated in the vacuum arc plasma source, a Langmuir probe array is employed to measure the saturated ion current of the vacuum arc plasma source. The time-dependence profiles of the saturated current density of the triple vacuum arc plasma source operated separately and simultaneously are given. Furthermore, the plasma characteristic of this vacuum arc plasma source is also presented in the paper.     

A gas-ion source with a grid-stabilized plasma cathode

A two-stage source of a broad beam of gas ions is described. The source contains a grid-stabilized plasma cathode and an anode stage with a multicusp magnetic field. The emission current of the plasma cathode (which is based on a glow discharge with a hollow cathode) is controlled between 0.1 and 1 A. The voltage that is applied to a bipolar diode between its cathode grid and anode plasma and determines the energy of fast electrons ranges from 50 to 200 V. The operating pressure of the argon in the anode stage is 4 × 10^–3–1 × 10^–1 Pa. A beam of argon ions having an energy of up to 5 keV and a current of >100 mA is formed by a two-electrode ion-optical system with a working area of 50 cm².__________Translated from Pribory i Tekhnika Eksperimenta, No. 2, 2005, pp. 107–111.Original Russian Text Copyright © 2005 by Gavrilov, Kamenetskikh.     

多路信号源在阵列天线测试系统中的应用

舰载超视距雷达阵列天线由于其特殊的使用环境,必须了解其幅相特性,作为雷达信号处理中的天线补偿参数.因此有必要制作一套专门的阵列天线测量系统,其中的关键设备之一是多路相位可控信号源.在测试系统中,该设备的数字化是提高测试系统自动化程度和测试速度的关键.     

Flash X-ray microscopy with a gas jet plasma source

A novel flash X-ray source, the gas jet plasma source, has been used for contact X-ray microscopy. Using a wavelength range of 2–7 nm a resolution of the order of 30 nm can be obtained. The gas jet plasma source provides a new and unique tool which should allow future imaging of wet live cells.     

Surface plasma source with anode layer plasma accelerator

Proposed plasma generation system can be used for high current negative ion beam production and for directed deposition by flux of sputtered neutrals and negative ions. The main mechanism of negative ion formation in surface plasma sources is the secondary emission from low work function surface bombarded by a flux of positive ion or neutrals. The emission of negative ions is enhanced significantly by introducing a small amount of cesium or other substance with low ionization potential. In the proposed source are used positive ions generated by Hall drift plasma accelerator (anode layer plasma accelerator or plasma accelerator with insulated channel, with cylindrical or race track configuration of emission slit). The target-emitter is bombarded by the ion beam accelerated in crossed ExB fields. Negative ions are extracted from the target surface with geometrical focusing and are accelerated by negative voltage applied between emitter and plasma, contacting with the plasma accelerator. Hall drift ion source has a special design with a space for passing of the emitted negative ions and sputtered particles through the positive ion source.     

Low-energy linear oxygen plasma source

A new version of a constricted plasma source is described, characterized by all metal-ceramic construction, a linear slit exit of 180 mm length, and cw operation (typically 50 kHz) at an average power of 1.5 kW. The plasma source is here operated with oxygen gas, producing streaming plasma that contains mainly positive molecular and atomic ions, and to a much lesser degree, negative ions. The maximum total ion current obtained was about 0.5 A. The fraction of atomic ions reached more than 10% of all ions when the flow rate was less then 10 SCCM O(2), corresponding to a chamber pressure of about 0.5 Pa for the selected pumping speed. The energy distribution functions of the different ion species were measured with a combined mass spectrometer and energy analyzer. The time-averaged distribution functions were broad and ranged from about 30 to 90 eV at 200 kHz and higher frequencies, while they were only several eV broad at 50 kHz and lower frequencies, with the maximum located at about 40 eV for the grounded anode case. This maximum was shifted down to about 7 eV when the anode was floating, indicating the important role of the plasma potential for the ion energy for a given substrate potential. The source could be scaled to greater length and may be useful for functionalization of surfaces and plasma-assisted deposition of compound films.     

Coaxial lower hybrid plasma source

We report the development of a coaxial radio frequency plasma source capable of producing pulsed plasmas of moderately high density (10(13)-10(14) cm(-3)). This device may be useful either as a general purpose laboratory plasma source or as an auxilliary source for a variety of fusion applications, such as providing target plasmas for mirror machines or producing cold plasma blankets to help isolate the hot plasma core of a toroidal plasma from the walls.     

Radiofrequency antenna for suppression of parasitic discharges in a helicon plasma thruster experiment

A radiofrequency (rf) antenna for helicon plasma thruster experiments is developed and tested using a permanent magnets helicon plasma source immersed in a vacuum chamber. A magnetic nozzle is provided by permanent magnets arrays and an argon plasma is produced by a 13.56 MHz radiofrequency helicon-wave or inductively-coupled discharge. A parasitic discharge outside the source tube is successfully suppressed by covering the rf antenna with a ceramic ring and a grounded shield; a decrease in the ion saturation current of a Langmuir probe located outside the source tube is observed and the ion saturation current on axis increases simultaneously, compared with the case of a standard uncovered rf antenna. It is also demonstrated that the covered antenna can yield stable operation of the source.     

Small plasma source for materials application

We describe a small hollow-cathode plasma source suitable for small-scale materials synthesis and modification application. The supporting electrical system is minimal. The gaseous plasma source delivers a plasma ion current of up to about 1 mA. Here we outline the source construction and operation, and present some of its basic performance characteristics.     

A compact Schwarzschild soft X-ray microscope with a laser-produced plasma source

A compact Schwarzschild soft X-ray microscope using a laser-produced plasma soft X-ray source has been developed. The laser-produced plasma source, which is small but of high brilliance, has made it possible to use the soft X-ray microscope in a small laboratory. The microscope is composed of a Schwarzschild objective and a grazing incidence mirror condenser. Image contrast for biological specimens in soft X-ray regions is investigated briefly. It is possible to observe the fine structures of a thin specimen at a wavelength of 15 nm; at this wavelength high-contrast images of biological specimens have been obtained with a single laser shot of pulse width of 8 ns at a resolution of 0·3 μm. The resolution of the system is limited by the detector.