摘要:

Ion beam assisted deposition (IBAD) is a coating technique which combines a thin‐film deposition method such as evaporation with irradiation by highly energetic ions from an ion source. Application of an ion source and a vapor source which are operated independently of each other render the IBAD technique highly controllable, reproducible, and flexible. Ion flux, atom flux, ion energy, ion impact angle, and other parameters can be controlled independently over a wide range. In order to take advantage of the beneficial features of this technique and obtain optimum process conditions ion sources with special properties are required. In this article different ion source types and equipment which has been used for IBAD to‐date are presented and their special features discussed. Ion sources which should be applicable for IBAD are described. Finally, general requirements of IBAD ion sources are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1143432

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

In this article the ion beam of H+and Ar+produced from the low‐pressure radio frequency ionized plasma is analyzed for beam divergence. The divergence measurement method adopted for a low‐energy beam is described. The divergence values for H+and Ar+, respectively, are 0.4° and 1.1° for a beam energy of 2.5 kV. It is found that the beam divergence varies with the extraction voltage. In case of H+beam, the divergence value varies from 2.8° to 0.4° for the extraction voltage of 500 V to 2.5 kV, and in the case of Ar+beam this value is from 1.3° to 1.1° for the extraction voltage of 1000 V to 2.5 kV. The extraction electrode is concave outward as shown in the figure of the extraction system. The rf plasma is diagnosed using the double‐probe technique for ion density estimation. The axial variation of the electron density and the electron temperature are obtained for both hydrogen as well as argon plasmas. The electron density is maximum, near the end of the coil.

ISSN:0034-6748    

DOI:10.1063/1.1143433

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A compact poloidal array of ten receiving antennae has been installed on the high‐field wall (x=+30 cm) of the Texas Experimental Tokamak (TEXT) opposite the electron cyclotron heating (ECH) microwave launch port (x=−45 cm, 60 GHz, 200 kW). Both these antennae and the launching structure are oriented to couple to the ordinary mode in plasma. The array serves as a diagnostic of the unabsorbed, first‐pass ECH microwave power, which includes both power refracted by the equilibrium plasma density gradients and power scattered by density fluctuations. Each antenna has a &Dgr;&thgr;y=13° poloidal and &Dgr;&thgr;z=32° toroidal half‐power beam width, corresponding to 12‐dB gain. For refraction studies, interchannel and intrachannel poloidal resolutions are &Dgr;y=3.5 and 2.5 cm, respectively, at the array aperture surface. For scattering studies, the wave number selectivity extends fromk⊥=0±2.5 cm−1tok⊥=7±2.5 cm−1.

ISSN:0034-6748    

DOI:10.1063/1.1143434

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The expression connecting the plasma parameters with the current‐voltage (I‐V) characteristic of the attracting probe is obtained, and it is compared with the electron branches of the experimental probeI‐Vcharacteristics in the range of the probe potentialsV≳0. The theoretical and experimental results are in a good agreement. Studies of the influence of a cylindrical Langmuir probe diameter on the ion branch of itsI‐Vcharacteristic are described. The transition of the ion charges from the plasma to the measuring circuit of the probe leads to a decrease of the ion concentration in the near‐probe region limited by the Debye length, as is shown. The relations given in the paper enable one to reconstruct the ion concentration by the experimentalI‐Vcharacteristic disturbed by the probe.

ISSN:0034-6748    

DOI:10.1063/1.1143435

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Collective Thomson scattering has long been utilized to study electrostatic turbulence in magnetic confinement fusion plasmas with a view to demonstrating a causal link to the observed anomolous transport of heat and particles. However, this goal has been severly hampered by the relatively poor spatial resolution available at the dominant turbulence wave numbers using standard experimental techniques. Good spatial resolution is necessary if adequate comparison of theory and experiment is to occur. The present paper describes the basic principles of a new technique utilizing simultaneous, multiple input beams, a detector array, and coherent tomographic inversion algorithm, which can substantially improve the available spatial resolution for these important measurements. The proposed multiple beam scattering diagnostic offers a spatial resolution of ∼10 cm at a fluctuation wave number of 5 cm−1when the angular envelope of the beams is 0.1 rad. Optical designs suitable for implementing the multiple beam diagnostic on a large tokamak have been developed.

ISSN:0034-6748    

DOI:10.1063/1.1143436

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Collective Thomson scattering measurements performed at 266 nm on an underdense, long scalelength laser‐produced aluminum plasma (nc∼1021cm−3,Z∼7,Te≥50 eV,L≥100 &mgr;m) under moderate irradiance conditions (1011W/cm2) are used to obtain temporally integrated, spatially resolved (30 &mgr;m) electron temperature, density, and radial fluid velocity contours. For an ultraviolet diagnostic wavelength, the effects of inverse bremsstrahlung heating perturbations and refractive turning are significantly reduced, allowing high density coronal conditions in the vicinity of one‐tenth critical to be investigated. Detailed knowledge of these plasma conditions are fundamental prerequisites for understanding the distributed absorption process within fusion plasmas and for validation of the modeling accuracy of hydrodynamic codes. Fluid equations with classical coefficients should accurately apply to the plasma in these experiments because electron thermal transport is in the Spitzer regime, and the authors report relatively good agreement between the experimental results and two‐dimensional LASNEX simulations.

ISSN:0034-6748    

DOI:10.1063/1.1143437

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We describe a rotating‐drum dust‐dispersal device, which we have used, in conjunction with an existingQmachine, to produce extended, steady state, magnetized plasma columns. The dusty plasma device (DPD) is to be used for the investigation of waves in dusty plasmas and of other plasma/dust aspects. The device is capable of generating dusty plasmas in which as much as ∼90% of the negative charge is attached to dust grains of 1–10 &mgr;m size.

ISSN:0034-6748    

DOI:10.1063/1.1143438

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Absolutely calibrated measurements of the neutron yield are important for the evaluation of plasma performance such as the fusion gainQin D–D operating tokamaks. The time‐resolved neutron yield is measured with235U and238U fission chambers and3He proportional counters in the JT‐60U tokamak. Theinsitucalibration was performed by moving the252Cf neutron source toroidally through the JT‐60 vacuum vessel. Detection efficiencies of three235U and two3He detectors were measured for 92 locations of the neutron point source in toroidal scans at two different major radii. The total detection efficiency for the torus neutron source was obtained by averaging the point efficiencies over the whole toroidal angle. The uncertainty of the resulting detection efficiency for the plasma neutrons is estimated to be ±11%.

ISSN:0034-6748    

DOI:10.1063/1.1143439

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Reflection of low‐energy (<100 eV) ions from surfaces can be applied as a method of producing high‐flux beams of low‐energy neutral particles, and is an important effect in several areas of plasma technology, such as in the edge region of fusion devices. We have developed a beam source based on acceleration and reflection of ions from a magnetically confined coaxial rf plasma source. The beam provides a large enough flux (over 4 A ion current, or 5×1016atoms/cm2 s at 10‐cm range) to allow the energy distribution of the reflected neutrals to be measured despite the inefficiency of detection, by means of an electrostatic cylindrical mirror analyzer coupled with a quadrupole mass spectrometer. Energy distributions have been measured for oxygen, nitrogen, and inert gas ions incident with from 15 to 70 eV reflected from amorphous metal surfaces of several compositions. For ions of lighter atomic mass than the reflecting metal, reflected beams have peaked energy distributions; beams with the peak at 4–32 eV have been measured. The energy and mass dependences of the energy distributions as well as measurements of absolute flux, and angular distribution and divergence are reported. Applications of the neutral beams produced are described.

ISSN:0034-6748    

DOI:10.1063/1.1143440

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We present the design and performance of a beamline which is the source of 5–50‐eV protons for surface scattering experiments. The beamline also incorporates a collector for measuring total secondary ion and electron yields. The beam forming optics are built around a commercially available gas discharge ion gun and produce a mass‐selected, energy‐filtered beam. Results of computer ray tracing are included to illustrate the operation of the beam optics. Tests have produced 50‐pA proton beams 3.5‐mm wide at 5 eV with an energy spread of about 1 eV.

ISSN:0034-6748    

DOI:10.1063/1.1143441

出版商:AIP    

年代:1992

数据来源: AIP