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In order to study the generation and extraction of negative ions for neutral beam injection application, a negative ion source is being designed and constructed at Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP). Through a four electrode grids system inside the accelerator, a negative ion beam will be extracted and accelerated up to −60 kV on a reduced scale extraction area of 12 × 50 cm 2 (the area of PG apertures is 185 cm 2 ). The beam optics is a key issue for the accelerator design, and greatly determine the source experimental performance in term of beam current, heat load on the grid, beam divergence, and so on. In this paper, the trajectories of electrons and negative ions were simulated in the electrode grids of the negative ion source. The filter capability of electron deflection magnet on the co-extracted electrons is evaluated and confirmed. The negative ion beam optics was designed according to the calculated results of beam divergence and beam radius along the beamlet in different acceleration voltages. The deflection effect of the electron deflection magnet on the negative ion beam was investigated in the single beamlet case and multi-beamlets case.

In order to accumulate the research experience and technical reserves for future negative ion sources of nuclear fusion reactors, a prototype negative ion source is being designed and constructed at ASIPP with a reduced scale extraction area (166 cm2 on the opening of 12 × 48 cm2). Based on the existing negative ion sources having the similar width, an external magnetic filter with permanent magnets is applied to the prototype negative ion source during the initial experiments. For the specific experiments of magnetic field dependence, an adjustable magnetic filter is required. Hence, the plasma grid current filter for short-pulse or long-pulse source and a combination filter using permanent magnets and plasma grid current are designed. The main design purpose is to produce a homogenous and sufficient filter field in front of the plasma grid, with the supply current as low as possible. The filter field distributions of these different magnetic filters are studied in detail by finite element method, especially on the plane paralleling with the plasma grid.

The low-frequency optical absorption properties of graphene nanoribbons in a composite magnetic field are investigated by using the gradient approximation. The spectral function exhibits symmetric delta-function like prominent peaks structure in a uniform magnetic field, and changes to asymmetric square-root divergent peaks structure when subjecting to a composite field. These asymmetric divergent peaks can be further classified into principal and secondary peaks. The spectral intensity and frequency of the absorption peaks depend sensitively on the strength and modulation period of the composite field. The transition channels of the absorption peaks are also analyzed. There exists an optical selection rule which is caused by the orthogonal properties of the sublattice wave functions. The evolution of the spectral frequency of the absorption peaks with the field strength is explored.

The reflectometry diagnostics on experimental advanced superconducting tokamak (EAST) are composed of Q-band (32–56 GHz), V-band (48–76 GHz) and W-band (72–110 GHz) microwave reflectometers with X-mode polarization. The three reflectometers with separate frequency bands were launched independently in previous experiments and now are combined together by applying advanced microwave technology. A quasi-optical (QO) combiner/de-combiner by using frequency selective surfaces (FSSs) has been built to combine the three bands so that these waves (32–110 GHz) can be transmitted to the antenna by using one single oversized waveguide. Two double-ridged horns are used for launcher and receiver. The received waves are decoupled by using a QO de-combiner, the same with the combiner. The designed parameters and laboratory test results of the upgraded system have been presented. The density pedestal evolution during the edge localized modes (ELMs) in EAST plasma have been presented as an example for the application of the updated reflectometers.

Rutherford backscattering and channeling is combined with X-ray diffraction to study the depth dependence of crystalline quality in InN layers grown by metalorganic chemical vapor deposition on sapphire substrate. The poorest crystalline quality in InN layer is produced at the intermediate region over 100 nm away from the InN/sapphire interface. With increasing layer thickness the crystalline quality improves to a certain degree dependent on the growth temperature. The InN sample grown at 450 °C is found to be more homogeneous than the sample grown at 550 °C. The difference in the defect profile is explained by the temperature-dependent growth modes. The inhomogeneity of structural quality and related properties such as carrier concentration and strain field is possibly the reason to observe a high energy wing in PL spectrum of the InN sample grown at 550 °C.

The in-plane orientation of epitaxial ZnO thin film on Al2O3(0 0 0 1) was determined by azimuthal scan of X-ray diffraction. Comprehensive structural characterizations, including the lattice strain in perpendicular direction, the defect density, were obtained from high resolution X-ray diffraction. It's found that a 30° rotation in ZnO against Al2O3, resulting in ZnO〈1 1 2 0〉//Al2O3〈1 0 1 0〉, can efficiently reduce the strain and defects in ZnO layer. Consequently, the optical property is significantly improved.

High-quality AlInGaN quaternary layers were grown on c-Al2O3 using a thick GaN template. A full width at half maximum of 0.075 degrees from AlInGaN(0004) rocking curve and a minimum yield of 5.6% from Rutherford backscattering/channelling spectrometry (RBS) prove the AlInGaN layer of a comparable crystalline quality with GaN layers. The chemical compositions (both of Al and In contents) of AlInGaN layers are directly obtained from RBS and elastic recoil detection analysis. The lattice parameters both in perpendicular and parallel directions are deduced from X-ray diffraction. The AlInGaN layer is found to process a compressive strain in parallel direction and a tensile strain in perpendicular direction. (c) 2006 Elsevier B.V. All rights reserved.

We report on structural characterization of AlGaN/GaN superlattices grown on sapphire. The superlattice formation is evidenced by high-resolution x-ray diffraction and transmission electron microscopy. The high resolution x-ray diffraction spectra exhibit a pattern of satellite peaks. The in-plane lattice constants of the superlattices indicate the coherent growth of the AlGaN layer onto GaN. The average At composition in the superlattices is determined to be 0.08 by Rutherford backscattering spectroscopy. The average parallel and perpendicular elastic strains for the SLs are determined to be (e(parallel to)) = +0.25% and (e(perpendicular to)) = -0.17%. (c) 2006 Elsevier Ltd. All rights reserved.

Rutherford backscattering/channeling (RBS/C) and X-ray diffraction (XRD) are used to comprehensively characterize a heterostructure of AlInGaN/GaN/Al2O3(0001). The AlInGaN quaternary layer was revealed to process a high crystalline quality with a minimum yield of 1.4% from RBS/C measurements. The channeling spectrum of (1 (2) under bar 13) exhibits higher dechanneling than that of (0001) at the interface of AlInGaN/GaN. XRD measurements prove a coherent growth of AlInGaN on the GaN template layer. Combining RBS/C and XRD measurements, we found that the interface of GaN/Al2O3 is a nucleation layer, composed of a large amount of disorders and cubic GaN slabs, while the interface of AlInGaN/GaN is free of extra disordering (i.e. compare with the GaN layer). The conclusion is further evidenced by transmission electron microscopy (TEM). (c) 2005 Elsevier Ltd. All rights reserved.

The strain state of 570nm AlXGa1-xN layers grown on 600nm GaN template by metal organic chemical vapor deposition was studied using Rutherford backscattering (RBS)/channeling and triple-axis X-ray diffraction measurements. The results showed that the degree of relaxation (R) of AlxGa1-xN layers increased almost linearly when x less than or equal to 0.42 and reached to 70% when x = 0.42. Above 0.42, the value of R varied slowly and AI(x)Ga(1-x)N layers almost full relaxed when x = 1 (AIN). In this work the underlying GaN layer was in compressive strain, which resulted in the reduction of lattice misfit between GaN and AlxGa1-xN, and a 570nm AlxGa1-xN layer with the composition of about 0.16 might be grown on GaN coherently from the extrapolation. The different shape of (0004) diffraction peak was discussed to be related to the relaxation. (C) 2004 Elsevier B.V. All rights reserved.

In this paper, an approach to determine the average In composition in InGaN/GaN multiple quantum wells (MQWs) was suggested. The period thickness and the average lattice constants (〈aepi〉 and 〈cepi〉) of MQWs were calculated from high-resolution X-ray diffraction (HRXRD). Then by applying the Vegard's law, the average In composition 〈x〉 was simultaneously determined by considering the relationship between the lattice constants under strain. At the same time, by using the period thickness, the average In composition was obtained from the simulation of the Rutherford backscattering spectroscopy (RBS). The results obtained from the two techniques are agreeable. So the approach of combining both HRXRD and RBS can tell reliable chemical composition in InGaN/GaN MQWs.

The objective of this study was to examine the effects of follicular cells on the in vitro development of porcine preantral follicles. In Experiment 1, one preantral follicle alone (Trt 1) was cocultured with a follicle of the same size with oocytes (Trt 2) or without oocytes (Trt 3). Preantral follicles cultured alone in vitro for 12 days had greater follicle diameters (1017 +/- 96 microm versus 706 +/- 69 or 793 +/- 72 microm, P0.05), growth rates (201 +/- 0.3 versus 103 +/- 0.2 or 128 +/- 0.2, P0.05) and oocyte survival rates (73% versus 48, or 25%, P0.05) than other groups. The inhibitory effects of follicle cells on the growth of preantral follicles and oocyte survival rates were not enhanced by the addition of oocytectomized preantral follicles (Experiment 2). Follicles were cocultured with different sources of follicular cells in other experiments. Coculture with cumulus cells enhanced oocyte survival compared to the control (without coculture) and mural follicular cell groups (Experiment 3). The growth and survival rates of oocytes collected from the group of follicles cocultured with cumulus cells from large antral follicles (3 mm) were greater (P0.05) than those from small antral follicles (3 mm), or than the control group (without cumulus cells, experiment 4). No significant differences in the follicular diameters (674 +/- 30 microm versus 638 +/- 33 and 655 +/- 28 microm) and growth rate (105% versus 94 and 105%) were observed among the preantral follicles of the different treatments (P0.05). Taken together, coculture with the cells from large antral follicles (3 mm) exerted a significant positive effect on oocyte survival. The growth and oocyte survival of preantral follicle cocultured with the same size of follicles (with or without oocyte) were inhibited. Growth and survival rates of preantral follicles and oocytes are improved by coculturing them with the cumulus cells derived from larger antral follicles.

A thin AlGaN layer, which is suitable for structural study using Rutherford backscattering (RBS)/channeling, was grown on an Al2O3(0 0 0 1) substrate by metalorganic chemical vapor deposition. The results show that the composition of the epilayer is Al0.05Ga0.95N and that although the epilayer is very thin (79 nm), it has a good crystalline quality (χmin=1.9%). The azimuthal orientation of the AlGaN epilayer relative to the Al2O3 substrate is AlGaN[0 0 0 1] // Al2O3[0 0 0 1] and AlGaN {1 1 2 0} // Al 2 O 3 {1 0 1 0} , showing that the AlGaN epilayer is rotated by 30° around the [0 0 0 1] axis with respect to the Al2O3 substrate which decreases the lattice mismatch between the epilayer and the substrate significantly. RBS angular scan was used to determine the strain-induced tetragonal distortion of the epilayer. Combined with X-ray diffraction, the perpendicular and parallel elastic strains of the AlGaN layer, e⊥=+0.31% and e∥=−0.28%, can be calculated.

InGaN and AlGaN layers were grown on Al2O3 substrate by metalorganic chemical vapor deposition (MOCVD) with a GaN intermediate layer. The thickness and the composition of the layers, 270 nm In0.18Ga0.82N and 765 nm Al0.28Ga0.72N, were determined by Rutherford backscattering (RBS). The elastic strain of these layers was determined by X-ray diffraction combined with RBS/channeling. The results show that these layers are partially strained with a perpendicular strain e⊥=+0.21%, parallel strain e||=−0.53% for the InGaN layer and e⊥=−0.16%, e||=+0.39% for the AlGaN layer. The signs of e|| and e⊥ of AlGaN are opposite to those of InGaN, since the lattice mismatch between AlGaN and GaN is negative while the lattice mismatch between InGaN and GaN is positive.

The ternary silicide, Er0.5Y0.5Si1.7 has been produced by channeled ion beam synthesis (CIBS) in a Si(1 1 1) substrate. The properties of the material have been compared with those of the binary silicides (i.e. ErSi1.7 and YSi1.7) produced by the same method. Analysis was carried out using Rutherford backscattering (RBS) and X-ray diffraction (XRD). The study revealed that the layer produced is of good crystalline quality, and is indeed composed of the Er0.5Y0.5Si1.7 ternary silicide as opposed to a mixture of the two binaries. It is epitaxial with respect to the Si substrate and possesses the same hexagonal (AlB2) structure exhibited by both binary silicides. The azimuthal orientation with respect to the substrate is Er0.5Y0.5Si1.7[0 0 0 1]//Si[1 1 1] and Er0.5Y0.5Si1.7{1 1 2 0}//Si{1 1 0}. The epilayer was found to be elastically strained with the perpendicular strain=−0.67% and the parallel strain=+0.34% similar to the values found for the Er and Y silicides.

A buried hexagonal YSi 1.7 layer is formed by channelled implantation of Y ions into (1 1 1) oriented silicon wafers. The orientation relationship between the epitaxial YSi 1.7 and the silicon is (0 0 0 1) YSi 1.7 ‖(1 1 1) Si with 〈1 1 2 0〉 YSi 1.7 ‖〈1 1 0〉 Si . Annealing at 600°C for 1 h and subsequently at 1000°C for 0.5 h improves the crystalline quality of the buried YSi 1.7 layer. On the other hand, Nd-disilicide cannot be grown epitaxially on a Si(1 1 1) substrate. However, by using a sequential implantation of Y and Nd ions, a buried hexagonal Nd 0.32 Y 0.68 Si 1.7 layer with good crystalline quality is formed in the Si(1 1 1) substrate.

Epitaxial ternary silicide Er0.49Gd0.51Si1.7 layers with a good crystalline quality (χmin of Er and Gd is 3.7%) have been formed by 60 keV Er and Gd ion implantation into Si(1 1 1) substrates to a total dose of 1.0 × 1017/cm2 at 450°C using channeled ion beam synthesis (CIBS). The composition, the structure, the strain and the thermal stability of these layers have been studied using energy dispersive spectroscopy (EDS), Rutherford backscattering (RBS)/channeling and X-ray diffraction (XRD). It is shown that the perpendicular and parallel elastic strains of the Er0.49Gd0.51Si1.7 epilayer are e⊥=−0.46% ± 0.02% and e‖=+0.73% ± 0.19%. The layer is stable up to 900°C. Annealing at 950°C results in a phase transformation.

Si(111) substrates were implanted with 70 or 90 keV 166 Er atoms to doses from 1.3 to 2.0×10 17 cm −2 at substrate temperatures from 450 to 530°C. During implantation, the Si substrates were tilted by 7° to minimize the channeling effect. The Er silicide layers formed under these conditions are not as good as Co silicide layers formed by Co implantation under similar conditions and the reason is discussed. One of the best results is an annealed sample containing a discontinuous epitaxial ErSi 1.7 layer with χ min of 40%. Rutherford backscattering and channeling spectrometry, X-ray diffraction and transmission electron microscopy have been used to study this heteroepitaxial ErSi 1.7 layer, showing that the epilayer is compressively strained and the azimuthal orientation of the epilayer is ErSi 1.7 [0001]∥Si[111] and ErSi 1.7 (10 1 0)∥Si( 11 2)

The magnetic viscosity of Sm 2 Fe 17 N x ( x =1.6−3.5) with different particle sizes was measured with a vibrating sample magnetometer at 10–373 K and during a period of t = 6–1000 s. The magnetic viscosity parameter S v was found to vary with the nitrogen concentration, showing a maximum value at x = 3.0. The relationship between log( S v ) and log( H c ) fits the Barbier linear plot fairly well, with a slope of about 0.9. The activation volume V of Sm 2 Fe 17 N x decreases as the nitrogen concentration increases. The value of V can be related to the H c value by H c = V − n ( n = 1.0−1.4).

An unusual Ni distribution with two completely separated buried and surface silicide layers has been observed after Ni ion implantation in Si(111) kept at a temperature of 300°C, with a dose of 1.1 × 10 17 /cm 2 and at a fixed energy of 90 keV. The Ni profile and its substrate temperature dependence, its dose dependence and the influence from the preceding Co implantation were studied by RBS, AES and TEM. A model based on the diffusion of the transition metal, defect annealing during the implantation, and the gettering power of the surface and the end-of-range defects is presented.

Direct measurements using a variable pressure low temperature liquid cell and infrared spectroscopy have shown that CH3OH, C2H5OH and H2S are considerably less soluble in liquid nitrogen and liquid oxygen, i.e. < 10−7 mole fraction at 135 K, compared with previously reported values of 10−5 mole fraction for CH3OH and C2H5OH in liquid oxygen at 77 K and 10−7 mole fraction for H2S in liquid nitrogen at 77 K using a gravimetric method. Some criteria for assessing and measuring the solubility of compounds in cryogenic liquids are proposed.