Search

In the negative hydrogen ion sources, the positive bias of the plasma grid with respect to the discharge chamber is often used to suppress co-extracted electrons. Because most of the co-extracted electrons are magnetically deflected onto the extraction grid, the difference between the extraction and acceleration current (i.e., Iext − Iacc) is commonly used to represent the number of co-extracted electrons. In the single-driver RF negative ion source at ASIPP, the variation of Iext − Iacc with the plasma grid bias voltage was accidentally found to have different trends with and without the Cs seeding. When the current density of Iacc (regarded as JH-) was larger than 120 A/m2 during Cs conditioning, the Iext − Iacc fell first and then rose with the increasing bias voltage. The previous research results from NIFS that the beam optics were changed by the bias voltage can be used to explain the phenomenon. In this paper, the electron temperature (Te) in front of the plasma grid was found to increase from the Langmuir probe measurement, when the bias voltage was higher than a threshold of 4.5 V to the float potential. Interestingly, the bias voltage corresponding to the trough of Iext − Iacc was higher than the float potential—a similar value of 4.1 V to the threshold of Te increasing. Since the negative hydrogen ions are easily destroyed by the high-energy electrons, the increasing of Te may also cause the change of beam optics and the increase in co-extracted electrons. The electron energy distribution function was used to explain the change of plasma parameters in front of the plasma grid. [ABSTRACT FROM AUTHOR]

The first examples of rare‐earth polyiodates, namely, REI5O14 (RE=Y and Gd), have been prepared by hydrothermal reactions of RE2O3 and H5IO6 in H3PO4 (≥85 wt % in H2O), with extremely high yields (>95 %). They crystalize in the polar space group Cm and feature a brand‐new semicircle‐shaped [I5O14]3− pentameric polyiodate anion composed of two IO3 and three IO4 polyhedra. Remarkably, both compounds exhibit very large second‐harmonic generation (SHG) signals (14× and 15×KH2PO4 (KDP) upon 1064 nm laser radiation for Y and Gd compounds, respectively). Our work shows that the hydrothermal reaction in a phosphoric acid medium facilitates the formation of rare‐earth polyiodates. [ABSTRACT FROM AUTHOR]

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 cm 2 on the opening of 12 × 48 cm 2 ). 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. [ABSTRACT FROM AUTHOR]

Three novel lead(ii) borate–nitrates were obtained through a facile hydrothermal reaction by adjusting the concentrations of the starting materials, namely, [Pb6(μ4-O)4(BO3)](NO3) (1), H[Pb6(μ3-O)2(BO3)2](NO3)3 (2) and H[Pb8(μ4-O)3(μ3-O)(BO3)2](NO3)3 (3). All three compounds feature lead(ii) oxo borate layers that are separated by nitrate anions. The 2D [Pb6(μ4-O)4(BO3)]+ layer parallel to the ab plane in 1 is built from 1D [Pb6(μ4-O)4]4+ chains along the a axis and bridging borate anions. The 2D H[Pb6(μ3-O)2(BO3)2]3+ layer in 2 which is perpendicular to the b axis is composed of “isolated” Pb2+ and tetranuclear [Pb4(μ3-O)2]4+ clusters interconnected by bridging BO3 groups. The [Pb8(μ4-O)3(μ3-O)(BO3)2]2+ (011) layer in 3 is composed of two types of lead(ii) oxo chains, namely, 1D chains of [Pb4(μ4-O)2]4+ and 1D chains of [Pb4(μ4-O)(μ3-O)]4+, both elongated along the a axis, which are further interconnected by bridging borate anions. This study also demonstrates that a small change in the concentration of the starting materials could result in a product with a different density of the π-conjugated planar units. [ABSTRACT FROM AUTHOR]

• NaMoO 3 (IO 3) is the first example of molybdenum(VI) iodate with 1D chain-like structure featuring a large birefringence (0.208@1064 nm). • Both 1D [MoO 3 (IO 3)]- anionic chain in NaMoO 3 (IO 3) and 3D [MoO 3 (IO 3)]- anionic framework in γ-KMoO 3 (IO 3) are assembled from 0D Λ-shaped cis -MoO 4 (IO 3) 2 units. • The polar 3D γ-KMoO 3 (IO 3) exhibits the largest SHG response (12 × KDP) among AMoO 3 (IO 3) family as well as a high LIDT value (52 × AGS). [Display omitted] Herein, we reported two alkali metal molybdenum(VI) iodates, namely, NaMoO 3 (IO 3) and γ-KMoO 3 (IO 3) with 1D and 3D [MoO 3 (IO 3)]− anionic architectures, respectively. The novel 1D chain in NaMoO 3 (IO 3) and the 3D network in γ-KMoO 3 (IO 3) are constructed by the 0D Λ-shaped cis -[MoO 4 (IO 3) 2 ]4− building units interconnected by bridging IO 3 − anions as well as the corner-sharing of oxo anions. Importantly, the polar γ-KMoO 3 (IO 3) exhibits a very large second-harmonic generation (SHG) effect of 12 × KH 2 PO 4 (KDP) under 1064 nm laser radiation, a high laser-Induced damage threshold value (52 × AgGaS 2), and a moderate birefringence of 0.087@1064 nm, whereas the centrosymmetric NaMoO 3 (IO 3) has a large birefringence of 0.208@1064 nm. This study further proves the useful route of exploring promising optical materials via assembling the 0D basic building units into higher dimensional anionic architectures. [ABSTRACT FROM AUTHOR]

A new thiogermanate–thioantimonate, namely, [AEPH2][GeSb2S6]·CH3OH (1) (AEP = N-(2-aminoethyl)piperazine) has been solvothermally synthesized, whose structure features a one-dimensional anionic ribbon of [GeSb2S6]n2n− built of the firstly observed tetranuclear {GeSb3S11} cluster as secondary building unit. The photocatalytic study indicated that 1 was able to degrade Rhodamine B under visible irradiation. [ABSTRACT FROM AUTHOR]

Systematic explorations of new phases in the AI–InIII–IV–O system by hydrothermal reactions led to five new compounds, namely, AIn(IO3)4(A = Li, Na), Rb3In(IO3)6and A2HIn(IO3)6(A = Rb, Cs). The structure of AIn(IO3)4(A = Li, Na) contains one-dimensional [In(IO3)4]−chains separated by Li+or Na+cations. In both compounds, each In3+cation is octahedrally coordinated by six IO3−anions, neighboring In3+cations are interconnected by bidentate bridging iodate anions into 1D chains. The structures of Rb3In(IO3)6and A2HIn(IO3)6(A = Rb, Cs) all feature isolated [In(IO3)6]3−anions with alkali metal ions (and H+ions) as spacers. Both optical diffuse reflectance spectrum measurements and band structure calculations based on DFT methods indicate that LiIn(IO3)4, NaIn(IO3)4, and Rb2HIn(IO3)6are insulators. [ABSTRACT FROM AUTHOR]

SrGe2B2O8 (I) and Sr3Ge2B6O16 (II) are synthesized by solid state reaction of stoichiometric mixtures of SrCO3, GeO2, and H3BO3 (Pt crucible, 900 °C, 3 d). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]