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Yu X.,Institute of High Energy | Meng L.,Institute of High Energy | Niu X.,Institute of High Energy
Zhenkong Kexue yu Jishu Xuebao/Journal of Vacuum Science and Technology | Year: 2010

The geometry of the 8 mm band TE01-HE11 mode converter with the improved waveguide axis sinusoidal curvature of the gyroklystron was modeled and numerically calculated on the basis of the mode coupling theory for the purpose of structure design optimization. And a novel TE01-HE11 mode converter was simulated and designed with the software package HFSS. The calculated and simulated results show that the transformation efficiency of the TE01-HE11 mode conversion system, made-up of these two converters, can be higher than 99% within 3% of the bandwidth at 30. 5 GHz. The hot test data indicate that satisfactory conversion of the TE01-HE11 mode can be obtained.

Teng B.,Qingdao University | Yu Z.-H.,Qingdao University | Zhong D.-G.,Qingdao University | Li J.-H.,Qingdao University | And 6 more authors.
Rengong Jingti Xuebao/Journal of Synthetic Crystals | Year: 2012

AFM (atomic force microscope) and optical microscopy were used to observe the surface topography of rapidly grown KH2PO4 crystals. It was found that two-dimension nucleation growth mechanism was more likely to occur at high growth temperature on {100} face. In the experimental conditions of this paper, the average height of macrosteps on {100} face is about 2.34 nm and the terraces widths of macrosteps are quite different from each other. Step accumulation and step bending induced by impurity ions were observed, and the interaction mechanism between impurity ions and growth steps was discussed. Dislocations in rapidly grown KDP crystal were studied by the white-beam synchrotron X-ray topography.

Zhong D.,Qingdao University | Teng B.,Qingdao University | Kong W.,Qingdao University | Li J.,CRYSTECH Inc. | And 6 more authors.
Materials Chemistry and Physics | Year: 2015

New mixed crystal of Yb: Y0.78Lu0.22VO4 with Yb ion concentration of 0.3 at% was grown by Czochralski method. Transmission synchrotron X-ray topography implies that this mixed crystal follows a rotational growth pattern. Crystal structure of this crystal was determined by X-ray diffraction. It showed that this crystal possesses a tetragonal zircon structure (ZrSiO4, space group I41/amd), as YVO4 and LuVO4 do. Thermal properties of this crystal were characterized by measuring its specific heat, thermal expansion coefficients and thermal conductivities. The specific heat was determined to be 0.500 J g-1 K-1 at 293 K. The average linear thermal expansion coefficients were calculated to be α11 = 1.73 × 10-6 K-1 and α33 = 9.43 × 10-6 K-1, over the temperature range of 300-777 K. The thermal conductivities were calculated to be κ11 = 5.47 W m-1 K-1 and κ33 = 6.64 W m-1 K-1 at 303 K. Continuous-wave (cw) laser test on Yb: Y0.78Lu0.22VO4 was conducted at room temperature in the wavelength range of 1035.7-1048.3 nm, and a 13.5% optical-to-optical efficiency was achieved. The good thermal properties of Yb:Y0.78Lu0.22VO4 mixed crystal and its attractive cw laser performance make it very suitable for practical applications. © 2015 Elsevier B.V.

Zhong D.,Qingdao University | Teng B.,Qingdao University | Kong W.,Qingdao University | Jiang X.,Qingdao University | And 3 more authors.
Zhongguo Xitu Xuebao/Journal of the Chinese Rare Earth Society | Year: 2015

Mixed Yb:YxLu1-xVO4 crystal was grown by Czochralski method. XRD showed that this crystal possessed tetragonal ZrSiO4 structure. The lattice parameters are a=b=0.7126(2) nm, c=0.6259(7) nm. Crystal defects were revealed by chemical etching and Synchrotron Radiation X-ray Topography. It was found that dislocations and low angle grain boundaries were dominated defects. Read-Shockley formula was used to analyze the low angle grain boundaries that changed in directions. It was found that there were dislocations with Burgers vector [100] in mixed Yb:YxLu1-xVO4 crystals. The formation reasons of dislocations and low angle grain boundaries were discussed. It is believed that the temperature fluctuation during crystal growth and annealing heat treatment, gave rise to the lattice deformation, which might induce dislocations and low angle grain boundaries. Thus, the processes of mixed crystal growth need more accurate control. ©, 2015, Chinese Rare Earth Society. All right reserved.

Teng B.,Qingdao University | Zhong D.-G.,Qingdao University | Cao L.-F.,Qingdao University | Wang S.-H.,Qingdao University | And 5 more authors.
Applied Mechanics and Materials | Year: 2013

KDP crystals were rapidly grown from point seeds by temperature reduction method. White-beam synchrotron radiation X-ray topography was used to study the growth imperfections in KDP crystals. Strong dislocation bunches originate on the prismatic faces of the seed were found. The producing reason of these dislocation bunches was discussed. Sector boundary between the prismatic sector and pyramid sector caused by the unbalance distribution of trivalent metal ions were also observed and analyzed. © (2013) Trans Tech Publications, Switzerland.

Zhong D.-G.,Qingdao University | Bing T.,Qingdao University | Yu Z.-H.,Qingdao University | Wang S.-H.,Qingdao University | And 3 more authors.
Crystal Research and Technology | Year: 2011

The regeneration of Z-cut KDP crystals is explored by analyzing the growth of thin surface layers formed. The structural defects and crystalline perfection of the thin surface layers are evaluated by white-beam synchrotron radiation topography and high-resolution X-Ray diffraction respectively. It shows that the thin surface layers have the same crystal structure as KDP crystal. There are large numbers of defects in thin surface layers and the crystalline quality is very poor. The growth velocity of thin surface layers is firstly accurately measured by a newly-designed in-situ crystal growth observation setup. It is found that the growth velocity of the thin surface layers strongly depends on the flow rate of the growth solution. The hindering effect of pyrophosphate (K4P2O7) on the growth of the thin surface layers is discussed. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhong D.,Qingdao University | Teng B.,Qingdao University | Cao L.,Qingdao University | Fei Y.,Qingdao University | And 5 more authors.
Optical Materials | Year: 2014

Mixed crystal of Yb:Yx Lu1 - x VO4 was grown by Czochralski method. Defects of dislocations and sub-grain boundaries in Yb:Y0.71Lu0.29VO4 single crystal were studied by using chemical etching and synchrotron X-ray topographic methods. Some of the three intersecting boundaries were revealed by chemical etching method in Yb:Y0.71Lu0.29VO4 crystal. The generalized Read-Shockley formula for intersecting boundaries was introduced to verify the one-to-one correspondence between etching pits along these sub-boundaries and edge dislocations with Burgers vectors of 〈1 0 0〉. Synchrotron X-ray topographic confirmed that the dominating imperfections in the studied Yb:Y0.71Lu0.29VO4 single crystal are a variously developed block structure and sub-grain boundaries. © 2013 Elsevier B.V. All rights reserved.

Zhong D.-G.,Qingdao University | Teng B.,Qingdao University | Yu Z.-H.,Qingdao University | He L.-X.,City University of Hong Kong | And 5 more authors.
Crystal Research and Technology | Year: 2012

Potassium dihydrogen phosphate (KDP) crystals were restrained to grow in two dimensions only, using a specially designed platform. This enables us to grow the blanks of frequency conversion elements that satisfy type-II phase matching direction out of a type-II phase-matched seed crystal. Synchrotron radiation topography was used to study the growth mechanism of these profiling grown KDP crystals. It is found that both dislocation growth mechanism and layer growth mechanism were involved in the growing process. Inclusions, growth striations and dislocations were the main defects that influenced the crystalline quality of these crystals. High-resolution X-ray diffraction was employed to study the lattice integrality of the crystal. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pan W.,Institute of High Energy
IPAC 2014: Proceedings of the 5th International Particle Accelerator Conference | Year: 2014

Many interesting proposals and programs for accelerator driven subcritical facilities for waste transmutation(ADS) in the world have been developed, which is to speed up from the basic study to the real facility in recent years, and the significant progresses in the development of accelerator technologies, in particular, in superconducting RF linacs for ADS have been made, but the key technologies in high power proton accelerator are still severe challenges which call for the close international cooperation. Copyright © 2014 CC-BY-3.0 and by the respective authors.

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