High structural and optical quality 1.3 mu m GaInNAs/GaAs quantum wells with higher indium content grown by molecular-beam expitaxy

High structural and optical quality 1.3 mu m GaInNAs/GaAs quantum well (QW) samples with higher (42.5%) indium content were successfully grown by molecular-beam epitaxy. The cross-sectional transmission electron microscopy measurements reveal that there are no structural defects in such high indium content QWs. The room-temperature photoluminescence peak intensity of the GaIn0.425NAs/GaAs (6 nm/20 nm) 3QW is higher than, and the full width at half maximum is comparable to, that of In0.425GaAs/GaAs 3QW, indicating improved optical quality caused by strain compensation effect of introducing N to the high indium content InGaAs epilayer. (C) 2005 American Institute of Physics.

1.3 mu m high indium content (42.5%) GaInNAs/GaAs quantum wells grown by molecular beam epitaxy

High structural and optical quality 1.3 mu m GaInNAs/GaAs quantum well (QW) samples with 42.5% indium content were successfully grown by molecular beam epitaxy. The growth of well layers was monitored by reflection high-energy electron diffraction (RHEED). Room temperature photoluminescence (PL) peak intensity of the GaIn0.425NAs/GaAs (6 nm / 20 nm) 3QW is higher than, and the full width at half maximum (FWHM) is comparable to, that of In0.425GaAs/GaAs 3QW, indicating improved optical quality due to strain compensation effects by introducing N to the high indium content InGaAs epilayer. The measured (004) X-ray rocking curve shows clear satellite peaks and Pendellosung fringes, suggesting high film uniformity and smooth interfaces. The cross sectional TEM measurements further reveal that there are no structural defects in such high indium content QWs. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

高温气冷堆He载气中H_2和CO转化实验研究

研究了H＿2和CO在CuO－ZnO＿Al＿2O＿3催化床中转化成H＿2O和CO＿2的实验装置和实验结果，论证了不同床层工作温度、系统压力、杂质浓度、流量及露点温度等因素对氧化铜床工作性能的影响；测得了H＿2和CO在CuO－ZnO－Al＿2O＿3床上的转化特性曲线等变化规律，获得了转化容量、工作周期和转化效率等实验数据，确定了最佳运行参数。结果表明，使用CuO＿ZnO－Al＿2O＿3床可使净化后的H＿2和CO的体积分数都小于2×l0￣（－6），满足高温气冷堆的净化要求。为高温气冷堆中氧化铜床装置提供了可靠的设计数据。

Material Growth and Device Fabrication of GaAs Based 1.3μm GaInNAs Quantum Well Laser Diodes

Material growth and device fabrication of the first 1.3μm quantum well （QW） edge emitting laser diodes in China are reported. Through the optimization of the molecular beam epitaxy （MBE） growth conditions and the tuning of the indium and nitrogen composition of the GalnNAs QWs, the emission wavelengths of the QWs can be tuned to 1.3μm. Ridge geometry waveguide laser diodes are fabricated. The lasing wavelength is 1.3μm under continuous current injection at room temperature with threshold current of 1kA/cm^2 for the laser diode structures with the cleaved facet mirrors. The output light power over 30mW is obtained.

近阈值下He原子的双电离实验反冲离子动量分析

利用最新发展起来的适用于低能电子入射的反应显微成像谱仪,对电子轰击He原子近阈值的双电离过程进行了研究,实验测量了反应后4个粒子的全部动量,获得了五重微分截面及出射粒子间的关联信息。着重分析了在入射电子束与出射电子构成的平面内,3个均分系统剩余能量的电子出射角关联关系,并与理论计算进行了比较。研究表明,当两个电子反向出射时,第3个电子垂直于这两个电子动量方向出射的几率最大。在1个电子垂直于平面出射时,通过理论计算结果与平面内出射角分布的比较,发现DS6C理论能够较好地描述实验结果。

经典过垒模型在Xe~(q+) +He碰撞中的应用

采用位置灵敏探测和飞行时间技术研究了高电荷态Xe离子 (q =15 ,17,19,2 1,2 3)与He原子碰撞中双电子转移截面与单俘获截面比随入射离子电荷态的变化规律。提出一步过程假定 ,对扩展的经典过垒(ECB)模型进行了修正 ,利用修正模型计算得到的单、双电子转移绝对截面与Andersson等人和Selberg等人的实验结果符合得很好 ,所得截面比与本实验得到的双电子转移截面与单电子俘获截面符合得比较好。

高电荷态Xe离子与He原子碰撞中的电子转移过程研究

采用位置灵敏探测和飞行时间技术研究了高电荷态Xe离子 (q =1 5 ,1 7,1 9,2 1 ,2 3)与He原子碰撞中双电子转移截面与单电子转移截面比随入射离子电荷态的变化规律 .提出一步过程假定 ,对扩展的经典过垒 (ECB)模型进行了修正 ,利用修正模型计算得到的单、双电子转移绝对截面与Andersson等人和Selberg等人的实验结果很好符合 ,所得截面比与本实验得到的双电子转移截面与单电子俘获截面比较好符合

Na离子和Cl离子引起He原子直接多重电离过程的研究

利用 2～ 8MeV的Naq+、Clq+( q =2 ,3,4 ,5 )轰击氦原子 ,对碰撞的直接多重电离过程进行研究。实验采用反冲离子 -散射离子飞行时间符合技术 ,通过反冲离子飞行时间谱区分不同价态反冲离子 ;利用静电偏转和位置灵敏探测技术区分不同电荷态散射离子 ;结合CAMAC -PC多参数获取系统得到一定价态散射离子所对应的反冲离子电荷态分布谱 ;经分析该谱得到直接多重电离截面与直接单电离截面之比R2 1。讨论了R2 1随入射离子速度和电荷态的变化关系

Double ionization of helium in collision with 20-500-keV/amu Cq+ and Oq+ (q=1-3) ions

Target ionization and projectile charge changing were investigated for 20-500 keV/u Cq+, Oq++He (q=1-3) collisions. Double- to single-ionization ratios R-21 of helium associated with no projectile charge change (direct ionization), single-electron capture, and single-electron loss were measured. The cross-section ratio R-21 depends strongly on the collision velocity v, the projectile charge state q, and the outgoing reaction channel. Meanwhile, a model extended from our previous work [J. X. Shao, X. M. Chen, and B. W. Ding, Phys. Rev. A 75, 012701 (2007)] is presented to interpret the above-mentioned dependences. Good agreement is found between the model and the experimental data.

Search for signature inversion in the pi i(13/2) circle times upsilon i1(3/2) bands in Au-182,Au-184,Au-186

Search for low-spin signature inversion in the pi i(13/2) circle times nu i(13/2) bands in odd-odd Au-182,Au-184,Au-186 has been conducted through the standard in-beam gamma-spectroscopy techniques. The experiments for Au-182 and 186Au have been performed in the Japan Atomic Energy Agency (JAEA) via the Sm-152(Cl-35,5n)Au-182 and Yb-172(F-19,5n)Au-186 reactions, respectively. A study of Au-184 has been made using a multi-detector array GASP in LNL, Italy, via the Tb-159(Si-29,4n)Au-184 reaction. The pi i(13/2) circle times nu i(13/2) bands in these three nuclei have been identified and extended up to high-spin states. In particular, the inter-band connection between the pi i(13/2) nu i(13/2) band and the ground-state band in 184 Au has been established, leading to a firm spin-and-parity assignment for the pi i(13/2) circle times nu i(13/2) band. The low-spin signature inversion is found in the pi i(13/2) circle times nu i(13/2) bands in Au-182,Au-184,Au-186 according to our spin-assignment and the signature crossing observed at high-spin states.

Measurements of bremsstrahlung spectra of Lanzhou ECR Ion Source No. 3 (LECR3)

In order to diagnose the electron cyclotron resonance (ECR) plasma, electron bremsstrahlung spectra were measured by a HPGe detector on Lanzhou ECR Ion Source No. 3 at IMP. The ion source was operated with argon under various working conditions, including different microwave power, mixing gas, extraction high voltage (HV), and so on. Some of the measured spectra are presented in this article. The dependence of energetic electron population on mixing gas and extraction HV is also described. Additionally, we are looking forward to further measurements on SECRAL (Superconducting ECR Ion Source with Advanced design at Lanzhou).

Transfer ionization of helium in collisions with Cq+ and Oq+ (q=1-3)

Cross-section ratios sigma(TI)/sigma(SC) of transfer ionization (TI) to single capture (SC) of Cq+- and Oq+-He (q = 1 - 3) collisions in the energy range of 15-440 keV/u (0.8-4.2 v(Bohr)) are experimentally determined. It is shown that sigma(TI)/sigma(SC) strongly depends on the projectile velocity, and there is a maximum for E(keV/u)/q(1/2) approximate to 150. Combining the Bohr-Lindhard model and the statistical model, a theoretical estimate is presented, in reasonable agreement with the experimental data when E(keV/u)/q(1/2) > 35.

Atomic Structures and Radiative Properties of He-like Ions in Debye Plasmas

A detailed investigation of plasma screening effects on atomic structure and transition properties are presented for He-like ions embedded in dense plasma environment. Multi-configuration Dirac-Fock calculations were carried out for these ions by considering a Debye-Huckel potential. A large-scale relativistic configuration-interaction method is adopted to calculate transition energies and transition probabilities and to allow for a systematic improvement of the calculations. Comparison of the presently calculated results with others, when available, is made.

A 3 Tesla Superconducting Magnet for Hall Sensor Calibration

A 3 T superconducting magnet with a 70 mm diameter warm bore and energy storage of 47 kJ has been successfully fabricated and tested, which can be used to calibrate Hall sensors in high magnetic field as well as conduct superconducting experiments. The magnet consists of three solenoid coils and an iron yoke. The homogeneity of the magnetic field in the region of interest (ROI) is +/- 6.0 x 10(-5). The coils of the magnet were fabricated with NbTi-Cu superconducting wire and the stray magnetic field is shielded by an iron yoke. The coils and yoke are fully immersed in a helium vessel. The optimized structural design, stress and quench simulation, fabrication and test results are presented in this paper.