微波激励源方案设计

在托卡马克实验装置上进行等离子体低杂波电流驱动和加热实验，需要输入兆瓦量级的微波功率。这是由多只大功率速调管并联运行而实现的，而这些速调管需要前级微波激励源进行驱动。我们目前使用的微波激励源经过十几年的使用，元器件老化和磨损严重，导致了整个设备工作性能的明显下降，不能满足低杂波电流驱动和加热实验的多管并联运行的实验要求。因此有必要设计一个新的微波激励源，工作部件全部采用固态微波器件，稳幅控制。模块化设计采用多路输出，新增加微波相位多路控制，以满足以后实验中低杂波电流驱动和加热两种不同工作方式的需求。     

Dark states and Aharonov-Bohm oscillations in multi-quantum-dot systems

We study the formation of dark states and the Aharonov-Bohm effect in symmetrically/asymmetrically coupled three-and four-quantum-dot systems.It is found that without a transverse magnetic field,destructive interference can trap an electron in a dark state.However,the introduction of a transverse magnetic field can disrupt the dark state,giving rise to oscillation in current.For symmetrically structured quantum-dot systems,the oscillation has a period of one flux quanta.But for asymmetrically structured dot systems,the period of oscillation is halved.In addition,the dephasing due to charge noise also blocks the formation of dark states,while it does not change the period of oscillation.     

Controlled Teleportation of Multi-Qudit Quantum Information

We present a controlled teleportation scheme for teleporting an arbitrary superposition state of an M-qudit quantum system. The scheme employs only one entangled state as quantum channel, which consists of the qudits from Alice, Bob and every agent. The quantum operations used in the teleportation process are a series of qudit Bell measurements, single-qudit projective measurements, qudit H-gates, qudit-Pauli gates and qudit phase gates. It is shown that the original state can be restored by the receiver only on the condition that all the agents collaborate. If any agent does not cooperate, the original state can not be fully recovered.     

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介绍了HL-2M装置低混杂波系统中3.7GHz微波激励源的设计。微波激励源设计为模块化形式,由3.7GHz点频固态源单元、功率分配器单元、功率放大器单元和现场控制器单元等组成。微波激励源有8路输出端口,每个端口的输出功率在0~10W范围内连续可调,并可以实现远程控制输出功率;采用取样鉴相锁相环技术使微波输出信号具有相位噪声低、频率稳定度高、杂散抑制好等优点。频偏1kHz时,相位噪声是-115dBc/Hz,频偏10kHz时,相位噪声是-117dBc/Hz,频偏100kHz时,相位噪声是-122dBc/Hz;输出频率稳定度≤0.03ppm/30min;杂散抑制≤-80dBc。     

Probabilistically implementing nonlocal operations between two distant qutrits

We propose a method to probabilistically implement a nonlocal operation, $% \exp {[}\i\xi U_{A}U_{B}{]}$, between two distant qutrits $A$ and $B$, where $% \xi \in [0,2\pi ]$ and $U_{A}$, $U_{B}$ are local unitary and Hermitian operations for qutrits $A$ and $B$ respectively. The consumptions of resource for one performance of the method are a single non-maximally entangled qutrit state and 1-trit classical communication. For a given $\xi $% , the successful probability of the method depends on the forms of both entanglement resource and Bob's partial-measurement basis. We systematically discuss the optimal successful probabilities and their corresponding conditions for three cases: adjustable entanglement resource, adjustable partial-measurement basis, adjustable entanglement resource and partial-measurement basis. It is straightforward to generalize the method for producing nonlocal unitary operations between any two $N$-level systems.     

Investigation of composite electromagnetic scattering from ship-like target on the randomly rough sea surface using FDTD method

Composite electromagnetic scattering from a two-dimensional (2D) ship-like target on a one-dimensional sea surface is investigated by using the finite-difference time-domain (FDTD) method. A uniaxial perfectly matched layer is adopted for truncation of FDTD lattices. The FDTD updated equations can be used for the total computation domain by choosing the uniaxial parameters properly. To validate the proposed numerical technique, a 2D infinitely long cylinder over the sea surface is taken into account first. The variation of angular distribution of the scattering changing with incident angle is calculated. The results show good agreement with the conventional moment method. Finally, the influence of the incident angle, the polarization, and the size of the ship-like target on the composite scattering coefficient is discussed in detail.     

Quantum thermal discord in a two-spin-1/2 XXZ model

We study the quantum discord in a two-spin-1/2 XXZ model in thermal equilibrium at temperature T in the presence of an external magnetic field B. Special attention is paid to the dependence of quantum discord on the temperature T and magnetic field B. It is found that quantum thermal discord is more robust than concurrence against temperature, in the sense that quantum thermal discord does not vanish at finite temperatures, but concurrence vanishes completely at a critical temperature.     

HL-2M 低杂波电流驱动系统研制

HL-2M 装置的 LHCD 系统已经完成了包括 2MW 波源、2MW 传输线和 4MW 天线的工程研制,该 系统参数指标为 3.7GHz/2MW/3s,使用 4 只 TH2103C1 型速调管。建成了 4 条 500kW 功率容量的传输线,研制 了 1 套 4MW 功率容量的低杂波天线,并完成了与系统配套的电源、微波源、传输部件、控保系统以及水冷、真 空、测量采集等辅助系统的研制。     

钴-聚吡咯-碳载PtNi燃料电池催化剂的制备及应用

采用脉冲微波辅助化学还原合成新型载体钴-聚吡咯-碳(Co-PPy-C)负载PtNi催化剂.利用透射电镜(TEM)和X射线衍射(XRD)研究了催化剂的结构和形貌,此外,利用循环伏安(CV)和线性扫描伏安(LSV)等方法测试了催化剂的电化学活性及耐久性. PtNi/Co-PPy-C催化剂的金属颗粒直径约为1.77 nm,催化剂在载体上分布均匀且粒径分布范围较窄. XRD结果显示, PtNi/Co-PPy-C中Pt(111)峰最强, Pt主要是面心立方晶格.CV结果显示,其电化学活性面积(ECSA)为72.5 m²·g^-1,明显高于商用催化剂Pt/C(JM)的56.9 m²·g^-1.为进一步考查催化剂耐久性,电化学加速5000圈耐久性测试后, PtNi/Co-PPy-C颗粒发生明显集聚, ECSA衰减率和0.9 V下比质量活性衰减率分别为38.2%和63.9%.此外,采用有效面积为50 cm²的单电池用于评价自制催化剂的性能,发现在70 ℃且背压为50 kPa时电池的性能最好,此时自制PtNi/Co-PPy-C催化剂制备膜电极(MEA)的最大功率密度达到523 mW·cm^-2.可见自制催化剂的电化学性能高于商用Pt/C(JM),在质子交换膜燃料电池(PEMFC)领域有一定的应用前景.     

HL-2M装置低混杂波电流驱动系统高精度数字温度测量仪的研制

为HL-2M低混杂波电流驱动系统研制了16路J型数字校准热电偶测温仪,可实现16通道温度测量,测温范围为0~250°C,测量范围内误差绝对值小于1°C,具有本地高清液晶显示温度值和电脑远程温度采集功能。该测温仪已成功用于HL-2M低混杂波加热系统的调试实验,对不同输出功率条件下高功率速调管输出腔温度进行了测量,保证了速调管运行的安全性。