China Spallation Neutron Source - an overview of application prospects

The China Spallation Neutron Source (CSNS) is an accelerator-based multidisciplinary user facility to be constructed in Dongguan, Guangdong, China. The CSNS complex consists of an H^－ linear accelerator, a rapid cycling synchrotron accelerating the beam to 1.6 GeV, a solid-tungsten target station, and instruments for spallation neutron applications. The facility operates at 25 Hz repetition rate with an initial design beam power of 120 kW and is     

The electrical transport behavior of Zn-treated Zn1-xMnxO bulks

Zn1-xMnxO bulks have been prepared by the solid state reaction method. Zn vapor treatment has been carried out to adjust the carrier concentration. For the Zn treated Zn1-xMnxO bulks, analysis of the temperature dependence of resistance and the field dependence of magnetoresistance demonstrates that the bound magnetic polarons (BMPs) play an important role in the electrical transport behavior. The hopping of BMPs dominates the electrical conduction behavior when temperature is below 170 K. At low temperature,paramagnetic Zn1-xMnxO bulks show a large magnetoresistance effect,which indicates that the large magnetoresistance effect in transition-metal doped ZnO dilute magnetic semiconductors is independent of their magnetic states.     

Determination of the sites of Fe atoms in Fe-substituted Mn12

In this paper neutron diffraction experiments were performed for Fe-substituted Mn12 in order to determine the sites of Fe atoms. The results of structure refinements for the sample with our accessed highest Fe content showed that all Fe atoms occupied Mn（3） sites in the Mn12 skeleton. The x-ray absorption fine structure experiments as well as multiple scattering simulations gave the same result. Thus we concluded that Fe atoms only occupied Mn（3） sites. This conclusion also means that Fe-substituted Mn12 series only includes the four single-molecule magnets of [Mn12-xFexO12（CH3COO）16（H2O）4]·2CH3COOH·4H2O （x = 1, 2, 3, and 4）, denoted by Mn11Fe1, Mn10Fe2, MngFe3, and Mn8Fe4, respectively.     

Quantum state measurement in double quantum dots with a radio-frequency quantum point contact

We study the dynamics of two electron spins in coupled quantum dots （CQDs） monitored by a quantum point contact （QPC） detector. Their quantum state can be measured by embedding the QPC in an LC circuit. We derive the Bloch-type rate equations of the reduced density matrix for CQDs. Special attention is paid to the numerical results for the weak measurement condintion under a strong Coulomb interaction. It is shown that the evolution of QPC current always follows that of electron occupation in the right dot. In addition, we find that the output voltage of the circuit can reflect the evolution of QPC current when the circuit and QPC are approximately equal in frequency. In particular, the wave shape of the output voltage can be improved by adjusting the circuit resonance frequency and bandwidth.     

EFFECT OF MANGANESE SUBSTITUTION IN R2AlFe16-x Mnx(R=Y,Ho,Nd AND Pr)COMPOUNDS ON STRUCTURAL AND MAGNETIC PROPERTIES

The structural and magnetic properties of R₂AlFe_16-xMn_x(0≤x≤8 for Y,Ho,0≤x≤10 for Pr, 0≤x≤16 for Nd)compounds have been investigated by means of X-ray diffraction and magnetization measurements.The R₂AlFe_16-xMn_x compounds have a hexagonal Th₂Ni₁₇-type structure for R=Y and Ho, and a rhombohedral Th₂Zn₁₇-type structure for Nd and Pr.With increasing x,the unit-cell volumes have a small increase initially,followed by a greater linear increase.The Curie temperature and the saturation magnetizati on of these compounds show marvelous drop with increasing x.Compensation point was observed in the temperature dependence of the magnetization for Ho₂AlFe₁₂Mn₄ compound.     

MAGNETIC PROPERTIES OF Pr2Co17-x Mx ( M＝Ga,Si) COMPOUNDS

The influence of Ga or Si substitution for Co on the structural and magnetic properties of Pr₂Co₁₇ compounds is investigated. All samples studied here are single phase and have the rhombohedral Th₂Zn₁₇-type structure. The unit-cell volume is found to increase linearly by the substitution of Ga for Co,but reduce by the substitution of Si for Co in Pr₂Co₁₇ compounds. In Pr₂Co_17-x M_x, the Curie temperature decreases monoto nically with increasing at an approximate rate of 153K per Ga atom and 175K per Si atom. The saturation magnetic moment of Pr₂Co_17-x M_x ( M=Ga,Si) decreases with increasing x. The rates of the decrease are larger than that expected as a simple dilution. For Pr₂Co_17-xSi_x ,the spin reorientation transition is observed above room temperature. The spin-reorientation temperature Tsrfirst decreases with increasing Si content and then increases at higher x values (x>2). The spin reorientat ion behavior is interpreted by the competition between the Pr and Co sublattice anisotropies. The easy magnetization direction in Pr₂Co_17-xGa_x compounds is perpendicular to the c-axis, and no spin reorientation transition is observed.     

Magnetic properties and magnetocaloric effect of the Cr-based spinel sulfides Co_(1-x)Cu_xCr_2S_4

Crystallographic structure, magnetic properties, and magnetic entropy change of the Cr-based spinel sulfides Co_(1-x)Cu_xCr_2S_4(x = 0–0.8) have been investigated. All these compounds crystallize into the cubic spinel structure, the Cu substitution shrinks linearly the lattice constant at a ratio of 0.0223 per Cu atom in the unit cell, and enhances linearly the Curie temperature and the spontaneous magnetization at the rates of 18K and 0.33 μB/f.u. per Cu atom in the unit cell,respectively. All these compounds show a typical behavior of second order magnetic transition, and a room temperature magnetic entropy change of 2.57 J/kg·K is achieved for Co_(0.4)Cu_(0.6)Cr_2S_4.     

Calculations of radioactivity and afterheat in the components of the CSNS target station

This paper shows the calculations of radioactivity and afterheat in the components of the China Spallation Neutron Source (CSNS) target station, with the Monte Carlo codes LAHET, MCNP4C and the multigroup code CINDER'90. These calculations provide essential data for the detailed design and maintenance of the CSNS target station.     

MAGNETIC PROPERTIES OF Dy2Fe17-xCrx AND Er2Fe17-xCrx(x=0-3)COMPOUNDS

The crystal structure and magnetic properties of R₂Fe_17-xCr_x(R=Dy,Er,0≤x≤3) compounds have been investigated by me ans of X-ray diffraction and magnetization measurements. These compounds have hexagonal Th₂Ni₁₇-type structure. The unit-cell volumes decrease with the increase of Cr concentration x. The Curie temperature T_c of the Er₂Fe_17-xCr_x compounds increases from 320 K for x=0 to 403 K for x=1.0 and then decreases with further increase of x. The Cur ie temperat ure T_c of Dy₂Fe_17-xCr_x compounds increases from 364 K for x=0 to 435 K for x=1.0 and then decreases with further increase of x. The saturation magnetization of these compounds shows an approximately linear decrease with the increase of x. Spin reorientation transitions occur s in Er₂Fe_17-xCr_x(x=2.0 and 3.0).     

Ho2Fe17Cx的结构与磁性

用快速急冷方法制备了Ho₂Fe₁₇C_x化合物,研究了它们的形成、结构与磁性。这些化合物在高温下是稳定的,随C含量的增加,晶体结构由六角Th₂Ni₁₇型转变为菱形Th₂Zn₁₇型。测量了Ho₂Fe₁₇C_x化合物在1.5K和室温下的饱和磁化强度,得到每个Fe原子磁矩近似与C含量无关。C原子的引 关键词：