Physical design of scanning gantry for proton therapy facility

A proton therapy facility based on a linac injector and a slow cycling synchrotron is proposed.To achieve effective treatment of cancer,a scanning gantry is required.The flexible transmission of beam and high beam position accuracy are the most basic requirements for a gantry.The designed gantry optics and scanning system are presented.Great efforts are put into studying the sensitivity of the beam position in the isocenter to the element misalignments.It shows that quadrupole shift makes the largest contribution and special attention should be paid to it.     

Investigation of the energy resolution with a RETGEM detector

A novel Micro-pattern gaseous detector (MPGD), thick GEM with electrodes made of a resistive material (RETGEM) is presented. In this paper we mainly investigate the energy resolution of a RETGEM in Ar+CO_2 with different gas mixtures. The results indicate that an energy resolution 30% in single and double mode can be obtained. The existence of an optimum energy resolution is discussed.     

微型平像场近红外光谱仪的消杂散光设计

设计和研制了结构紧凑、杂散光低的微型平像场近红外光谱仪。在分光系统设计中不采用附加杂散光遮挡装置的常规方法,而是在准直物镜前设置一块直径为8．5mm的平面反射镜,通过调节平面反射镜改变入射光束的空间角,使光束全部被准直镜接收,不再产生旁光,从而有效地消除系统内的杂散光,使仪器整体杂散光水平降低了1．13％。另外,该光谱仪选择线阵CCD作为探测器件,不再设置冷却系统也避免了平面光栅带有扫描旋转机构。由于使用CCD作探测器和新的消杂散光设计方法,该光谱仪实现了微型化。     

在化学教学中培养学生变量控制能力的实施和分析

设计受控实验是科学实验实证的重要手段,这种科学探究的核心能力,也是教育部在《普通高中化学课程标准(2017年版2020年修订)》中对学生能力的评价之一.在分析学生能力现状、教材内容后,经过教学实施,充分利用教材,帮助学生认识变量控制要素,达成能系统地综合应用变量控制解决实际问题的教学目标.     

矩形毛细微槽横截面上气液分界面形状理论分析

对背面有热流输入的矩形毛细微槽群横截面上的气液分界面形状进行了理论分析,在一定条件下对Wayner蒸发模型进行简化,根据等壁温条件推出蒸发薄液膜区域热流密度近似为定值,通过流体动力学理论推导出了微槽横截面薄液膜区域液膜厚度变化的关系式,并与Wayner蒸发模型的计算结果进行了比较。进一步提出了全新的交界线区域长度的判定方法,根据蒸发薄液膜区域总换热量计算得到蒸发薄液膜区域的长度,交界处接触角,以及固有弯月面区域的曲率半径,从而最终得出了微槽横截面整个气液分界面的形状曲线,理论分析表明:槽宽、热流密度、过热度等因素对蒸发薄液膜区域长度、接触角以及固有弯月面曲率半径等参数有较大的影响。     

Excitation and propagation of axisymmetric longitudinal guided waves in pipes immersed in infinite liquid media

The transient elastodynamic responses of the vacuum-filled and liquid-filled pipes surrounded by infinite liquid to external axisymmetric forces are simulated by employing the acoustic-structural coupled finite element method. The time-frequency distributions of the transients waveforms are obtained by the short-time Fourier transform （STFT）. Then the influence of the distribution of the external forces on the excitation of the guided waves is analyzed. The study shows that the L（O, 2） mode in the vacuum-filled pipe surrounded by the liquid is suitable for the pipe inspection because it is the fastest mode in a weakly dispersive and at- tenuative region of frequency. And it can be excited with high efficiency in the above region of frequency if the axisymmetric external force is applied on the inner or outer surface of the pipe axially. Analogously, the L（0,3） and L（0,4） modes in the liquid-filled pipe surrounded by the liquid are suitable for the pipe inspection.     

Normally-Ordered Time Evolution Operator for Mass-Varying Harmonic Oscillator and Wigner Function of Squeezed Number State

For investigating dynamic evolution of a mass-varying harmonic oscillator we constitute a ket-bra integration operator in coherent state representation and then perform this integral by virtue of the technique of integration within an ordered product of operators. The normally ordered time evolution operator is thus obtained. We then derive the Wigner function of u（t）｜n,〉, where ｜n〉 is a Fock state, which exhibits a generalized squeezing, the squeezing effect is related to the varying mass with time.     

Investigation of the energy resolution with a RETGEM detector

A novel Micro-pattern gaseous detector （MPGD）, thick GEM with electrodes made of a resistive material （RETGEM） is presented. In this paper we mainly investigate the energy resolution of a RETGEM in Ar＋CO2 with different gas mixtures. The results indicate that an energy resolution 30% in single and double mode can be obtained. The existence of an optimum energy resolution is discussed.     

First experimental research of the bunch compressor at CAEP

Magnetic bunch compressor is one of the key technologies on the path to next generation accelerator driven facilities. In this paper we report the design principles and the first experimental research of the bunch compressor developed at Chinese Academy of Engineering Physics （CAEP）. The length of the bunch after compressor is found to be about 0.7 ps （rms） and the peak current exceeds 500 A when operated in the optimized condition. The sensitivity of the bunch length on the phase of the acceleration field and magnetic field of the bunch compressor was also measured and analyzed.     

A revisit to the neutron skin thickness of neutron-rich nuclei in the statistical abrasion ablation model

The cross sections of the fragments produced in the projectile fragmentation reactions of the even calcium isotopes from A=36 to A=52 are calculated using the statistical abrasion ablation model.The neutron skin thickness are studied by investigating the fragments isotopic cross section distributions.The neutron-skin thicknesses of the calcium isotopes have a good linear correlation to the peak positions of their fragment isotopic cross section distributions.The correlation between the neutron skin thickness and the neutron density distributions of 48 Ca is investigated by introducing a parameter to adjust the diffuseness parameter in the fermi-type density distribution.