激光驱动的光阴极研究

论述激光驱动的光阴极实验研究。包括直流高压真空试验系统,测试装置和实验结果及其分析讨论。LaB6、纯金属铜(Cu）和钐（Sm）以及半导体碲化铯(Cs2Te）三类有代表性光阴极的量子效率分别是6×10-4、3.8×10-4、11.6×10-4和(2~6)×10-4。利用KrF激光,18kV极间电压下饱和电流密度分别为70A/cm2、50 A/cm2、102A/cm2和57A/cm2。用多孔板法测得的归一化发射度约10pmm· mrad,相应的归一化亮度约1010A/m2· rad2。     

10MeV LIA强流电子束的聚焦

研究了10MeV直线感应加速器（LIA）的输出束在螺线管透镜作用下的聚焦特性。通过解非线性电子轨迹方程获得实验所需的磁场范围,并解析分析空间电荷效应、发射度、透镜球面像差和色散像差对最小焦斑直径的限制,同时,对束质心螺旋运动影响束聚焦的情况亦做了较为详细的分析。实验结果表明：在合适的螺线管聚焦磁场下,可获得直径≤6mm的电子束焦斑,与理论分析结果基本一致。     

Conceptual design of Hefei advanced light source

The conceptual of Hefei Advanced Light Source, which is an advanced VUV and Soft X-ray source, was developed at NSRL of USTC. According to the synchrotron radiation user requirements and the trends of SR source development, some accelerator-based schemes were considered and compared; furthermore storage ring with ultra low emittance was adopted as the baseline scheme of HALS. To achieve ultra low emittance, some focusing structures were studied and optimized in the lattice design. Compromising of emittance, on-momentum and off-momentum dynamic aperture and ring scale, five bend acromat (FBA) was employed. In the preliminary design of HALS, the emittance was reduced to sub nm·rad, thus the radiation up to water window has full lateral coherence. The brilliance of undulator radiation covering several eVs to keVs range is higher than that of HLS by several orders. The HALS should be one of the most advanced synchrotron radiation light sources in the world.     

基于CT算法的束团横向相空间测量

精确测量束团的发射度和横向相空间, 在高亮度电子束的产生和应用中具有重要意义. 传统测量方法在测量发射度时需要对束团在相空间内分布进行初始假设, 且只能给出相椭圆的twiss参数;基于CT(computerized tomography)算法的束团横向相空间测量方法无需先验假设, 能给出粒子在相空间内的真实分布, 测量结果更为精确. 介绍了基于CT算法的束团横向相空间测量的原理和初步实验结果, 并与四极透镜扫描法测量的结果进行了比较.     

合肥光源高亮度模式Lattice设计

介绍了一组合肥光源新高亮度模式的Lattice. 新的设计维持了储存环上所有元件和光束线位置不变,也没有加入新的元件. 取得了较低发射度. 所有直线节处的垂直方向β函数值都很小，适合插入件的运行. 跟踪计算表明新Lattice具有足够大的动力学孔径用于注入和储存粒子.     

Rumford and the Reflection of Radiant Cold: Historical Reflections and Metaphysical Reflexes

In this paper I examine the debate regarding the positive reality of cold: whether it is merely an absence of heat, or a quality or entity in its own right. Marc-Auguste Pictet stimulated this debate by showing that radiation from a cold object apparently could be focused by concave mirrors to cool another object some distance away from it. Pictet and other believers in material theories of heat, most notably Pierre Prevost, sought to understand this phenomenon as a result of the radiation of caloric in a peculiar arrangement. By contrast, Count Rumford saw in Pictet's experiment a genuine action of “frigorific rays,” and performed striking new experiments to support his view. For Rumford heat and cold radiation consisted in sound-like undulations in the ether, a mechanism compatible with his own vibration theory of heat, and discordant with the caloric theory. Rumford's strong arguments were overruled only because of the general dominance of the caloric theory of heat. However, Rumford did push the caloric theory to develop in a direction that eventually led to its downfall. I revisit this debate without preconceived notions of the metaphysical nature of cold and heat.     

LIA注入器发射度增长机理研究及其抑制措施

根据直线感应加速器(LIA)的特点采用了轴对称直流模型,结合E.P.Lee的理论导出了发射度增长的微分方程,提出了一种直线感应加速器发射度增长的机理,根据该机理计算了从均匀分布到高斯分布的演变过程中发射度增长的大小,指出直线感应加速器(LIA)注入器阶段束流发射度增长主要是由于非线性效应导致的束刨面电流密度分布变化引起的.根据研究结果,提出了相应的抑制发射度增长的措施.     

射频腔光阴极注入器发射度研究

 在激光驱动的光阴极注入器产生的高亮度电子束中，空间电荷引起发射度的增长。分析了射频腔中引起发射度增长的因素以及解决这个问题的办法——在射频腔的阴极附近加一个螺旋聚焦磁场进行补偿，也给出了补偿后电子束的发射度并和数值模拟结果进行比较，实验测试表明，所得结果比较符合。     

Equipartition and rate of energy exchanges in a model of a radiant cavity

Results of calculations on a model of a radiant cavity, performed in order to explore the relation between stochasticity and geometrical structure of phase space, are presented. The rate of energy exchanges, as indicator of stochasticity, is found to be quite effective. Furthermore, a trend to equipartition for such a quantity is observed at increasing energy, and this implies an increasing rigidity of high harmonic modes also in the stochastic regime of motion. Such a feature may be correlated to the shape of the spectrum which characterizes the radiant cavity with respect to nonlinear chains.     

光阴极电子枪中金属光阴极的热发射度研究

对光阴极电子注入器中金属光阴极的热发射度进行了理论研究.金属光阴极的热发射度由两部分构成.一方面对于理想平坦的阴极,光电子穿越表面势垒后有一定的残余动能,造成一定的热发射度,这部分前人已经做过一些理论研究.本文改进已有的模型,进一步给出了理想平坦光阴极的热发射度.另一方面,阴极表面的粗糙度将造成热发射度的增加,本文首次解析地分析了表面粗糙度对光阴极电子枪热发射度的影响,得到表面粗糙度造成的热发射度的估计公式.本文对金刚石车削后的铜、镁的表面形貌进行了测量,表明粗糙度造成的热发射度大约0.4mm·mrad.本文的热发射度理论能够较好的解释目前国际上铜、镁阴极的热发射度的测量结果.