脉冲软X光辐射三种材料的喷射冲量实验研究

在强光一号脉冲加速器上进行了国内首次的实验室软X光辐射三种材料的喷射冲量研究。结果表明，在能量为(0.2～0.33)keV、平均脉宽为39ns左右的X光辐射下，对灰漆、白漆和硬铝，在能注量分别为(92～152)J/cm2、(115～136)J/cm2和(163～192)J/cm2时，它们的冲量耦合系数分别为(0.61～0.80)Pa·s/(J·cm-2)、(0.58～0.97)Pa·s/(J·cm-2)和(0.61～0.84)Pa·s/(J·cm-2)。     

氢气对薄反应区湍流火焰详细火焰结构影响研究

氢是一种非常有前景的清洁可再生能源载体.掺氢燃料预混稀燃是当前开发清洁高效的低排放燃气轮机最重要的能源转化方式之一。本文基于预混CH₄/H₂/air本生灯火焰,对氢气掺混影响下的湍流火焰详细火焰结构进行了测量和表征。实验采用CH₂O和OH基平面激光诱导荧光(PLIF,Planar Laser Induced Fluorescence)同步测量技术,获得了火焰预热区、反应区以及已燃区的详细火焰结构信息。本文对反应区和预热区火焰厚度进行了提取和统计。研究表明,氢气对火焰反应区、预热区均有明显作用。结果表明,掺氢小幅度增厚反应区厚度,但能够比较明显地降低预热区厚度。     

笼中阴离子基团对Nd~(3+)掺杂C12A7粉体红外发光的影响

采用自蔓延燃烧法制备了不同Nd3+掺杂浓度的具有笼状结构的12Ca O·7Al2O3(C12A7∶x%Nd3+)粉体材料。在808 nm波长的激发下,观测到了位于887,1 069,1 340 nm附近的3个近红外发射峰,分别归属于Nd3+的4F3/2→4IJ/2(J=9,11,13)跃迁。Nd3+掺杂摩尔分数达到0.5%时,红外光发射较强,且没有观察到杂质相。在H2气氛下对样品进行1 300℃热处理之后,笼中OH-和H-浓度增加,笼子发生畸变,晶粒尺寸变大,样品的结晶性变好。通过在空气下热处理,减少了高能振动基团OH-的数目,进一步增强了近红外光发射。变温光致发光谱测量结果表明,C12A7∶x%Nd3+样品具有较高的热激活能,在红外激光器上有潜在的应用前景。     

Analysis of the microbunching instability in a mid-energy electron linac

Microbunching instability usually exists in the linear accelerator (linac) of a free electron laser (FEL) facility. If it is not controlled effectively, the beam quality will be damaged seriously and the machine will not operate properly. In the electron linac of a soft X-ray FEL device, because the electron energy is not very high, the problem can become even more serious. As a typical example, the microbunching instability in the linac of the proposed Shanghai Soft X-ray Free Electron Laser facility (SXFEL) is investigated in detail by means of both analytical formulae and simulation tools. In the study, a new mechanism introducing random noise into the beam current profile as the beam passes through a chicane-type bunch compressor is proposed. The higher-order modes that appear in the simulations suggest that further improvement of the current theoretical model of the instability is needed.     

X射线自由电子激光试验装置

X射线自由电子激光试验装置(以下简称"SXFEL试验装置")是中国第一台X射线相干光源,其输出波长小于9 nm。这台基于0.84 GeV直线加速器、以掌握装置相关技术和实验演示种子型自由电子激光(FEL)级联与短波长回声型FEL为主要目标的自由电子激光装置,于2020年11月通过国家验收。本文将介绍SXFEL试验装置的基本情况和主要进展。     

基于Faraday效应的光纤陀螺频率特性评估方法

由于角振动台的振动频率有限,无法实现光纤陀螺的高带宽测试。提出了基于Faraday效应的光纤陀螺频率特性评估方法,采用正弦电流激励下的Faraday相位差等效Sagnac相位差,解决了激励信号输出频率有限的问题。根据光纤中的Faraday效应原理,分析了该评估方法与光纤陀螺角振动台测试方法的等效性;搭建了评估系统,使用该评估系统来模拟某型号光纤陀螺的信号处理过程,进行等效评估实验,得到了等效评估的光纤陀螺闭环带宽为9 kHz,实现了高带宽光纤陀螺的频率特性评估测试,为改善光纤陀螺的动态特性提供了有效的验证平台。     

12CaO·7Al2O3/5CaO·3Al2O3：Sm3+新型红色荧光粉的制备及发光性质

采用自蔓延燃烧法制备了不同Sm³⁺掺杂浓度的12CaO·7Al₂O₃（C12A7：x%Sm³⁺）荧光粉。在404 nm近紫外光激发下,观察到了位于565,599,648 nm附近的3个光发射峰,分别归属于Sm³⁺的⁴G_5/2→⁶H_J/2（J=5,7,9）能级跃迁。随着Sm³⁺掺杂浓度增加,红光发射强度呈现了先增大后减小的规律,优化的Sm³⁺掺杂摩尔分数为1.5%,发光的浓度猝灭效应可归因于Sm³⁺之间发生了交叉弛豫过程。采取混相策略,通过降低初始粉体的煅烧温度至900℃获得了12CaO·7Al₂O₃/5CaO·3Al₂O₃：1.5%Sm³⁺（C12A7/C5A3：Sm³⁺）混相荧光粉,进一步提高了红光发射强度。利用变温光致发光谱计算得到混相样品的热激活能约为200 meV,结果表明该混相荧光粉具有良好的热稳定性。     

褶皱管束流能量稳定器(英文)

输出脉冲稳定性的需求对驱动自由电子激光产生的电子直线加速器装置束流稳定性提出了严格的要求,包括电子束平均能量、峰值流强、束团到达时间抖动和横向位置抖动等参数。基于正在建设的大连相干光源用户装置,探讨了最近提出的褶皱管用作能量稳定器的可行性。采用解析计算和数值模拟结合的方法,结合大连相干光源直线加速器的设计,在设计参数条件下能量稳定性至少提升10%。同时提供了褶皱管尾场设计的一般步骤。     

Simulation studies on laser pulse stability for Dalian coherent light source

Dalian Coherent Light Source will use a 300 MeV LINAC to produce fully coherent photon pulses in the wavelength range between 150–50 nm by high gain harmonic generation free electron laser(FEL)scheme.To generate stable FEL pulses,a stringent tolerance budget is required for the LINAC output parameters,such as the mean beam energy stability,electron bunch arrival time jitter,peak current variation and the transverse beam position ofset.In order to provide guidance for the design of the Dalian Coherent Light Source,in this paper,the sensitivity of FEL pulse energy fluctuation to various error sources of the electron bunch was performed using intensive start-to-end FEL simulations.     

Rapid classification of copper concentrate by portable laser-induced breakdown spectroscopy combined with transfer learning and deep convolutional neural network

This paper investigates the combination of laser-induced breakdown spectroscopy 〔LIBS〕 and deep convolutional neural networks 〔CNNs〕 to classify copper concentrate samples using pretrained CNN models through transfer learning. Four pretrained CNN models were compared. The LIBS profiles were augmented into 2D matrices. Three transfer learning methods were tried. All the models got a high classification accuracy of >92%, with the highest at 96.2% for VGG16. These results suggested that the know...