Design of NO2 photoacoustic sensor with high reflective mirror based on low power blue diode laser

An NO2 photoacoustic sensor system with a high reflective mirror based on a low power blue diode laser is developed in this work. The excitation power is enhanced by increasing the number of reflections. Comparing with a traditional photoacoustic system, the pool constant is improved from 300.24(Pa·cm)/W to 1450.64(Pa·cm)/W, and the signal sensitivity of the photoacoustic sensor is increased from 0.016 μV/ppb to 0.2562 μV/ppb. The characteristics of temperature and humidity of the new photoacoustic sensor are also obtained, and the algorithm is adjusted to provide a quantitative response and drift of the resonance frequency. The results of this research provide a new method and concept for further developing the NO2 photoacoustic sensors.

A high quality surface finish grinding process to produce total reflection mirror for x-ray fluorescence analysis

Total reflection x-ray fluorescence analysis is applied to trace element detection in liquid for effective environmental monitoring.This analytical approach requires x-ray total reflection mirrors.In order to achieve high sensitivity element detection,the mirrors require high surface quality for high x-ray reflectivity.Surface finishing for x-ray mirrors is typically conducted through a series of abrasive processes,such as grinding and polishing,and is thus time consuming.The purpose of this study is to streamline and enhance the surface finishing process based on unique high quality grinding techniques for the production of x-ray total reflection mirrors.

Cleaning of two mirrors in the first mirror unit using radiofrequency capacitively coupled plasma

First mirror(FM)cleaning,using radio frequency(RF)plasma,has been proposed to recover FM reflectivity in nuclear fusion reactors such as the International Thermonuclear Experimental Reactor(ITER).To investigate the influence of simultaneous cleaning of two mirrors on mirror cleaning efficiency and uniformity,experiments involving single-mirror cleaning and dual-mirror cleaning were conducted using RF capacitively coupled plasma in the laboratory.For the test and simultaneous cleaning of two mirrors,the FM and second mirror(SM),both measuring 110 mm×80 mm,were placed inside the first mirror unit(FMU).They were composed of 16 mirror samples,each with a dimension of 27.5 mm×20 mm.These mirror samples consist of a titanium-zirconium-molybdenum alloy substrate,a 500 nm Mo intermediate layer and a 30 nm Al_(2)O_(3) surface coating as a proxy for Be impurities.The cleaning of a single first mirror(SFM)and the simultaneous cleaning of the FM and SM(DFM and DSM)lasted for 9 h using Ar plasma at a pressure of 1 Pa.The total reflectivity of mirror samples on the DSM did not fully recover and varied with location,with a self-bias of−140 V.With a self-bias of−300 V,the total reflectivity of mirror samples on the SFM and DFM was fully recovered.The energy dispersive spectrometer results demonstrated that the Al_(2)O_(3) coating had been completely removed from these mirror samples.However,the mass loss of each mirror sample on the SFM and DFM before and after cleaning varied depending on its location,with higher mass loss observed for mirror samples located in the corners and lower loss for those in the center.Compared with SM cleaning,the simultaneous cleaning of two mirrors reduced the difference between the highest and lowest mass loss.Furthermore,this mass loss for the mirror samples of the DFM facing the DSM was increased.This indicated that mirror samples cleaned face to face in the FMU simultaneously could influence each other,highlighting the need for special attention in future studies.

Further Improvement of Reflection Efficiency of a Magnetic Mirror and Replenishment against Loss of Escaping Deuteron Ions

We reported previously the idea to improve reflection-ability of a magnetic mirror by installing a cyclotron resonance space in the front part of the mirror. However, since the previous analysis was insufficient from the examination after that, we complement the following two things in this work: 1) A simpler procedure of design to make a supplemental magnetic mirror with the simplest magnetic configuration, compared with the procedure reported previously. 2) A peculiar characteristic arising only in reflection of a nonrelativistic charged particle (a deuteron ion).

SMONTE CARLO CALCULATION FOR CALIBRATION FUNCTIONS IN TOTAL REFLECTION X-RAY FLUORESCENCE SPECTROMETRY

Simulation approach includes such processes as photon emissions from X-ray tube with a spectral distribution, total reflection on the sample support, photoelectric effect in thin layer sample, as well as characteristic line absorption and detection. The calculation results are in agreement with experimental ones.

Development of aperiodic multilayer mirrors operated at W-Lβline for plasma diagnostics application

Multilayer interference mirrors play a pivotal role in spectroscopic diagnostic systems,which probe electron temperature and density during inertial confinement fusion processes.In this study,aperiodic Mo/B_(4)C multilayer mirrors of varied thick-nesses were investigated for X-ray plasma diagnostics at the 9.67-keV W-Lβline.The thickness distribution of the aperiodic multilayers was designed using the first Bragg diffraction condition and then optimized through a simplex algorithm to realize a narrow bandwidth and consistent spectral response.To enhance spectral accuracy,further refinements were undertaken by matching the grazing incidence X-ray reflectivity data with actual structural parameters.X-ray reflectivity measurements from the SSRF synchrotron radiation facility on the optimized sample showed a reflectivity of 29.7±2.6%,flat-band range of 1.3 keV,and bandwidth of 1.7 keV,making it suitable for high-temperature plasma diagnostics.The study explored the potential of predicting the 9.67 keV reflectivity spectrum using the fitting data from the grazing incidence X-ray reflectivity curves at 8.05 keV.Additionally,the short-term thermal stability of an aperiodic multilayer was assessed using temperature-dependent in situ X-ray measurements.Shifts in the reflectivity spectrum during annealing were attributed to interdiffusion and interfacial relaxation.The research team recommends the aperiodic Mo/B_(4)C multilayer mirror for operations below 300℃.

热像仪的光轴热稳定性仿真及拓扑优化研究

热成像仪由于工作环境较为恶劣,且自身发热量较大,容易导致热像仪光轴发生热偏移,严重影响其瞄准性能。为了提高红外热像仪的光轴热稳定性,以某型热像仪光轴敏感部件——折转镜为主要研究对象,研究其在不同环境温度条件下的光轴变化情况,并通过构建折转镜的有限元仿真模型以及试验测试系统,获得与试验数据一致性较好的有限元模型;以此为基础,采用基于变密度法的拓扑优化仿真技术,以刚度最大化为设计目标,以体积分数为约束,对折转镜座进行了拓扑优化设计。通过试验测试得出,优化设计的折转镜座的光轴高温偏移量由46.1″减小到25.5″,减小了44.7%,折转镜座的光轴低温偏移量由92.9″减小到51.0″,减小了45.1%,极大地提高了折转镜的光轴热稳定性。最后,将优化后的折转镜安装到某型热像仪中进行整机试验测试,热像仪整机的高温光轴偏移量由0.461 mrad减小到0.340 mrad,下降了26.2%,低温光轴偏移量由0.485 mrad减小到0.296 mrad,下降了39.0%,证明了仿真与拓扑优化模型的可行性与有效性,为后续红外热像仪整机的轻量化设计与性能提升奠定了基础。

螺钉预紧力变化对热像仪光轴稳定性的影响机理分析

热像仪工作环境中的冲击、振动载荷会导致热像仪光轴发生偏移从而影响成像质量。然而,当前的研究大多是分析基于模态叠加法获得的线弹性可回复变形对热像仪光轴冲振稳定性的影响,忽视了螺纹连接预紧力这一类非线性因素产生的不可逆变形造成的影响。为了探究螺纹连接预紧力对热像仪光轴振动稳定性的影响机理,建立了螺纹连接的详细模型,并采用瞬态结构动力学分析方法分析了振动导致螺纹连接预紧力减小的机理,仿真结果表明螺纹回转松动是导致预紧力减小的主要原因。进一步地,建立了螺纹连接等效模型分析了某型红外热像仪折转镜组螺钉预紧力变化对光轴偏移的影响,仿真结果表明反射镜镜座安装螺钉预紧力的变化是影响光轴偏移的主要因素,并通过实验验证了反射镜镜座安装螺钉预紧力的变化对第一反射镜偏移的影响,仿真结果和实验结果的误差在10%左右。最后基于螺纹连接详细模型从螺钉类型、螺纹接触面摩擦系数、支承面摩擦阻力、螺纹点胶四个方面分析了提高螺纹连接可靠性的措施,对实际生产过程中提高螺纹连接可靠性来保证热像仪光轴振动稳定性具有指导意义。

2.7~3.0μm波段高反镜反射率测量研究

中红外激光领域广泛使用高性能高反射光学元件,高反射率高精度测试技术是制备高性能反射光学元件的基础。针对2.7~3.0μm波段光学元件高反射率测量的实际需求,基于量子级联激光器建立了连续光腔衰荡反射率测试实验装置,通过优选2.7~3.0μm波段反射带内水汽吸收较弱的测试波长,分析空气中水汽吸收对衰荡时间和反射率测量的影响,并比较空气和氮气环境下反射率测量结果,实现了2.7~3.0μm波段高反镜反射率的准确测量,在反射率约99.95%时绝对测量精度优于2×10-5。实验结果显示,采用测试波长2.9μm并在测量时保证初始腔和测试腔腔长相同,无需使用氮气环境,直接在实验室空气环境可实现高反射率的精确测量。

多波段共孔径共焦面光学系统综述

多波段共孔径共焦面光学系统由于具备“一个光学镜头与一个探测器”的性能等效于传统光学系统(两个光学镜头搭配两个探测器)的能力,共口径共焦面成像能够实现视场与目标信息的匹配,为后续各波段信息融合提供前提条件。基于其光学元件数量少、体积小等特点,已经成为多波段光学系统新的研究方向。特别是环形反射式光学系统,凭借其体积小的优势,在枪瞄准镜、导引头、机器视觉等领域占据着重要的位置。本文以多波段共孔径共焦面光学系统发展为主线,分析了多波段共孔径共焦面光学系统的研究现状,全面介绍了多种类型的多波段共孔径共焦面光学系统,讨论了其光学结构特点、光学系统性能,并比较了这几种光学系统的优缺点,供光学设计领域研究人员共同研讨。

相机位姿求解的复用镜像约束法

针对参照物不在视场范围内的问题,提出一种复用镜像约束求解相机位姿的方法。具体步骤为:①依据相机位姿求解方法得到镜像相机位姿;②根据平面镜反射对称性构建单张图像镜像相机与相机位姿间线性约束关系;③复用镜像相机姿态,建立多张图像之间约束关系,在获得3张图像情况下,可得18个线性约束条件,提高相机位姿求解精度。试验结果表明:旋转矩阵和平移向量均误差分别为0.009°和1.866 mm,较对比方法,旋转矩阵均误差平均降低0.009°,平移向量均误差平均降低2.292 mm,且具有较强适应性。在真实试验中,平均重投影误差为0.492像素,优于对比方法,能够准确求解参照物不在视场范围内的相机位姿。

红外双反射镜折转光学系统的MTF测量

为了压缩总长度,红外热像仪普遍采用双反射镜折布局(U型)及箱式壳体,而现有传函仪仅能测量非折转布局(一字型)的光学系统的调制传递函数(Modulation Transfer Function,MTF),导致传函仪无法接到U型光学系统的像面,因此无法测量其MTF。为了解决该难题,本文采用光瞳衔接的方式,设计和加工一个中继镜组把U型光学系统的像面引出,通过测量组合系统的MTF,再计算出U型光学系统的MTF,从而解决其MTF测量的难题。然后使用6个同一个型号的红外热像仪对测量方法进行验证,在排除影响测量的干扰因素以后,通过测量组合系统MTF,再计算出U型光学系统的MTF。同时,在测量过程中发现5#、6#红外热像仪的U型光学系统的MTF下降较多,通过红外中心偏差测量仪的测量,发现第三、四镜片的中心偏差较大,故重新装调和控制,从而使U型光学系统的MTF有大幅提升。该方法为U型光学系统的MTF测量和性能提升提供了新的思路。

定日镜场的输出热功率计算模型

基于全国大学生数学建模竞赛赛题的定日镜场分布数据,根据太阳视运动方法,建立太阳跟踪运动模型、阴影挡光效率理论模型、相邻定日镜遮挡选取模型与镜面反射光锥模型,得出了定日镜场的年平均光学效率、年平均输出热功率,以及单位面积的镜面年平均输出热功率,最后通过输出功率的拟合结果展现了模型的合理性。

Reflectivity measurement technology of special high reflective mirrors and uncertainty analysis of measurement results

In order to meet the reflectivity measurement requirements of any incident angle at different points of the large size special high mirror,a rotating cavity ring-down spectroscopy high reflectivity measurement system was built,in which the rotation function of the resonant cavity was set,and the lifting and parallel travelling mechanism of the measured mirror was added.Furthermore,the uncertainty of the measurement results was analyzed and calculated.The results showed that the reflectivity of a high reflective mirror measured by the system was 99.9795%,the measurement accuracy reached the order of 10-6,and the combined standard uncertainty of reflectivity measurement was 0.0028%.Collectively,these results provide a detection guarantee for the maintenance of the large size special high mirror,and provide ideas and methods for the uncertainty analysis of measurement results of similar equipment parameters.

对镜图中的女性形象与“自我”意识

从古至今,镜子与女性有一种天然的亲密联系,也不乏呈现女性与镜子关系的文学艺术作品。文章主要以仕女对镜图为研究对象,从日常生活、画像写真、民间习俗等五个方面来探析古代女性的内心世界,以说明女性借助镜像逐渐深化对自我的认知,在无意识中流露出的“自我”意识。

Effects of deposition temperature on optical properties of MgF2 over-coated Al mirrors in the VUV

Both long-term environmental durability and high reflectance of protected-Al mirrors are of great importance for developing the optical instruments in the vacuum ultraviolet(VUV) applications. In this paper, the dependence of spectral property and environmental durability of MgF2 over-coated Al mirrors using a 3-step method on deposition temperature of the outermost MgF2 layer are investigated in detail. Optics(reflectance), structure(surface morphology and crystalline), and environmental durability(humidity test) are characterized and discussed. The results show that both optical and moistureresistant properties of MgF2 over-coated Al mirrors are dependent on MgF2 deposition temperature, and the optimal deposition temperature for the outermost MgF2 layer should be between 250℃ and 300℃ for MgF2 over-coated Al mirrors to have both reasonably high reflectance in the VUV spectral range and high moisture resistance for long lifetime applications.

Influence of Long-Term Plasma Irradiation on Metallic First Mirrors in HT-7 Tokamak

The first mirror （FM） samples made of polycrystal （PC） stainless steel （SS）, molybdenum （Mo） and tungsten （W） were mounted at different locations in HT-7 tokamak to investigate the surface modifications caused by erosion and deposition. The optical transmission characteristics of first mirror samples were measured by a spectrophotometer. It was found that different irradiation environment had different influences on the first mirror surfaces, especially with wave antenna nearby. In addition, the erosion made the reflectivity of FM degrade to some extents as a whole. But the deposition on the mirror influences more than erosion does. Comparing the mirrors of SS, W and Mo, irradiated in the same environment, the W-mirror had the least changes in reflectivity with regularity, while the SS-mirror had most serious changes.

Diffracted field distribution from a knife-edge truncated semi-Gaussian beam as an atomic （molecular） mirror

We investigate the diffraction characteristics of an incident Gaussian beam cut by a straight edge bounding a semi-infinite opaque plane using Kirchhoff scalar wave theory in the Fresnel limit, and propose a new and simple mirror scheme to reflect atoms by using the intensity gradient induced by a blue-detuned semi-Gaussian laser beam. The optical potential of the diffracted light of the knife-cut semi-Gaussian beam for 85 Rb atom and its spontaneous emission probability are calculated and compared with the performance of the evanescent-wave mirror. Our study shows that the optical potential of the diffracted light of the semi-Gaussian beam is far higher than that of the evanescent light wave, and the maximum normal velocity of the incident atoms can be far greater than that of the evanescent light wave under the same parameters, so the blue-detuned semioGaussian beam, as a novel atomic mirror, can be used to efficiently reflect cold atoms with a normal velocity of greater than 1 m/s. However, the intensity gradient （force） of the diffracted light of the semi-Gaussian-beam is much smaller than that of the evanescent light wave, so its spontaneous emission probability is greater than that from the evanescent-wave when the normal velocity of incident atoms is greater.

Ultrafast structural dynamics using time-resolved x-ray diffraction driven by relativistic laser pulses

Based on a femtosecond laser plasma-induced hard x-ray source with a high laser pulse energy(>100 mJ)at 10 Hz repetition rate,we present a time-resolved x-ray diffraction system on an ultrafast time scale.The laser intensity is at relativistic regime(2×10^(19)W/cm^(2)),which is essential for effectively generating K_(α)source in high-Z metal material.The produced copper K_(α)radiation yield reaches to 2.5×10^(8)photons/sr/shot.The multilayer mirrors are optimized for monochromatizating and two-dimensional beam shaping of Kαemission.Our experiment exhibits its ability of monitoring the transient structural changes in a thin film SrCoO_(2.5)crystal.It is demonstrated that this facility is a powerful tool to perform dynamic studies on samples and adaptable to the specific needs for different particular applications with high flexibility.

Hard X-ray focusing resolution and efficiency test with a thickness correction multilayer Laue lens

The multilayer Laue lens(MLL) is a diffractive focusing optical element which can focus hard X-rays down to the nanometer scale. In this study, a WSi_(2)/Si multilayer structure consisting of 1736 layers, with a 7.2-nm-thick outermost layer and a total thickness of 17 μm, is prepared by DC magnetron sputtering. Regarding the thin film growth rate calibration, we correct the long-term growth rate drift from 2 to 0.6%, as measured by the grazing incidence X-ray reflectivity(GIXRR). A one-dimensional line focusing resolution of 64 nm was achieved,while the diffraction efficiency was 38% of the-1 order of the MLL Shanghai Synchrotron Radiation Facility(SSRF) with the BL15U beamline.