同步辐射在ICF研究中的应用

介绍同步辐射在ICF研究中的应用,对多种ICF实验诊断用软X光探测元器件及设备利用北京同步辐射装置(BSRF)-3W1B作能量响应绝对标定.首先采取透射光栅分光和软X光面陈CCD观测记录,对光源进行性能研究.在50—1500eV能区分7个能段,通过不同材料的前置滤片抑制高次谐波,获得单色性好于95%的单色光.采用美国IRD公司生产的AXUV-100硅光二极管作次级标准探测器.利用BSRL的反射率计靶室及其相关联动调束系统,获得连续可调的单色光标定束.在该束线上进行了多轮实验.获得大量探测器标定数据用于ICF实验研究,提高了实验精度.     

北京同步辐射装置软X光束线通量谱的绝对测量与计算

在北京同步辐射装置(BSRF)上用全吸收平行板充氙电离室作一级标准探测器,对硅光电二极管(AXUV—100)的效率在光子能量5—6.5keV进行了标定,建立了二级标准探测器;AXUV—100硅光电二极管在50eV-6keV有很好的线性响应,将其在硬X射线波段已标定的效率曲线外推到软X射线波段,并对BSRF3B1A和4B9B光束线在软X射线波段光子通量谱进行了初步地测量,测量结果与理论计算结果较为符合.在3B1A软X光学实验站,利用二级标准探测器对用于惯性约束聚变(ICF)的软X光探测器的灵敏度进行了标定,并取得了满意的结果.     

惯性约束聚变软X射线在线标定系统概念设计

长期以来，惯性约束聚变（ICF）研究软X射线诊断科学仪器设备的元器件标定工作主要依赖同步辐射光源X射线辐射计量站进行。该类装置通常与用于开展ICF研究的大型激光装置分处两地，难以满足ICF研究软X射线元器件实时实地的标定应用需求。另外，由于同步辐射和ICF激光等离子体产生的X射线辐射特性存在较大差异，同步辐射计量站的标定结果事实上也不能完全反映元器件在ICF实验应用中的计量响应特性。本文首先介绍一种基于单光学元件的软X射线紧凑型无谐波光源单色化技术，以此为基础提出研制基于ICF激光等离子体X射线源的同源、同几何位形、双束比较校准的多能量通道光源单色化系统，用于ICF应用软X射线元器件的在线标定。新系统一方面可望满足ICF软X射线元器件实时实地的标定应用需求；另一方面，其提供的标定光束的技术特征将最大可能地接近ICF激光等离子体X射线辐射本身。配备相应的X射线二极管（XRD）和标准探测器之后，该系统将形成一套具有在线自校准功能的新型多通道δ能量响应软X射线能谱仪。     

基频光腔靶辐射温度定标

研究腔靶辐射温度和X光耦合效率与靶结构及激光辐照条件的依赖关系。利用神光-Ⅱ基频光(波长1．053μm,能量3～5kJ／8束,脉宽0．6～0．9ns)辐照金腔靶。采用软X光能谱仪及平响应探测器分别测量腔靶诊断口辐射X光功率谱及其能量角分布。同时,利用五针孔时、空分辨成像技术对腔靶诊断口发射软X光进行实验观测,给出辐射温度推算中需要的等效诊断口面积修正因子。在北京同步辐射软X光标定站,对上述诊断用软X光探测元器件进行了全谱范围(0．05～1．5kev)的绝对标定,以提高X光辐射功率和黑腔辐射温度的诊断精度．     

软X光能谱仪探测元件响应曲线标定

报道了软X光能谱仪探测元件的能量响应曲线标定工作.实验利用北京同步辐射装置–3W1B束线及反射率计靶室,在束流40—80mA、贮存环电子能量2.2GeV专用光运行模式下,在150—1500eV能区的四个能段,做了铝阴极X射线二极管、滤光片及掠入射平面反射镜能量响应标定实验.通过实验数据比对及分析,最终给出X射线二极管在不同能量段最大可能的测量误差范围.     

软X射线条纹相机的静态性能研究

软X光扫描相机是对软X光时间持性进行研究的主要诊断工具,我们利用 同步辐射作为光源,对它的静态性能：能量响应、增益等性能进行了相对标定,给出了软X 光条纹相机的能量响应曲线和增益特性曲线,并与利用B.L.Henke的经验公式计算给出的响 应曲线比较,其结果与理论较符合。     

软X射线条纹相机静态能量响应的绝对标定

软X光扫描相机是对软X光时间特性进行研究的主要诊断工具.利用同步辐射作为光源,采用美国NIST的标准,对它的静态能谱响应进行了绝对标定,给出了X光条纹相机在100—1000eV能区的绝对谱响应,不确定度小于23%.     

软X光能谱仪探测元件晌应曲线标定

报道了软X光能诺仪探别元件的能量响应曲线标定工作．实验利用北京同步辐射装置-3W1B束经及反射率计靶室，在束流40—80mA、贮存环电子能量2.2GeV专用光运行模式下，在150—1500eV能区的四个能段，做了铝阴极X射线二权管、滤光片及擦入射平面反射镜能量响应标定实验，通过实验数据比对及分析，最终给出X射线二极管在不同能量段最大可能的测量误差范围。     

同步辐射标定平面镜反射率不确定度分析方法研究

为了提高多通道软X射线能谱仪的测量精度,2009年在北京同步辐射(BSRF)软X束线源上对多种材料的掠入射平面镜的反射率进行了标定.在标定实验的基础上,对光源的单色性、高次谐波以及源强稳定性、探测器响应一致性和数据采集统计误差等多项不确定因素进行了评估,给出了反射率的修正方法和相应的不确定度分析结果.     

在同步辐射软X射线能区硅光电二极管的自标定

在同步辐射软X光能区(50—2000eV)进行了硅光电二极管的自标定实验.因为消除了二极管的“死区”并采用很薄层的SiO₂作窗,使得可以用简单的模型来分析实验结果.由实验测得的光电流,计算出硅光电二极管的量子效率,并求得入射同步辐射的光通量.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.