空间太阳望远镜主镜精密温度控制方案介绍

通过光-机-热集成分析，用简单可靠的热控方法，对空间太阳望远镜直径为1m的主镜进行了热设计：采用周边绝热、将热量从正面传导到背面，再设计装有控温回路和热管的集热板，以及与卫星平台辐射器冷板连接散热，保证了主镜的温度水平和稳定性；在主镜压紧结构前设置挡光板，减少压紧结构引起的主镜温度不均匀．结果表明，利用智能型高准确度控温仪和加热回路的优化设计实现主构架均匀性热设计，采用高传热性能热管排散准直镜热反射面极高热流密度，可以消除主镜周围热环境对主镜温度影响的结论．     

热补偿腔镜热变形的研究

采用ANSYS有限元软件,系统模拟了强激光作用下的热补偿全反射硅镜的温度场分布和热变形.详细地研究了不同区域的热补偿和不同的热补偿功率大小对镜面变形峰谷值的影响.结果表明有效的热补偿对镜面变形峰谷值有很大的影响,在非光照区进行热补偿可以大大降低镜体的温度梯度,从而明显减小镜面变形的峰谷值.热补偿腔镜特别适合于机载或车载军用强激光器.     

高能量密度激光器腔镜有限元分析

 通过对高能量密度激光器运行过程中腔镜存在的表面及背面吸收热量的有限元分析,得出腔镜表面在不同吸收热流密度和约束条件条件下热变形分布。指出提高腔镜反射率,改变腔镜的基底材料以及优化腔镜的约束条件是显著降低腔镜反射面变形的有效途径。     

真空罐内应用的太阳模拟灯阵热设计

为了解决太阳模拟灯阵整体放在真空罐内使用时的导热问题,采用热管导热的方案,设计了专门的氙灯导热机构。计算了液氮系统的导热能力,结果显示,真空罐液氮冷却系统的温度升高ΔT为2074 1 K,小于其过冷度4 K,表明真空罐液氮冷却系统完全可以将太阳模拟灯阵的热量导出。采用热管导热技术,设计了导热机构,用有限元分析法进行了热仿真分析,分析结果表明,氙灯阴阳极温度维持在100 ℃左右,氙灯灯泡维持在655 ℃左右,满足氙灯正常工作的温度条件;积分器和反射镜组件温度维持在200 ℃左右,椭球镜温度维持在135 ℃左右,亦满足正常工作的温度条件,从而验证了热设计的正确性。     

大口径轻量化主镜的温度场等效模型理论计算

针对大口径望远镜主镜在环境温度变化和太阳辐照变化引起的温度场变化进行了理论分析,根据圆柱坐标下设立的非稳态热传导方程和边界条件,利用分离变量法和格林函数法求解了主镜的温度场分布。为了验证求解的有效性,利用求得的温度场解析式和有限元软件分别分析了2.8 m口径望远镜实心主镜,反射面径向温度分布具有良好的一致性。表明该理论解析式能够较好地反映主镜反射面的温度场分布。将轻量化主镜进行无筋板的薄型镜热模型等效,并分别对两种镜子的温度场进行仿真计算,以此验证等效模型的正确性。轻量化主镜温度场的等效理论计算结果在主镜的早期设计研究阶段具有良好的参考价值。     

强激光热管冷却镜的数值研究

 为消除强激光微沟道水冷镜冷却水压力和扰动对激光输出稳定性的影响和冷却水道对冷却水流量的限制,提出并设计了热管冷却镜。采用ANSYS有限元软件,模拟计算了相同结构下镜面热吸收为12 W/cm²,实心镜、微沟道水冷镜与热管冷却镜连续工作60 s下镜体温升和镜面变形量。计算结果表明：热管冷却镜镜面轴向位移最大峰谷值为0.109 4 μm,微沟道水冷镜最大峰谷值为0.845 μm,实心镜镜面最大峰谷值为1.33 μm,热管冷却镜对镜面变形改善显著。     

Design and analysis of radial support for a large-aperture rotating mirror

Effective support ways can contribute to the good performance of a large-scale optical system. An adjustable three-segment surface-contact radial support way is proposed to facilitate the movement process of a large-scale rotating mirror. Under a most dangerous working condition, the supporting angle is optimized by a two-step optimization method, which makes the maximum PV value reduce by 10.26% relative to that before optimization and that the maximum von Mises stress has a very little increase. Moreover, the coupling analysis of thermal stress in the rotating mirror caused by some thermal factors, such as motor heat, is carried out to validate the assembly design. The supporting way, as an effective radial mounting for dynamic optical elements, can be valuable for the reference of similar opto-mechanical design.     

Simultaneous measurement of thethermal diffusivity and specific heat near phase transitions

A technique for measuring the absolute thermal diffusivity along with the relative specific heat is introduced which is readily adaptable to a wide variety of applications. The thermal diffusivity and specific heat of CoO, near the antiferromagnetic transition; of SrTiO₃, near the structural phase transition; of Cr, near the first-order SDW-paramagnetic transition; and of EuO, near the ferromagnetic Curie point were measured. Except for SrTiO₃, the thermal diffusivities are found to mirror the specific heats, with no evidence for anomalies in the thermal conductivities, contrary to some earlier reports. A step increase in the thermal conductivity is observed on passing through the structural transition of SrTiO₃ from below which is of the same relative size as the step decrease of specific heat at T_c.     

相变制冷复合镜研究

提出一种新的复合式腔镜结构,利用硅镜(钼镜)和铜镜的优点,避免它们的缺点,可以有效地减小热畸变.对钼、铜复合镜作了与硅镜的对比实验.实验结果表明钼、铜复合镜的热畸变比硅镜的约小一半.     

相变制冷复合镜研究

 提出一种新的复合式腔镜结构,利用硅镜（钼镜）和铜镜的优点,避免它们的缺点,可以有效地减小热畸变。对钼、铜复合镜作了与硅镜的对比实验。实验结果表明钼、铜复合镜的热畸变比硅镜的约小一半。     

空间相机光机结构导热特性分析与计算

对空间相机进行热光学分析,必须掌握相机的非稳态温度场和热致位移场。要计算温度场,必须对其光机结构的热特性有一定的了解。对空间相机的各个主要光学组件（ 前、后组校正镜组、球面与平面反射镜、窗口玻璃组件） 建立简化传热模型,进行等效热阻计算,给出了它们的温差表达式,分析了各镜组件的导热特性,为热光学分析的温度场计算工作提供条件。     

Output beam drift and deformation in high-power COIL

During the operation of a chemical oxygen iodine laser (COIL) with an unstable resonator of a large Fresnel number, as the output power increases, an instability of the output laser beam will appear, behaving mainly as far-field beam spot drift and deformation. In order to interpret this phenomenon, thermal expansion analysis on the scraper with finite element analysis method and a simulation of the output beam mode of this kind of laser by the method of Fast Fourier Transform were developed. From the experimental measurement and the calculation, we proposed that the presence of the nonuniform temperature distribution of scraper causes the front surface of the scraper to tilt and bulge due to thermal expansion. As the output power is increasing, all the mirror surfaces, especially the scraper's, will absorb more and more heat, causing thermal expansion of the mirror front surface to occur more seriously, thus resulting in the tilting and deformation of the far-field beam spot. The initial misalignment of the direction is also an important factor leading to the far-field beam spot drift and deformation.     

Finite Element Analysis Of Thermal Characteristics in Continuous Wave Long Wavelength Surface Emitting Lasers (I): Dielectric Cavity Structures

We numerically analyzed the thermal characteristic in continuous wave (cw) GalnAsP/InP surface emitting lasers with dielectric multilayer mirrors by using finite element method. From the simulation of temperature distribution in cw devices, we found that MgO/Si multilayer mirror which has a high thermal conductivity is effective for heat sinking; the thermal resistance of device using MgO/Si mirror is nearly half of that using SiO₂/Si one, almost independently of their thicknesses. It was also indicated that the optimum design for other structural parameters, especially the thickness of active region, is important to effectively suppress the temperature increase. The minimum threshold current was estimated to be 3 mA under cw condition for the active region diameter of 4 μm and thickness of 0.5 μm.     

腔镜热变形对非稳腔光场特性的影响

 研究了高功率气体激光器中谐振腔腔镜热变形效应。采用时间离散化方法,利用虚共焦折叠非稳腔3维物理光学负载模型和ANSYS热效应计算程序,将光腔稳态模式的快变过程与镜面变形的慢变过程耦合起来,研究了真实器件的腔镜变形和光场模式的相互作用;计算给出了16 s热变形下硅镜和石英镜面输出功率的下降程度和远场光束质量的退变程度：在16 s热效应下,硅镜实际光斑半径与理想光斑半径的比值变化小于1.5,而石英镜值变化达到4,可知长时运行下选用硅镜明显优越于选用石英镜。     

Optimizing X‐ray mirror thermal performance using matched profile cooling

To cover a large photon energy range, the length of an X‐ray mirror is often longer than the beam footprint length for much of the applicable energy range. To limit thermal deformation of such a water‐cooled X‐ray mirror, a technique using side cooling with a cooled length shorter than the beam footprint length is proposed. This cooling length can be optimized by using finite‐element analysis. For the Kirkpatrick–Baez (KB) mirrors at LCLS‐II, the thermal deformation can be reduced by a factor of up to 30, compared with full‐length cooling. Furthermore, a second, alternative technique, based on a similar principle is presented: using a long, single‐length cooling block on each side of the mirror and adding electric heaters between the cooling blocks and the mirror substrate. The electric heaters consist of a number of cells, located along the mirror length. The total effective length of the electric heater can then be adjusted by choosing which cells to energize, using electric power supplies. The residual height error can be minimized to 0.02 nm RMS by using optimal heater parameters (length and power density). Compared with a case without heaters, this residual height error is reduced by a factor of up to 45. The residual height error in the LCLS‐II KB mirrors, due to free‐electron laser beam heat load, can be reduced by a factor of ～11 below the requirement. The proposed techniques are also effective in reducing thermal slope errors and are, therefore, applicable to white beam mirrors in synchrotron radiation beamlines.     

Wave Instabilities of a Collisionless Plasma in Fluid Approximation

Wave properties and instabilities in a magnetized, anisotropic, collisionless, rarefied hot plasma in fluid approx‐imation are studied, using the 16‐moments set of the transport equations obtained from the Vlasov equations. These equations differ from the CGL‐MHD fluid model (single fluid equations by Chew, Goldberger, and Low [5,9]) by including two anisotropic heat flux evolution equations, where the fluxes invalidate the double polytropic CGL laws. We derived the general dispersion relation for linear compressible wave modes. Besides the classic incompressible fire hose modes there appear four types of compressible wave modes: two fast and slow mirror modes – strongly modified compared to the CGL model – and two thermal modes. In the presence of initial heat fluxes along the magnetic field the wave properties become different for the waves running forward and backward with respect to the magnetic field. The well known discrepancies between the results of the CGL‐MHD fluid model and the kinetic theory are now removed: i) The mirror slow mode instability criterion is now the same as that in the kinetic theory. ii) Similarly, in kinetic studies there appear two kinds of fire hose instabilities ‐ incompressible and compressible ones. These two instabilities can arise for the same plasma parameters, and the instability of the new compressible oblique fire hose modes can become dominant. The compressible fire hose instability is the result of the resonance coupling of three retrograde modes ‐ two thermal modes and a fast mirror mode. The results can be applied to the theory of solar and stellar coronal and wind models (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

高重复频率水冷Nd:YAG激活镜放大器的温度特性

为解决高重复频率大能量激光放大器的热管理问题,采用数值模拟与实验分析的方法,对背面水冷Nd:YAG激活镜放大器的流体散热进行了研究.基于低雷诺数k-ε湍流模型,建立了流-固共轭传热多物理场藕合分析模型,对比分析了近壁面处理方法对流体流动、对流扩散和热传导过程及温度分布的影响,分析研究了不同冷却液流量和泵浦参数对流场特性、激光介质温度和波前分布的影响.数值模拟表明:激光介质的温度分布与固液边界层内的黏性作用密切相关,且冷却液的热扩散主要发生在100μm范围内;激光介质的热沉积分布中心对称,而温度分布沿水流方向不对称,最大温升位于出水口端且基本保持不变;增益介质前表面的温度分布与介质的波前分布随冷却液流量非线性变化,而随泵浦参数线性变化;实验结果与数值模拟符合较好.     

腔镜变形对平凹稳腔激光振荡模式影响的数值研究

 用Fox-Li迭代法研究了激光谐振腔镜面变形对激光振荡模式的影响, 给出了几种镜面变形条件下的激光谐振腔自再现模,即镜面上光场振幅和位相分布的模拟结果。对平凹稳定腔,为获得严格的基模激光振荡,应将这种镜面变形控制在1/20波长范围内;若镜面变形超过1/10波长,则该谐振腔不存在严格的基模自再现模。同时,高功率激光腔镜的边缘冷却方式将造成较大的镜面形状变化,从而影响激光光束质量。     

干涉检测中环境温度引起的镜面变形分析

在达到1 nm量级的光学元件表面面形干涉检验时,被检元件由温度变化引起的面形偏差是不能忽略的.分析了干涉检验时存在的各种环境温度情况,对不同情况下被检元件内外温度分布进行了仿真,并将温度场作为静力学分析的载荷条件,进行了镜面温度变形分析.计算出了带支撑的直径为300 mm凸球面透镜在不同温度分布下的镜面变形量,并通过球...     

Thermo-optically driven adaptive mirror for laser applications

An adaptive mirror is investigated that is based on the deformation of the reflective surface due to thermal expansion of an underlying material that can be locally heated with an external light source. The mirror is made from a glass plate coated with a 1-mm-thick layer of a material with a large thermal expansion coefficient that was finally sputter coated with a thin gold film. The adaptive mirror is thermo-optically heated with an incandescent lamp. To generate the desired temperature pattern an aperture mask is used. The deformation of the adaptive mirror is measured with a Michelson interferometer. It is shown that the spatial resolution and amplitude of the deformation are sufficient for the application as an adaptive mirror. As a possible application the suitability of this mirror type as part of a laser resonator to generate a super-Gaussian mode is discussed. PACS 42.60.Jf; 42.60.By; 42.79.-e