1.Introduction

The Experimental Advanced Super conducting Tokamak(EAST)is designed based on the latest tokamak achievements of the last century,aimed at the world fusion research forefront.EAST construction and physical research provide direct experience for the construction of the International Thermonuclear Experimental Reactor(ITER)project.EAST plays a leading role in high-performance steady-state plasma physical research,and it ultimately contributes to the development of ITER and fusion energy.During the ITER construction,EAST will be one of only a few international devices providing an important experimental test bench for conducting ITER-related steady-state advanced Plasma Science and Technology research.Many complicated physical mechanisms and Engineering technological problems should be first investigated on EAST,and plasma wall interaction is one of the most Significant physical problems[1–3].

（3）供试品溶液的制备：精密量取浓缩液50 mL，用水饱和正丁醇振摇提取4次，每次40 mL，合并正丁醇液，用氨试液充分洗涤2次，每次40 mL，弃去氨液，正丁醇液蒸干，残渣用甲醇溶解定容至5 mL量瓶中，摇匀，即得供试品溶液。

EAST is a fully superconducting tokamak with double divertors for long pulse operations and it will inevitably lead to strong plasma interactions with plasma facing components(PFCs),resulting in increased impurity deposition,fuel retention and material erosion[4].In EAST,PFCs will be exposed to a high heat load and particle fluxes and it may cause the surface morphology of the PFCs to change due to material erosion and redeposition processes from plasma wall interactions.The states of the PFC surface will seriously affect the performance of the long-pulse or steady state plasma discharge in a tokamak,and it may even become an enormous threat to the operation and the safety of the fusion plasma device.A PFC surface morphology measurement could provide important information regarding the real-time status of PFCs or the damage status,and it would give a better understanding of the plasma wall interaction process and mechanism.Meanwhile,by monitoring the distribution of dust deposition in tokamaks and providing an upper limit on the amount of loose dust,a PFC surface morphology measurement could indirectly contribute to ensuring fusion operational limits and fusion device safety.

Figure 1.Schematic of the reserved windows for in situ PFC surface morphology measurement.(a)Port H of EAST.(b)Top view of two reserved windows.

The speckle interferometry approach is regarded as the most promising technique for monitoring the PFC surface morphology evolution[5–8],but before it can be applied to a fusion device,such a promising technique still needs targetdirectional development and improvement with further principle validation works in a laboratory.A remote speckle interferometry measurement for real divertor tiles retired from EAST was carried out in the laboratory to simulate a long distance detection for EAST with an in situ experiment condition.EAST has a first wall surface area of 60 m2and its major radius is 1.7 m with a 3.5 T toroidal magnetic field[9].Port H of EAST and the material-plasma evaluation system(MAPES)are shown in figure 1(a),and two windows(window 1 and window 2)under the MAPES are reserved for in situ PFC surface morphology measurement.The distance from the windows to the facing first wall is 2626 mm,as shown in figure 1(b).On port H of EAST,the detecting laser can be guided into EAST through window 1(as the colored solid lines show in figure 1(b))and the reflected laser will be collected through window 2(as the colored dotted lines show in figure 1(b)).A broad range of PFCs facing port H could be observed by the speckle interferometry approach utilizing these two reserved windows.

Aiming at in situ PFC surface morphology measurement,a laboratory experimental platform DUT-SIEP(speckle interferometry experimental platform)based on the speckle interferometry approach has been constructed at the Dalian University of Technology(DUT).Depending on the directional specific design,and focusing on a real detection condition on the EAST tokamak,DUT-SIEP has realized a 3000mm far field optical non-contacted imaging measurement to demonstrate the feasibility of an in situ surface morphology measurement.The preliminary surface morphology of divertor tiles reproduced by the reconstructed geometric image is discussed in this paper.

2.Experiment

2.1.Morphology measurement setup

The measurement area can cover the whole surface of one divertor tile via scanning and it bene fits from the introduction of three adjustable plane reflectors.On the divertor tiles retired from EAST,there are geometric gaps between every two small pieces of tiles as a grid distribution.The divertor tiles were exposed to 12 165 plasma shots during the 2015–2016 EAST campaign,shown in figure 3.The color changes and horizontal scratches on the surface of the divertor tiles are clear to see,and it indicates that the divertor tiles’surface,especially the region adjacent to the gap,experienced a complex plasma interaction,such as an erosion process and deposition process.

The phase unwrapping algorithm can unwrap the surface morphology information and deformation from the phase difference between the interference patterns,and then it reconstructs the surface morphology geometric image.The three main categories of the phase unwrapping algorithms are global algorithms,region-growing algorithms and path-following algorithms[13],where the path-following algorithms have less computational complexity compared with the global algorithms and the region-growing algorithms.In our numerical model of the phase unwrapping algorithm,the quality guided path-following approach is adopted and the unwrapping path will be determined according to the quality parameters of the interference patterns.

The principle of the optical imaging measurement for PFC surface morphology is based on the speckle interferometry technique,and the measurement setup has a modified Michelson interference structure,shown schematically in figure 2,where one reflector is replaced by the divertor tiles retired from EAST as a detection branch path;in the other reference branch path,the reflector is constituted by a combination of a piezoelectric transducer and a reference mirror to artificially produce a phase shift.To simulate a far field measurement at the real distance between two reserved windows on port H and the PFCs on EAST,two adjustable plane reflectors(R1 and R2 in figure 2)are introduced in the detection branch path with a distance of 1500 mm,and another adjustable plane reflector(R3 in figure 2)is put into the collected light path of the reflected light from the divertor tile surface.Therefore,the probe laser will travel a distance of over 3000 mm before it illuminates the divertor tiles,and the reflected light from the divertor tile surface will also travel over 3000 mm via the plane reflector in the collected light path.

Figure 2.Remote imaging measurement setup for divertor tiles adopted from EAST.L1,L2:laser alignment and beam expansion lenses;L3,L4:optical collected imaging lenses;R1,R2,R3:adjustable plane reflector.The distance between R1 and R2 is 1500 mm.

Figure 3.Photo of a real divertor tile retired from the EAST tokamak device.

2.2.Speckle interferometry technique

where φo′is the new phase shift induced by the surface morphology variation in the detection branch path,and it can be expressed and replaced by

Surface morphology deformation in the incident direction of the probe laser will change the image of the interference patterns;as a consequence,when the erosion or redeposition process occurs on the divertor tiles,it can be regarded as an out-of-plane displacement and the corresponding phase shift related to the surface morphology variation will be introduced into the interference patterns.Before the surface morphology is changed,the laser beams in the detection branch path and the reference branch path form an interference on each pixel of the CCD camera with an intensity value[12]of

where Io,Irrespectively represent the intensities in the detection branch path and in the reference branch path.With the surface morphology variation,the intensity changes to

The speckle interferometry technique takes advantage of the speckle patterns,which are intensity patterns.The interference pattern is formed in mutual interference by superposing a set of wavefronts together[10].The surface morphology information can be wrapped into the interference patterns by the phase-shifting method[11],while the phase unwrapping algorithm will reconstruct the surface morphology information by unwrapping the wrapped phase in the interference patterns.

So,the intensity after the surface morphology variation is

where Δφ is the core factor of the speckle interferometry measurement because the information regarding the surface morphology variation is contained in this factor.The surface morphology deformation Δz in the incident direction of the probe laser can be calculated via the formula of the optical path difference

In this study,two different laser wavelengths are used for the speckle interferometry measurement,and they can provide a variable dynamic measurement range,which is much larger than the measurement just utilizing a single laser wavelength.This will greatly expand the measurement range of the surface morphology in a practical situation because the dimension limitation of a single laser wavelength is extended by a new synthetic wavelength.The synthetic wavelength Λ depends on the two-laser wavelength λ1 and λ2 as below

Here,the intensities Io,Irin the detection branch path and in the reference branch path are substituted as Ir = a2and Io = b2.Four interferograms I(x,y),(i = 1,2,3,4)are stored with four different phase shifts and the phase shift Δφ will be directly calculated by the four-quadrant arctangent equation[12]:

企业应充分认识精神激励和物质激励的关系，坚持开展精神激励和物质激励，满足企业人才的精神需求和物质需求；其次，企业应积极完善物质激励机制，加快分配制度改革，积极完善职工的薪酬分配，建立健全的薪酬体系。并且，企业应建立合理的员工考评标准，优化员工考评体系，增强员工考评的科学性，进而为职工激励提供科学依据；最后，企业应积极优化精神激励，对职工进行理想目标激励、奖惩激励、情感激励、信任激励、荣誉激励等，提高职工的工作满意度。

2.3.Phase-shifting method

The temporal phase shifting method is taken into account to simplify the Δφ solving process.The phase shift Δφ in the detection branch path emerges from the surface morphology variation,and the other specific phase shift in the reference branch path is artificially introduced by changing the piezoelectric　transducer.　According　to　the　classical　four bucket algorithm[13],four-step phase shifts are introducedso it is possible to generate a well known phase shift in the cosine function and then the intensity value of the interference on each pixel of the CCD camera can be rewritten in the following form:

From the phase difference between the interference patterns before and after the surface morphology variation,surface morphology deformation can be obtained,but the absolute value equation shows that it is a periodic function of Δφ factor,and it is difficult to find the direct solution of Δφ value.

where λ is the laser wavelength,

The new phase information corresponding to the synthetic wavelength Λ can also be acquired from the measurement results of four-step phase-shifting speckle interferometry at two laser wavelengths λ1 and λ2 respectively.Laser speckle interference patterns using λ1 = 632.8 nm and λ2 = 532 nm with four-step phase-shifting of 0,π/2,π,3 π/2 are shown in if gures 4(b),(c).

3.Results and discussion

3.1.Phase unwrapping algorithm

A laser beam is split into two branches by a laser beam splitter and these two branches cause a reflection respectively and then form an interference pattern in the front of a CCD camera.

During the phase unwrapping process of the quality guided path-following method,the calculation of the quality parameters is introduced in order to avoid adverse impacts because of the noise existence,discontinuous fringes and other inevitable factors.The distribution of the quality parameter from the wrapped phase map can evaluate the image quality of the speckle interference patterns and show the spatial difference of the geometric characteristics in the pattern image corresponding to the pixels.When the quality parameter of a pixel is much closer to 1,the accuracy of the reconstruction image for this pixel is much better.The distribution of the quality parameter in the synthetic wavelength phase map( figure 5(c))reveals that the quality parameter is mainly distributed between 0.6–0.9,as shown in figure 6,and it indicates that the image quality of our measurement is good enough to guarantee the reconstructed process of the surface morphology information.The phase unwrapping path is guided by a quality parameter,and the pixels with a better quality parameter take priority over the calculations of other pixels with a lower quality parameter.Therefore,it will significantly improve the quality and reliability of the speckle interference pattern reconstruction results.

(2)拆解前先进行故障痕迹寻找(跑、冒、滴、漏、有否异样、明显损伤及变形)记录在案，对整体外部清洗，观察故障痕迹。

3.2.Reconstruction of the surface morphology image

From the surface morphology reconstruction results,a gap between two adjacent tiles on the divertor tiles retired from EAST is presented,and the surface morphology of the tiles can be specifically investigated.Firstly,the gap width between two adjacent tiles is measured through the absolute value of the phase difference from two-wavelength laser speckle interference patterns in figure 7,and the width of this gap is approximately 2.2mm,which is calculated by the multiplication of the image pixels along the horizontal axis corresponding to the actual space dimension(under this measurement condition,one pixel corresponds to 3.5 μm on the horizontal axis and the vertical axis respectively).

Figure 4.The gap region between two adjacent tiles on the divertor tiles retired from the EAST tokamak.(a)The morphology image of a gap on the divertor tiles;(b)laser speckle interference patterns using a laser wavelength of 632.8 nm;and(c)laser speckle interference patterns using a laser wavelength of 532 nm via the measurement with four-step phase shifting of the 0,π/2,π,3 π/2 method.

Figure 5.Phase difference images of laser speckle interference patterns corresponding to 632.8 nm(a),532 nm(b)and the synthetic wavelength 3.339 μm(c).

Figure 6.The distribution of the quality parameter in the synthetic wavelength phase difference image.

In our further study,a local surface morphology of the gap and parts of two adjacent tiles retired from EAST during the 2015–2016 EAST campaign is investigated and the analysis area is marked with a red dotted box in figure 4(a).Just from the photo image of this region,the color changes and horizontal scratches on the tile surface are clearly shown near the right side of the gap.It strongly implies that this piece of divertor tile experienced a complex plasma interaction and mechanical injury.The surface of this tile should be damaged by a Significant erosion process resulting in large surface morphology roughness with a transverse sheet structure.These features are all well validated in the reconstruction result of the local surface morphology,as shown in figure 8.The relative erosion depths of the surface morphology changes are between 10–20 μm and the horizontal scratches on the tile surface caused by mechanical injury are 50 μm in the transverse sheet structure.The spatial dimension of the measurement area is approximately 7mm×4mm and the measurement accuracy is controlled in the sub-micron scale.A more detailed analysis and explanation will be provided in the next section.

Figure 7.The absolute value of the phase difference from two-wavelength laser speckle interference patterns(λ1 = 632.8 nm,λ2 = 532 nm,Λ = 3.339 μm).

Figure 8.The reconstructed local surface morphology of the gap and parts of two adjacent tiles retired from EAST during the 2015–2016 EAST campaign.

3.3.Analysis and discussion

The two-wavelength laser speckle interferometry approach(λ1 = 632.8nm,and λ2 = 532nm)is employed in this measurement and it has a large dynamic measurement range(Λ = 3.339 μm)which is much larger than the measurement just utilizing a single laser wavelength.It greatly expands the surface morphology measurement range from the nanometer scale to the micrometer scale.However,this relatively large dynamic measurement range is still too short for the gap depth measurement,and the gap depth between two adjacent divertor tiles is usually a few centimeters.In the surface morphology reconstruction results,as shown in figure 8,the depth information of the gap region between two adjacent tiles has inevitable errors because of the deficiency of the periodic parameter in the phase difference.The reason is that the gap may form an abrupt step change and the depth of this step change is much larger than the dynamic measurement range of the two-wavelength speckle interferometry.Nevertheless,the width measurement of this gap will not be subject to any influence because the lateral width of the gap is in the horizontal plane rather than the depth direction.The lateral width of the gap is directly projected on the pixels of the camera and it just has spatial correlation in the horizontal plane.The absolute value of the phase difference from the two-wavelength laser speckle interference patterns in figure 7 is just calculated within one period,and it is not necessary to consider the existence of the periodic parameter,so the lateral width of the gap between the two adjacent tiles can be measured at a distance of three meters.This means that we can observe a microscale change in millimeters at a remote distance of a few meters and this microscale change can be real-time monitored.Thus,the laser speckle interferometry approach is also an optimal method for monitoring the displacement and shape distortion of PFCs in the surface plane.

在四川工商学院，德育放在学校的首位。学校采取寝室走访、学生谈话和课堂教学等多方位形式进行德育，培养具有良好德行的当代大学生。

1.借助学分银行，实现继续教育与各类培训、学历教育的衔接与沟通。银行是个金融术语，指以开展信用经营为主，为资金的借贷双方提供中介平台的机构。“学分银行”是借鉴了金融领域的银行术语在教育领域的运用，指学习者把在学校教育、职业技能培训机构等多渠道获得学习成果进行学分化转换，以量化的学分记录在其学习档案中，并存在一个类似于银行数据交换中心的系统中，供学校、企业、政府等有关机构去查询其学习成果等。当学习者的学分积累够一定的学分量，达到某专业毕业所需的学分后，可以申请该专业的学历毕业证书，亦可通过积累一定量的学分申请某些职业技能证书。

The speckle interference technique obtains the surface information and deformation through the calculation of the phase difference between the interference patterns before and after the surface morphology variation,and the absolute depth transformation on the surface morphology is regarded as an outof-plane displacement corresponding to a phase shift.In an off line measurement situation,the interference patterns of the divertor tiles at the initial state are missing,so the absolute depth transformation may not be obtained,but through the phase difference between one pixel and its surrounding pixels in the same interference pattern,the relative depth transformation can still be reconstructed.The variation of the relative erosion depth and the morphology of the horizontal scratches on the divertor tile surface in figure 8 are calculated using this approach.The areal distribution of the relative erosion depth variation corresponds to the color change region in the red dotted box in figure 4(a),and the horizontal scratches caused by mechanical injury on the tile surface are mainly produced by the surface Friction during its transportation and the wire-electrode cutting during the process of divertor disassembling.The friction injury on the metal surface and the influence of wire-electrode cutting are both in tens of microns scale,so the transverse sheet structure in figure 8 with a surface roughness of 50μm is reasonable.The interference patterns of the divertor tiles at the initial state will make the measurement of the absolute depth transformation possible;meanwhile,it also demonstrates the necessity of speckle interferometry on-line measurement for PFCs on EAST.

4.Conclusions

A remote speckle interferometry surface morphology measurement was carried out at a distance of three meters for real divertor tiles retired from EAST to simulate a long-distance detection for in situ experiment conditions on EAST.It demonstrated the feasibility and reliability of the speckle interferometry approach as the most promising real-time in situ monitoring method for the surface morphology of PFCs on EAST.The surface morphology of the divertor tiles was reconstructed from the interference patterns and it could provide important information regarding the PFC status or damage status.The measurement of the surface morphology of PFCs also contributed to a better understanding of plasma wall interactions.More intensive experimental research related to PFCs should be carried out,and the progress and accumulation of speckle interferometry measurement will contribute to its practical application in EAST or other fusion devices in the future.

思维导图又叫心智图，是表达发散性思维的有效的图形思维工具，它简单，却又极其有效，是一种革命性的思维工具。思维导图运用图文并重的技巧，把各级主题的关系用相互隶属与相关层级图表现出来，把主题关键词与图像、颜色等建立记忆链[3]。在无机化学的授课过程中授课教师可以利用思维导图来引导学生理清学习内容的思路。协助学生更好的学习无机化学的知识。如在讲授强电解质和弱电解质时，可以引入思维导图，方便学生理解，提高学习质量（见图1）。

This work was supported by the National Magnetic Confinement　Fusion　Science　Program　of　China　(No.2013GB109005),National Natural Science Foundation of China(Nos.11175035,11475039)and Chinesisch-Deutsches Forschungs project(GZ768).

非洲猪瘟虽然发病率和死亡率较高，会在猪群体中快速传播，但是该疫病是非人畜共患病，而且也不会感染其他动物，因此一旦发生也不必恐慌。因为该病的病毒不耐高温，可用高温进行灭活。为避免我国发生此类猪病，必须加强检验检疫预防工作，建立监测机制和预防体系，做好养殖场的清洁工作，一旦发生疫病则必须做好全面封锁工作，并对病猪进行扑杀。

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