本文選題：L-H和H-L模轉(zhuǎn)換 + 動力學(xué)　； 參考：《中國科學(xué)技術(shù)大學(xué)》2017年博士論文

【摘要】：L-H模轉(zhuǎn)換機(jī)理是磁約束聚變界35年沒有完全解決的難題,理解其機(jī)理將有助于實(shí)現(xiàn)和穩(wěn)態(tài)維持H模。ITER是按照H模的約束性能來設(shè)計(jì)的,ITER建成初期的加熱功率將剛剛達(dá)到按照經(jīng)驗(yàn)定標(biāo)率外推的閾值,能否順利進(jìn)入H模運(yùn)行,仍然存在不確定性!較低的L-H模轉(zhuǎn)換閾值功率將會大大縮減ITER以及未來聚變堆的工程造價(jià),接近閾值功率條件下的L-H模轉(zhuǎn)換是聚變界關(guān)注的焦點(diǎn)問題之一。本論文依托EAST托卡馬克,主要利用高時(shí)空分辨的快速往復(fù)式探針診斷系統(tǒng),針對L-H模轉(zhuǎn)換動力學(xué)及其閾值功率進(jìn)行系統(tǒng)的實(shí)驗(yàn)研究。EAST是第一個(gè)建成的具有和ITER類似先進(jìn)磁場位形的全超導(dǎo)托卡馬克,采用射頻波加熱為主以及ITER-like鎢銅偏濾器,研究EAST上的L-H模轉(zhuǎn)換的閾值功率對ITER具有重要指導(dǎo)意義。我們在EAST上開展了 L-H模轉(zhuǎn)換動力學(xué)及其閾值功率的系統(tǒng)的實(shí)驗(yàn)研究,發(fā)現(xiàn):(1)在中、高密度區(qū)(ne2.0 ×1019),單獨(dú)低雜波、單獨(dú)離子回旋波加熱或單獨(dú)中性束加熱下L-H模轉(zhuǎn)換功率閾值都接近國際托卡馬克定標(biāo)率。表明國際托卡馬克L-H模轉(zhuǎn)換功率閾值定標(biāo)率適用于EAST,支持這一定標(biāo)率的可靠性。在低密度區(qū)(ne2.0 × 1019),以及采用的低雜波和離子回旋波加熱方式,首次觀察到L-H模轉(zhuǎn)換功率閾值對密度的U形依賴關(guān)系。這種現(xiàn)象與加熱方式是否有關(guān),需要在未來實(shí)驗(yàn)中驗(yàn)證。ITER主要以射頻波加熱為主的,在低密度下進(jìn)入H模的難度可能進(jìn)一步加大。(2)EAST采用了化學(xué)性質(zhì)很活潑的鋰來涂覆面對等離子體的器壁,在此之前很難取得H模。在較低的鋰涂層注入量(500 g),使得進(jìn)入等離子體的碳、氧等輕雜質(zhì)含量減少,降低有效Z;在較多的鋰涂層注入量后,使得器壁上的中性粒子的返流得到了顯著的抑制,等離子體邊界的中性粒子密度降低了接近一倍,從而顯著降低了中性粒子對剪切流的阻尼。最終使得L-H模轉(zhuǎn)換得閾值功率降低了接近一倍,低于國際定標(biāo)率。ITER將采用鈹作為第一壁材料,鈹?shù)奶匦院弯囶愃?EAST的實(shí)驗(yàn)結(jié)果為ITER在低加熱功率下實(shí)現(xiàn)H模運(yùn)行提供了重要的依據(jù),具有重要意義。(3)研究了偏濾器位型和離子梯度漂移方向?qū)-H模轉(zhuǎn)換行為及其閾值功率的影響。EAST在鋰涂層壁處理下的全碳壁和鉬/碳壁,都表現(xiàn)出在雙零位型(DN)下功率闞值最低。對于單零位型(SN),當(dāng)離子梯度漂移背離主X點(diǎn)時(shí)其功率閾值低于漂移指向主X點(diǎn)。通過靜電探針觀測到,低場側(cè)刮削層平行流與Pfirsh-Schluter流的幅值及其時(shí)間演化具有相關(guān)性,并且依賴于縱場方向。對于W型偏濾器結(jié)構(gòu),當(dāng)外中平面到偏濾器靶板的連接長度較短,即刮削層粒子輸運(yùn)沉積在外靶板時(shí),粒子可以有效地被排出、屏蔽,進(jìn)而有利于L-H模轉(zhuǎn)換。在國際上率先提出了參與驅(qū)動刮削層等離子體平行流的Pfirsh Schuter流在決定L-H模轉(zhuǎn)換的閾值功率上起到了關(guān)鍵性的作用,從而打破了刮削層參與L-H轉(zhuǎn)換的物理機(jī)制的缺口。然而,當(dāng)上偏濾器更換為ITER-like的鎢銅偏濾器,上單零位型(USN)等離子體在離子梯度漂移指向主X點(diǎn)時(shí)其閾值功率較低。上下不對稱的偏濾器結(jié)構(gòu)使得低場側(cè)刮削層流指向上偏濾器,對于不同的離子梯度漂移方向只是刮削層流的幅度不同,這和低場側(cè)Pfirsh-Schluter流的指向具有相關(guān)性。此外,相比標(biāo)準(zhǔn)的偏濾器位形,EAST準(zhǔn)雪花位形下的L-H模轉(zhuǎn)換功率閾值高很多。EAST準(zhǔn)雪花位形其等離子體控制的打擊點(diǎn)偏離偏濾器靶板區(qū)域,不利于粒子的排出和屏蔽。實(shí)驗(yàn)觀測到,邊界中性粒子密度在準(zhǔn)雪花位形下較高。L-H模轉(zhuǎn)換行為和位型、偏濾器抽氣效率及離子梯度漂移方向有一定的依賴關(guān)系,帶有中間態(tài)的所謂'dithering L-H'模轉(zhuǎn)換更加容易出現(xiàn)在雙零位型且抽氣效率低的情況,而且dithering的形態(tài)在不同位型下也表現(xiàn)出不同的行為特征。單步的轉(zhuǎn)換'single-step L-H'經(jīng)常出現(xiàn)在離子梯度漂移方向背離主X點(diǎn)的位型下。在DⅢ-D和AlcatorC-Mod的實(shí)驗(yàn)結(jié)果證明了在離子梯度漂移指向主X點(diǎn)的位形下L-H模轉(zhuǎn)換的閾值功率更低。不同的是,JET發(fā)現(xiàn)離子梯度漂移背離有效偏濾器時(shí)L-H模轉(zhuǎn)換的閾值功率相差不大或者較小。在ASDEX-U、MAST和NSTX也發(fā)現(xiàn)最小的閾值功率出現(xiàn)在DN位形。這意味著我們在研究L-H模轉(zhuǎn)換時(shí)還忽略了其它重要因素,如中性粒子再循環(huán)和偏濾器幾何位形等。EAST裝置與眾不同的表現(xiàn),對L-H模轉(zhuǎn)換的研究有著重要意義。(4)在加熱功率接近L-H模轉(zhuǎn)換功率閾值的條件下,研究了 L-H模轉(zhuǎn)換的中間振蕩狀態(tài)(limit cycle oscillations,LCOs),發(fā)現(xiàn)了等離子體湍流驅(qū)動的剪切流、壓力梯度主導(dǎo)的平衡流和湍流在L-H模轉(zhuǎn)換過程中共同起作用,決定了 L-H模轉(zhuǎn)換前的振蕩態(tài)以及L-I-H、L-I-L模轉(zhuǎn)換。(5)在一些實(shí)驗(yàn)中發(fā)現(xiàn)雷諾協(xié)強(qiáng)太小而不足以驅(qū)動流剪切,L-H模轉(zhuǎn)換過程中并未觀察到湍流驅(qū)動的剪切流。我們實(shí)驗(yàn)首次發(fā)現(xiàn),E×B流剪切導(dǎo)致湍流徑向譜移把湍流能量散射到強(qiáng)粘滯阻尼的高徑向波數(shù)空間而被耗散,湍流幅度的減小導(dǎo)致壓力梯度的增長進(jìn)一步增強(qiáng)E × B流剪切的譜移,這樣的正反饋使得湍流能夠被快速抑制,為觸發(fā)L-H模轉(zhuǎn)換提供了一種新的思路。(6)分析了 EAST托卡馬克L-H和H-L模轉(zhuǎn)換前出現(xiàn)的振蕩態(tài),它們都表現(xiàn)出(m = 1,n = 0)的磁擾動結(jié)構(gòu)。
[Abstract]:The mechanism of L-H mode conversion is a difficult problem that has not been completely solved for 35 years in the magnetic confinement fusion. Understanding its mechanism will help to realize and maintain the H mode.ITER in the steady state according to the constraints of the H mode. The heating power in the initial stage of ITER will just reach the threshold value extrapolated according to the empirical calibration rate, and whether it can enter the H mode and still exist, still there is no problem. Certainty! The lower L-H mode conversion threshold power will greatly reduce the cost of ITER and future fusion reactor, and the L-H mode conversion under the threshold power condition is one of the focus problems in the fusion field. This paper relies on the EAST Tokamak, mainly using high time space-time resolution fast reciprocating probe diagnosis system, for L-H mode conversion .EAST is the first complete superconducting tokamak with ITER similar advanced magnetic field configuration, using radio frequency wave heating and ITER-like tungsten copper bias filter. The study of the threshold power of L-H mode conversion on EAST has important guiding significance for ITER. We carry out on EAST The experimental study of the L-H mode conversion dynamics and the threshold power system shows that: (1) in the middle, high density region (ne2.0 x 1019), single low clutter, single ion cyclotron wave heating or single neutral beam heating, the L-H mode conversion power threshold is close to the international Tokamak calibration rate. It shows that the international Tokamak model conversion power threshold calibration The rate is suitable for EAST to support the reliability of this certain rate. In the low density zone (ne2.0 x 1019) and the low clutter and ion cyclotron heating mode, the U dependence of the L-H mode conversion power threshold on the density is observed for the first time. This phenomenon is related to the heating mode. It is necessary to verify the.ITER in the future experiment with the radio frequency wave. Heating mainly, the difficulty of entering the H mode at low density may further increase. (2) EAST uses a highly chemically active lithium to cover the plasma wall, and it is difficult to obtain the H mold before this. The lower injection amount of lithium coating (500 g) reduces the content of light impurities such as carbon and oxygen into the plasma, and reduces the effective Z; in comparison, the effective Z is reduced. After the injection of lithium, the reflux of neutral particles on the wall has been significantly suppressed. The neutral particle density of the plasma boundary is nearly doubled, thus significantly reducing the damping of the neutral particles on the shear flow. Finally, the threshold power of the L-H mode is reduced by nearly double the threshold power, which is lower than the international calibration rate of.ITER. By using beryllium as the first wall material, the properties of beryllium and lithium are similar. The experimental results of EAST provide important basis for the implementation of the H mode operation under low heating power. (3) the influence of the displacement of the filter and the direction of the ionic gradient drift on the conversion behavior of the L-H mode and the threshold power of the L-H are studied..EAST under the treatment of the lithium coating wall Both the full carbon wall and the molybdenum / carbon wall show the lowest power threshold at the two zero position type (DN). For the single zero position type (SN), the power threshold is lower than the drift pointing to the main X point when the ion gradient drift deviates from the main X point. The parallel flow in the low field scraping layer is correlated with the amplitude and time evolution of the Pfirsh-Schluter flow. For the structure of the W type filter, when the connection length of the outer middle plane to the filter target plate is short, that is, when the scraping layer particles transport and deposit on the outer target plate, the particles can be effectively discharged, shielded and thus beneficial to the L-H mode conversion. In the world, the first proposed Pfirsh Sc to participate in the parallel flow of the plasma of the scraping layer. The Huter flow plays a key role in determining the threshold power of the L-H mode conversion, thus breaking the gap in the physical mechanism of the scraping layer participating in the L-H conversion. However, when the upper partial filter is replaced by a tungsten copper bias filter of ITER-like, the upper single zero position (USN) plasma has a lower threshold power when the ion gradient drift points to the main X point. The symmetrical bias filter structure makes the low field side scraping laminar flow pointing to the upper partial filter. For the different direction of the ion gradient drift, the amplitude of the scraping laminar flow is different. This is related to the direction of the Pfirsh-Schluter flow on the low field side. In addition, the L-H mode conversion power threshold under the EAST quasi snowflake configuration is much higher than that of the standard filter position. The plasma controlled strike point of AST quasi snowflake deviates from the target plate area of the filter, which is not conducive to the discharge and shielding of the particles. The experimental observation shows that the neutral particle density at the boundary is higher in the.L-H mode conversion behavior and the position type under the quasi snowflake shape, and has a certain dependence on the suction efficiency of the filter and the direction of the ion gradient drift, with the intermediate state. The so-called'dithering L-H'mode conversion is more likely to occur in the case of double zero type and low pumping efficiency, and the morphology of dithering shows different behavior characteristics under different types. The single step transformation of'single-step L-H' often occurs in the position of the main X point in the direction of the ionic gradient drift. In D III -D and AlcatorC-Mod real. The test results show that the threshold power of the L-H mode conversion is lower under the position of the ion gradient drift pointing to the main X point. The difference is that the threshold power of the L-H mode conversion is small or small when JET finds the ion gradient drift deviates from the effective filter. In ASDEX-U, MAST and NSTX also find that the minimum threshold power appears in the DN bit. This means that I have the lowest threshold power in the DN bit. In the study of L-H mode conversion, other important factors, such as the unusual performance of the neutral particle recirculation and the geometric configuration of the bias filter, are important for the study of the L-H mode conversion. (4) the intermediate oscillation state of the L-H mode conversion (limit CYC) is studied under the condition that the heating power is close to the L-H mode conversion power threshold. Le oscillations, LCOs), the shear flow driven by the plasma turbulence is found, the pressure gradient dominated equilibrium flow and the turbulence play a role in the L-H mode conversion process. The oscillating state before the L-H mode conversion and the L-I-H, L-I-L mode conversion are determined. (5) in some experiments, it is found that the Reynolds co intensity is too small to drive the flow shear, and the L-H mode is converted over. The shear flow driven by turbulence is not observed in the process. In our experiment, it is found for the first time that the E x B flow shear leads to the turbulent radial spectral shift to scatter the turbulent energy into the high radial wave space with strong viscous damping and is dissipated. The decrease of the turbulence amplitude causes the increase of the pressure gradient to further enhance the spectral shift of the shear of the E x B flow, so that the positive feedback makes turbulence. The flow can be quickly suppressed to provide a new idea for triggering L-H mode conversion. (6) the oscillating states before the EAST Tokamak L-H and H-L mode conversion are analyzed. They all show the magnetic disturbance structure of (M = 1, n = 0).
【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：TL631.24

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