Nitrogen (N) seeding is routinely applied in tokamaks with tungsten (W) walls to control the power exhaust toward the divertor. Open questions, concerning the interaction of N with W, are the influence of ion energy and W temperature on retention of implanted N and the erosion by deuterium (D) of the tungsten nitride being formed. Moreover, the extremely high particle fluxes in ITER and DEMO will erode the W tiles and the sputtered atoms will re-deposit forming W-based layers with a different behaviour toward the interaction with N seeded D plasmas.

In this work, W films with different morphology and structure were exposed to the N seeded D plasma of the linear device GyM, in order to address all these issues. The experiments were performed at the fixed N${}_2$/D${}_2$ partial pressure ratio of $\sim$4% keeping the total pressure constant at 5.3$\times 10^{-4}$ mbar. The exposure conditions were: (i) sample temperature of $\sim$850 K, (ii) particle fluxes of $2-2.2\times 10^{20}$ ions$\cdot$m${}^{-2}\cdot$s⁻¹ and (iii) particle energies up to $\sim$320 eV. W columnar films (c-W) with properties close to those of virgin W coatings deposited on the tiles of JET Iter-Like Wall and ASDEX Upgrade and W amorphous films (a-W) resembling nanostructured W-based deposits found in present-day tokamaks and expected in ITER and DEMO, were considered. W columnar and amorphous coatings were produced by means of magnetron sputtering and pulsed laser deposition, respectively. The specimens were characterised by profilometry, X-ray depth-profiling photoelectron spectroscopy, optical microscopy, scanning electron microscopy, atomic force microscopy and X-ray diffraction. The main evidence is that the behaviour of the W films upon D+N plasma exposure in GyM strictly depends on their morphology and nanostructure. For all the films, a surface N-enriched layer, which is thermally stable and does not decompose at least up to $\sim$850 K, is observed. Moreover, blisters are not present on the surface of the samples. The c-W coatings erode faster than the a-W ones and have a higher nitrogen retention and diffusivity. The mechanisms behind these results are here discussed together with their possible implications from the point of view of the topic of plasma–wall interaction in tokamaks.

通常在具有钨（W）壁的托卡马克中使用氮（N）播种，以控制朝向分流器的动力排放。关于N与W的相互作用的悬而未决的问题是离子能量和W温度对注入的N的保留以及所形成的氮化钨的氘（D）腐蚀的影响。此外，ITER和DEMO中极高的粒子通量将腐蚀W瓷砖，溅射的原子将重新沉积，形成具有不同行为的W基层，这些行为与N种D等离子体相互作用。

在这项工作中，为了解决所有这些问题，将具有不同形态和结构的W膜暴露于线性器件GyM的N种子D等离子体中。实验在固定的N下进行${}_2$/ D${}_2$ 的分压比 $〜$4％将总压力保持在5.3不变$\times \mathrm{1个}{0}^{-4}$毫巴 暴露条件为：（i）样品温度为$〜$850 K，（ii） $2-2。2\times \mathrm{1个}{0}^{20}$ 离子$\cdot$米${}^{-2}\cdot$s ^-1和（iii）粒子能量高达$〜$320 eV。W柱状薄膜（cW）具有与JET Iter-Like Wall和ASDEX Upgrade瓷砖上沉积的原始W涂层相近的性能，W非晶态薄膜（aW）类似于当今托卡马克中发现的纳米结构W基沉积物，预计在考虑了ITER和DEMO。分别通过磁控溅射和脉冲激光沉积制备W柱状和无定形涂层。通过轮廓测定，X射线深度轮廓光电子能谱，光学显微镜，扫描电子显微镜，原子力显微镜和X射线衍射对样品进行表征。主要证据是，W膜在GyM中暴露D + N等离子体后的行为严格取决于其形态和纳米结构。对于所有薄膜，表面都富含N，$〜$观察到850K。此外，样品表面上不存在气泡。连续波涂层的腐蚀速度比连续波涂层的快，并且具有更高的氮保持率和扩散率。从托卡马克中的等离子体-壁相互作用的主题的角度，讨论了这些结果背后的机制及其可能的含义。