I–V traces of strongly emitting emissive probes are investigated in a multidiople filament discharge. It is found that at sufficiently high neutral pressure and emitting current, the variation of the I–V traces and their associated inflection points no longer follow the previous predictions of space charge limited (SCL) models. A new, steep slope region of the I–V trace appears near the plasma potential when the probe is strongly emitting, causing the inflection point and the floating potential to increase towards the plasma potential as emission current increases, rather than staying constant. This is, to our knowledge, the first experimental evidence that the effects predicted by Campanell et al's inverse sheath theory (2017 Physics of Plasmas 24 057101) not only affect the floating potential but also a region in the I–V trace of an emissive probe. It is also found that the double inflection point structure when the probe is biased below the ionization energy of the working gas is highly likely to be an emission retardation effect from enhanced virtual cathode formation due to the increased local electron density. The implications of these findings on hot cathode sources are briefly discussed.

中文翻译：

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强电子发射探针IV迹线鞘效应的实验研究

在多偶极灯丝放电中研究了强发射发射探针的 I-V 迹线。发现在足够高的中性压力和发射电流下，I-V 迹线及其相关拐点的变化不再遵循空间电荷限制 (SCL) 模型的先前预测。当探针强烈发射时，I-V 轨迹的一个新的陡坡区域出现在等离子体电位附近，导致拐点和浮动电位随着发射电流的增加而向等离子体电位增加，而不是保持恒定。据我们所知，这是 Campanell 等人预测的影响的第一个实验证据 s 逆鞘理论（2017 Physics of Plasmas 24 057101）不仅影响浮动电位，而且影响发射探头的 I-V 轨迹中的区域。还发现，当探针偏置低于工作气体的电离能时，双拐点结构很可能是由于局部电子密度增加而增强虚拟阴极形成的发射延迟效应。简要讨论了这些发现对热阴极源的影响。