We present extreme ultraviolet (EUV) transmission measurements of two thin-film filters designed to obtain improved images of plasmaspheric He+, and the first global images of O+/O++ in the dense oxygen torus. Compared to previous He+ 30.4 nm imaging that used an Al filter, we show that a combined Al+C filter achieves superior rejection of 58.4 nm background from neutral helium (He I). We show that an indium filter provides both the required transmission at 83.4 nm and adequate rejection of brighter He I (58.4 nm) and H I (121.6 nm) background emissions. We find that the In transmission at 58.4 nm is a factor of ∼16 lower than predicted based on optical constants that rely on interpolations at λ<68 nm. We show that the observed lower 58.4 nm transmission is consistent with alternative optical constants derived from previous lab measurements.

中文翻译：

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用于等离子体层冷离子成像的两个薄膜滤光片的新极紫外透射测量

我们展示了两种薄膜滤光片的极紫外 (EUV) 透射测量，这些滤光片旨在获得等离子体层 He+ 的改进图像，以及稠密氧环中的 O+/O++ 的第一张全局图像。与之前使用 Al 滤光片的 He+ 30.4 nm 成像相比，我们发现组合的 Al+C 滤光片可实现对中性氦 (He I) 58.4 nm 背景的出色抑制。我们证明，铟滤光片既能提供 83.4 nm 所需的透射率，又能充分抑制较亮的 He I (58.4 nm) 和 HI (121.6 nm) 背景发射。我们发现，58.4 nm 处的 In 透射比基于依赖于 λ<68 nm 插值的光学常数预测的值低约 16 倍。我们表明，观察到的较低 58.4 nm 透射率与先前实验室测量得出的替代光学常数一致。