Positron annihilation lifetime measurements were performed on polyethylene films [low-density polyethylene and ultra-high molecular weight polyethylene (UHMWPE)] with a thickness of 15–2000μm using a Na-22 positron source enclosed in a Kapton film. For thin films, some positrons will pass through the film and annihilate behind it. Using a single film in a commercial anti-coincidence system, by placing an annealed stainless steel (SUS304) cover behind the sample, it is possible to sufficiently measure the long-lifetime ortho-positronium (o-Ps) component even in thin films. Additionally, calculated intensities of the o-Ps component determined from the estimated film transmittance agreed well with the measured values. Furthermore, by applying this method to uniaxially stretched UHMWPE, we were able to observe structural changes owing to the stretching consistent with shorter measured o-Ps lifetime and increased o-Ps intensity.

使用封装在 Kapton 薄膜中的 Na-22 正电子源对厚度为 15-2000 μm的聚乙烯薄膜 [低密度聚乙烯和超高分子量聚乙烯 (UHMWPE)] 进行正电子湮没寿命测量。对于薄膜，一些正电子会穿过薄膜并在其后面湮灭。在商业反巧合系统中使用单膜，通过在样品后面放置退火不锈钢（SUS304）覆盖层，即使在薄膜中也可以充分测量长寿命的邻正电子（ o -Ps）成分。此外，计算出的o的强度-由估计的薄膜透射率确定的 Ps 分量与测量值非常吻合。此外，通过将该方法应用于单轴拉伸的 UHMWPE，我们能够观察到由于拉伸与更短的o -Ps 寿命和增加的o -Ps 强度相一致的结构变化。