Research and development on the pulsed slow positron beam to analyze surface of polymer

为了研究聚合物的表面，脉冲显示正电子束（PSPB）是必要的，以确定在所研究的聚合物的注入时间。在这个项目中，已经使用放射性同位素建造了一个桌面大小的小型仪器。采用预聚束、t-2理想电位聚束、主聚束、1/4腔射频聚束的混合方法获得脉冲聚束。第一个聚束器可以产生半高宽为2ns的脉冲光束。激光束聚焦在射频腔加速间隙的差距处，主聚束器可将半高宽为0.5ns的脉冲激光束聚束。这种分辨率足以分析聚合物，其中正电子素的寿命为2至3 ns。在本项目中，我们成功地建立了一套脉冲聚束装置，并将其应用于聚乙烯、环氧树脂、环氧树脂复合材料以及铁金属和聚乙烯多层膜等聚合物的寿命测量。在此应用中，获得了环氧树脂的表面和本体的热膨胀系数。在聚乙烯中观察到随着深度的增加，正电子素形成的增加。用非破坏性方法观察了复合材料的表层。

In order to study the surface of polymers a pulsed show positron beam (PSPB) is necessary to determine the injection time in the investigated polymer. In this project, a small apparatus desk-top size has been built using radio isotopes. The bunched and pulsing beam was obtained by the hybrid method : (1) pre-buncher, t-2 ideal electrical potential bunching, (2) main buncher, RF buncher using 1/4 cavity. The first buncher could make a pulsed beam with 2ns full width at half maximum (FWHM). The beam was focused on the gap of the acceleration gap of the RF cavity, the main buncher could bunch the pulsed beam with 0.5ns FWHM. This resolution is good enough to analyze polymer, in which positronium has 2 to 3 ns lifetime. However this is still wider to analyze the lifetime in metals.In this project, the apparatus to obtain a pulsed and bunched beam was successfully built and was applied to measure lifetime of polymers : polyethylene, epoxy resin, epoxy composite, and multi-layer of Fe metal and polyethylene. In this application, the heat expansion coefficient of the surface and the bulk of epoxy resin was obtained. The increase in the positronium formation with increasing the depth was observed in polyethylene. The skin layer of the composite materials was observed by a non destructive method.