Development of 4.2K Cryo-transfer Appratus for Electron Microscope Observation of Low Temperature Neutron-Irradiated Specimens

为了实现低温中子辐照金属试样中的新生位移级联损伤的观察，并将其从辐照恒温器冷转移到电子显微镜中，JEOL公司设计并制造了一种新型的低温转移TEM保持器。保持器可以在TEM观察期间以及在从低温转移室到TEM样品室的低温转移期间在样品位置处冷却到9 K。我们研制的装置已成功地用于LLNL装置上15 K下D-T中子辐照金属的位移级联损伤的初生态观察。使用HELI-TRAN低温恒温器辐照预薄TEM试样。辐照后，将低温恒温器送入我们在这项工作中制造的低温转移室。将辐照恒温器放置在腔室中，不对样品进行预热。在18 K以下将样品冷转移到低温转移TEM保持器中。使用特殊设计的小车移动保持器，保持样品低于18 K并保持它们清洁。在20 K下，通过透射电镜观察确定了级联损伤结构.还观察到在加热过程中的试样如何在其结构中的位移级联损伤放松。

To make possible the observation of nascent displacement cascade damages in metal specimens which are irradiated at very low temperature by neutrons and cold-transferred from irradiation cryostat to electron-microscope, a new type of cryo-transfer TEM holder is designed and fabricated by JEOL. The holder can be cooled down to 9 K at the specimen position during a TEM observation and also during a cryo-transfer from cryo-transfer chamber to TEM specimen chamber. The appratus we fabricated was sucessfully used to observe the nascent state of displacement cascade damages in metals which were irradiated at 15 K by D-T neutrons at RTNS-II in LLNL. Pre-thinned TEM specimens were irradiated using HELI-TRAN cryostat. After the irradiation cryostat was feeded to the cryo-transfer chamber that we fabricated in this work. The irradiation cryostat was dismounted in the chamver without warm-up the specimens. The specimens were cold-transferred to cryo-transfer TEM holder below 18 K. The holder was moved using special designed car keeping the specimen below 18 K and also keeping them clean. The cascade damage structure was determined by TEM observation at 20 K. It was also observed during heat-up of specimens how the displacement cascade damage relax in their structure.