石墨烯薄膜制备及其在激光聚变诊断技术中的应用研究

X-ray diagnostics plays a very important position in inertial confinement fusion (ICF) experiments. In diagnostic equipment, X-ray photocathode is needed to converts x-ray into electric current. In order to support the photoemissive material, certain strength of the organic film (thickness of about 200nm) is required as a substrate in the traditional photocathode. Thicker substrate (200nm) in traditional photocathode is nonconductive and reduces x-ray transmission. These seriously affect spectral response sensitivity of the diagnostic equipment. Graphene has a very high x-ray transmittance, excellent conductivity, high strength and stability. Ultra-thin graphene replacing the substrate and the conductive layer in the traditional photocathode will greatly improve the spectral response sensitivity of the diagnostic equipment. This project designs and prepares a new graphene-substrate compound photocathode, photoelectric emission materials are Au and CsI, which have spectral response complementary. Through theoretical design and experimental fabrication, the spectral response sensitivity and response flatness are improved by adjusting the material structure. This type of compound photocathode has not been reported at home and abroad，with strong innovation. It has an important application for the hohlraum radiation temperature measurement and diagnostic of x-ray spectrum. Graphene fabricated in this project can also be use as the ideal support material of fragile detector elements of x-ray filter and single-stage diffraction grating in ICF diagnostic equipment.

X光诊断在激光惯性约束核聚变(ICF)实验中占有非常重要的地位。诊断设备均需使用光阴极将X光转换为光电流。为了支撑光电发射材料，在传统光阴极中需要具有一定强度的有机膜（厚度约为200nm）作为衬底，较厚的有机膜不仅不导电且降低X光透过率，严重影响诊断设备的谱响应灵敏度。石墨烯具有极高的X光透过率、极好的导电性、较高的强度和稳定性。利用超薄石墨烯代替传统光阴极的衬底和导电层将极大改善诊断设备的谱响应灵敏度。本项目设计制备以石墨烯为衬底的新型复合光阴极，光电发射材料为Au和CsI，利用两者光谱响应间的互补性，通过理论设计和实验制备，调节各层材料结构提高光阴极的谱响应灵敏度和响应平整度。该复合光阴极国内外未见报道，具有较强的创新性。该型阴极在黑腔辐射温度测量和X光谱诊断中具有重要的应用前景。本项目所制备的石墨烯也可以作为ICF诊断中大量使用的X光滤片和单级衍射光栅等脆弱探测元件的理想支撑材料。

X光诊断在激光惯性约束核聚变(ICF)实验中占有非常重要的地位。诊断设备均需使用光阴极将X光转换为光电流。为了支撑光电发射材料，在传统光阴极中需要具有一定强度的有机膜作为衬底，较厚的有机膜不仅不导电且降低X光透过率，严重影响诊断设备的谱响应灵敏度。石墨烯具有极高的X光透过率、极好的导电性、较高的强度和稳定性。利用超薄石墨烯代替传统光阴极的衬底和导电层将极大改善诊断设备的谱响应灵敏度。本项目设计制备以石墨烯为衬底的新型复合光阴极，光电发射材料为Au和CsI，利用两者光谱响应间的互补性，通过理论设计和实验制备，调节各层材料结构提高光阴极的谱响应灵敏度和响应平整度。本项目主要研究内容包括：高质量、大面积和超薄石墨烯的制备、调控及性能（光学、电学等）研究；石墨烯为衬底的高灵敏平响应新型复合光阴极理论设计、制备、优化及标定; 新型复合光阴极在激光聚变物理实验中的应用研究。项目已经按照研究计划已完成既定研究。经过几年研究，已申报专利6项，发表高水平论文2篇，3篇已投稿，后续结果正在整理中。通过在北京同步辐射对新型光阴极标定，发现石墨烯复合光阴极(Au/CsI/Graphene)的灵敏度比单一材料(Au/CH膜和CsI/CH膜)光阴极高出5~6倍。因此，可以预见新型光阴极在ICF中的使用将极大提高黑腔电子温度探测灵敏度和精度，对实现ICF点火有重要的意义。