用于高速摄影变象管的软X射线光电阴极

SOFT X-RAY PHOTOCATHODE OF IMAGE TUBE FOR HIGH SPEED PHOTOGRAPHY

光阴极由衬底(包括介质阴极的导电基底)和光电发射膜构成。采用了聚丙烯、Formvar和Paylene三种有机薄膜作阴极衬底。建立了这些薄膜的制备技术。用一台自制的软X射线单色仪在277—7469ev光子能量范围内测量了这些薄膜的透过率。 研究了CsI、CsBr、Au和MgF_2四种光电阴极的光电发射特性和光电发射与阴极厚度的关系,找出了最佳阴极厚度。用软X射线单色仪在277—7469ev光子能量范围内测量了最佳厚度阴极的绝对量子效率,四种阴极最大值分别为4.50、2.90、0.25和0.12。我们还在同一阴极衬底上分区制备了四种阴极,在变象管荧光屏上比较其亮度,结果和测量的一致。 用LAB5型表面分析仪对CsI和Au阴极的光电子初能量分布作了测量,CsI阴极光电子初能量分布半高宽远小于Au。因此CsI是适用于高速摄影变象管比较理想的软X射线光电阴极。

The photocathode consists of a substrate (involving a conductive base film for dielectric cathode) and a photoemission film. Polypropylene, Formvar and Parylene thin films were used for the photocathode substrates. We have established the preparation technique of these substrates. The transmissions of these substrates in the photoenergy range from 277 to 7469 eV had been measured with a soft X-ray monochromatic source that we have established in our laboratory.The photoemission characteristics of CsI, CsBr, Au and MgF2 photocathodes and the relationship between photoemission and cathode thickness were investigated. The optimum thickness of these photocathodes had been found and the quantum efficiency of the optimum thickness photocathodes in the photoenergy range from 227 to 7469 eV had been measured with above saft X-ray monochromatic source. The maximum values of CsI, CsBr, Au and MgF2 photocathodes are 4.50, 2.90, 0.25 and 0.12 respectively. We also prepared these photocathodes on a same substrate and observed the brightness on the screen of image tube. The result obtained is coincided with that of measured.The photoelectron energy distributions of CsI, and Au photocathodes had been measured with MICROLAB 5 surface analyser. The results show that the half width of photoelectron energy distribution of CsI photocathode is much smaller than that of Au so that the CsI photocathode is more suitable for the high speed photography