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我们在二级玻璃汞扩散泵的真空系统上使用了室温的镉膜阱,证明镉膜阱能有效地捕集汞蒸气,使被抽容器达到气压力10~(-5)—10~(-7)毫米汞数量级的高真空。我们较系统地试验了镉膜的条件对于极限气压的影响,实验结果表明,新蒸发的镉膜效果最好;将镉膜在10~(-2)毫米汞的气压下搁置10小时后对于极限气压的影响不大;但若将其在大气下搁置10小时,则极限气压约升高一个数量级;进一步延长在大气中的暴露时间(达300天),对极限气压无更大的影响。初步的寿命试验表明,扩散泵工作140小时之后,极限气压才较显著地上升。降低镉膜阱的温度、增加镉膜阱的数目和被抽容器的高温烘烤都是提高真空度的有效途径;在实验中考虑了这些因素,我们曾获得了气压低达10~(-9)毫米汞数量级的超高真空。
We used a room temperature cadmium trap on the vacuum system of the secondary glass mercury diffusion pump to demonstrate that the trapped cadmium trap effectively trapped the mercury vapor to a pressure of 10-5 (-10) 7) mmHg high vacuum on the order of magnitude. We systematically tested the effect of the cadmium film on the limiting pressure. The experimental results show that the newly evaporated cadmium film is the best. After the cadmium film is allowed to stand for 10 hours under the pressure of 10-2 mmHg, However, if it is left in the atmosphere for 10 hours, the ultimate pressure is about an order of magnitude higher. Further prolonging the exposure time in the atmosphere (up to 300 days) has no greater effect on the ultimate pressure. Preliminary life tests showed that the limiting pressure increased significantly after 140 hours of operation of the diffusion pump. Lowering the temperature of the cadmium trap, increasing the number of trapped cadmium traps and the high temperature baking of the drawn vessel are all effective ways to increase the vacuum. Taking into account these factors in experiments, we have obtained atmospheric pressure as low as 10-9 ) Mm Hg-level ultra-high vacuum.