MEASUREMENT OF THE SORPTION CHARACTERISTICS OF NEG COATED PIPES: THE TRANSMISSION FACTOR METHOD
MEASUREMENT OF THE SORPTION CHARACTERISTICS OF NEG COATED PIPES: THE TRANSMISSION FACTOR METHOD
复制标题
负涂层管道吸附特性的测量：传输系数法
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
S. Raimondi
中科院分区：
文献类型：
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作者：
A. Bonucci;A. Conte;P. Manini;S. Raimondi
真空室非蒸发吸气剂(NEG)涂层已应用于粒子加速器中，以降低运行条件下的气压。为此，NEG涂层的实际泵浦速度的表征是一个关键问题。它是采用ASTM F798-82标准的动态吸附方法进行的，对样品(试片)进行离线处理，适当地放置在待涂覆的腔体内，并在过程后回收。为了现场评价吸气剂涂层吸气室的吸附特性，本文介绍了一种不同的测量技术(传输系数法)。它是基于测试气流下涂层管道入口和出口的压力比的测量。校准曲线允许从压力比评估涂层表面的粘连概率。使用参考样品来校准方法是相当困难的。一种更好的方法是模型化的方法，找出压力比对平均粘着概率、管道长度、截面几何形状和尺寸的依赖关系。将给出初步的实验结果。
ZrTiV Non Evaporable Getter (NEG) coatings of vacuum chambers have found application in particle accelerators to lower the gas pressure, during the operative conditions. For that, the characterization of the actual pumping speed of the NEG coating is a key issue. It is carried out by means of the dynamic sorption method according to ASTM F798-82 standard, conducted “offline” on a sample (coupon), suitably positioned inside the chamber to be coated and recovered after the process. To evaluate in-situ the sorption characteristics of getter coated chambers, a different measurement technique (Trasmission Factor Method) is here described. It is based on the measurement of pressures ratio at the inlet and the outlet of a coated pipe, under a flow of test gas. A calibration curve permits to evaluate sticking probability of the coated surface from the pressure ratio. The use of reference samples to calibrate the method is quite difficult. A better approach is a modellistic one, finding the dependency of pressure ratio on the average sticking probability, the pipe length, the section geometry and dimensions. Preliminary experimental results will be shown.