真空校准室内分子流场分布的理论分析与计算

THEORETICAL ANALYSIS AND CALCULATION OF MOLECULE FLOW DISTRIBUTION IN VACUUM CALIBRATION CHAMBER

在动态流量校准系统中,气体分子流场分布非均匀性是造成被校规测量值出现偏差的原因,也是校准装置系统误差的来源。介绍校准室内分子流场分布的理论计算方法,这种方法不仅能分析分子流场分布的非均匀性,还能够直接计算被校规室内的分子密度,给出规室内分子密度与进入校准室气体流量之间的函数关系。计算时考虑了校准室的几何结构,最大限度的减小了校准室结构设计对分子流场分布带来的影响。对返流比β和有效抽速Seff的计算方法,为动态流量校准装置系统参数的蒙特卡罗模拟提供了理论依据。

The non-uniformity of the gas molecule density distribution in the continuous gas expansion vacuum standards is the cause of the error of the metrical value of the gauge to be calibratedby. It＇s the also the source of systematic error of these standards. This paper presents theoretical calculation method of molecule flow distribution in calibration chamber. This method not only can entirely analyse the non-uniformity of the gas molecule density distribution, but also can calculate the molecule density in the calibrated gauge volume. It indicate the function relation between the molecule density in the calibrated gauge volume and the throughput enter into the calibration chamber. Thus minimizing the drawbacks of the geometric structure influence of the molecule density distribution. The calculation method of the backstreaming coefficient β and effective pumping speed Seff present theory foundation for the calibration system parameter Monte Carlo simulation.