Abstract

The thickness gauge systems based on beta radiation were widely used in the industry for online, continuous and non-contact measurements. One of the important parameters in beta thickness gauge is the accuracy which the system was evaluated based on it. The effective factors in the measurement accuracy of these systems consist of the mechanical and detection sections. In the mechanical section, the detection system (source and detector) was moved throughout the factory line (without sheet) in order to measure the mechanical error. In the detection part, the detection set-up was stopped in its parking lot and the biaxially oriented polypropylene sheets with different thicknesses were placed between the source and detector to determine the contribution of detection error. In this research, a beta thickness gauge with a ¹⁴⁷Pm source (half-life of 31 months) was evaluated in biaxially oriented polypropylene sheet production lines in order to determine the mechanical and detection errors. The contribution of the mechanical error due to system motion and the contribution of the system’s detection error were measured individually. The total error is the sum of the acquired errors of two mechanical and detection sections. In this study, the 2sigma (standard deviation) criterion was used as a system error. The mechanical error was calculated 0.12 by moving of system and without the sheet. Also, the detection error was determined 0.1 by placing the sheet between source and detector and stopping of the system. The total error was estimated 0.16 using the error correlation relation. The acquired results showed for producing of biaxially oriented polypropylene sheets with 15-µm thickness and the maximum acceptable error of ±0.2 µm, the system can be used for 40 months at the precision measurement time (zero time). If the mechanical error is reduced by 50%, the using time of the radioactive source increases to 16 months (56 months). The reducing of the mechanical error can minimize cost, radiation safety, and shielding requirements.

中文翻译：

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机械误差对β测厚仪性能的影响及系统运行时间的预测

摘要

基于β辐射的测厚仪系统已广泛用于在线，连续和非接触式测量行业。Beta测厚仪中的重要参数之一是根据其评估系统的准确性。这些系统的测量精度中的有效因素包括机械部分和检测部分。在机械部分，检测系统（源和检测器）在整个工厂生产线上（无纸）移动，以测量机械误差。在检测部分，将检测装置停在其停车场中，并将具有不同厚度的双轴拉伸聚丙烯片材放置在源和检测器之间，以确定检测误差的影响。在这项研究中，带有¹⁴⁷的β测厚仪为了确定机械误差和检测误差，在双轴取向聚丙烯片材生产线中评估了Pm来源（半衰期为31个月）。分别测量了由于系统运动而引起的机械误差的贡献和系统的检测误差的贡献。总误差是两个机械部分和检测部分所获取的误差之和。在这项研究中，将2sigma（标准偏差）标准用作系统误差。机械误差的计算是通过移动系统和不使用纸张来进行的，误差为0.12。另外，通过将薄片放置在源和检测器之间并停止系统，可将检测误差确定为0.1。使用误差相关关系估计总误差为0.16。获得的结果表明，该产品可生产厚度为15 µm的双轴取向聚丙烯片材，最大可接受误差为±0.2 µm，该系统可以在精密测量时间（零时间）使用40个月。如果将机械误差降低50％，则放射源的使用时间将增加到16个月（56个月）。机械误差的减小可以使成本，辐射安全性和屏蔽要求最小化。