A systematic study is performed to measure the ion backflow fraction of the GEM detectors. The effects of different voltage configurations and Ar/CO${}_2$ gas mixtures, in ratios of 70:30, 80:20 and 90:10, on positive ion fraction are investigated in detail. Moreover, a comparative study is performed between single and quadruple GEM detectors. The ion current with detector effective gain is measured with various field configurations and with three proportions of gas mixtures. The ion backflow fraction for the GEM is substantially reduced with the lower drift field. A minimum ion backflow fraction of 18% is achieved in the single GEM detector with Ar/CO${}_2$ 80:20 gas mixture, however, a minimum ion backflow fraction of 3.5%, 3.0%, and 3.8% are obtained for a drift field of 0.1 kV/cm with Ar/CO${}_2$ 70:30, 80:20 and 90:10 gas mixtures, respectively for quadrupole GEM detector. Similar values of effective gain and ion backflow fraction have been found by calculating the current from pulse height spectrum method, obtained in the Multi Channel Analyser.

进行系统研究以测量 GEM 检测器的离子回流分数。不同电压配置和 Ar/CO 的影响${}_2$详细研究了比例为 70:30、80:20 和 90:10 的气体混合物对正离子分数的影响。此外，还对单颗和四颗 GEM 探测器进行了比较研究。具有检测器有效增益的离子电流是用各种场配置和三种比例的气体混合物测量的。GEM 的离子回流分数随着较低的漂移场而显着降低。使用 Ar/CO 的单个 GEM 检测器实现了 18% 的最小离子回流分数${}_2$ 然而，80:20 的气体混合物，对于 0.1 kV/cm 的漂移场和 Ar/CO 获得的最小离子回流分数为 3.5%、3.0% 和 3.8%${}_2$分别用于四极杆 GEM 检测器的 70:30、80:20 和 90:10 气体混合物。通过在多通道分析仪中获得的脉冲高度谱法计算电流，已发现有效增益和离子回流分数的类似值。