Gas Electron Multipliers (GEM) are widely used as amplification stages in gaseous detectors exposed to high rates. The GEM consists of a polyimide foil which is coated by two thin copper layers. Charges collected into the holes or created during the amplification process may adhere to the polyimide part inside the holes. This is often accompanied by a change of the effective gain. The effect is commonly known as the “charging-up effect”.

This work presents a systematic investigation of the effect under well-controlled and monitored conditions for a single standard GEM foil in Ar/CO${}_2$ (90/10) gas for varying rates of X-ray interactions in the detector and for different gains of the foil. In order to cover a wide range of different rates, we apply two different methods. The first one is based on a current measurement while the second one relies on the analysis of ⁵⁵Fe spectra over time. Both methods give consistent results, showing an initial increase of the effective gain with time and an asymptotic saturation, which can be well described by a single-exponential function. We find that the characteristic time constants extracted from our measurements scale inversely proportional to the rate of incoming electrons for a given GEM voltage. Introducing characteristic quantities, which describe either the number of incoming electrons per hole or the total number of electrons in a hole per characteristic time, we find consistent numbers for measurements taken at the same GEM voltages. For measurements taken at different GEM voltages, however, also the characteristic total number of electrons inside the hole, which is supposed to take into account the different effective gains, is found to be higher by a factor of about 3.5 for $U_{\mathrm{GEM}}=\text{350}\text{V}$ ($n_{\mathrm{tot}}=8.8\times 10^8$) compared to 400 V ($n_{\mathrm{tot}}=2.4\times 10^8$). This hints at a residual dependence of the charging-up characteristics on the GEM voltage.

气体电子倍增器（GEM）被广泛用作暴露于高速率的气体检测器中的放大级。GEM由一层聚酰亚胺箔组成，该箔上覆有两个薄铜层。收集到孔中或在扩增过程中产生的电荷可能会粘附到孔内的聚酰亚胺部分。这通常伴随着有效增益的变化。该效应通常称为“充电效应”。

这项工作对在Ar / CO中单一标准GEM箔在良好控制和监测条件下的效果进行了系统的研究。${}_2$（90/10）气体用于检测器中X射线相互作用的速率不同以及箔片的增益不同。为了涵盖各种不同的费率，我们采用了两种不同的方法。第一个基于电流测量，而第二个则基于对⁵⁵的分析 随时间变化的铁谱。两种方法都给出了一致的结果，显示了有效增益随时间的初始增加和渐近饱和，这可以通过单指数函数很好地描述。我们发现，对于给定的GEM电压，从测量中提取的特征时间常数与输入电子的速率成反比。引入特征量（描述每个孔的入射电子数或每个特征时间的孔中电子总数），我们发现在相同的GEM电压下进行测量所得到的一致数。但是，对于在不同GEM电压下进行的测量，还应考虑到空穴内部电子的特征总数，该总数应考虑到不同的有效增益，${ü}_{\mathrm{宝石}}=\text{350}\text{V}$ （${ñ}_{\mathrm{小孩}}=8。8\times \mathrm{1个}{0}^8$）与400 V（${ñ}_{\mathrm{小孩}}=2。4\times \mathrm{1个}{0}^8$）。这暗示了充电特性对GEM电压的残余依赖性。