Determination of ionic cluster size in gas detectors by using Rayleigh scattering

In gas detectors, ions have negative effects on the healthy operation of the detector. The effects on the signal through electromagnetic induction and their clustering in the detector volume and disrupting the electric field configuration in the environment can be counted as the main problems. Especially in large volume gas detectors such as TPC (Time Projection Chamber), this problem is frequently discussed by scientific circles today. In fact, although some attempts have been made to solve this problem, a successful approach has not been found yet. However, as an accepted approach, it is important to first determine the behavior of the ions in the detector for solving the problem. While there is an intense opinion in the literature that ions have no effect on the signal, it has been stated in the articles published in scientific journals recently that these ions have significant effects on the signal. In fact, these ions, which emerge during the formation of primary electrons in the detector volume, turn into ionic clusters until they reach the cathode (Kalkan, 2015). As an alternative tool for determining the size of ionic clusters, scattering experiments with light atoms or photons stand out. These studies attracted the attention of scientists working on detector physics on ions, but they were insufficient to fully explain the behavior of ions. The results regarding the sizes of ionic clusters, which are based on estimations based purely on theoretical calculations, need to be proven experimentally. Although scientific researches show the existence of ionic clusters consisting of 1-3 atoms or molecules, some scientific authorities argue that hundreds of atoms or molecules can form ionic clusters in the environment. As a result, by knowing the sizes of ionic clusters, more comprehensive information about the problem they create in the detector will be given, and the solutions to be put forward will be directed. Within the scope of this thesis; A laser beam was sent to the area in the detector where ions were formed and entrained by the electric field. Experimental evidence for the existence and size of ionic clusters has been provided by analyzing the scattered beam (Rayleigh Scattering). Volume determination using Rayleigh scattering has been used for a long time. However, there are significant differences between the method to be used in this thesis and the literature. For example; The ionic clusters formed do not move by vacuum, but by electric field effect. It is also not possible to channel the formed ionic clusters into a thin nozzle. In order to solve the problem, only the method of these studies in the literature will be used. The aim is to obtain the first experimental results about the dimensions of the ionic clusters formed in the operating parameters of gas detectors (pressure, temperature, humidity, gas mixture used, etc.) and to share them with the literature.