A novel technique for the measurement of the avalanche fluctuations of a GEM stack using a gating foil

TL;DR

This paper introduces a new method using a gating foil to measure avalanche fluctuations in GEM-based gaseous detectors, which can improve understanding of detector performance in high-energy physics experiments.

Contribution

A novel technique employing a gating foil to measure avalanche fluctuations and control electron transmission in GEM stacks for TPC applications.

Findings

Measured gas gain variance using the gating foil method.

Analyzed the impact of avalanche fluctuations on spatial resolution.

Demonstrated the technique with GEMs in Ar-CF4-isobutane gas mixture.

Abstract

We have developed a novel technique for the measurement of the size of avalanche fluctuations of gaseous detectors using a gating device (gating foil) prepared for the time projection chamber in the international linear collider experiment (ILD-TPC). In addition to the gating function, the gating foil is capable of controlling the average fraction of drift electrons detected after gas amplification. The signal charge width and shape (skewness) for electron-ion pairs created by a pulsed UV laser as a function of the transmission rate of the gating foil can be used to determine the relative variance of gas gain for single electrons. We present the measurement principle and the result obtained using a stack of gas electron multipliers (GEMs) operated in a gas mixture of Ar-CF$_4$(3%)-isobutane(2%) at atmospheric pressure. Also discussed is the influence of the avalanche fluctuations on the spatial resolution of the ILD-TPC.