M.Sc. degree thesis
accepted by Weizmann Institute of Science, Rehovot, Israel 2013

Adam Rubin

Supervisor: Amos Breskin

THGEM-detector investigations: electron-avalanche asymmetry and operation with resistive anodes

 Keywords:

• Micropattern gaseous detectors (MSGC, GEM, THGEM, RETHGEM, MHSP, MICROPIC, MICROMEGAS, InGrid, etc)
• Optical detector readout concepts
• Materials for gaseous detectors
• Resistive-plate chambers

 Abstract:
The THick Gas Electron Multiplier (THGEM) was developed at the Weizmann group in 2004. It is a simple device, in which radiation-induced electrons are multiplied in millimeter-scale holes drilled in a printed-board circuit. THGEMs have been studied extensively, becoming a basic detector element in numerous applications. Like many other gas-avalanche detectors, occasional discharges limit the dynamic range of THGEM-based detectors. In this thesis I report on two investigations that were carried out: on the one hand, trying to understand some potential origins of discharges and on the other, trying to expand the dynamic range of these multipliers. My research focused on the study of avalanche formation inside THGEM holes and on coupling THGEM electrodes to readout anodes of high bulk resistivity. I found that although the avalanche develops asymmetrically inside the hole, it does not develop on its circumference; therefore it should not be prone to surface defects.
I also found that highly resistive anode materials can be good candidates for increasing the dynamic range of THGEM detectors.