Speaker
Description
Resistive plates in gaseous detectors are commonly modelled as parallel RC circuits, possibly with a voltage-dependent resistance.
This approach has enabled substantial progress in the description of resistive-protection techniques, including induced-signal formation, rate capability, dynamic field fluctuations and charging-up times. However, real materials exhibit ideal RC-like behaviour only within a limited frequency range, if at all. As a result, deviations from the model are often absorbed into effective parameters, making it difficult to distinguish genuine material response from experimental uncertainty.
To clarify this situation, we performed impedance-spectroscopy measurements between 0.1 Hz and 10 MHz, complemented by DC measurements, on five resistive-plate materials: Bakelite, Chinese glass, low-resistive Williams glass, float glass and Fe₂O₃/YSZ ceramics, using different electrode contacts. The measurements were carried out as a function of temperature, allowing us to identify relaxation mechanisms and extract the corresponding activation energies. The observed behaviour is rich, but broadly falls into two classes: materials in which relaxation and conduction share the same activation energy, as expected for ion-conducting systems, and materials in which the two processes are decoupled, as more commonly found in electron-conducting systems.
We present the experimental results, discuss the implications of these different material classes for gaseous-detector operation, and compare standard RC predictions with those obtained from the measured response functions for several key performance quantities.