A standalone simulation program for Resistive Cylindrical Chamber (RCC)

TL;DR

The paper tackles the challenge of characterizing avalanche growth and signal induction in a novel Resistive Cylindrical Chamber (RCC) by delivering a fast, standalone semi-phenomenological simulator that extends RPC-inspired models to cylindrical geometry. It implements a stepwise avalanche model with space-charge disk approximations and uses the Ramo–Shockley weighting-field framework to compute induced charges, validated against planar RPC data and then applied to RCC geometries. Key findings include a detailed mapping of how geometry and voltage polarity affect avalanche growth, induced charge, and detection efficiency, revealing pronounced asymmetries between RPC and RCC configurations. The work provides a practical tool for rapid parameter scans and design optimization within the TANGO_RD project, enabling quantitative guidance on RCC performance prior to extensive full microscopic simulations.

Abstract

In recent years, the Resistive Cylindrical Chamber (RCC) has been introduced as a novel gaseous detector, extending the well-established Resistive Plate Chambers (RPCs) to the case of cylindrical electrode geometry. Preliminary experimental studies have highlighted several promis- ing features of this configuration, motivating the need for further systematic investigations of its operation. In contrast, from the simulation perspective, detailed studies of the RCC have not been performed yet, despite the fact that the cylindrical geometry introduces new degrees of freedom- such as cylinder electrodes radii and voltage polarity- which lead to asymmetric behaviour of the avalanche development according to the polarity of the applied voltage between the electrodes. In this work we present a standalone simulation program specifically designed to model avalanche growth and signal induction in both RPC and RCC geometries. The code implements a stepwise transport model for electron multiplication, includes approximate space-charge effects, and evalu- ates the induced signals on an external electrode. The simulation has been validated against experimental data for planar RPCs and subsequently applied to RCC geometries. The results demonstrate that key observables such as induced charge and efficiency for the planar geometry are well reproduced and highlights the role of electric-field asymmetry in the cylindrical configuration. These findings provide quantitative insights into the impact of detector geometry on avalanche dynamics.

Figures (25)

• Figure 1: Townsend ($\alpha$), attachment ($\eta$) and effective Townsend ($\alpha_{\mathrm{eff}}$=$\alpha$-$\eta$) coefficient vs Electric field as evaluated by MagBoltz and than rescaled by a factor 1.43 for the standard RPC gas mixture.
• Figure 2: Left plot: Evolution of the number of electrons generated during the avalanche development starting at $x=0$. The horizontal axis shows the distance $x$ in mm covered by the avalanche since the generation, and the vertical axis represents the number of electrons on the avalanche front at each step, illustrating the evolution of the avalanche under the influence of the uniform external electric field and the space charge field. Right plot: Profile of the positive ion density left along the avalanche path upon arrival at the anode. The ions are assumed stationary during the avalanche time scale, thus providing a snapshot of the space charge distribution at the end of the avalanche development.
• Figure 3: Electric field experienced by the electron cloud as it moves from $x_0=0$ to $x=2$ mm, considering both the external field and the field due to space charge. The reduction of the effective electric field near the anode due to space charge effects limits the exponential growth of the electron avalanche.
• Figure 4: Electric field (left) and effective Townsend coefficient (right) as a function of the radial position for the RCC operated at 5800 V.
• Figure 5: Evolution of the number of electrons along the avalanche path for the cylindrical RCC in both negative and positive polarity (left) and profile of positive ion density left along the avalanche path at the time of arrival at the anode (right) without space-charge effects included.