Space charge effects in Resistive Plate Chambers

Abstract

We extend an existing one dimensional simulation model for avalanche mode RPCs by the inclusion of diffusion and space charge effects. We investigate the influence of space charge on charge spectra, signal rise time, time resolution and charge-to-time correlation. We present a 1.5-dimensional model, which allows fast simulation of events and a two dimensional model that is slower but allows to study the transverse dispersion of avalanches due to space charge. [3,4]. They are constructed of two resistive electrode plates made of bakelite as shown schematically in Fig. 1a. Timing RPCs [5] with gas gaps of 0.2 to 0.3 mm are used in multi gap configurations [6] for Time-Of-Flight purposes [7]. They provide 99% efficiency and time resolutions down to 50 ps [8,9,10,11]. Different technologies with one or more resistive electrode plates are used. The two single gap designs investigated in this publication are shown in Fig. 1. Preprint submitted to Elsevier Science

Development of high-rate timing RPCs

“…Currently, the detection of MIPs over large areas can be made at rates close to 3 kHz/cm 2 [1,2], while at medium gas gains, around 10 5 , and small active areas counting rates over 10 7 Hz/cm 2 [3,4] have been demonstrated. For timing RPCs [5]-RPCs used for time-offlight measurements-the current maximum counting rate capability is close to 2 kHz/cm 2 [6].…”

“…For timing RPCs [5]-RPCs used for time-offlight measurements-the current maximum counting rate capability is close to 2 kHz/cm 2 [6]. However, these counters operate at rather extreme conditions (enormous gas gain over 10 12 and avalanche development in a deeply space-charge saturated mode [7]), which may make the operation at high counting rates difficult due to instabilities arising from the cathodes [3]. In practice, the counting rate capability of RPCs is also strongly conditioned by the availability of suitable electrode materials with medium resistivity and good mechanical characteristics.…”

Current Challenges and Perspectives in Resistive Gaseous Detectors: a manifesto from RPC 2012.

“…A simulation mile-stone was achieved in 2004 with the description of the avalanche evolution in Resistive Plate Chambers under its own space-charge, largely utilizing first principles [43]. The simulations resorted to the minimal framework for realism, the 1.5D hydrodynamic model [43,63], that allows for a realistic calculation of the electric field during the avalanche evolution, yet within a reasonable computation time.…”

“…The simulations resorted to the minimal framework for realism, the 1.5D hydrodynamic model [43,63], that allows for a realistic calculation of the electric field during the avalanche evolution, yet within a reasonable computation time. In order to approximately account for the fluctuations in the multiplication process, the equations of evolution were solved in Monte Carlo (MC) fashion through a particle in cell (PIC) -like procedure.…”

“…Fortunately, it is not difficult to improve the situation, for cases where such an additional sophistication is needed: typical RPC dimensions suggest a conceptual separation between avalanche formation and signal readout, so an 'after-burner' based on an 'induction + transmission + readout model' might suit many practical cases, by treating diverse avalanche models on equal foot [59,65]. This framework, conceptually based on the pioneering approach sketched in W. Riegler's works [81,82], relies on Multi-Conductor Transmission Line theory (MTL) together with a 2D electrostatic solver, and can potentially extend the 1.5D hydrodynamic framework introduced in [43] to a much higher level of realism. This is due to its ability to include practical problems connected to the system response like the characteristic impedance matrix and charge sharing phenomena (required for the description of a multi-strip/pad situation), transmission losses, connections, amplifiers and noise, without making critical approximations.…”