Electron swarm coefficients in 1,1,1,2 tetrafluoroethane (R134a) and its mixtures with Ar

Analytical calculation of the charge spectrum generated by ionizing particles in Resistive Plate Chambers at low gas gain

“…The apparent excellent empirical agreement between the experimental data and For a typical applied electric field in 0.3 mm gaps of around 90 kV/cm the effective first Townsend coefficient will be close to 100 mm -1 for the base gas (C 2 H 2 F 4 ) typically used [12]. r ≤ we conclude that the cluster density λ should be at least close to 100 mm -1 , which seems to be a complete impossibility for minimum ionizing particles.…”

“…If 1 G >> (most likely the interesting practical case) one may consider a slightly inaccurate but handier approximation by noting that for large G ‡ Generalized binomial expansion. § ( ) (12) and therefore…”

Challenges for resistive gaseous detectors towards RPC2014

“…But, first, a thorough revision of the gas parameters that characterize the electron swarm is pertinent. Exemplarily, early estimates of the multiplication (Townsend) coefficient from the Magboltz code (circa 2004), that is generally acknowledged to represent the state of the art for gaseous detector simulations, differ by as much as 20% from the recently measured values on the main RPC gas, C 2 H 2 F 4 [66] (see [65] for a comparison). According to [67], contemporary versions of Magboltz (beyond 8.X.X) have been tuned in order to describe the systematics measured in [66], although there is work still ongoing on this direction.…”

“…Exemplarily, early estimates of the multiplication (Townsend) coefficient from the Magboltz code (circa 2004), that is generally acknowledged to represent the state of the art for gaseous detector simulations, differ by as much as 20% from the recently measured values on the main RPC gas, C 2 H 2 F 4 [66] (see [65] for a comparison). According to [67], contemporary versions of Magboltz (beyond 8.X.X) have been tuned in order to describe the systematics measured in [66], although there is work still ongoing on this direction. It will be very interesting to see how the conclusions of previous simulation works are modified with much more precise parameters of the swarm, at least for a simple C 2 H 2 F 4 -only scenario (gas mixtures add another level of complexity to Magboltz calculations, due to the presence of new hetero-nuclear atomic and molecular processes that are not present in the pure gases).…”

Cross sections for electron collisions with tetrafluoroethane (C<inf>2</inf>H<inf>2</inf>F<inf>4</inf>)

“…Electron attachment, dissociative excitation and ionization cross sections were calculated by using the Quantemol code. That set was normalized by using a Boltzmann equation solver and a Monte Carlo code, so as to obtain the electron swarm parameters -drift velocity, W, and effective ionization coefficient, ( -)/N, consistent with experimental data [4]. Calculations were made for pure gas and mixtures with Ar of various compositions.…”