#
73rd Annual Gaseous Electronics Virtual Conference

## Volume 65, Number 10

##
Monday–Friday, October 5–9, 2020;
Time Zone: Central Daylight Time, USA.

### Session KT3: Plasmas in Liquids

3:00 PM–4:30 PM,
Tuesday, October 6, 2020

Chair: David Staack, Texas A&M

### Abstract: KT3.00001 : Electron transport and streamer propagation in gases and nonpolar liquids and their applications in modelling of particle detectors

3:00 PM–3:30 PM
Live

Preview Abstract
Abstract

####
Author:

Sasa Dujko

(Institute of Physics University of Belgrade, Serbia)

In this work, we discuss the physics of resistive plate chambers (RPCs),
including the electron transport and streamer propagation in the gas filled
gaps, and signal induction in the system of electrodes. RPCs are used for
timing and triggering purposes in many high-energy physics experiments at
CERN, including ATLAS, ALICE and CMS. Using the pulsed-Townsend measurements
and calculations of the electron drift velocity, longitudinal diffusion
coefficient and effective ionization coefficient in pure
C$_{\mathrm{2}}$H$_{\mathrm{2}}$F$_{\mathrm{4}}$ and its mixtures with Ar,
we propose a complete and consistent set of cross sections for electron
scattering in C$_{\mathrm{2}}$H$_{\mathrm{2}}$F$_{\mathrm{4}}$. Electron
transport coefficients, required as an input in fluid-equation based models,
are calculated from numerical multi term solutions of Boltzmann's equation
and Monte Carlo simulations in a variety of RPC gas mixtures, as a function
of the reduced electric field. We have developed a 1.5D classical fluid
model with photoionization to investigate the streamer development in
various RPCs at CERN and elsewhere. Among many important points, it is found
that the electron absorption on the anode has a large influence on the space
charge effects and positive streamer formation. The classical fluid model is
extended by considering the model in which the source term in the equation
of continuity is expanded in terms of the powers of the number density
gradient operator. The expansion coefficients are calculated over a wide
range of the reduced electric fields using a Monte Carlo simulation
technique. Both fluid models are developed to demonstrate how the nature of
transport data affects the results of an RPC modelling. Transport of
electrons and propagation of streamers, are also considered in liquid noble
gases. Solutions of Boltzmann's equation and Monte Carlo method for
electrons in dilute neutral gases, are extended and generalized to consider
the transport processes of electrons in liquid Ar and liquid Xe by
accounting for the coherent and other liquid scattering effects. We focus on
the way in which electron transport coef?cients and streamer properties are
in?uenced by a representation of the inelastic energy losses, highlighting
the need for a correct representation of elementary scattering processes in
modeling of liquid discharges. The present work has been done in
collaboration with D. Bosnjakovic, I. Simonovic, Z.Lj. Petrovic and R.D.
White.