Drift Velocity, Longitudinal and Transverse Diffusion in Hydrocarbons derived from Distributions of Single Electrons

Abstract

A time of flight method is described which allows the simultaneous measurement of drift velocity w and the ratios of the longitudinal and transverse diffusion coefficients to mobility (DL/JL, DT/JL) of electrons in gases. The accuracy achieved in this omnipurpose experiment is comparable with that of specialised techniques and is estimated to be ±1 % for w and ±5% for the D / JL measurements .. Results for methane, ethane, ethene, propane, propene and cyclopropane for values of E/N (the electric field strength divided by the number density) ranging from 0·02 to 15 Td are presented and discussed (1 Td = 10-21 Vm 2 ).

Scanning drift tube measurements of electron transport parameters in different gases: argon, synthetic air, methane and deuterium

“…A scanning drift tube apparatus, capable of mapping the complete spatial and temporal development of electron swarms has been employed to determine transport coefficients (bulk [49], Davies et al [50], Hunter et al [51], Schmidt and Roncossek [6], Berghöfer et al [5], Yoshida et al [11]. drift velocity, longitudinal diffusion coefficient, the effective ionization frequency and Townsend ionization coefficient) of electrons in different gases: argon, synthetic air, methane and deuterium.…”

“…For comparison we include data from the following works. Al-Amin et al [49] used the TOF technique with a fixed drift gap length to obtain the drift velocity and the longitudinal diffusion coefficient within the range 0.28-848 Td; Davies et al [50] determined the transport coefficients of electron swarms initiated by UV light illumination, in a drift tube with variable gap length; Hunter et al [51] provided data for the drift velocity and the effective ionization coefficient using the pulsed Townsend technique; Schmidt and Roncossek [6] used two-photon ioniz ation by intense UV laser light within the gas phase to create electron swarms and determined the drift velocity, as well as D L and D T , at low reduced electric fields, limited to E N / ⩽15 Td; Berghöfer et al [5] used as well UV laser ionization in the gas phase, however, in this experiment two laser beams were used to ionize the gas at two different positions, and the difference between the arrival times of the two particle clouds were measured; Yoshida et al [11] employed a double shutter drift tube and measured the arrival time 'spectrum' of electrons. The results obtained in all these experiments show a high degree of consistency, and a good agreement is also found with our present data, especially for the drift velocity values shown in figure 7(a).…”

“…Experiments have been carried out recently for gases like CF 4 [12], CF 3 I [13], and tetraethoxysilane [14], which have become important in processing applications. Other gases, like SF 6 , CF 3 I, hydrofluoroolefine, He + H 2 O generated interest in swarm experiments because of their relevance to global warming, high voltage insulation, and biomedicine [15][16][17][18]. Particular transport effects [19][20][21] in specific gas mixtures (like negative differential conductivity) also motivate further experimental studies.…”

“…These systems have been based on different operating principles (photoelectric pulsed drift tubes, double-shutter drift tubes, systems based on photoionization of the gas, etc), see, e.g. [2][3][4][5][6]. As to the detection of the particles, in part of the systems the displacement current generated in the electrode gap by the moving charges [7][8][9] is sensed, while in other systems the counting of particles arriving at a detector has been employed [3,10,11].…”

Electron swarm parameters in C$_2$H$_2$, C$_2$H$_4$ and C$_2$H$_6$: measurements and kinetic calculations

“…in [13][14][15][16][17] for C 2 H 2 , in [13,[16][17][18][19][20][21][22][23] for C 2 H 4 , and in [13, 15-17, 19, 24, 25] for C 2 H 6 , further experimental transport and ionization coefficients have less frequently been reported for these hydrocarbon gases. Measurements of the longitudinal component of the diffusion tensor under time-of-flight (TOF) conditions were additionally reported in [14] for C 2 H 2 , [18][19][20] for C 2 H 4 , and [19,24] for C 2 H 6 . Hasegawa and Date [13] also determined the effective ionization coefficient by the steady-state Townsend (SST) method for seven organic gases including acetylene, ethylene, and ethane.…”