COMPUTER-SIMULATION STUDY OF CORRESPONDENCE BETWEEN EXPERIMENTAL AND THEORETICAL ELECTRON-DRIFT VELOCITIES IN AR GAS .3. EFFECT OF THE INITIAL ELECTRON PULSE-SHAPE

The time variations of the gap current I(t) and the voltage log[V(t)] determined respectively from Schlumbohm's and Frommhold's experimental procedures for drift velocity measurement are simulated by using the Monte Carlo technique in Ar gas for five cases of the initial electron pulse shapes, such as the Dirac's delta function, Gaussian distributi ons with half widths of 10 ns and 20 ns, and Raether's distributions w ith half widths of 10 ns and 20 ns, under the condition at which ioniz ation is appreciable. The results show that the time variation of the gap current I(t) is affected by the shape and/or the value of the half width of the initial electron pulse, namely, the profiles of I(t) obt ained for the five cases of the initial pulses have different profiles . Therefore, the transit time T-SC obtained the from the different pro files of I(t) shows different values, However, it is found that the dr ift velocity W-SC calculated from the gradient of a T-SC against d plo t does not depend on the shape and/or the value a: the half width of t he initial pulse since T-SC against d plots obtained for five cases of the initial pulses show good linearity and practically the same gradi ent. Similar to the case of T-SC, although the rime variation of log[V (t)] and the transit time T-FD are affected by the shape and/or the va lue of the half width of the initial pulse, T-FD against d plots show good linearity and practically the same gradient. Therefore, it is con cluded that the drift velocity W-FD calculated from the gradient of th e T-FD against d plot does not depend on the shape or the value of the half width of the initial pulse.