1304.0916 (Makoto Kobayashi)

An estimation of the effective number of electrons contributing to the
coordinate measurement with a TPC II    [PDF]

Makoto Kobayashi

For time projection chambers the accuracy in measurement of track coordinates along the pad-row direction deteriorates with the drift distance (z): (Resolution)**2 = D**2 * z / Neff, where D is the diffusion constant and Neff is the effective number of electrons. Experimentally it has been shown that Neff is smaller than the average number of drift electrons per pad row (). In the previous work we estimated Neff by means of a simple numerical simulation, taking into account the diffusion of electrons only in the pad-row direction. The simulation showed that Neff could be as small as 30% of because of the combined effect of statistical fluctuations in the number of drift electrons (N) and in their multiplication in avalanches. In this paper, we evaluate the influence of the diffusion along the direction of pad-row normal on the effective number of electrons.

View original: http://arxiv.org/abs/1304.0916