An electrostatic lens to reduce parallax in gas detectors with cylindrical geometry

Cylindrical gas detectors are often used in fixed-target experiments, because they are free of parallax effects in the equatorial plane. However, there is a growing demand to increase the width of these detectors in order to be more efficient or to cover more solid angle, hence a parallax effect starts to limit the resolution in that direction. In this paper, we propose a hardware correction for this problem which reduces the parallax error thanks to an applied potential on the front window that makes the electrostatic field lines at the entrance window radially point to sample position. A detailed analytical analysis of the solution is also presented.