A practical method to determine the spatial resolution of GEM detector

A new method to determine the spatial resolution of a one-dimensional gaseous electron multiplication (GEM) prototype is demonstrated via an experimental test using an Fe-55 source with an adjustable slit. In this method, the total variance of the incident position σ tot 2 , contributed by the GEM spatial resolution and the geometrical acceptance of the slit, is presented as a function of the event rate n under the full energy peak, with the latter being employed to calibrate the square of the slit width. Using a linear fit to the experimental data, a spatial resolution of σ g = 56 ± 15 μ m ( 1 σ ) is measured. Compared to the existing methods, the novel method presented here is robust considering the inaccuracy in the direct measurements of the slit widths, and hence greatly circumvents machining difficulties.