The effect of grid misalignment on the uniformity of response of gas proportional scintillation counters

In the present work we revisit the simplifying assumptions of an earlier theoretical work on the effect of grid misalignnent on the performance of planar GPSCs. Experimental results that quantitatively establish this effect are presented. The magnitude of the effect is not as large as predicted due in part to the reduced dependence of the electroluminescence yield on the reduced electric field near threshold and due to electron cloud size. For the reduced fields normally used in the scintillation region of an optimized GPSC, misalignments as large as 3% have less than a 1% effect on pulse-amplitude variations. This effect is less than the statistical fluctuations in the number of primary electrons nominally produced in the absorption of X-rays. For reduced fields closer to the scintillation threshold, 15% variations in pulse amplitudes are possible, although it is unlikely that a GPSC would be operated under those conditions.