An ultra-long global-local grouping 1-D MSGC for very-large-area gas detector

Now we are developing a very-large-area position-sensitive neutron detector for a next generation Japanese spallation neutron source, J-PARC. Recently, we have proposed a new global-local grouping method to reduce the scale of front-end electronics for two-dimensional microstrip gas chambers. In this method we divide a signal charge into two parts: one provides a coarse position and the other provides a fine position. The method relies on a multi-layer microfabrication technique but we could successfully confirm the principle of this encoding method. In this paper, we propose another variation of the global-local grouping method which utilizes a geometrical charge division method for cathode signals. Basically, positive ions created near an anode strip are split in neighboring two cathode strips. In this method we can improve the position resolution to ~10 times at the signal to noise ratio of 40. We have fabricated an ultra-long microstrip detector whose sensitive length was 640 mm. Test measurement with 8 keV X-rays provided a fine position resolution of 1-3 mm. We have successfully demonstrated the principle of our method