PVDIS GEM strip occupancy has been shown to be as high as 80% in GEM 1 due to photon backgrounds. In the downstream GEMs the photon hot spot is well separated from the high xbj DIS electrons and rates can be reduced by turning off high voltage in the areas of the GEMs outside the signal stripe. Upstream, the photon hot spot is not separated from the DIS stripe, and dead HV regions can do little to reduce the maximum occupancy. It has instead been suggested to divide some of the GEM strips into two substrips, one at low radius and one at high radius, to be read out separately, with about half the background rate in each compared to an undivided strip.
The digitization code has been modified to improve simulation of dead HV regions and provide for divided strips, and occupancies have been estimated using these enhancements.