Methods are disclosed for operating a device having a high energy particle detector wherein the particles create first incoming traversal events, outgoing backscatter events, higher-order in and out events and incoming events caused by particles which backscatter out of the device, hit nearby mechanical structures and are scattered back into the device. Exemplary method steps include discriminating incoming traversal events from outgoing backscatter events, higher-order in and out events and incoming events by limiting dose rate to a level at ensures that separate events do not overlap and discriminating events from background and from other events based on total energy in each event; discriminating backscatter events from incoming traversal events based on electron path shape; or determining that a first event and a second event are coincident with each other and separating incoming form backscatter events based on electron path shape and energy level.