This is where an electron detector is mounted, usually in the form of a 40 mm microchannel plate paired with a fluorescent screen. Electron detection events are recorded using an outside camera and are counted in hundreds of thousands of separate angle vs. kinetic energy channels.
The location for an electron detector is here, usually consisting of a 40 mm microchannel plate paired with a fluorescent screen.  Electron detection events are captured by an external camera and then counted in numerous angles versus kinetic energy channels.