Cutaway diagram of the INCA sensor and a schematic of how the sensor operates. Energetic Neutral Atoms (ENA's) pass through a collimmator region with high voltages (to sweep charged particles away from the entrance apeture) and then pass through a very thin entrance foil. Secondary electrons generated in the entrance foil are steered to a 1 dimensional imaging microchannel plate (the start MCP) where the entrance position of the ENA (along the entrance slot ) is determined as is the start time for a Time-of-Flight (TOF) measurment. The ENA proceeds to the back of the sensor where it passes through another thin foil and then encounters a 2-dimensional imaging microchannel plate (stop MCP) where the (x, y) postion of the striking position is determined as is the stop time for the TOF measurment. Secondary electrons from the back foil are also steered to a third, coincidence microchannel plate. Onboard processing utilizes this coincidence signal to substantially reduce the background of the measurment. Finally, the pulse-height of the MCP signals from the star t and stop MCP's are recorded. A TOF versus pulse-height matrix allows the onboard processor to sort the events by energy and mass species. The final measurment product for the sensor is ENA arrival direction, energy and mass species (Hydrogen and Oxygen).
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