sentences:  The detector, a silicon surface-barrier type with an area of 100 mm2 and a thickness of 3 mm, was shielded so as to prevent protons below 30 MeV from reaching it from directions other than via the aperture.The aperture was covered by a very thin foil to prevent light impinging on the detector and generating noise.The signal from the detector was broken up into nine channels, the lowest six dedicated to electron detection and the highest three to protons and heavier ions.