The UVCS detectors collect the incoming photons (now focused, dispersed into a spectrum, and presumably free of contamination from the solar disk) and translates them into electronic signals that can be sent back down to Earth and analyzed.
The UV detectors in the LYA and OVI channels consist of a stack of microchannel plates (MCPs) and a crossed-delay-line (XDL) anode. The MCPs have photo-sensitive surfaces that produce electrons when struck by photons (via the photoelectric effect). Additional electrons are produced when the freed photoelectric electrons are accelerated by an electric potential and continue to collide with the surfaces inside the MCP. These electrons produce a drifting "charge cloud" that carries an electric current and is collected at the orthogonally positioned grid of XDL anodes.
The XDL detectors consist of 1024 pixels in the spectral direction (i.e., the direction of grating dispersion perpendicular to the slit) and 360 pixels in the spatial direction (i.e., along the slit). An example portion of the detector is illustrated below:
where the horizontal direction is spectral and the vertical direction is spatial. Note the bright spectral lines surrounded by relatively dark regions of wavelength. Software on board SOHO is used to select several subsets (often called "windows" or "panels") of the full detector image to transmit to the ground.
The WLC detector is considerably simpler because there is just one "pixel" to transmit. This detector is a photomultiplier tube which works in the same general way as an MCP.
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