SNAPIN reads all of the 10 chord-integrated electron density measurements provided by the vertically-viewing MIRI diagnostic. A proper normalization of the Thomson scattering profile measurement of ne(R) to one of these chords would iteratively
However, up through release 6.0 of SNAP this algorithm is not used. Instead, irrespective of which MIRI chord is selected as the one to be used for normalization, it is treated as a horizontal line integral measurement of . The Thomson scattering measurement is then normalized so that its horizontal integral of equals the MIRI value. Note that the Thomson measurement of ne(R) is performed in the horizontal midplane, so mapping to minor radius is not required to evaluate its in this algorithm. The practical consequences of using this more rudimentary algorithm are:
Using one of the individual MIRI chords for normalization (i.e. not FM-YI-NE) will effectively overestimate the plasma density by its elongation , which for typical plasmas is an error of a few percent.