- a reference gain
- the X and Y coordinates of the two calibration sources in unlinearized coordinates (these are converted in linearized coordinates of user selected pixel size inside the program and are not reported here).

- on
*energy*through the Be absorption cross section (computed from atomic coefficients hardcoded in the programs), and - through the typical
*thickness*of the window and of the strongback (currently stored in files`m{1,2,3}_thick_be.dat`), and equal to- for M1 : 51.5 micron (window) plus 600 micron (strongback)
- for M2 : 54.5 micron (window) plus 600 micron (strongback)
- for M3 : 53.5 micron (window) plus 600 micron (strongback)

- and on
*position*, due to the presence of the strongback structure (this must be convolved with the Point Spread Function of the optics alone)

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Fig. 4.5-I : Transmission of a Be layer with nominal thicknesses

of the MECS entrance window (solid) and its supporting strongback (dotted).

The dashed black line is the overall transmission in a point

at x,y = (0,5) mm, i.e. on the edge of the strongback.

Namely, the transmission at one given position x,y is computed combining the
transparencies of the two thicknesses *t _{window}*
and

wheretau_{w}= Z(E,x,y) exp (-mu(E)t_{window}) + (1-Z(E,x,y) exp (-mu(E)t_{strongback})

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