Linearity between FAM and ACIS positions

We consider data for a front-illuminated device exposed to 2.29 keV photons as a typical case. Correlation between the ACIS measured positions and the FAM Y values for horizontal displacement of FAM is shown at Fig. 6.17. Mean scatter of the experimental points (standard deviation) is 1.79 $\mu$m. Here we should take into account that an error in FAM positioning is not less than 1 $\mu$m, which results in a formal ACIS error of less than 1.5 $\mu$m.

 

Figure 6.17: Plot of centroid of ACIS Y,Z positions vs. FAM Y,Z  

Results shown in Fig. 6.17 demonstrate that accompanying the FAM movement in the horizontal direction there is also a change in the vertical positions of ACIS. That means that the ACIS-2C camera has been installed with a rotation angle of 18 arc min around the FAM X axis.