ACIS Spectral Resolution Analysis

Device w140c4r in S1 (BI)

In backside devices the energy scale is not as linear as it appears in front illuminated devices. Figure 61 (Figure 1.5 in the ACIS calibration report) shows the linear energy scale residuals for the back-illuminated devices. Depending on energy, these residuals show extensive deviations with up to +/-30 eV near oxygen, which more than 20% of the spectral resolution in w140c4r, which averages to about 135 eV at O-K in the phase I data analysis. Table 123 and figure 123 show the spectral resolution of w40c4r averaged over the whole node for XRCF phase I data (from table 1.7 of the ACIS Calibration Report). The fits in figure 123, unlike fits to front side devices, are best fit polynomials with no physical meaning.

Spatial variation analysis in preparation.......