spatial variation of the energy scale

Saclay/France, 2003 Sept 24-25offset map correctionEPIC Calibration Meeting, K. Dennerl

Spatial variation of the energy scale

Energy correction for pixels with an incorrect value in the offset map

Investigation of additional spatial offsets


rev 332 59 ks calclosed

20 adu image



20 adu image: localizing bright pixels



E = 5.908 +/- 0.0004 keV

20 adu image: bright pixels



20 adu image: bright pixels shifted

E = 5.896 +/- 0.0004 keV



Energy shifts and 20 adu brightness



20 adu image: intensity classes



Low intensity




High intensity




Very high intensity




20 adu image



20 adu image, after energy correction


rev 344 75 ks

20 adu image, normalized to 1 ks


rev 349 36 ks



rev 522 90 ks



rev 523 76 ks



rev 525 82 ks



rev 526 93 ks



rev 527 100 ks



rev 528 82 ks



rev 544 121 ks



rev 548 89 ks



Median image of norm. 20 adu images

rev 548 89 ks

rev 344 75 ksrev 349 36 ks rev 522 90 ksrev 523 76 ks

rev 544 121 ks rev 528 82 ks

rev 526 93 ks rev 525 82 ks

rev 527 100 ks

844 ks


rev 344 75 ks



rev 344 75 ks

20 adu image – median, normalized


rev 349 36 ks



rev 522 90 ks



rev 522 90 ks

offset map (filtered)


rev 523 76 ks



rev 525 82 ks



rev 526 93 ks



rev 527 100 ks



rev 528 82 ks



rev 544 121 ks



Correlation between pixel contents

rev 522 90 ks



rev 523 76 ks



rev 525 82 ks



rev 526 93 ks



rev 527 100 ks



rev 528 82 ks



rev 544 121 ks



rev 544 121 ks

rev 522 90 ksrev 523 76 ks rev 525 82 ks rev 526 93 ks rev 527 100 ks rev 528 82 ks


Values for energy correction


Values for energy correction

add: if:

Q 0 Q 1 Q 2 Q 3

- 2 adu -0.09 -0.07

-0.12 –0.04

-0.50 –0.19

-0.12 –0.17

- 1 adu -0.07 –0.02

-0.04 –0.01

-0.19 –0.07

-0.17 –0.06

+ 1 adu 0.05 - 0.21

0.03 – 0.13

0.11 – 0.49

0.12 – 0.46

+ 2 adu 0.21 - 0.61

0.13 – 0.36

0.49 – 1.34

0.46 – 1.24

+ 3 adu 0.61 – 1.24

0.36 – 0.68

1.34 – 2.65

1.24 – 2.30

+ 4 adu 1.24 – 2.27

0.68 – 1.38

2.65 – 4.00

2.30 – 2.46

+ 5 adu 2.27 – 4.00


Recipe for energy correction

If (residual) offset map is available: - take energy shifts directly from it

Otherwise: - compute 20 adu image from all raw events - subtract median filtered reference map - read correction values from reference table (CCD 6 may require a special treatment)

Note: subsequent cleaning for events >= 20 adu may be appropriate

spatial variation of the energy scale

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