Calibration Ops Meeting Vilspa 23-24 Mar 2004 1 MOS Timing Mode Spectral Features and Possible...
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Calibration Ops Meeting V ilspa 2 3-24 Mar 2004 1 MOS Timing Mode Spectral Features and Possible Improvements Tony Abbey, Leicester University
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Transcript of Calibration Ops Meeting Vilspa 23-24 Mar 2004 1 MOS Timing Mode Spectral Features and Possible...
Calibration Ops Meeting Vilspa 23-24 Mar 2004
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MOS Timing Mode Spectral Features and Possible Improvements
Tony Abbey, Leicester University
Calibration Ops Meeting Vilspa 23-24 Mar 2004
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Overview of current concerns
• Timing mode has poor DNL because:– Timing mode sequences free run– Design decision was therefore not to use Gatti
because communication with the EMCR control processor would interrupt the timing flow
• Next slide explains Gatti and DNL
Calibration Ops Meeting Vilspa 23-24 Mar 2004
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DNL and Gatti
DNL – Differential Noise Linearity is caused by different digital values of the ADC having differing channel widths due to internal accuracy and noise.
Gatti – sliding scale baseline offset technique which applies a precise analogue offset before ADC conversion and removes it digitally from the result. In the case of the MOS, this offset is changed every frame in imaging modes.
Gatti causes the DNL to be smeared out over the width of the offset range (256 DN for MOS), and become invisible.
Calibration Ops Meeting Vilspa 23-24 Mar 2004
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PSR0540 spectrum
PSR0540 rev 041 timing spectrum pattern 0 events
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Calibration Ops Meeting Vilspa 23-24 Mar 2004
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3C273 spectra with/without DNL3C273 rev 382 timing spectrum pattern 0 events
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3C273 rev 735 timing spectrum pattern 0 events
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3C273 rev 382 SW spectrum pattern 0 events
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Calibration Ops Meeting Vilspa 23-24 Mar 2004
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Capella LW rev 0043 without/with Gatti
Calibration Ops Meeting Vilspa 23-24 Mar 2004
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1700-37 rev 219 comparison1700-37 rev 219 timing spectrum pattern 0 events
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Calibration Ops Meeting Vilspa 23-24 Mar 2004
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Binning1707-37 Timing Mode MOS1 0219 Binned X16 with start point -8DN
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Calibration Ops Meeting Vilspa 23-24 Mar 2004
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Binning2Her X1 Timing Mode MOS1 0207_0134120101 Binned X16 with start point -8DN
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Calibration Ops Meeting Vilspa 23-24 Mar 2004
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Alternative – bring back Gatti
• Gatti DAC could be incremented by EMCR every timing frame
• Slight asyncronism in setting and subtracting could result in a few events getting 1DN error (negligible effect compared with energy resolution)
• Discuss with Saclay if software mod is needed
Calibration Ops Meeting Vilspa 23-24 Mar 2004
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Timing diagram
Calibration Ops Meeting Vilspa 23-24 Mar 2004
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Timing mode sequence in the EMCR/EDU
HEADER
TRAILER
DATA
DATA
DATA
EOL
EOL
EOL
EOL
EOL
EOL
EOL
TIME
TIME
DATA
Y=1024
RECOGNIZED TIMING EVENTS
SDD HBR
start sequence
LBR A/C
stop sequence
EOI
Start Observation
LBR A/CInterface : LBR C/H
Stop Observation
