SSD chip gain calib
Updated on Tue, 2015-02-17 12:09. Originally created by bouchet on 2015-02-17 09:55.
Calibration table for SSD chip
proposal to change the gain calibration to be done at the DaqMaker level.
Pros :
1) Structure of the table
![](https://drupal.star.bnl.gov/STAR/system/files/table.png)
The table will have 1920 elements. Unlike the hotChip table (where the adress of chips to flag were saved), here we saved all the elements. 1 will be the default gain (meaning no gain)
2) table is initialized in StSstDbMaker
![](https://drupal.star.bnl.gov/STAR/system/files/table_dbmaker.png)
3) Access from another maker is done using the method chipGain()
![](https://drupal.star.bnl.gov/STAR/system/files/table_value_dbmaker.png)
4) making the calibration
Some histograms are saving the total ADC for each chips (signal of ach channel in a chip) as well as the number of counts for each chip, over a number of events processed by the BFC chain (example here)
Then the relative gain between P and N side is the ratio of the average ADC on P side over the average ADC on N side.
gain = <ADC_sideP> / <ADC_sideN>
We need to be careful to do the inversion of the chip index of N-side to associate the same chips of P and N sides.
bal blah
proposal to change the gain calibration to be done at the DaqMaker level.
Pros :
- less possible errors done in strips mapping
- possibility to do the calibration chip-by-chip, instead of wafer by wafer as it is right now
- previous calib were on the hit/cluster level ; here the plan is to correct ADC at the strip level
- histograms of the total ADC per chip and side (P,N)
- histograms of # of counts (= channels) per chip and side (P,N)
- the gain will be ratio = ( ADC_sideP / counts_sideP) / (ADC_sideN / counts_sideN )
- then the correction is done in the DaqMaker when writing spa_strip table and by correcting , if side = N , by adc * ratio
1) Structure of the table
![](https://drupal.star.bnl.gov/STAR/system/files/table.png)
The table will have 1920 elements. Unlike the hotChip table (where the adress of chips to flag were saved), here we saved all the elements. 1 will be the default gain (meaning no gain)
2) table is initialized in StSstDbMaker
![](https://drupal.star.bnl.gov/STAR/system/files/table_dbmaker.png)
3) Access from another maker is done using the method chipGain()
![](https://drupal.star.bnl.gov/STAR/system/files/table_value_dbmaker.png)
4) making the calibration
Some histograms are saving the total ADC for each chips (signal of ach channel in a chip) as well as the number of counts for each chip, over a number of events processed by the BFC chain (example here)
Then the relative gain between P and N side is the ratio of the average ADC on P side over the average ADC on N side.
gain = <ADC_sideP> / <ADC_sideN>
We need to be careful to do the inversion of the chip index of N-side to associate the same chips of P and N sides.
bal blah
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