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Status Report For Threshold Scans

This report showcases new trimming techniques for threshold scans, focusing on drop-off point calculations for shapers and samplers. It also explores the correlation between pixel statistics and the effects of applying a trim. The report includes threshold scan results, histograms, and analysis of various pixel behaviors.

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Status Report For Threshold Scans

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  1. Status Report For Threshold Scans

  2. Shaper/Sampler Drop Trims • As promised new and improved trimming techniques have been developed. • As suggested, we will focus on trims calculated according to drop-off point, calculated separately for shapers and samplers. • Here, drop-off is defined as the highest threshold where the bin content is greater than half the maximum bin content recorded. Owen Miller 19/05/2008

  3. Performance of different trims in the Shapers - Untrimmed -Basic Mean Trim - Separate Shaper and Sampler Drop-off trim Owen Miller 19/05/2008

  4. Performance of different trims in the Samplers - Untrimmed -Basic Mean Trim - Separate Shaper and Sampler Drop-off trim Owen Miller 19/05/2008

  5. Correlation Between Pixel Stats • This is essentially an attempt to find out whether or not individual pixel statistics from their threshold scans are consistently related. • Specifically the statistics studied are: Mean threshold, peak threshold and 50% drop-off. Owen Miller 19/05/2008

  6. Mean Vs Drop-off Shapers Samplers Owen Miller 19/05/2008

  7. Mean Vs Peak Shapers Samplers Owen Miller 19/05/2008

  8. Trim Vs Shift • This study is (hopefully) primarily a sanity check, ensuring that the alterations in pixel behaviour caused by applying a trim are both consistent and predictable. • The following graphs are based on a comparison between trimmed and untrimmed runs, showing how much the position of the drop-off changes with the trim applied to the pixel. Owen Miller 19/05/2008

  9. Histogram Showing the effects of Applying a Trim Owen Miller 19/05/2008

  10. Fe55 runs • Several sets of per-pixel threshold scan runs were performed with an Fe55 source next to the sensor. • The following slides show the threshold scans of several pixels with and without the Fe55 source. Owen Miller 19/05/2008

  11. Sensor 13, Column 0, Row 0 Fe55 No Source Owen Miller 19/05/2008

  12. Sensor 13, column 118, row 47 Fe55 No Source Owen Miller 19/05/2008

  13. Pedestals & Noise • The pedestal of a pixel is related to its mean threshold (on a threshold scan). • The noise of a pixel is related to the sigma of its threshold scan. Owen Miller 19/05/2008

  14. RMS of Pixels in the Sensor Owen Miller 19/05/2008

  15. Means of Pixels in the Sensor Owen Miller 19/05/2008

  16. Maximums of Pixels in the Sensor Owen Miller 19/05/2008

  17. Variation in Pixel Behaviour for Different Quadrants • c1 • - c2 Owen Miller 19/05/2008

  18. Fit Results for Sensor 16 • From the graphs on the previous slide we can get the following statistics: • Shaper Capacitor Region 1: • Mean=5.2±24.0 • Sigma=12±1.95 • Shaper Capacitor Region 2: • Mean=5.5±24.35 • Sigma=14.74±2.1 Owen Miller 19/05/2008

  19. Fitting Program • Marcel has been working on fitting program to deal with the ‘flat-top’ threshold scan distributions seen in the shapers. • The program attempts to fit a Gaussian distribution to an individual pixel threshold scan. • So far the program produces reasonable results in 90% of cases. Owen Miller 19/05/2008

  20. Pixel Threshold Scan, data and fitted Gaussian Owen Miller 19/05/2008

  21. Reliability of fitting Owen Miller 19/05/2008

  22. Laser Runs • We are in the process of starting a study of the sensor using the laser. • The laser will cover an area approximately 10 pixels by 10 pixels, this beam size is achieved purely by shutter control (no defocusing). Owen Miller 19/05/2008

  23. Sensor 18, Column 55, Row 85 Laser No Laser Owen Miller 19/05/2008

  24. Sensor 18, Column 82, Row 96 Laser No Laser Owen Miller 19/05/2008

  25. Variation in Trim Values Applied Owen Miller 19/05/2008

  26. Variation In Drop-offs Owen Miller 19/05/2008

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