Open questions in x-ray measurement results Marco Rossini Institute - - PowerPoint PPT Presentation

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Open questions in x-ray measurement results Marco Rossini Institute - - PowerPoint PPT Presentation

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Open questions in x-ray measurement results Marco Rossini Institute for Particle Physics, ETH Zrich 26. March 2012 Marco Rossini (ETH) X-ray measurement issues 26. March 2012 1 / 8 Overview Shift of threshold when doing s-curves under

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SLIDE 1

Open questions in x-ray measurement results

Marco Rossini

Institute for Particle Physics, ETH Zürich

  • 26. March 2012

Marco Rossini (ETH) X-ray measurement issues

  • 26. March 2012

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SLIDE 2

Overview

◮ Shift of threshold when doing s-curves under x-ray radiation ◮ Shift in pulse height when under x-ray radiation ◮ Strange behaviour with WBC → 0

Marco Rossini (ETH) X-ray measurement issues

  • 26. March 2012

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SLIDE 3

Threshold shift

Entries 4089 Mean 61.22 RMS 1.238 Underflow Overflow Integral 4089 Threshold (VCal units) 52 54 56 58 60 62 64 66 68 70 # Pixels 200 400 600 800 1000 1200 Entries 4089 Mean 61.22 RMS 1.238 Underflow Overflow Integral 4089

Threshold (xray)

Entries 4089 Mean 4.648 RMS 0.6896 Underflow Overflow 2 Integral 4087 Noise (VCal units) 1 2 3 4 5 6 7 8 9 10 # Pixels 200 400 600 800 1000 1200 1400 1600 1800 Entries 4089 Mean 4.648 RMS 0.6896 Underflow Overflow 2 Integral 4087

Noise (xray)

Xray on Xray off Xray on Xray off

∼ 100 MHz/cm2 ∼ 100 MHz/cm2

Measurement and observations:

◮ S-curve test run without x-rays (just a scan varying VCal) [blue]

compared to an s-curve test with x-rays on [red]

◮ Noise increases as one would expect ◮ Threshold seems to go up (or VCal weaker)

Marco Rossini (ETH) X-ray measurement issues

  • 26. March 2012

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SLIDE 4

Threshold shift

Entries 4089 Mean 3.226 RMS 0.8115 Underflow Overflow Integral 4089 Threshold difference (VCal units)

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2 4 6 8 10 # Pixels 200 400 600 800 1000 1200 Entries 4089 Mean 3.226 RMS 0.8115 Underflow Overflow Integral 4089 Threshold offset Entries 4089 Mean 1.624 RMS 0.7627 Underflow Overflow 33 Integral 4056 Noise difference (VCal units)

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1 2 3 4 5 # Pixels 200 400 600 800 1000 1200 Entries 4089 Mean 1.624 RMS 0.7627 Underflow Overflow 33 Integral 4056

Sigma offset

Difference in threshold and noise for each pixel:

Marco Rossini (ETH) X-ray measurement issues

  • 26. March 2012

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SLIDE 5

Pulse height shift

Xray on Xray off Xray on Xray off VCal = 60 VCal = 200 Measurement:

◮ High rate pixel map with additional calibrate signal into one pixel ◮ With [red] and without x-rays [blue] ◮ Pulse height for all pixels is stored in a histogram ◮ Pulse height (gain) calibration used to convert to VCal units

Marco Rossini (ETH) X-ray measurement issues

  • 26. March 2012

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SLIDE 6

Pulse height shift

100 MHz/cm2

Rate dependence (Xray: green = off, red = 2 mA, blue = 80 mA):

Marco Rossini (ETH) X-ray measurement issues

  • 26. March 2012

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SLIDE 7

Strange WBC behaviour

10 20 30 40 50 10 20 30 40 50 60 70 80 5 10 15 20 25 30 35

Pixel hit map module (double edge)

WBC = 1

10 20 30 40 50 10 20 30 40 50 60 70 80 10 15 20 25 30 35

Pixel hit map module (double edge)

WBC = 100 Setting WBC to insensible values produces results nonetheless.

◮ Even WBC = 0 works ◮ Rate does not depend on WBC (at low rate) ◮ Pixel decoding errors occur below WBC = 20 and their rate

increases toward WBC = 0

Marco Rossini (ETH) X-ray measurement issues

  • 26. March 2012

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SLIDE 8

Strange WBC behaviour

Marco Rossini (ETH) X-ray measurement issues

  • 26. March 2012

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