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Timepix Studies: Medipix Collaboration Summary and More Timewalk Plots

Timepix Studies: Medipix Collaboration Summary and More Timewalk Plots. Alessandra Borgia Marina Artuso Syracuse University Group Meeting – Thursday 20 May 2010. Medipix Collaboration slides. 2. Lab Setup. Laser width = 20ns 3Hz laser pulse

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Timepix Studies: Medipix Collaboration Summary and More Timewalk Plots

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  1. Timepix Studies:MedipixCollaboration Summary and More Timewalk Plots Alessandra Borgia Marina Artuso Syracuse University Group Meeting – Thursday 20 May 2010

  2. Medipix Collaboration slides 2

  3. Lab Setup • Laser width = 20ns • 3Hz laser pulse • Rising edge of Timepix shutter triggers the start of the delay for the laser pulse. • ~6.5μs delay • 1060nm laser • via Maurice Glaser • 2 attenuators • Many degrees of freedom for motion Thanks to Jan and Richard! Trig for laser 3Hz clk NIM to TTL Trig for timepix shutter 20 May 2010 Alessandra Borgia -- Medipix Mtg 3

  4. Investigation of Cluster Charge as a Function of Number of Pixels 1 pixel cluster 2 pixel cluster 4 pixel cluster 2 Dim Spread of hits in pixels separately Spread of hits in all pixels summed 20 May 2010 Alessandra Borgia -- Medipix Mtg 4

  5. Results • Note on Settings: • THL = 411 • 59 DACs above noise • 1475 e-s above noise • Ikrum = 5 • All others same as test beam – see backup slide 27 20 May 2010 Alessandra Borgia -- Medipix Mtg 5

  6. Same Effect Seen inTimepix TestBeam 2009 Entries 1 Pixel ~125 2 Pixels ~150 DUT at 0º 4 Pixels ~200 TOT Counts Testbeam response of the timepix assembly showed that the total charge in the clusters created by minimum ionizing particles had a clear dependence on the number of pixels in the clusters: for each extra pixel in the cluster, an extra ~25 counts were seen. 20 May 2010 Alessandra Borgia -- Medipix Mtg 6

  7. Investigation of offsetwith Test Pulses Test Pulse Data Using the new test pulse facility, we can show that this is an intrinsic property of the Timepix response: *There is an offset in the relationship between deposited charge and pixel response. This could be digitally removed in a future version of the chip, in order to optimize our use of the bits available. TOT Counts Test Pulse Charge (arbitrary scale) Data and fits thanks to Atreyi, Paula and Richard. 20 May 2010 Alessandra Borgia -- Medipix Mtg 7

  8. Pixel to Pixel Uniformity:Method Aim: To measure several pixels for uniformity. • Chose 10 random pixels • Ensured laser located in center of pixel • Measure TOT for each over 100 frames • Re-measure first pixel at end of run for drift check Timepix 10 5 8 6 4 1 2 7 3 9 y 20 May 2010 Alessandra Borgia -- Medipix Mtg 8 x

  9. Results • Settings: • THL = 411 • 59 DACs above noise • 1475 e-s above noise • Ikrum = 10 • All others same as test beam Same pixel * Note: scale set from 60 to 120 to show small difference in each point *Small change in the TOT, gives a handle on the measurement accuracy *Fit indicates any drift - more linear than expected. 20 May 2010 Alessandra Borgia -- Medipix Mtg 9

  10. Results Over 10 pixels, the variation in the measured TOT never exceeds 5.5 counts. Each individual measurement shows a spread of about 5%. This comes from a combination of variation in laser power, and variation in pixel response Mean % = 4.23% 20 May 2010 Alessandra Borgia -- Medipix Mtg 10

  11. Timewalk:Laser Method 1. Use the laser to illuminate a group of pixels. 2. Ensure that over 100 events the TOT is stable to ~5%. 3. Switch to TOA mode. 4. Look at timewalk as a function of input charge 5. Chessboard correction needed Y-Axis TOA: Method of extraction Get TOA of each pixel Subtract it from the central pixel to get a ΔrawTOA per pixel. Mean of this ΔrawTOA*25ns is y-axis quantity. 20 May 2010 Alessandra Borgia -- Medipix Mtg 11

  12. Laser Stability Y, pixel number X, pixel number All laser signal within shutter time Alessandra Borgia -- Medipix Mtg 12

  13. Result *Plot at multiple preamp values with proper chess board correction + * o Preamp DAC 140 Preamp DAC 200 Preamp DAC 255 1 MIP! • Settings: • THL = 411 • 59 DACs above noise • 1475 e-s above noise • Ikrum = 10 • All others same as test beam There is no change with respect to Preamplifier setting. 20 May 2010 Alessandra Borgia -- Medipix Mtg 13

  14. Close up of the Timewalk Measurement x + * o Preamp DAC 140 – Test Pulse Preamp DAC 140 Preamp DAC 200 Preamp DAC 255 Preamp DAC setting 255 is unstable. + * o Preamp DAC 140 Preamp DAC 200 Preamp DAC 255 • Settings: • THL = 411 • 59 DACs above noise • 1475 e-s above noise • Ikrum = 10 • All others same as test beam 20 May 2010 Alessandra Borgia -- Medipix Mtg 14

  15. Timewalk result with Test Pulse • Settings for Laser data: • THL = 411 • 59 DACs above noise • 1475 e-s above noise • Ikrum = 10 • All others same as test beam • Settings for Test Pulse data: • THL = 410 • 43 DACs above noise • 1075e-s above noise • Ikrum = 10 • All others same as test beam x + Preamp DAC 140 – Test Pulse Preamp DAC 140 **Difference still needs to be understood. 20 May 2010 Alessandra Borgia -- Medipix Mtg 15

  16. Conclusions • The offset of multiple pixel clusters exists and is consistent between all measurements, but not necessarily a constant • Pixel to pixel variation is very small ~5.5 TOT counts • The timewalk is visible at the minimum ionization particle energy (~50 TOT counts) • Preamplifier DAC value does not seem to effect the timewalk • Preamplifier DAC value 255 seems unstable in laser measurements • Timewalk slightly off between test pulse and laser data 20 May 2010 Alessandra Borgia -- Medipix Mtg 16

  17. Conclusion and Future Studies • Important measurements can be done with laser • A new 660nm laser now in use • Smaller penetration depth 20 May 2010 Alessandra Borgia -- Medipix Mtg 17

  18. Back Up Slides 20 May 2010 Alessandra Borgia -- Medipix Mtg 18

  19. All DAC settings for all datai.e. Test Beam settings 20 May 2010 Alessandra Borgia -- Medipix Mtg 19

  20. Timewalk measurement without chessboard correction + Preamp DAC 140 • Settings: • THL = 411 • 59 DACs above noise • 1475 e-s above noise • Ikrum = 10 • All others same as test beam All values in this area are below 0.

  21. Chessboard Correction:Method • Central pixel known • Call this A (white square) • Create the chessboard pattern with the remaining pixels (whether they have been illuminated or not) • Add ½ clock cycle (12.5ns) from those marked B (white square) A B A B A B B B A A B B A A A B A A B B A B A B A 20 May 2010 Alessandra Borgia -- Medipix Mtg 21

  22. More Timewalk plots All with TB settings except for: THL Preamp Ikrum 22

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  24. Close up 24

  25. Test Pulse by Veerle(on 19 May 2010 yesterday) According to Xavi, at the TB DAC settings Ikrum=10, 1 MIP ≈ ~50 TOT counts 25

  26. Timewalk comparison: TP and laser 26

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