Newer
Older
Presentations / Sbt_testbeam / Sbt_testbeam14thMar_13 / SuperPix0 / superpix0_charact_v0.tex
@Marcin Chrzaszcz Marcin Chrzaszcz on 28 Jul 2013 4 KB update
  1. \documentclass[twocolumn]{article}
  2.  
  3. \usepackage{graphicx}
  4. \usepackage[english]{babel}
  5. \usepackage[utf8]{inputenc}
  6. \usepackage{amsmath}
  7. \usepackage[english, thickspace]{SIunits}
  8.  
  9. %\onehalfspacing
  10. %\pagestyle{plain}
  11.  
  12. %== Set up margins
  13. \setlength{\oddsidemargin}{0.0in} %- this really means 1.0 + 0.75 = 1.75 in
  14. \setlength{\textwidth}{6.5in} %- right margin = 8.5 - 1.6 - 5.8 = 1.1 in
  15. %
  16. \setlength{\topmargin}{-0.5in} %- this really means 1.0 + (-0.5) = 0.5 in
  17. \setlength{\headheight}{0.3in} % so the page number will sit 0.8 in from top
  18. \setlength{\headsep}{0.3in} % and text will start 1.1 in from top
  19. %
  20. \setlength{\footskip}{0.4in}
  21. \setlength{\textheight}{8.4in} %- bottom margin = 11.0 - 1.1 - 8.8 = 1.1 in
  22. %\setlength{\textheight}{8.8in} %- bottom margin = 11.0 - 1.1 - 8.8 = 1.1 in
  23.  
  24.  
  25.  
  26.  
  27. \begin{document}
  28.  
  29. \title{Chip Characterization}
  30. \author{Giulia Casarosa}
  31. \maketitle
  32.  
  33. The chip matrix has been characterized in terms of noise, threshold dispersion and gain, the sensor response
  34. has also been tested.
  35. A photograph of the front-end chip connected by bump-bonding to the high resistivity pixel sensor
  36. matrix of $200\ \micro\meter$ thickness is reported in Fig.~\ref{fig:SPix0}.
  37. \begin{figure}
  38. \centering
  39. \includegraphics[width=3.0in]{./SuperPix0_bond.png} %
  40. \caption{Photograph of the bump-bonded chip, the sensor matrix and the front-end chip are
  41. visible as well as the bondings to the carrier.}
  42. \label{fig:SPix0}
  43. \end{figure}
  44.  
  45. The first lab tests have shown a problem in the readout architecture that has been investigated with dedicated tests and
  46. fully understood.
  47. A particular data acquisition configuration in the lab allowed us to overcome the problem but the measurements were limited to
  48. 3\% of the pixels of the matrix for each run. Time constraints allowed us to characterize the front-end electronics
  49. of around 10-20\% of the pixels in each matrix, depending on the chip.
  50.  
  51. The absolute gain calibration of the chip matrix has been performed using an internal calibration circuit, implemented in the pixel, that allows to inject a charge from $0$ to $12\ \femto\coulomb$ in each channel preamplifier.
  52. An average gain of 38\ \milli\volt/\femto\coulomb\ has been measured with a typical dispersion of about 6\% inside the examined
  53. piece of matrix. %, mainly due to XX.
  54.  
  55. Noise measurement and evaluation of threshold dispersion have been performed measuring the hit rate as a function of the discriminator threshold. With a fit to the turn-on curve we report a pixel average equivalent noise charge (ENC) of about 77 $e^-$ with 15\% dispersion inside the matrix and a threshold dispersion of about 500\ $e^-$. The latter is a little bit too high and therefore
  56. a threshold tuning circuit at pixel level is scheduled in the next submission.
  57. In Table~\ref{tab:chip_charact} we report threshold dispersion, ENC and gain values for each of the 5 chips
  58. characterized in lab.
  59. During test-beam the noise and the threshold dispersion have been re-evaluated for more than 98\% of the pixels
  60. showing compatible results with the lab characterization.
  61.  
  62. \begin{table}
  63. \begin{center}
  64. \begin{tabular}{c|ccc}
  65. \hline
  66. \hline
  67. chip & thr. disp. ($e^-$) & ENC ($e^-$) & gain (\milli\volt/\femto\coulomb)\\
  68. \hline %characterization in lab
  69. 12 & $460 \pm 30$ & $71 \pm 1$ & 37.3 \\
  70. 19 & $500 \pm 30$ & $85 \pm 1$ & 38.7 \\
  71. 53 & $520 \pm 30$ & $77 \pm 1$ & 38.6 \\
  72. 54 & $500 \pm 30$ & $77 \pm 1$ & 39.2 \\
  73. 55 & $580 \pm 30$ & $77 \pm 1$ & 36.9 \\
  74. \hline
  75. \hline
  76. \end{tabular}
  77. \caption{Lab characterization of the 5 chips tested during the test-beam.}
  78. \label{tab:chip_charact}
  79. \end{center}
  80. \end{table}
  81.  
  82. A radioactive source of $^{90}$Sr has been used in order to test the sensor response and the
  83. interconnection between the pixel electronics and the sensor.
  84. \begin{figure}[t!]
  85. \centering
  86. \includegraphics[width=3.2in]{./rate_Hz3.png}
  87. \caption{Hit rate ($\hertz$) measured with chip 19 exposed to a $^{90}$Sr source.}
  88. \label{fig:sr90}
  89. \end{figure}
  90. In Fig.~\ref{fig:sr90} we report the hit rate as seen from the sensor matrix. The illumination
  91. of the matrix is not uniform due to the collimation of the source. The two blank columns
  92. are due to a known problem on the front-end chip. All five chips has shown a very good quality of the
  93. interconnection at $50\ \micro\meter$ pitch and a responding sensor.
  94. Only $2\times 10^{-4}$ over more than 20\kilo\ channels have shown interconnection problems.
  95.  
  96.  
  97.  
  98. \end{document}
  99.