1 | \documentclass{JINST} |
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2 | \usepackage[pdftex]{graphicx} |
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3 | \usepackage[figuresright]{rotating} |
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4 | %\usepackage{graphicx} |
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5 | %\usepackage[T1]{fontenc} |
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6 | \usepackage{eurosym} |
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7 | %\usepackage{rotating} |
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8 | %\usepackage[dvips]{color} |
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9 | |
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10 | |
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11 | %used explicitly in the text |
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12 | \newcommand{\refTab}[1]{Tab.~\ref{#1}} |
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13 | \newcommand{\refFig}[1]{Fig.~\ref{#1}} |
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14 | \newcommand{\refSec}[1]{Sec.~\ref{#1}} |
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15 | |
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16 | |
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17 | |
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18 | |
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19 | \title{PARISROC, a Photomultiplier Array Integrated Readout Chip.} |
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20 | % |
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21 | |
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22 | \author{S. Conforti$^a$, Second Author$^b$\thanks{Corresponding |
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23 | author.}~ and Third Author$^b$\\ |
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24 | \llap{$^a$}Laboratoire de l'Accélérateur Linéaire, IN2P3-CNRS, Université Paris-Sud 11, |
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25 | Bât. 200, 91898 Orsay Cedex, France\\ |
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26 | \llap{$^b$}Name of Institute,\\ |
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27 | Address, Country\\ |
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28 | E-mail: \email{conforti@lal.in2p3.fr}} |
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29 | |
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30 | |
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31 | |
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32 | |
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33 | \abstract{ |
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34 | PARISROC is a complete read |
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35 | out chip, in AMS SiGe 0.35 \begin{math}\mu{}\end{math}m technology |
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36 | \cite{ref1} |
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37 | %[1] |
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38 | , for photomultipliers array. It allows triggerless acquisition for |
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39 | next generation neutrino experiments and it belongs to an R\&D program |
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40 | funded by French national agency for research (ANR) called |
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41 | PMm2: "`Innovative electronics for photodetectors array |
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42 | used in High Energy Physics and Astroparticles"' |
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43 | \cite{ref2} |
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44 | %[2] |
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45 | (ref.ANR-06-BLAN-0186). The ASIC integrates 16 independent and auto |
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46 | triggered channels with variable gain and provides charge and time |
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47 | measurement by a 12-bit ADC and a 24-bit Counter. The charge |
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48 | measurement should be performed from 1 up to 300 pe with a good |
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49 | linearity. The time measurement allowed to a coarse time with a 24-bit |
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50 | counter at 10 MHz and a fine time on a 100ns ramp to achieve a |
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51 | resolution of 1 ns. The ASIC sends out only the relevant data through |
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52 | network cables to the central data storage. |
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53 | }%end of abstract |
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54 | |
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55 | %\pacs{13.30.a,14.20.Dh,14.60.Pq,26.65.t+,29.40.Gx,29.40.Ka,29.40.Mc,95.55.Vj,95.85.Ry, |
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56 | %97.60.Bw} |
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57 | |
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58 | %\submitto{Journal of Instrumentation} |
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59 | |
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60 | \keywords{Keyword1; Keyword2; Keyword3} |
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61 | |
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62 | \begin{document} |
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63 | %use BST file provided by SPIRES for JHEP and modify it to forbid "to lower case" title |
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64 | \bibliographystyle{Campagne} |
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65 | |
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66 | \section{Introduction} |
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67 | \label{sec:Intro} |
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68 | |
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69 | The PMm2 project: "`Innovative electronics for |
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70 | photodetectors array used in High Energy Physics and |
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71 | Astroparticles"' \cite{ref2} |
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72 | %[2] |
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73 | proposes to segment the large surface of photodetection in macro |
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74 | pixel consisting of an array of 16 photomultipliers connected to an |
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75 | autonomous front-end electronics () and powered by a common High |
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76 | Voltage. These large detectors are used in next generation proton decay |
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77 | and neutrino experiment (i.e. the post-SuperKamiokande detectors as |
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78 | those that will take place in megaton size water tanks) and will |
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79 | require very large surfaces of photo detection and a large volume of |
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80 | data. The micro-electronics group's (OMEGA from the LAL at Orsay) |
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81 | purpose is the front-end electronics conception and |
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82 | realization. This R\&D \cite{ref2} |
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83 | %[2] |
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84 | involves three French laboratories (LAL Orsay, LAPP Annecy, IPN |
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85 | Orsay) and ULB Bruxells for the DAQ. It is funded for three years by |
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86 | the French National Agency for Research (ANR) under the reference |
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87 | ANR-06-BLAN-0186. |
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88 | |
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89 | |
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90 | LAL Orsay is in charge of the design and tests of the readout chip |
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91 | named PARISROC which stands for Photomultiplier ARrray Integrated in |
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92 | Si-Ge Read Out Chip. |
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93 | |
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94 | \begin{figure}[htb] |
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95 | \begin{center} |
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96 | \includegraphics[width=0.7\columnwidth]{img0.jpg} |
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97 | \caption{Principal of PMm2 proposal for megaton scale Cerenkov water |
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98 | tank.} |
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99 | \label{fig:1} |
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100 | \end{center} |
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101 | \end{figure} |
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102 | |
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103 | The detectors such as SuperKamiokande, are large tanks covered by a |
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104 | significant number of large photomultipliers (20"), |
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105 | the next generation neutrino experiments will require a bigger surface |
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106 | of photo detection and thus more photomultipliers. As a consequence the |
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107 | total cost has an important relief \cite{ref1}. |
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108 | \begin{itemize} |
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109 | \item A smaller number of electronics, thanks to the 16 PMTs macropixel with |
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110 | a common electronics, even if it induces more electronic channels; |
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111 | \item A common High Voltage for the 16 PMTs so a reduced number of |
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112 | underwater cables, cables that are also used to brought the DATA to |
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113 | the surface; |
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114 | \item The front-end closed to the PMTs that allow a suppression of |
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115 | underwater connector. |
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116 | \end{itemize} |
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117 | |
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118 | The general principle of PMm2 project is that the ASIC and a FPGA |
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119 | manage the dialog between the PMTs and the surface controller (\refFig{fig:2}). |
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120 | |
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121 | \begin{center} |
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122 | \begin{figure}[htb] |
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123 | %%\includegraphics[width=0.7\columnwidth]{img1.eps} |
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124 | \caption{Principle of the PMm2 project.} |
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125 | \label{fig:2} |
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126 | \end{figure} |
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127 | \end{center} |
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128 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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129 | \section{PARISROC architecture} |
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130 | \label{sec:PARISROCArchi} |
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131 | The ASIC Parisroc is composed of 16 analogue channels managed by a |
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132 | common digital part (\refFig{fig:3}). |
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133 | |
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134 | \begin{center} |
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135 | \begin{figure}[hbtp] |
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136 | %%\includegraphics[width=0.7\columnwidth]{img2.eps} |
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137 | \caption{PARISROC global schematic.} |
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138 | \label{fig:3} |
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139 | \end{figure} |
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140 | \end{center} |
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141 | |
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142 | Each analogue channel is made of a low noise preamplifier with |
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143 | variable and adjustable gain. The variable gain is common for all |
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144 | channels and it can change from 8 to 1 on 4 bits. The gain is also |
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145 | tuneable channel by channel to adjust the input detector's gain, up to |
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146 | a factor 4 to an accuracy of 7\% with 8 bits. |
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147 | |
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148 | The preamplifier is followed by a slow channel for the charge |
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149 | measurement in parallel with a fast channel for the trigger output. |
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150 | |
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151 | The slow channel is made by a slow shaper followed by an analogue |
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152 | memory with a depth of 2 to provide a linear charge measurement up to |
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153 | 50~pC; this charge is converted by a 12-bits Wilkinson ADC. One follower |
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154 | OTA is added to deliver an analogue multiplexed charge measurement. |
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155 | |
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156 | The fast channel consists in a fast shaper (15~ns) followed by 2 low |
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157 | offset discriminators to auto-trig down to 50~fC. The thresholds are |
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158 | loaded by 2 internal 10-bit DACs common for the 16 channels and an |
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159 | individual 4bit DAC for one discriminator. The 2 discriminator outputs |
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160 | are multiplexed to provide only 16 trigger outputs. Each output trigger |
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161 | is latched to hold the state of the response until the end of the clock |
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162 | cycle. It is also delayed to open the hold switch at the maximum of the |
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163 | slow shaper. An "`OR"' of the 16 trigger gives a 17th output. |
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164 | |
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165 | |
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166 | For each channel, a fine time measurement is made by an analogue |
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167 | memory with depth of 2 which samples a 12-bit ramp, common for all |
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168 | channels, at the same time of the charge. This time is then converted |
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169 | by a 12 bit Wilkinson ADC. |
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170 | |
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171 | The two ADC discriminators have a common ramp, of 8/10/12 bits, as |
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172 | threshold to convert the charge and the fine time. In addition a bandgap bloc provides all voltage references. |
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173 | |
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174 | \begin{center} |
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175 | \begin{figure}[hbtp] |
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176 | %%\includegraphics[width=0.7\columnwidth]{img3.eps} |
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177 | \caption{PARISROC Layout.} |
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178 | \label{fig:4} |
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179 | \end{figure} |
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180 | \end{center} |
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181 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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182 | \subsection{Analogue Channel description and simulations} |
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183 | \label{ssec:AnalogChannel} |
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184 | %%%%%%%%%%%%%%%%%%%%%%%%%%% |
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185 | \refFig{fig:5} represents, in a schematic way, the detail of one channel analogue |
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186 | part. |
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187 | |
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188 | \begin{center} |
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189 | \begin{figure}[hbtp] |
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190 | %%\includegraphics[width=0.7\columnwidth]{img4.eps} |
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191 | \caption{PARISROC one channel analogue part schematic.} |
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192 | \label{fig:5} |
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193 | \end{figure} |
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194 | \end{center} |
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195 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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196 | \subsection{Preamplifier} |
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197 | \label{ssec:Preamplifier} |
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198 | %%%%%%%%%%%%%%%%%%%%%%%%%%% |
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199 | The input preamplifier is a low noise preamplifier with variable gain |
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200 | thanks to the switched input ($C_{in}$) and feedback ($C_f$) capacitors that |
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201 | can be adjusted (\refFig{fig:6}). |
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202 | |
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203 | This gain can vary changing $C_{in}$, which is |
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204 | common to the 16 channels, over 4 bits and $C_{f}$, to adjust preamplifier |
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205 | gain channel by channel. This adjustment allows correction of the PMT |
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206 | gain dispersion due to a use of a common HV. |
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207 | |
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208 | \begin{center} |
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209 | \begin{figure}[htb] |
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210 | %%\includegraphics[width=0.7\columnwidth]{img5.eps} |
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211 | \caption{PARISROC preamplifier schematic.} |
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212 | \label{fig:6} |
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213 | \end{figure} |
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214 | \end{center} |
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215 | |
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216 | The preamplifier is designed as a voltage |
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217 | preamplifier in p-type Cascode structure to allow the acquisition of a |
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218 | fast input signal with a large dynamic range. |
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219 | |
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220 | The input transistor is a PMOS in common source |
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221 | configuration: $W = 800~\mu$m; $L = 0.35~\mu$m; the big input transistor is |
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222 | chosen to keep the preamplifier noise contribution low and to achieve a |
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223 | high gm. It supplies the output (the drain terminal) to the input |
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224 | terminal (source terminal) of the second stage transistor: $W = 100~\mu$m; |
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225 | $L = 0.35~\mu$m; the output transistor must be small to reach preamplifier |
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226 | high speed performances. The utility of the cascode preamplifier is in |
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227 | the large input impedance of the common source (with also the |
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228 | characteristic of Current Buffer) and better frequency response of a |
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229 | common Gate. An output buffer stage is designed in order to adapt the |
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230 | output impedance to the loaded impedance. The input dc level is high |
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231 | (about 2.6~V) while the output dc level is low (about 1~V). Because of |
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232 | the single side structure of preamplifier, it is hard to use the |
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233 | external reference voltage to set the dc operating point; the idea is |
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234 | to use an OTA as the dc feedback amplifier. |
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235 | |
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236 | In \refFig{fig:7} are shown preamplifier's output waveforms |
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237 | for fixed gain and different input signal (left panel) and for fixed |
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238 | input signal and different preamplifier gain (right panel). |
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239 | |
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240 | \begin{center} |
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241 | \begin{figure}[hbtp] |
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242 | %%\includegraphics[width=0.7\columnwidth]{img6.eps}%%\includegraphics[width=0.7\columnwidth]{img7.eps} |
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243 | \caption{Simulated preamplifier output waveforms for different input |
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244 | signals with fixed gain (left panel) and for fixed input |
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245 | signal at different gain (different input capacitor values (right |
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246 | panel).} |
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247 | \label{fig:7} |
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248 | \end{figure} |
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249 | \end{center} |
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250 | |
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251 | The input signal, used in simulation, is a triangle signal with 4.5~ns |
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252 | rise and fall time and 5~ns of duration as shown in \refFig{fig:8}. This current |
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253 | signal is sent to an external resistor (50~Ohms) and varies from 0 to 5~mA |
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254 | in order to simulate a PMT charge from 0 to 50~pC which represents 0 |
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255 | to 300 photo-electrons when the PM gain is $10^{6}$. |
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256 | |
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257 | \begin{center} |
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258 | \begin{figure}[hbtp] |
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259 | %%\includegraphics[width=0.7\columnwidth]{img8.eps} |
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260 | \caption{Simulation input signal.} |
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261 | \label{fig:8} |
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262 | \end{figure} |
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263 | \end{center} |
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264 | |
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265 | The \refFig{fig:9} displays the input dynamic range allowed to the preamplifier |
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266 | linearity performance. \refTab{tab:1} lists the residuals obtained for different |
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267 | gains and shows a good linearity (better than $\pm 1\%$). |
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268 | |
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269 | \begin{center} |
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270 | \begin{figure}[hbtp] |
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271 | %%\includegraphics[width=0.7\columnwidth]{img9.eps} |
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272 | \caption{Preamplifier linearity.} |
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273 | \label{fig:9} |
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274 | \end{figure} |
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275 | \end{center} |
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276 | |
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277 | |
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278 | \begin{table} |
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279 | \centering |
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280 | \caption{TO BE COMPLETED} |
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281 | \label{tab:1} |
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282 | \begin{tabular}{|c|c|c|c|} |
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283 | \hline |
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284 | $G_{pa}$ & $V_{out-max}$ & $Qi_{max}/n_{pe}$ & Residuals (\%) \\ |
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285 | \hline |
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286 | 8 & 1.394~V & 40~pC/250~pe & -0.6 to 0.2 \\ |
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287 | 4 & 0.841~V & 48~pC/300~pe & -0.1 to 0.3 \\ |
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288 | 2 & 0.417~V & 48~pC/300~pe & -0.2 to 0.3 \\ |
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289 | \hline |
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290 | \end{tabular} |
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291 | \end{table} |
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292 | |
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293 | |
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294 | |
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295 | The \refFig{fig:10} displays the preamplifier noise with an |
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296 | rms value of 13~fC and a Signal to Noise ratio of $\approx 12$. |
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297 | \refTab{tab:2} summarizes the results obtained. |
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298 | |
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299 | \begin{center} |
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300 | \begin{figure}[hbtp] |
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301 | \%%includegraphics{img10.eps} |
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302 | \caption{Preamplifier noise simulation; $G_{pa}=8$; $C_{in}=4$~pF and |
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303 | $C_{f}=0.5$~pF.} |
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304 | \end{figure} |
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305 | \label{fig:10} |
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306 | \end{center} |
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307 | |
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308 | \begin{table} |
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309 | \centering |
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310 | \caption{TO BE COMPLETED} |
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311 | \label{tab:2} |
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312 | \begin{tabular}{|c|c|c|} |
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313 | \hline |
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314 | RMS & SNR & $V_{out}(1 p.e)$ \\ |
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315 | \hline |
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316 | $468~\mu$V ($\approx 1/12$~p.e, $\approx 13$~fC ) & 11.6 & 5.43~mV\\ |
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317 | \hline |
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318 | \end{tabular} |
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319 | \end{table} |
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320 | |
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321 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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322 | \subsection{Trigger output} |
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323 | \label{ssec:Trigger} |
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324 | %%%%%%%%%%%%%%%%%%%%%%%%%%% |
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325 | The PARISROC is a self-triggered device. The fast channel has been |
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326 | conceived for this purpose.The amplified signal flows in a fast shaper that is a CRRC filter with |
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327 | a time constant of 15~ns. Its high gain allows to send high signal to |
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328 | the discriminator and thus to trigger easily on 1/3 of photo-electron. |
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329 | It has a classical design: differential pair is followed by a buffer. |
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330 | |
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331 | \begin{figure}[hbtp] |
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332 | \centering |
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333 | %%\includegraphics[width=0.7\columnwidth]{img11.eps} |
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334 | \caption{Fast shaper schematics.} |
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335 | \label{fig:11} |
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336 | \end{figure} |
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337 | |
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338 | The \refFig{fig:12} represents the fast shaper output |
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339 | waveforms for a variable input signal. The \refTab{tab:3} lists the fast |
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340 | shaper principal characteristics obtained in simulation. |
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341 | |
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342 | \begin{figure}[hbtp] |
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343 | \centering |
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344 | %%\includegraphics[width=0.7\columnwidth]{img12.eps} |
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345 | %%\includegraphics[width=0.7\columnwidth]{img13.eps} |
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346 | \caption{Simulated fast shaper outputs ($G_{pa} = 8$ with input from 1-10~pe (left panel) |
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347 | and from 1/3~pe to 2~pe (right panel).} |
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348 | \label{fig:12} |
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349 | \end{figure} |
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350 | |
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351 | \begin{table} |
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352 | \centering |
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353 | \caption{To be completed} |
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354 | \label{tab:3} |
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355 | \begin{tabular}{|c|c|c|c|} |
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356 | \hline |
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357 | RMS & SNR & $V_{out}(1 p.e)$ & $T_p$ \\ |
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358 | \hline |
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359 | $2.36~\mu$V ($\approx 1/16$~p.e, $\approx 10$~fC ) & 16 & 37.85~mV & 8~ns\\ |
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360 | \hline |
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361 | \end{tabular} |
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362 | \end{table} |
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363 | |
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364 | The fast shaper (15~ns) is followed by a low |
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365 | offset discriminator to auto-trig down to 50~fC (1/3~pe at $10^6$ gain). |
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366 | |
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367 | |
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368 | The two discriminators can be used alone or |
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369 | simultaneously. Their outputs are multiplexed to ease the choice. Both |
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370 | are simple low offset comparators with the same schematic. The |
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371 | difference comes from the way to set the threshold. The first |
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372 | discriminator has the threshold sets by one 10-bit DAC, common to all |
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373 | 16 channels, and one 4-bit DAC for each channel. The second |
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374 | discriminator has the threshold sets by only the 10 bit common DAC. |
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375 | Each output trigger is latched to hold the state of the response in SCA |
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376 | channel. In \refFig{fig:13} are shown the triggers and the zoom of the triggers rise |
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377 | time in order to see the time walk of around 4~ns. |
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378 | |
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379 | |
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380 | \begin{figure}[hbtp] |
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381 | \centering |
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382 | %%\includegraphics[width=0.7\columnwidth]{img14.eps} |
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383 | %%\includegraphics[width=0.7\columnwidth]{img15.eps} |
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384 | \caption{Simulated trigger output (input charge from 0 to 10~p.e; |
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385 | threshold at 1/3~p.e). Zoom of trigger rise time on right |
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386 | pannel.} |
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387 | \label{fig:13} |
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388 | \end{figure} |
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389 | |
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390 | Each output trigger is latched to hold the |
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391 | state of the response in SCA channel. SCA channel is the also called |
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392 | "`Analogue memory"'. The SCA has a |
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393 | depth equal to two; this means that there are two T\&H for time |
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394 | measurement as well as for charge measurement. |
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395 | |
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396 | \begin{figure}[hbtp] |
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397 | \centering |
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398 | %%\includegraphics[width=0.7\columnwidth]{img16.eps} |
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399 | \caption{SCA (switched capacitor array) scheme.} |
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400 | \label{fig:14} |
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401 | \end{figure} |
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402 | |
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403 | The voltage level of the signal coming from |
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404 | slow shaper or ramp TDC cell is memorised in the T\&H capacitor (500~fF) |
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405 | so "`Track \& Hold Cell"' allows |
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406 | to lock the capacitor value only when a calibrated trigger (from fast |
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407 | channel) occurs within the selected column. The SCA column is selected, read and erased by |
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408 | the digital part. |
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409 | |
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410 | \begin{figure}[hbtp] |
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411 | \centering |
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412 | %%\includegraphics[width=0.7\columnwidth]{img17.eps} |
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413 | \caption{Operation of T\&H cell.} |
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414 | \label{fig:15} |
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415 | \end{figure} |
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416 | |
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417 | On \refFig{fig:15} is illustrated the T\&H cell mode of |
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418 | operation: when a signal arrives in the discriminator cell is detected |
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419 | and the output trigger signal is sent to the T\&H cell. |
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420 | The output trigger is delayed and calibrated before being sent. |
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421 | |
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422 | |
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423 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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424 | \subsection{Charge channel} |
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425 | \label{ssec:Charge} |
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426 | %%%%%%%%%%%%%%%%%%%%%%%%%%% |
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427 | The charge channel is the slow channel: the signal amplified by the |
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428 | variable gain preamplifier is sent to the slow shaper, a typical |
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429 | $\mathrm{CRRC}^2$ filter with variable peaking time. The |
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430 | peaking time can be set from 50~ns (default value) to 200~ns thanks to |
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431 | the switched feedback capacitors. |
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432 | |
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433 | On left part of \refFig{fig:16} are represented the slow shaper waveforms for |
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434 | different shaping times and the same input signal. The noise value (\refTab{tab:4} |
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435 | and right part of \refFig{fig:16}), from $980~\mu$V to $1.6$~mV (simulation results), foresee |
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436 | good noise performance. |
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437 | |
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438 | \begin{figure}[hbtp] |
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439 | \centering |
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440 | %%\includegraphics[width=0.7\columnwidth]{img18.eps} |
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441 | %%\includegraphics[width=0.7\columnwidth]{img19.eps} |
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442 | \caption{Slow shaper output waveforms simulation (left panel). Slow shaper |
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443 | output noise simulation (right panel).} |
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444 | \label{fig:16} |
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445 | \end{figure} |
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446 | |
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447 | \begin{table} |
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448 | \centering |
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449 | \caption{TO BE COMPLETED. $G_{pa} = 8$} |
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450 | \label{tab:4} |
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451 | \begin{tabular}{|c|c|c|c|} |
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452 | \hline |
---|
453 | Time constant & RMS & SNR & $V_{out}(1 p.e)$ \\ |
---|
454 | \hline |
---|
455 | 50~ns & \parbox[t]{20mm}{$1.68$~mV \\ $\approx 1/17$~p.e \\ $ \approx 9$~fC} |
---|
456 | & 11 |
---|
457 | & \parbox[t]{20mm}{$29$~mV \\ $T_p = 48$~ns } \\ |
---|
458 | 100~ns & \parbox[t]{20mm}{$1.26$~mV\\$\approx 1/12$~p.e \\ $ \approx 20$~fC} |
---|
459 | & 8 |
---|
460 | & \parbox[t]{20mm}{$15$~mV \\ $T_p = 78$~ns }\\ |
---|
461 | 200~ns & \parbox[t]{20mm}{$0.98$~mV\\$\approx 1/5$~p.e \\ $ \approx 32$~fC} |
---|
462 | & 5 |
---|
463 | & \parbox[t]{23mm}{$8$~mV \\ $ T_p = 141.5$~ns } \\ |
---|
464 | \hline |
---|
465 | \end{tabular} |
---|
466 | \end{table} |
---|
467 | |
---|
468 | The \refFig{fig:17} and \refTab{tab:5} illustrate the linearity performance for |
---|
469 | different time constants. Simulations show a good linearity with |
---|
470 | residuals from -0.5\% to 0.2\% at $T_p = 50$~ns, from |
---|
471 | -1\% to 0.3\% at $T_p =100$~ns and -0.7\% to 0.3\% at |
---|
472 | $T_p=200$~ns. |
---|
473 | |
---|
474 | \begin{figure}[hbtp] |
---|
475 | \centering |
---|
476 | %%\includegraphics[width=0.7\columnwidth][width=273pt]{img20.eps} |
---|
477 | \caption{Slow shaper linearity simulation.} |
---|
478 | \label{fig:17} |
---|
479 | \end{figure} |
---|
480 | |
---|
481 | \begin{table} |
---|
482 | \centering |
---|
483 | \caption{TO BE COMPLETED} |
---|
484 | \label{tab:5} |
---|
485 | \begin{tabular}{|c|c|c|c|} |
---|
486 | \hline |
---|
487 | Time constante & $V_{out-max}$ & $Qi_{max}/n_{pe}$ & Residuals (\%) \\ |
---|
488 | \hline |
---|
489 | 50~ns & 1.437~V & 13~pC/80~pe & -0.5 to 0.2 \\ |
---|
490 | 100~ns & 1.493~V & 24~pC/150~pe & -1.0 to 0.3 \\ |
---|
491 | 200~ns & 1.385~V & 48~pC/300~pe & -0.7 to 0.3 \\ |
---|
492 | \hline |
---|
493 | \end{tabular} |
---|
494 | \end{table} |
---|
495 | |
---|
496 | The Slow shaper maximum value, therefore the charge value, is then |
---|
497 | memorized in the analogue memory, with a depth of 2, thanks to the |
---|
498 | delayed trigger. \refFig{fig:18} gives the simulated slow shaper and SCA |
---|
499 | signals. |
---|
500 | |
---|
501 | \begin{figure}[hbtp] |
---|
502 | \centering |
---|
503 | %%\includegraphics[width=0.7\columnwidth][width=207pt]{img21.eps} |
---|
504 | \caption{Slow shaper \& SCA simulation.} |
---|
505 | \label{fig:18} |
---|
506 | \end{figure} |
---|
507 | This charge, stored as a voltage value, is then converted in digital |
---|
508 | value thanks to the 8/10/12 bit Wilkinson ADC. |
---|
509 | |
---|
510 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
511 | \subsection{Time measurement} |
---|
512 | \label{ssec:Timemeas} |
---|
513 | %%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
514 | For each channel, a fine time measurement is performed by the analogue |
---|
515 | memory with a depth of 2 which samples a 12 bit ramp (100~ns), common |
---|
516 | for all channels, at the same time of the charge. |
---|
517 | |
---|
518 | In \refFig{fig:19} is represented the TDC Ramp general schematic. The current, |
---|
519 | which flows in feedback, charges the capacitance $C_f$ when the switch is |
---|
520 | off. When the switch is turned off, $C_f$ discharges. Signals \verb|start\_ramp| and |
---|
521 | \verb|start\_ramp\_b| manage the switches. The rising signal starts the ramp |
---|
522 | and the falling signal stop the ramp (\refFig{fig:19}). |
---|
523 | |
---|
524 | \begin{figure}[hbtp] |
---|
525 | \centering |
---|
526 | %%\includegraphics[width=0.7\columnwidth]{img22.eps} |
---|
527 | %%\includegraphics[width=0.7\columnwidth]{img23.eps} |
---|
528 | \caption{TDC Ramp general schematic.} |
---|
529 | \label{fig:19} |
---|
530 | \end{figure} |
---|
531 | In order to avoid the large falling time of the ramp due to the $C_f$ |
---|
532 | discharge time and the problem of non linearity at the start and the |
---|
533 | end of ramp signal (\refFig{fig:20}), the real ramp is created from two |
---|
534 | ramps. |
---|
535 | |
---|
536 | \begin{figure}[hbtp] |
---|
537 | \centering |
---|
538 | %%\includegraphics[width=0.7\columnwidth]{img24.eps} |
---|
539 | \caption{TDC Ramp.} |
---|
540 | \label{fig:20} |
---|
541 | \end{figure} |
---|
542 | |
---|
543 | The signal start ramp, coming from the digital |
---|
544 | part, enters in two delay cells. The two delayed signals create the |
---|
545 | first and second ramps. Commutating alternatively two switches the 100~ns ramp TDC is created |
---|
546 | (\refFig{fig:21} and \refFig{fig:22}). |
---|
547 | |
---|
548 | \begin{figure}[hbtp] |
---|
549 | \centering |
---|
550 | %\includegraphics[width=0.7\columnwidth]{img25.eps} |
---|
551 | \caption{TDC Ramp scheme.} |
---|
552 | \label{fig:21} |
---|
553 | \end{figure} |
---|
554 | |
---|
555 | \begin{figure}[hbtp] |
---|
556 | \centering |
---|
557 | %\includegraphics[width=0.7\columnwidth]{img26.eps} |
---|
558 | \caption{TDC Ramp simulation.} |
---|
559 | \label{fig:22} |
---|
560 | \end{figure} |
---|
561 | |
---|
562 | This time value, stored as a voltage value, is then converted in |
---|
563 | digital value tanks to the 8/10/12 bit Wilkinson ADC. |
---|
564 | |
---|
565 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
566 | \subsection{ADC ramp} |
---|
567 | \label{ssec:ADCramp} |
---|
568 | %%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
569 | In \refFig{fig:23} is represented the Ramp ADC general scheme. It is the |
---|
570 | same as TDC ramp one, the difference is in a variable current source |
---|
571 | which allows obtaining 8bit/10bit/12bit ADC according to the injected |
---|
572 | current. \refTab{tab:6} gives, for each ramp, the time duration to reach 3.3~V. |
---|
573 | |
---|
574 | \begin{figure}[hbtp] |
---|
575 | \centering |
---|
576 | %\includegraphics{img27.eps} |
---|
577 | \caption{ADC ramp schematic.} |
---|
578 | \label{fig:23} |
---|
579 | \end{figure} |
---|
580 | |
---|
581 | \begin{table} |
---|
582 | \centering |
---|
583 | \caption{TO BE COMPLETED} |
---|
584 | \label{tab:6} |
---|
585 | \begin{tabular}{|l|l|} |
---|
586 | \hline |
---|
587 | Header 1 & Header 2 \\ |
---|
588 | 12 bit ADC & From 0.9~V to 3.3~V in $102.0~\mu{}$s \\ |
---|
589 | 10 bit ADC & From 0.9~V to 3.3~V in $25.6~\mu{}$s \\ |
---|
590 | \phantom{ }8 bit ADC & From 0.9~V to 3.3~V in $6.4~\mu{}$s \\ |
---|
591 | \hline |
---|
592 | \end{tabular} |
---|
593 | \end{table} |
---|
594 | |
---|
595 | Then the ADC ramp is compared thanks to a Discriminator to the voltage |
---|
596 | values, which corresponds to charge and fine time values, stored in the |
---|
597 | SCA. The digital converted DATA are then treated by the digital part. |
---|
598 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
599 | \subsection{Digital part} |
---|
600 | \label{ssec:Digital} |
---|
601 | %%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
602 | The digital part of PARISROC is built around 4 modules which are "`acquisition"', "`conversion"', "`readout"' and "`top manager"'. Actually, PARISROC is based on 2 memories. During acquisition, |
---|
603 | discriminated analog signals are stored into an analog memory (the SCA: |
---|
604 | switched capacitor array). The analog to digital conversion module |
---|
605 | converts analog charges and times from SCA into 12 bits digital values. |
---|
606 | These digital values are saved into registers (RAM). At the end of the |
---|
607 | cycle, the RAM is readout by an external system. The block diagram is |
---|
608 | given on \refFig{fig:24}. |
---|
609 | |
---|
610 | |
---|
611 | \begin{figure}[hbtp] |
---|
612 | \centering |
---|
613 | %\includegraphics{img28.eps} |
---|
614 | \caption{Block diagram of the digital part.} |
---|
615 | \label{fig:24} |
---|
616 | \end{figure} |
---|
617 | |
---|
618 | This sequence is made thanks to the top manager module which controls |
---|
619 | the 3 other ones. When 1 or more channels are hit, it starts ADC |
---|
620 | conversion and then the readout of digitized data. The maximum cycle |
---|
621 | length is about $200~\mu$s. During |
---|
622 | conversion and readout, acquisition is never stopped. It means that |
---|
623 | discriminated analog signals can be stored in the SCA at any time of |
---|
624 | the sequence shown in on \refFig{fig:25}. |
---|
625 | |
---|
626 | \begin{figure}[hbtp] |
---|
627 | \centering |
---|
628 | %\includegraphics{img29.eps} |
---|
629 | \caption{Top manager sequence.} |
---|
630 | \label{fig:25} |
---|
631 | \end{figure} |
---|
632 | |
---|
633 | The first module in the sequence is the acquisition |
---|
634 | which is dedicated to charge and fine time measurements. It manages the |
---|
635 | SCA where charge and fine time are stored as a voltage like. It also |
---|
636 | integrates the coarse time measurement thanks to a 24-bit gray counter |
---|
637 | with a resolution of 100~ns. Each channel has a depth of 2 for the SCA |
---|
638 | and they are managed individually. Besides, SCA is treated like a FIFO |
---|
639 | memory: analog voltage can be written, read and erased from this |
---|
640 | memory. |
---|
641 | |
---|
642 | |
---|
643 | \begin{figure}[hbtp] |
---|
644 | \centering |
---|
645 | %\includegraphics{img30.eps} |
---|
646 | \caption{SCA analogue voltage} |
---|
647 | \label{fig:26} |
---|
648 | \end{figure} |
---|
649 | |
---|
650 | Then, the conversion module converts analog values stored in |
---|
651 | the SCA (charge and fine time: cf. \`refFig{fig:26}) in digital ones thanks to a 12-bit |
---|
652 | Wilkinson ADC. The counter clock frequency is 40~MHz, it implies a |
---|
653 | maximum ADC conversion time of $103~\mu$s |
---|
654 | when it overflows. This module makes 32 conversions in 1 run (16 |
---|
655 | charges and 16 fine times). |
---|
656 | |
---|
657 | Finally, the readout module permits to empty all the registers |
---|
658 | to an external system. As it will only transfer hit channels, this |
---|
659 | module will tag each frame with its channel number: it works as a |
---|
660 | selective readout. The pattern used is composed of 4 data: 4-bit |
---|
661 | channel number, 24-bit coarse time, 12-bit charge and 12-bit fine time. |
---|
662 | The total length of one frame is 52 bits. The maximum readout time |
---|
663 | appears when all channels are hit. About 832 bits of data are |
---|
664 | transferred to the concentrator with a 10~MHz clock: the readout takes |
---|
665 | about $100~\mu$s with $1~\mu$s between 2 frames. |
---|
666 | |
---|
667 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
668 | \section{ASIC Laboratory tests} |
---|
669 | \label{sec:ASICLAbTest} |
---|
670 | %%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
671 | The PARISROC has been submitted in June 2008; a first batch of 6 ASICs |
---|
672 | has been produced and received in January 2009 (a second batch of 14 |
---|
673 | ASICs in May 2009. |
---|
674 | |
---|
675 | The ASIC test has been a critical step in the PARISROC planning due to |
---|
676 | the ASIC complexity.A dedicated test board has been designed and realized for this purpose |
---|
677 | (\refFig{fig:27}). Its role is to allow the characterization of the chip and the |
---|
678 | communication between photomultipliers and ASIC. This is possible |
---|
679 | thanks to a dedicated Labview program that allows sending the ASIC |
---|
680 | configuration (slow control parameters; ASIC parameters, etc) and |
---|
681 | receiving the output bits via a USB cable connected to the test board. |
---|
682 | The Labview is developed by LAL. |
---|
683 | |
---|
684 | \begin{figure}[h] |
---|
685 | \centering |
---|
686 | %\includegraphics{img31.eps} |
---|
687 | \caption{Test Board.} |
---|
688 | \label{fig:27} |
---|
689 | \end{figure} |
---|
690 | |
---|
691 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
692 | \subsection{General tests} |
---|
693 | \label{ssec:GeneralTest} |
---|
694 | %%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
695 | On \refFig{fig:28} is shown the Test Bench used in laboratory. It is composed by a |
---|
696 | test board, a signal generator, an oscilloscope, multimeters and PC to |
---|
697 | run labview program. |
---|
698 | |
---|
699 | \begin{figure}[hbtp] |
---|
700 | \centering |
---|
701 | %\includegraphics{img32.eps} |
---|
702 | \caption{Test Bench.} |
---|
703 | \label{fig:28} |
---|
704 | \end{figure} |
---|
705 | |
---|
706 | The signal generator is a TEKTRONIX single |
---|
707 | channel function generator. It is used to create the input charge |
---|
708 | injected in the ASIC. The signal injected has the shaping as similar as |
---|
709 | possible to the PMT signal. On \refFig{fig:28} is represented the generator input |
---|
710 | signal and its characteristics. |
---|
711 | |
---|
712 | \begin{figure}[hbtp] |
---|
713 | \centering |
---|
714 | %\includegraphics{img33.eps} |
---|
715 | %\includegraphics{img34.eps} |
---|
716 | \caption{Input signals} |
---|
717 | \label{fig:29} |
---|
718 | \end{figure} |
---|
719 | |
---|
720 | At the beginning all the standard electrical |
---|
721 | characteristics have been tested: DC levels, analogue output signals, |
---|
722 | the analogue part characteristics and then the pedestals, the DAC |
---|
723 | linearity, S\-curves (trigger efficiency as a function of the injected |
---|
724 | charge or the threshold), the ADC linearity. The first purpose is the |
---|
725 | comparison between simulation results and test measurements; most of |
---|
726 | them are in agreement with the ASIC characteristics, obtained in |
---|
727 | simulation. |
---|
728 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
729 | \subsection{Analogue tests} |
---|
730 | \label{ssec:AnalogueTest} |
---|
731 | %%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
732 | The DC level characterization is the first step in ASIC |
---|
733 | characterization; in particular the DC uniformity of the analogue part |
---|
734 | DC level for the different channels has to be measured. |
---|
735 | |
---|
736 | In \refFig{fig:30} are represented the preamplifier, slow |
---|
737 | shaper and fast shaper DC uniformity plots. The DC uniformity test has a small dispersion |
---|
738 | of 0.4\%, 0.1\% and 0.05\% respectively for the preamplifier, the slow |
---|
739 | shaper and the fast shaper (\refTab{tab:7}). |
---|
740 | |
---|
741 | \begin{figure}[hbtp] |
---|
742 | \centering |
---|
743 | %\includegraphics{img35.eps} |
---|
744 | %\includegraphics{img36.eps} |
---|
745 | %\includegraphics{img37.eps} |
---|
746 | \caption{DC uniformity.} |
---|
747 | \label{fig:30} |
---|
748 | \end{figure} |
---|
749 | |
---|
750 | \begin{table} |
---|
751 | \centering |
---|
752 | \caption{TO BE COMPLETED} |
---|
753 | \label{tab:7} |
---|
754 | \begin{tabular}{|l|c|c|c|} |
---|
755 | \hline |
---|
756 | DC level & RMS \\ |
---|
757 | Preamplifier & 3.8~mV (0.40~\%) \\ |
---|
758 | Slow shaper & 1.3~mV (0.10~\%) \\ |
---|
759 | Fast shaper & 1.0~mV (0.05\%) \\ |
---|
760 | \hline |
---|
761 | \end{tabular} |
---|
762 | \end{table} |
---|
763 | |
---|
764 | The second step is the analogue part output signals: Injecting a |
---|
765 | charge equivalent to 10~pe, and setting a preamplifier gain at 8, are |
---|
766 | observed and compared with simulation results all the output waveforms. |
---|
767 | |
---|
768 | There is a good agreement in preamplifier results ( \refFig{fig:31} and \refTab{tab:8}), the |
---|
769 | amplitude has the same value while time rise value has a difference of |
---|
770 | 3~ns. This difference is due to the output buffer placed in the test |
---|
771 | board. |
---|
772 | |
---|
773 | \begin{figure}[hbtp] |
---|
774 | \centering |
---|
775 | %\includegraphics{img38.eps} |
---|
776 | %\includegraphics{img39.eps} |
---|
777 | \caption{Measurement and simulation of the preamplifier output for |
---|
778 | an input charge of 10~pe.} |
---|
779 | \label{fig:31} |
---|
780 | \end{figure} |
---|
781 | |
---|
782 | \begin{table} |
---|
783 | \centering |
---|
784 | \caption{TO BE COMPLETED. Preamplifier parameters.... $G_{pa} = 8$. WHY not same parameters 1~pe and 10~p.e} |
---|
785 | \label{tab:8} |
---|
786 | \begin{tabular}{|l|c|c|} |
---|
787 | \hline |
---|
788 | & Measurement & Simulation \\ |
---|
789 | \hline |
---|
790 | Maximum voltage (10~pe) & 50.00~mV & 50.83~mV \\ |
---|
791 | Rise time (10~pe) & 7.78~ns & 4.79~ns \\ |
---|
792 | RMS noise & 1~mV & 0.47~mV \\ |
---|
793 | without USB cable & 0.66~mV & \\ |
---|
794 | Noise in pe & 0.2 & 0.086 \\ |
---|
795 | without USB cable & 0.132 & \\ |
---|
796 | Maximum voltage (1~pe) & 5.00~mV & 5.43~mV \\ |
---|
797 | SNR (1~pe ????) & 5 & 11.6 \\ |
---|
798 | without USB cable & 7.5 & \\ |
---|
799 | \hline |
---|
800 | \end{tabular} |
---|
801 | \end{table} |
---|
802 | |
---|
803 | The slow shaper waveforms are shown in \refFig{fig:32} while \refTab{tab:9} |
---|
804 | summarizes the results. The first differences appear: a different value |
---|
805 | in amplitude for slow shaper signal and fast shaper signal that is |
---|
806 | probably associate, also, to the Output Buffer. The second relevant |
---|
807 | difference is in noise value, in particular in slow shaper noise |
---|
808 | performance (\refTab{tab:9}). |
---|
809 | |
---|
810 | \begin{figure}[hbtp] |
---|
811 | \centering |
---|
812 | %\includegraphics{img40.eps} |
---|
813 | %\includegraphics{img41.eps} |
---|
814 | \caption{Measurement and simulation of the slow shaper output for an |
---|
815 | input charge of 10~pe.} |
---|
816 | \label{fig:32} |
---|
817 | \end{figure} |
---|
818 | |
---|
819 | \begin{table} |
---|
820 | \centering |
---|
821 | \caption{TO BE COMPLETED. $G_{pa} = 8$ and $RC = 50$~ns.} |
---|
822 | \label{tab:9} |
---|
823 | \begin{tabular}{|l|c|c|} |
---|
824 | \hline |
---|
825 | & Measurement & Simulation \\ |
---|
826 | \hline |
---|
827 | Maximum Voltage (10~pe) & 117~mV & 290~mV \\ |
---|
828 | Rise time (10~pe) & 18.0~ns & 19.1~ns \\ |
---|
829 | RMS noise & 4.0~mV & 1.7~mV \\ |
---|
830 | Noise in pe & 0.3 & 0.08 \\ |
---|
831 | Maximum Voltage (1~pe) & 12~mV & 19~mV \\ |
---|
832 | SNR & 3 & 11 \\ |
---|
833 | \hline |
---|
834 | \end{tabular} |
---|
835 | \end{table} |
---|
836 | |
---|
837 | The Fast shaper results are shown in \refFig{fig:33} |
---|
838 | and \refTab{tab:10}. |
---|
839 | \begin{figure}[htb] |
---|
840 | \centering |
---|
841 | %\includegraphics{img73.eps} |
---|
842 | %\includegraphics{img72.eps} |
---|
843 | \caption{Measurement and simulation of the fast shaper output for an |
---|
844 | input charge of 1 pe.} |
---|
845 | \label{fig:33} |
---|
846 | \end{figure} |
---|
847 | |
---|
848 | |
---|
849 | \begin{table} |
---|
850 | \centering |
---|
851 | \caption{TO BE COMPLETED. $G_{pa} = 8$.} |
---|
852 | \label{tab:10} |
---|
853 | \begin{tabular}{|l|c|c|} |
---|
854 | \hline |
---|
855 | & Measurement & Simulation \\ |
---|
856 | \hline |
---|
857 | RMS noise & 2.5~mV & 2.4~mV \\ |
---|
858 | Noise in pe & 0.08 & 0.05 \\ |
---|
859 | Maximum Voltage (1~pe) & 30~mV & 42~mV \\ |
---|
860 | SNR & 12 & 18 \\ |
---|
861 | \hline |
---|
862 | \end{tabular} |
---|
863 | \end{table} |
---|
864 | Another important characteristic is the |
---|
865 | linearity. The output voltage in function of the input injected charge |
---|
866 | is plotted for the different analogue signals. \refFig{fig:34} gives few examples for |
---|
867 | the preamplifier at different gains. \refTab{11} summarizes the fit |
---|
868 | results of these linearities. Good linearity performances are shown by |
---|
869 | residuals (better than $\pm 2~\%$) value but for a |
---|
870 | smaller dynamic range than simulation. |
---|
871 | |
---|
872 | \begin{figure}[hbtp] |
---|
873 | \centering |
---|
874 | %\includegraphics{img42.eps} |
---|
875 | %\includegraphics{img43.eps} |
---|
876 | %\includegraphics{img44.eps} |
---|
877 | \caption{Preamplifier linearity for different gains.} |
---|
878 | \label{fig:34} |
---|
879 | \end{figure} |
---|
880 | |
---|
881 | \begin{table} |
---|
882 | \centering |
---|
883 | \caption{TO BE COMPLETED} |
---|
884 | \label{tab:11} |
---|
885 | \begin{tabular}{|c|c|c|c|} |
---|
886 | \hline |
---|
887 | Preamplifier Gains & Maximum voltage & Charge/Nb of pe & Residuals \\ |
---|
888 | \hline |
---|
889 | 8 & 0.52~V & 12~pC / 78~pe & -1.0~\% to 0.8~\% \\ |
---|
890 | 4 & 0.64~V & 32~pC / 198~pe & -1.0~\% to 1.0~\% \\ |
---|
891 | 2 & 0.51~V & 50~pC / 312~pe & -2.0~\% to 1.5~\% \\ |
---|
892 | \hline |
---|
893 | \end{tabular} |
---|
894 | \end{table} |
---|
895 | |
---|
896 | |
---|
897 | \refFig{fig:35} represents an example of slow shaper |
---|
898 | linearity for a time constant of 50~ns and a preamplifier gain of 8 |
---|
899 | with residuals better than $pm 1~\%$. |
---|
900 | |
---|
901 | \begin{figure}[hbtp] |
---|
902 | \centering |
---|
903 | %\includegraphics{img45.eps} |
---|
904 | \caption{Slow shaper linearity; $RC =50$~ns and $G_{pa}=8$.} |
---|
905 | \label{fig:35} |
---|
906 | \end{figure} |
---|
907 | |
---|
908 | \refFig{fig:36} gives an example of the fast shaper linearity until an injected |
---|
909 | charge of 10~pe. Residuals better than $ \pm 2~\%$ |
---|
910 | are obtained. |
---|
911 | |
---|
912 | \begin{figure}[hbtp] |
---|
913 | \centering |
---|
914 | %\includegraphics{img46.eps} |
---|
915 | \caption{Fast shaper linearity up to 10~pe.} |
---|
916 | \label{fig:36} |
---|
917 | \end{figure} |
---|
918 | |
---|
919 | The preamplifier linearity in function of |
---|
920 | variable feedback capacitor value with an input charge of 10~pe and |
---|
921 | with residuals from $-2.5~\%$ to $1.4~\%$ is represented on \refFig{fig:37} . The gain |
---|
922 | adjustment linearity is nice at 2~\% on 8 bits. |
---|
923 | |
---|
924 | \begin{figure}[hbtp] |
---|
925 | \centering |
---|
926 | %\includegraphics{img47.eps} |
---|
927 | \caption{Preamplifier linearity vs feedback capacitor value.} |
---|
928 | \label{fig:37} |
---|
929 | \end{figure} |
---|
930 | |
---|
931 | On \refFig{fig:38} is given the gain uniformity. For the |
---|
932 | different preamplifier gains is plotted the maximum voltage value for |
---|
933 | all channels in order to investigate the homogeneity among the whole |
---|
934 | chip, essential for a multichannels ASIC. Residual dispersion of 0.05~\%, |
---|
935 | 0.013~\% and 0.012~\% have respectively been obtained for gain 8, 4 and |
---|
936 | 2. |
---|
937 | |
---|
938 | \begin{figure}[hbtp] |
---|
939 | \centering |
---|
940 | %\includegraphics{img48.eps} |
---|
941 | \caption{Gain uniformity for $G_{pa}=8, 4, 2$.} |
---|
942 | \label{fig:38} |
---|
943 | \end{figure} |
---|
944 | |
---|
945 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
946 | \subsection{DAC linearity} |
---|
947 | \label{ssec:DAClinearity} |
---|
948 | %%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
949 | The DAC linearity has been measured and it consists in measuring the |
---|
950 | voltage DAC ($V_{dac}$) amplitude obtained for different DAC register |
---|
951 | values. \refFig{fig:39} gives the evolution of $V_{dac}$ as a function of the register for the two |
---|
952 | DACs and residuals from $-0.1~\%$ to $0.1~\%$. |
---|
953 | |
---|
954 | \begin{figure}[hbtp] |
---|
955 | \centering |
---|
956 | %\includegraphics{img49.eps} |
---|
957 | %\includegraphics{img50.eps} |
---|
958 | \caption{DAC linearity; DAC1 and DAC2 respectively.} |
---|
959 | \label{fig:39} |
---|
960 | \end{figure} |
---|
961 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
962 | \subsection{Trigger output} |
---|
963 | \label{ssec:TriggerMeas} |
---|
964 | %%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
965 | The trigger output behavior was studied scanning the threshold for |
---|
966 | different injected charges. At first no charge was injected which |
---|
967 | corresponds to measure the fast shaper pedestal. The result is |
---|
968 | represented on \refFig{fig:40} for each channel. The S-curves |
---|
969 | are superimposed meaning good homogeneity. The spread |
---|
970 | is of one DAC count ($LSB DAC = 1.78$~mV) or 0.06~pe. |
---|
971 | |
---|
972 | \begin{figure}[hbtp] |
---|
973 | \centering |
---|
974 | %\includegraphics{img51.eps} |
---|
975 | \caption{Pedestal S-curves for channel 1 to 16.} |
---|
976 | \label{fig:40} |
---|
977 | \end{figure} |
---|
978 | |
---|
979 | The trigger efficiency was then measured for a |
---|
980 | fixed injected charge of 10~pe. On \refFig{fig:41} are represented the S-curves |
---|
981 | obtained with 200 measurements of the trigger for all channels varying |
---|
982 | the threshold. The homogeneity is proved by a spread of 7 DAC unit (0.4~pe) and a noise of 0.07 pe ($RMS =2.19$). |
---|
983 | |
---|
984 | \begin{figure}[hbtp] |
---|
985 | %\includegraphics{img52.eps} |
---|
986 | %\includegraphics{img53.eps} |
---|
987 | %\includegraphics{img54.eps} |
---|
988 | \caption{Fast shaper and trigger (top panel); S-curves for input of 10~pe (left panel); |
---|
989 | uniformity plot for channel 1 to 16 (right panel).} |
---|
990 | \label{fig:41} |
---|
991 | \end{figure} |
---|
992 | |
---|
993 | The trigger output is studied also by scanning |
---|
994 | the threshold for a fixed channel and changing the injected charge. On \refFig{fig:42} |
---|
995 | on the left panel is shown the trigger efficiency versus the DAC unit and on |
---|
996 | the right panel is plotted the threshold versus the injected charge but only |
---|
997 | until 0.5~pC. From these measurements a noise of 10~fC has been |
---|
998 | extrapolated. Therefore the threshold is only possible above $10~\sigma$ of the noise due to the discriminator coupling |
---|
999 | (\refFig{fig:43}). |
---|
1000 | |
---|
1001 | \begin{figure}[hbtp] |
---|
1002 | \centering |
---|
1003 | %\includegraphics{img55.eps} |
---|
1004 | %\includegraphics{img56.eps} |
---|
1005 | \caption{Trigger efficiency vs DAC count up to 300~pe (left panel) and |
---|
1006 | until 3~pe (right panel).} |
---|
1007 | \label{fig:42} |
---|
1008 | \end{figure} |
---|
1009 | |
---|
1010 | \begin{figure}[hbtp] |
---|
1011 | \centering |
---|
1012 | %\includegraphics{img57.eps} |
---|
1013 | \caption{Threshold vs injected charge up to 500~fC. It is shown the 1~p.e threshold for a PMT gain of $10^6$.} |
---|
1014 | \label{fig:43} |
---|
1015 | \end{figure} |
---|
1016 | |
---|
1017 | The trigger coupling illustrated in \refFig{fig:44} with the |
---|
1018 | injected charge in channel 1 and output signal observed in channel 2, |
---|
1019 | shows a coupling signal around 25~mV (10~fC). This coupling signal is |
---|
1020 | due, probably, to the input power supply ($V_{dd-pa}$ and $V_{ss}$). |
---|
1021 | |
---|
1022 | \begin{figure}[hbtp] |
---|
1023 | %\includegraphics{img58.eps} |
---|
1024 | \caption{Trigger coupling signal.} |
---|
1025 | \label{fig:44} |
---|
1026 | \end{figure} |
---|
1027 | |
---|
1028 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
1029 | \subsection{ADC characterisation} |
---|
1030 | \label{ssec:ADCMeas} |
---|
1031 | %%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
1032 | The ADC performance has been studied alone and with the whole chain. Injecting to the |
---|
1033 | ADC input directly a DC voltage by the internal DAC, |
---|
1034 | in order to have a voltage level as stable as possible, were measured |
---|
1035 | the ADC values for all channels (\refFig{fig:45}). |
---|
1036 | |
---|
1037 | The measurement is repeated 10000 times for |
---|
1038 | each channel and in the first plot of the LabView front panel window (\refFig{fig:45}). The |
---|
1039 | minimal, maximal and mean values, over all acquisitions, for each |
---|
1040 | channel are plotted. In the second plot there is the rms charge value |
---|
1041 | versus channel number with a value in the range $[0.5, 1]$ ADC unit. |
---|
1042 | Finally the third plot shows an example of charge amplitude |
---|
1043 | distribution for a single channel: a spread of 5 ADC counts is |
---|
1044 | obtained. |
---|
1045 | |
---|
1046 | \begin{figure}[hbtp] |
---|
1047 | \centering |
---|
1048 | %\includegraphics{img59.eps} |
---|
1049 | \caption{ADC measurements with DC input 1.45~V (middle scale).} |
---|
1050 | \label{fig:45} |
---|
1051 | \end{figure} |
---|
1052 | |
---|
1053 | The ADC is suited to a multichannel conversion |
---|
1054 | so the uniformity and linearity are studied in order to characterize |
---|
1055 | the ADC behaviour. On \refFig{fig:46} is represented the ADC transfer function for the |
---|
1056 | 10-bit ADC versus the input voltage level. All channels are represented |
---|
1057 | and have plots superimposed. |
---|
1058 | |
---|
1059 | \begin{figure}[hbtp] |
---|
1060 | \centering |
---|
1061 | %\includegraphics{img60.eps} |
---|
1062 | \caption{10 bits ADC transfer function vs input charge.} |
---|
1063 | \label{fig:46} |
---|
1064 | \end{figure} |
---|
1065 | |
---|
1066 | The good homogeneity observed is confirmed by |
---|
1067 | the linear fit parameters comparison. In are plotted the slope and the |
---|
1068 | intercept distributions for all channels. The RMS slope value of 0.143 |
---|
1069 | and the RMS intercept value of 0.3 confirm the 10-bits ADC uniformity |
---|
1070 | (\refTab{tab:12}). |
---|
1071 | |
---|
1072 | \begin{figure}[hbtp] |
---|
1073 | \centering |
---|
1074 | %\includegraphics{img61.eps} |
---|
1075 | %\includegraphics{img62.eps} |
---|
1076 | \caption{Evolution of the fit parameters (slope on the |
---|
1077 | left panel and intercept on the right panel) as a function of the channel |
---|
1078 | number.} |
---|
1079 | \label{fig:47} |
---|
1080 | \end{figure} |
---|
1081 | |
---|
1082 | \begin{table} |
---|
1083 | \centering |
---|
1084 | \caption{TO BE COMPLETED. 10 bits ADC parameter fits.... 25 acquisitions per channel, $LSB = 1.06$~mV...} |
---|
1085 | \label{tab:12} |
---|
1086 | \begin{tabular}{|l|c|c|} |
---|
1087 | \hline |
---|
1088 | & Slope & Intercept \\ |
---|
1089 | Mean & 936.17 & 859.8 \\ |
---|
1090 | RMS & 0.14 & 0.3 \\ |
---|
1091 | \hline |
---|
1092 | \end{tabular} |
---|
1093 | \end{table} |
---|
1094 | |
---|
1095 | In \refFig{fig:48} are shown respectively the 12, 10 and 8 bits ADC |
---|
1096 | linearity plots with the 25 measurements made for each input voltage |
---|
1097 | level. The average ADC count value is plotted versus the input signal. |
---|
1098 | The residuals from $-1.5$ to $0.9$ ADC units for the 12-bits ADC; from $-0.5$ |
---|
1099 | to $0.4$ for the 10-bit ADC and from $-0.5$ to $0.5$ for the 8-bit ADC. This prove |
---|
1100 | the good ADC behaviour in terms of Integral non linearity. |
---|
1101 | |
---|
1102 | \begin{figure}[hbtp] |
---|
1103 | %\includegraphics{img63.eps} |
---|
1104 | %\includegraphics{img64.eps} |
---|
1105 | %\includegraphics{img65.eps} |
---|
1106 | \caption{12, 10, 8 bit ADC linearity.} |
---|
1107 | \label{fig:48} |
---|
1108 | \end{figure} |
---|
1109 | In terms of Differential non linearity, the |
---|
1110 | value from $-1.0$ to $0.65$ for the 10 bit ADC and from $-0.3$ to $0.2$ for the 8 |
---|
1111 | bit ADC, show us a good behaviour even if the plots are the results of |
---|
1112 | preliminary measurements. |
---|
1113 | |
---|
1114 | \begin{figure}[htb] |
---|
1115 | %\includegraphics{img66.eps} |
---|
1116 | %\includegraphics{img67.eps} |
---|
1117 | \caption{Differential non linearity.} |
---|
1118 | \label{fig:49} |
---|
1119 | \end{figure} |
---|
1120 | |
---|
1121 | Once the ADC performances have been tested |
---|
1122 | separately, the measurements are performed on the complete chain. The |
---|
1123 | results of the input signal autotriggered, held in the T\&H and |
---|
1124 | converted in the ADC are illustrated in where are plotted the 10-bit |
---|
1125 | ADC counts in function of the variable input charge (up to 50~pe). A |
---|
1126 | good linearity of $1.4~\%$ and a noise of 6 ADC units are obtained. In \refTab{tab:13} |
---|
1127 | are listed the setting value for measurements. |
---|
1128 | |
---|
1129 | \begin{table} |
---|
1130 | \centering |
---|
1131 | \caption{TO BE COMPELTED. $G_{pa}=14$ ($C_{in}=7$~pF , $C_f=0.5$~pF), |
---|
1132 | Slow shaper $RC=50$~ns, |
---|
1133 | DAC delay: $bit<0> = 1$ \& $bit<2> = 1$. |
---|
1134 | } |
---|
1135 | \label{tab:13} |
---|
1136 | \begin{tabular}{|l|c|c|c|} |
---|
1137 | \hline |
---|
1138 | Parameters & 12 bits ADC & 10 bits ADC & 8 bits ADC\\ |
---|
1139 | \hline |
---|
1140 | LSB & $0.27$ & $1.06$~mV & $4.26$~mV\\ |
---|
1141 | Min ADC count at 3~pe& $509$ & $132$ & $33$ \\ |
---|
1142 | Max ADC count at 50~pe & $3873$ & $989$ & $241$ \\ |
---|
1143 | Residuals in ADC units &$[21,54]$ & $[6,14]$ & $[2,3]$ \\ |
---|
1144 | \hline |
---|
1145 | \end{tabular} |
---|
1146 | \end{table} |
---|
1147 | |
---|
1148 | \begin{figure}[hbtp] |
---|
1149 | \centering |
---|
1150 | %\includegraphics{img68.eps} |
---|
1151 | \caption{10 bit ADC linearity.} |
---|
1152 | \label{fig:50} |
---|
1153 | \end{figure} |
---|
1154 | |
---|
1155 | On \refFig{fig:51} is plotted the 8-bit linearity at $1.4~\%$ |
---|
1156 | and a noise of 1.53 ADC unit. In \refTab{tab:13} are listed the setting value for |
---|
1157 | measurements. |
---|
1158 | |
---|
1159 | \begin{figure}[hbtp] |
---|
1160 | \centering |
---|
1161 | %\includegraphics{img69.eps} |
---|
1162 | \caption{8 bit ADC linearity.} |
---|
1163 | \label{fig:51} |
---|
1164 | \end{figure} |
---|
1165 | |
---|
1166 | On \refFig{fig:53} is plotted the 12-bit linearity |
---|
1167 | at $1.4~\%$ and a noise of 23.69 ADC unit. In \refTab{tab:13} are listed the setting |
---|
1168 | value for measurements. |
---|
1169 | |
---|
1170 | \begin{figure}[hbtp] |
---|
1171 | %\includegraphics{img70.eps} |
---|
1172 | \caption{12 bit ADC linearity.} |
---|
1173 | \label{fig:52} |
---|
1174 | \end{figure} |
---|
1175 | |
---|
1176 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
1177 | \section{Measurements with PMTs} |
---|
1178 | \label{sec:MeasWithPMT} |
---|
1179 | %%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
1180 | The first measurements with a photomultiplier at input are started in |
---|
1181 | IPNO at Orsay. |
---|
1182 | |
---|
1183 | \begin{figure}[hbtp] |
---|
1184 | \centering |
---|
1185 | %\includegraphics{img71.eps} |
---|
1186 | \caption{TO BE COMPLETED} |
---|
1187 | \label{fig:53} |
---|
1188 | \end{figure} |
---|
1189 | |
---|
1190 | \acknowledgments |
---|
1191 | %\begin{acknowledgments} |
---|
1192 | This work, especially one of the author, is supported by the National Reasaerch Agency under contract ANR-06-BLAN-0186. |
---|
1193 | %\end{acknowledgments} |
---|
1194 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
---|
1195 | \newpage |
---|
1196 | %\section*{References} |
---|
1197 | \bibliography{campagne} |
---|
1198 | \end{document} |
---|
1199 | |
---|
1200 | |
---|