Changeset 150 in JEM-EUSO for ICRC2013/EusoBalloonDetector/trunk/icrc2013-EBDet-morettodagoret.tex
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ICRC2013/EusoBalloonDetector/trunk/icrc2013-EBDet-morettodagoret.tex
r149 r150 8 8 9 9 %The paper title 10 \title{ Detaileddescription of EUSO-BALLOON instrument}10 \title{Global description of EUSO-BALLOON instrument} 11 11 12 12 %The short title to appear at the header of the pages. 13 \shorttitle{Instrumentation for JEM 13 \shorttitle{Instrumentation for JEM-EUSO } 14 14 15 15 %All paper authors 16 16 \authors{ 17 17 18 C. Moretto$^{1}$, S. Dagoret-Campagne$^{1}$, J.H. Adams$^{19}$, P. von Ballmoos$^{2}$,P. Barrillon$^{1}$, J. Bayer$^{5}$, M. Bertaina$^{12}$, S. Blin-Bondil$^{1}$, F. Cafagna$^{7}$, M. Casolino$^{13,10,11}$, C. Catalano$^{2}$, P. Danto$^{4}$, A. Ebersoldt$^{6}$, T. Ebisuzaki$^{13}$, J. Evrard$^{4}$, Ph. Gorodetzky$^{3}$, A. Haungs$^{6}$, A. Jung$^{14}$, Y. Kawasaki$^{13}$, H. Lim$^{14}$, G. Medina-Tanco$^{15}$, H. Miyamoto$^{1}$, D. Monnier-Ragaigne$^{1}$, T. Omori$^{13}$, G. Osteria$^{9}$, E. Parizot$^3$, I.H. Park$^{14}$, P. Picozza$^{13,10,11}$, G. Pr\'ev\^ot$^{3}$, H. Prieto$^{13,17}$, M. Ricci$^{8}$, M.D. Rodrguez Fras$^{17}$, A. Santangelo$^{5}$, J. Szabelski$^{16}$, Y. Takizawa$^{13}$, K. Tsuno$^{13}$18 C. Moretto$^{1}$, S. Dagoret-Campagne$^{1}$, J.H. Adams$^{19}$, P. von Ballmoos$^{2}$,P. Barrillon$^{1}$, J. Bayer$^{5}$, M. Bertaina$^{12}$, S. Blin-Bondil$^{1}$, F. Cafagna$^{7}$, M. Casolino$^{13,10,11}$, C. Catalano$^{2}$, P. Danto$^{4}$, A. Ebersoldt$^{6}$, T. Ebisuzaki$^{13}$, J. Evrard$^{4}$, Ph. Gorodetzky$^{3}$, A. Haungs$^{6}$, A. Jung$^{14}$, Y. Kawasaki$^{13}$, H. Lim$^{14}$, G. Medina-Tanco$^{15}$, H. Miyamoto$^{1}$, D. Monnier-Ragaigne$^{1}$, T. Omori$^{13}$, G. Osteria$^{9}$, E. Parizot$^3$, I.H. Park$^{14}$, P. Picozza$^{13,10,11}$, G. Pr\'ev\^ot$^{3}$, H. Prieto$^{13,17}$, M. Ricci$^{8}$, M.D. Rodrguez Frias$^{17}$, A. Santangelo$^{5}$, J. Szabelski$^{16}$, Y. Takizawa$^{13}$, K. Tsuno$^{13}$ 19 19 for the JEM-EUSO Collaboration$^{19}$. 20 20 } … … 25 25 $^2$ Institut de Recherche en Astrophysique et Plan\'etologie, Toulouse, France\\ 26 26 $^3$ AstroParticule et Cosmologie, Univ Paris Diderot, CNRS/IN2P3, Paris, France\\ 27 $^4$ Centre National d' Etudes Spatiales, Centre Spatial de Toulouse, France\\27 $^4$ Centre National d'\'Etudes Spatiales, Centre Spatial de Toulouse, France\\ 28 28 $^5$ Institute for Astronomy and Astrophysics, Kepler Center, University of T\"{u}bingen, Germany\\ 29 29 $^6$ Karlsruhe Institute of Technology (KIT), Germany\\ … … 50 50 This telescope will be the payload of a stratospheric balloon operated by CNES, starting its flight campaign in 2014. 51 51 Current technical developments for JEM-EUSO have been implemented in EUSO-Balloon. 52 In this article, the complete design of this instrument will be presented. It consists of an advanced telescope structure, including a set of three Fresnel lenses having an excellent focusing capability onto its pixelized UV Camera. This camera is very sensitive to single photons, with 6 orders of magnitude dynamic range thanks to an adaptive gain, and fast enough to observe speed-of-light phenomena. The camera is an array of multianodes photomultipliers, whose dynodes are driven by Crockoft Walton HV \textbf{(faut-il d\'eja donner des spécificités sur l'instrument dans l'abstract?)}generators capable of switching down the gain in few microseconds to protect the photodetectors against strongly luminous events.52 In this article, the complete design of this instrument will be presented. It consists of an advanced telescope structure, including a set of three Fresnel lenses having an excellent focusing performance onto its pixelized UV Camera. This camera is very sensitive to single photons, accepting signals within 6 orders of magnitude through an adaptive gain, and able to observe speed-of-light phenomena. The camera is an array of multi-anodes photomultipliers, whose dynodes are driven by Crockoft Walton HV generators capable of switching down the gain in few microseconds to protect the photodetectors against strongly luminous events. 53 53 Analog signals of the anodes are digitised continuously each time window (2.5 $\mu$s) by ASICs, performing two kinds of signal measurements and readout by a FPGA applying a first level trigger algorithm. 54 54 The electronics is operated by a digital processing unit comprising a CPU associated to Clocks generators board and a GPS receiver, an event filtering board based on a FPGA and an House-Keeping unit for the instrument monitoring. The CPU controls both acquisition and the data storage. … … 67 67 \section{Introduction} 68 68 EUSO-Balloon is a telescope aiming at verifying the conceptual design as well as the technologies foreseen to be applied for the construction of the future space telescope JEM-EUSO ~\cite{bib:EUSOperf}. Even if this instrument is a reduced version of JEM-EUSO, it however includes almost all the required components of the original space mission. The scientific and technical goals on its mission are reviewed in the reference~\cite{bib:EBpath}. This instrument will be the payload of a stratospheric balloon operated by CNES, 69 to perform a series of night-flights at altitudes of 40 km, at various earth locations, lasting from a few hours to tens of hours. This program requires payload recovery after landing either in water or hard soil, and repairing after each mission. The special atmospheric environmental conditions and recovery requirements involve much precautions in the design and imply dedicated tests forthe realisation of prototypes.69 to perform a series of night-flights at altitudes of 40 km, at various earth locations, lasting from a few hours to tens of hours. This program requires payload recovery after landing either in water or hard soil, and repairing after each mission. The special atmospheric environmental conditions and recovery requirements involve much precautions in the design and imply dedicated tests with the realisation of prototypes. 70 70 71 71 This paper is organised as follows. First, section~\ref{sec:OverviewInstrument} gives the overview of the instrument, including its particular mechanical design adapted to the balloon flights. Section~\ref{sec:Subsystems} provides details on the subsystems and highlights reasons for the chosen design. Afterward, the section~\ref{sec:AssemblyTest} deals with the series of preliminary measurements and tests which are mandatory before the commissioning of the instrument for exploration. Finally, the control and analysis tasks to be performed during the operation are mentioned in section ~\ref{sec:Operation}. … … 75 75 \label{sec:OverviewInstrument} 76 76 77 The EUSO-balloon instrument structure is shown in the figure~\ref{fig:globalview} and its main characteristics are given in the table~\ref{tab:properties}. These parameters will be justified in the section~\ref{sec:Subsystems} devoted to the subsystems. This parallelepiped telescope78 presents a wide field of view of 12$^ o\times$12$^o$ for a collecting surface of 1.2 m$\times$1.2m. It points to the nadir direction toward the earth.77 The EUSO-balloon instrument structure is shown in the figure~\ref{fig:globalview} and its main characteristics are given in the table~\ref{tab:properties}. These parameters will be justified in the section~\ref{sec:Subsystems} devoted to the subsystems. This parallelepiped-shaped telescope 78 presents a wide field of view of 12$^\circ\times$12$^\circ$ for a collecting surface of 1 m$\times$1 m. It points to the nadir direction toward the earth. 79 79 It basically consists in an optical bench associated to an instrument booth placed at the focal position. 80 80 The optical bench comprises two lenses. The instrument booth includes the whole electronics inside a pressurised watertight box. One side of the instrument booth is provided by the third lens. … … 89 89 90 90 \subsection{General characteristics and functions} 91 The optical subsystem includes the optical bench which have the purpose of focusing parallel light rays in a narrow focal point on a pixelized surface, consisting in an array of photodetectors called MAPMTs (Multi-Anode Photomultipliers). This focal surface is instrumented by an electronics which has the properties of a very high sensitivity in the UV range, fast measurement rate within the microsecond timescale, auto-triggering capability, event filtering and event recording. This electronics is capable to record on disk a burst of 128 consecutive sky pictures separated each-other by a Gate Time Unit (GTU) of 2.5 $\mu$s. 92 93 \begin{table}[h!] 94 \begin{center} 95 %{\tiny 96 \begin{tabular}{|c|c|}\hline 97 \multicolumn{2}{|c|}{{\tiny General parameters} } \\ \hline 98 {\tiny Field of View } & {\tiny 12$^o \times $12$^o $ } \\ 99 {\tiny Aperture} & {\tiny 1 m $\times$ 1 m} \\ 100 {\tiny Height} & {\tiny 2.66 m} \\ 101 {\tiny Width} & {\tiny 1.24 m (without crash pads)} \\ 102 {\tiny Weight }& {\tiny 300 kg }\\ \hline 103 \multicolumn{2}{|c|}{{\tiny Optics} } \\ \hline 104 {\tiny Focal Length } & {\tiny 1.62 m} \\ 105 {\tiny Focal Point Spread (RMS)} & {\tiny 2.6 mm} \\ \hline 106 \multicolumn{2}{|c|}{ {\tiny Focal Surface} } \\ \hline 107 {\tiny Curvature Radius} & {\tiny 2.5 m} \\ 108 {\tiny Number of Pixels} & {\tiny 2304} \\ 109 {\tiny Pixel FOV} & {\tiny 0.25$^o \times$ 0.25$^o$} \\ 110 {\tiny Pixel size} & {\tiny 2.88 mm $\times$ 2.88 mm} \\ 111 {\tiny BG3 UV Filter transmittance} & {\tiny 98 \%} \\ 112 {\tiny Wavelength range} & {\tiny 290 nm - 430 nm} \\ 113 {\tiny Number of MAPMTs} & {\tiny 6 $\times$ 6} \\ \hline 114 \multicolumn{2}{|c|}{{\tiny PhotonDetection (MAPMTs)}} \\ \hline 115 {\tiny Number of channels} & {\tiny 64} \\ 116 {\tiny Photon detection efficiency} & {\tiny 35 \%} \\ 117 {\tiny Gain} & {\tiny 10$^6$} \\ 118 {\tiny Pulse duration} & {\tiny 2 ns} \\ 119 {\tiny Two pulses separation} & {\tiny 5 ns} \\ 120 {\tiny Dynamic Range} & {\tiny 1 - 100 photons} \\ 121 {\tiny Maximum tube current} & {\tiny 100 $\mu$A} \\ \hline 122 \multicolumn{2}{|c|}{{\tiny Signal Measurement (ASIC)}} \\ \hline 123 {\tiny Sampling period (GTU)} & {\tiny 2.5 $\mu$s} \\ 124 {\tiny Photon Counting (64 ch), photoelectrons} & {\tiny 0.3 pe (50 fC) - 30 pe (5 pC)} \\ 125 {\tiny Charge to Time Conv (8 ch)} & {\tiny 2 pC (10 pe) - 200 pC (100 pe)} \\ 126 {\tiny Readout Clock} & {\tiny 40 MHz} \\ \hline 127 \multicolumn{2}{|c|}{ {\tiny Triggers (FPGA, Virtex 6(L1) and Virtex 4(L2))} }\\ \hline 128 {\tiny L1 rate} & {\tiny 7 Hz (1-100 Hz)} \\ 129 {\tiny L2 rate} & {\tiny Max 50 Hz} \\ \hline 130 \multicolumn{2}{|c|}{ {\tiny Event readout and DAQ (CPU, Clocks, GPS)}} \\ \hline 131 {\tiny Event size} & {\tiny 330 kB} \\ 132 {\tiny Data flow} & {\tiny 3.24 Mb/s} \\ 133 {\tiny Readout Clock} & {\tiny 40 MHz} \\ 134 {\tiny Event dating} & {\tiny at $\mu$s level} \\ \hline 135 %\multicolumn{2}{|c|}{ {\tiny Instrument Monitoring (microcontroler)}} \\ \hline 136 %\multicolumn{2}{|c|}{ {\tiny On/Off capability, alarms, temperature and voltage control }}\\ \hline 137 \multicolumn{2}{|c|}{{\tiny Power supply}} \\ \hline 138 {\tiny 60 batteries cells} & {\tiny 225 W during 24 hours, V: 28 V} \\ \hline 139 \end{tabular} 91 The optical subsystem includes the optical bench which have the purpose of focusing parallel light rays in a narrow focal point on a pixelized surface, consisting in an array of photodetectors called MAPMTs (Multi-Anode Photomultipliers). This Focal Surface (FS) is instrumented by an electronics which has the properties of a very high sensitivity in the UV range, fast measurement rate within the microsecond time scale, auto-triggering capability, event filtering and event recording. This electronics is capable to record on disk a burst of 128 consecutive sky pictures separated each-other by a Gate Time Unit (GTU) of 2.5 $\mu$s. 92 93 \begin{table}[h!] 94 \centering 95 \includegraphics[width=0.48\textwidth]{InstrumentTable} 140 96 \caption{Typical parameters of the instrument} 141 97 \label{tab:properties} 142 %\par}143 \end{center}144 98 \end{table} 145 99 146 \subsection{Instrument mechanics and architectrure}147 The mechanics of the instrument is made of Fibrelam\textregistered panels, arranged together through fibreglass sections.148 The instrument will be coated by an insulating cover to protect the instrument's componentfrom fast temperature changes during balloon ascent and descent.100 \subsection{Instrument structure} 101 The mechanics of the instrument is made of Fibrelam\textregistered \ panels, arranged together through fibreglass sections. 102 The instrument is coated by an insulating cover to protect the instrument's components from fast temperature changes during balloon ascent and descent. 149 103 Special watertight valves inserted in the optical bench are used to enable pressure equilibrium with the atmosphere. Wherever the after-flight landing location occurs, the instrument must be recovered with the smallest damages. 150 104 The bottom part is equipped with crash-pads which absorb brutal deceleration (up to 15 G) when landing on ground. A baffle with special holes in the optical bench are used as a piston-effect to damp the shock for a fall over water. 151 The instrument booth which is a totally watertight sealed box, consists of a central aluminium plate on which the various electronic boxes are fixed. One of its side is the third lens. The opposite one is an aluminium radiator used to dissipate the heat generated by electronics equipment .152 The instrument is surrounded by buoys to avoid sinking i f sea landingand to raise straight up the instrument booth above the water level.153 \section{The instrument Subsystems}105 The instrument booth which is a totally watertight sealed box, consists of a central aluminium plate on which the various electronic boxes are fixed. One of its side is the third lens. The opposite one is an aluminium radiator used to dissipate the heat generated by electronics equipments. 106 The instrument is surrounded by buoys to avoid sinking in case of splashdown and to raise straight up the instrument booth above the water level. 107 \section{The Instrument Subsystems} 154 108 \label{sec:Subsystems} 155 The instrument is broken down into subsystems defined to be the optics, the Focal Surface (FS), the Photo-detector with the MAPMT, the signal measurement with the ASICs, the trigger readout with the Photo-Detector Module Board (PDMB) and the Cluster Control Board (CCB). The Data Acquisition System (DAQ) and the utilities like the monitoring also called the House-Keepting (HK) and the power supplies. Those subsystems are all described succinctlybelow.109 The instrument is broken down into subsystems defined to be the optics, the Focal Surface (FS), the photodetector with the MAPMTs, the signal measurement with the ASICs, the trigger readout with the Photo-Detector Module Board (PDMB) and the Cluster Control Board (CCB). The Data Acquisition System (DAQ) and the utilities like the monitoring also called the House-Keepting (HK) and the power supplies. Those subsystems are all described below. 156 110 \subsection{Optics subsystem} 157 The optics subsystem involves th e three lenses.158 Its goal is to provide the best foc alisation for the smallest focal distance. The focalisation requirement is constrained by the pixel size of the photodetection system.159 Due to the wide angular field of view, it is necessary to combine 3 flat lenses. External ones are focusing Fresnel type on a side and the middle lens is purely dispersive to correctchromatic aberrations. These lenses are manufactured in PMMA material~\cite{bib:Optics}. The ray tracing calculations including the temperature profile expected for flights in cold and warm cases provide a focal length of 1.62 m and a focal point spread width of the order of 2.6 mm, smaller than the pixel size.111 The optics subsystem involves three lenses. 112 Its goal is to provide the best focusing for the smallest focal distance. The focusing requirement is constrained by the pixel size of the photodetection system. 113 Due to the wide angular field of view, it is necessary to combine 3 flat lenses. External ones are focusing one-sided Fresnel lens and the middle one is purely dispersive to correct for chromatic aberrations. These lenses are manufactured in PMMA material~\cite{bib:Optics}. The ray tracing calculations including the temperature profile expected for flights in cold and warm cases provide a focal length of 1.62 m and a focal point spread width of the order of 2.6 mm, smaller than the pixel size. 160 114 161 115 \subsection{Front-End Electronics} 162 116 MAPMTs constituting the FS, provide anode signals measured and digitised by ASICs, themselves readout by FPGA to run the trigger algorithm. The FS is arranged into a so-called Photo-Detector Module (PDM) whose design and effective realisation is described in details in~\cite{bib:FrontEndEl}. We review in the following the main properties of this electronics. 163 \paragraph{Focal Surface} The focal Surface is a slightly curved surface, similarly to that of the JEM-EUSO central PDM, being an array of 48$\times$48 pixels of 2.88 mm $\times$ 2.88 mm size exceeding slightly the focal point spread. This granularity fits perfectly the accuracy requirements to make the longitudinal profile image of Air-showers above $10^{18}$ eV. Practically, the focal surface of the PDM is broken up into a set of 9 identical Elementary Cells (ECs), which are matrixes of 2$\times$2 MAPMTs. Inside the PDM structure, the 9 ECs are disposed and tilted according to the appropriate shape required for the FS. 164 \paragraph{MAPMTs} They are photon detectors consisting of a matrix of 8$\times$8 pixels. Each pixel is associated to an anode generating a charge or a current in output. Their sensitivity is as low as a few tens of photoelectrons and their dynamic range can extend up to few 100 photoelectrons per $\mu$s when working at high gain ($10^6$). 165 \textbf{This high gain is achieved through 14 dynodes (not 12??) polarised by High Voltage Power Supplies (HVPS) for which the photocathode is set at -900 V. Limited power consumption is obtained with a Crockoft-Walton (CW) high voltages supplier. Dynamic range can be extended up to 10$^6$ photons (??) if the gain is reduced automatically gradually from 10$^6$ to 10$^4$, 10$^2$ or 30 by fast switches (SW) reacting to the micro-second timescale in case of large current flow is detected in the anodes. In the PDM, there is 9 independent HVPS controlling the 9 ECs. 166 Because a large photon flux generating anode current above 100$\mu$A would destroy the tube, an automatic control system reducing the gain or switching off the MAPMT is mandatory to guaranty the tube survival. 167 Practically this switching decision logic is implemented in a FPGA reading out the ASICs.} 117 118 \paragraph{Focal Surface} The focal surface is a slightly curved surface, similarly to that of the JEM-EUSO central PDM. It is an array of 48$\times$48 pixels of 2.88 mm $\times$ 2.88 mm size exceeding slightly the focal point spread. Practically, the focal surface of the PDM is broken up into a set of 9 identical Elementary Cells (ECs), which are matrices of 2$\times$2 MAPMTs. The photocathode is covered by a BG3 UV filter. Inside the PDM structure, the 9 ECs are disposed and tilted according to the appropriate shape required for the FS. 119 120 \paragraph{MAPMTs} They are photon detectors consisting of a matrix of 8$\times$8 pixels. Each pixel is associated to an anode generating a charge or a current in output. Their sensitivity is as low as a few tens of photoelectrons and their dynamic range can extend up to few thousands photoelectrons per $\mu$s when working at high gain ($10^6$). 121 122 \paragraph{High voltage power supply} 123 MAPMTs require to be polarised with 14 high voltages. The latter are generated by a high voltage power supply (Crockoft-Walton type to \hyphenation{li-mits} the power consumption). The nominal high voltage of the photocathode is -900 V for a MAPMT gain of $10^6$. The effective dynamic range can be extended up to 10$^7$ photons/$\mu$s by reducing gradually the gain down to 30. Fast switches reactive at $\mu$s time scale adapt HV values to tune the MAPMT gain according to the intensity of photon flux. 124 Because a large photon flux generating anode current above 100$\mu$A would destroy the tube, this automatic control system can even switch off the gain. Practically this switching decision logic is implemented in a FPGA reading out the \mbox{ASICs}. In the PDM, there is 9 independent HVPS controlling the 9 ECs. 125 126 168 127 \paragraph{ASICs} 36 SPACIROC~\cite{bib:ASIC} type ASICs are used to perform the anode signals measurement and digitisation of the 36 MAPMTs. These ASICs have 64 channels. Their analog inputs are DC-coupled to the MAPMT anodes. They process the 64 analog signals in parallel in two modes : 1) in photoelectron counting mode, in a range from 1/3 of photoelectrons up to 100 photoelectrons, by discriminating over a programmed threshold each of the channels, 2) by estimating the charge from 20~pC to 200~pC, by time over threshold determination for exclusive groups of 8 anodes current sums. The 64 analog channels are balanced each-other relatively by gain matching over 8-bits. 169 The discrimination voltage level used in the photo-counting is provided by a 10-bit DAC (Digital to Amplitude converter). 170 In both cases the digitisation is performed by 8-bits counters every GTU. There is no data buffering on the ASIC. The data are transferred to the FPGA each GTU under the sequencing of a 40MHz clock. 171 \paragraph{Trigger} The Instrument includes two trigger stages. The level 1 trigger (L1) implemented in the FPGA of a PDM-Board (PDMB), belonging to the Front-End Electronics. The PDMB readouts the data from the 36 ASICs from a PDM each GTU to compute the trigger L1. Its principle consists in counting an excess of signals over background in groups of 3$\times$3 pixels over a preseted time value. The background rate seen by pixel is monitored continuously to adjust in real-time the trigger threshold which is adjusted such as the L1 rate is kept at a fixed level of a few Hz compatible with the DAQ readout rate. The trigger is evaluated each GTU. Because Air-Showers may extend over 100 GTU, this trigger has the buffering capability of 128 consecutive GTU. 172 To reduced the dead-time induced by event readout, the event buffer is doubled. 128 The discrimination voltage level used in the photon-counting is provided by a 10-bit DAC (Digital to Amplitude converter). 129 In both cases the digitisation is performed by 8-bits counters every GTU. There is no data buffering on the ASIC. The data are transferred to the FPGA each GTU under the sequencing frequency of a 40MHz clock. 130 131 \paragraph{Trigger} The Instrument includes two trigger stages. The level 1 trigger (L1) implemented in the FPGA (Xinlinks Virtex 6) of a PDM-Board (PDMB), belonging to the Front-End Electronics. The PDMB readouts the data from the 36 ASICs into its internal memory (the event buffer) each GTU to compute the trigger L1. Its principle consists in counting an excess of signals over background in groups of 3$\times$3 pixels lasting more than a preset persistence time. The background rate seen by pixel is monitored continuously to adjust in real-time the trigger threshold which is adjusted such as the L1 rate is kept at a fixed level of a few Hz compatible with the DAQ recording rate. The trigger is evaluated each GTU. Because Air-Showers may extend over 100 GTU, this trigger has the buffering capability of 128 consecutive GTU. 132 To reduce the dead-time induced by event readout, the event buffer is doubled. 133 173 134 \subsection{Data acquisition} 174 135 The data acquisition system is part of the computing system DP (Data Processing). 175 It comprises the CCB designed to produce the second level trigger L2, which is described in~\cite{bib:CCB}. For each generated L1 trigger, the CCB reads the data corresponding to the 128 consecutive GTU from the PDMB buffer. In JEM-EUSO, the CCB is devoted to the combination of 9-PDMB triggers and to reduce the resulting combined trigger rate to about a few Hz or less compatible with the data storage capabilities of the DAQ. The triggering role of the CCB in EUSO-Balloon is marginal as there is only one PDM. However it has the task to read the whole event from the Front-End and to pass it to the CPU. The L2 decision is propagated to the Clock-Board (CLK-B, based on a Xilinks Virtex5 FPGA) generating all the clocks used by the electronics, itself associated with a GPS-Board (GPSB)to provide the event time tagging data with an accuracy of a few microseconds.136 It comprises the CCB designed to produce the second level trigger L2, which is described in~\cite{bib:CCB}. For each generated L1 trigger, the CCB reads the data corresponding to the 128 consecutive GTU from the PDMB buffer. In JEM-EUSO, the CCB is devoted to the combination of 9-PDMB triggers and to reduce the resulting combined trigger rate to about a few Hz or less compatible with the data storage capabilities of the DAQ. The triggering role of the CCB in EUSO-Balloon is marginal as there is only one PDM. However it has the task to read the whole event from the Front-End and to pass it to the CPU. The L2 decision is propagated to the Clock-Board (CLK-B, based on a Xilinks Virtex5 FPGA) generating all the clocks used by the electronics, itself associated with a GPS-Board to provide the event time tagging data with an accuracy of a few microseconds. 176 137 The CPU (Motherboard iTX-i2705 model, processor Atom N270 1.6 GHz) merges the event data with the time tagging data to build an event of a size of 330 kB, leading to a data flow of 3MB/s for a 10 Hz L1-L2 trigger. The CPU write all the data on disks (1 TB CZ Octane SATA II 2.5Ó SSD) and may also send to telemetry a subset of flagged events by CCB for event monitoring. 138 177 139 \subsection{Monitoring} 178 140 The instrument behaviour is controlled at low frequency by the House-Keeping system (HK) which is a part of DP. It is based on a commercial micro controller board (Arduino Mega 2560) designed to control temperatures, voltages, and alarms raised by several boards. The CPU poll from time to time the alarms and initiate corresponding foreseen actions. HK is connected to the telemetry system to receive basic commands namely those that allow to turn on-off most of the boards power supplies through relay control. 141 179 142 \subsection{Power supply and electrical architecture} 180 The instrument runs autonomously thanks to a set of 60 batter ies providing 28 V (225 W during 24 H) to a set of Low-Voltage boards generating isolated-decoupled lower voltages to the PDM (HVPS and PDM-B), DP (CPU, CCB and HK). The electrical architecture follows the EMC rules to prevent floating reference voltage induced by bad grounding (ground current loop effect).143 The instrument runs autonomously thanks to a set of 60 battery cells providing 28 V (225 W during 24 H) to a set of Low-Voltage boards generating isolated-decoupled lower voltages to the PDM (HVPS and PDMB), DP (CPU, CCB and HK). The electrical architecture follows the EMC rules to prevent floating reference voltage induced by bad grounding (ground current loop effect). 181 144 182 145 \section{Assembly and Tests} … … 184 147 After fabrication, the subsystems directly related to the physics measurements need to be calibrated in an absolute way. 185 148 The goal of the absolute calibration is to relate a measured digitised signal into the true number of photons impinging on the Focal Surface or on the first lens. 186 Thus the Optics and the photo -detection done by the MAPMTs will be calibrated.149 Thus the Optics and the photodetection done by the MAPMTs will be calibrated. 187 150 Other subsystems like the trigger has to be tested once the instrument is close to final assembly. 188 151 Each of the subsystems of the instrument are calibrated if necessary and tested before the full integration. Then the assembled instrument is then tested entirely. … … 192 155 193 156 \subsection{Measuring the MAPMT performances} 194 Each channel of the MAPMT is characterised by its photodetection efficiency (product of the photocathode quantum efficiency and the collection efficiency) and by the gain of the phototubes. This efficiency is firstly measured before the mounting of MAPMTs inside EC-Units (see~\cite{bib: PMT}) and also after the EC-Units assembly. \textbf{to be reformulated}195 This measur ment is done by illuminating by a LED (controlled by a NIST) the photocathodein single photoelectron mode~\cite{bib:Calib} to measure the single photoelectron spectrum for each of the 2304 pixels of the instrument camera.157 Each channel of the MAPMT is characterised by its photodetection efficiency (product of the photocathode quantum efficiency and the collection efficiency) and by the gain of the phototubes. This efficiency is firstly measured before the mounting of MAPMTs inside EC-Units (see~\cite{bib: PMT}) and also after the EC-Units assembly. 158 This measurement is done by illuminating the photocathode with a LED (monitored with a NIST-photodiode). The MAPMT operates in single photoelectron mode~\cite{bib:Calib} to measure the single photoelectron spectrum for each of the 2304 pixels of the instrument camera. 196 159 This procedure allows to determine the exact high voltage to apply to each MAPMTs photocathodes. 197 160 \subsection{The ASIC settings} … … 210 173 \label{sec:Operation} 211 174 During the balloon flight operation, the instrument will be controlled from ground by an operator using a control program~\cite{bib:OffOnLineAna} interfaced to the TC/TM system (Telecommand and Telemetry) NOSYCA of CNES. 212 At a given altitude reached by the ballo n, a command will be issued to turn on the instrument. The HK system will turn on one by one each of the subsystems while the monitoring parameter will be downloaded at ground.175 At a given altitude reached by the balloon, a command will be issued to turn on the instrument. The HK system will turn on one by one each of the subsystems while the monitoring parameter will be downloaded at ground. 213 176 When every parameters looks perfect, the balloon operator can launch the DAQ program running on the CPU. He will control basic run parameters, namely the background rate calculated by the PDMB. Conventionally the thresholds auto-adapt to the required L1-L2 rates unless the operator forces another mode of trigger settings. At any moment, the operator can shut down the instrument. This will be done when the balloon descent will be activated. 214 177 215 178 216 179 \vspace*{0.5cm} 217 \footnotesize{{\bf Acknowledgment:}{ This work was strongly supported by CNES180 \footnotesize{{\bf Acknowledgment:}{ This work was technically and financially supported by \mbox{CNES} and the JEM-EUSO collaboration. 218 181 } 219 182 220 183 \begin{thebibliography}{} 221 184 222 \bibitem{bib:EUSOperf} J.H. Adams Jr. et al.- JEM-EUSO Collaboration, Astroparticle Physics 44 (2013) 76-90 http://dx.doi.org/10.1016/j.astropartphys.2013.01.008223 \bibitem{bib:EBpath} P. von Ballmoos et al.- EUSO-BALLOON: a pathfinder for observing UHECR's from space, this proceedings, paper 1171,224 \bibitem{bib:EBSimulation} T. Mernik et al.ESAF-Simulation of the EUSO-Balloon, this proceedings, paper 875,185 \bibitem{bib:EUSOperf} J.H. 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