Caponetto, L

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29th International Cosmic Ray Conference Pune (2005) 5, 287290The ANTARES Local Control Modules and their functional test benchcharacterisationL. Caponetto on behalf of the ANTARES Collaboration(a) I.N.F.N. Sez. Catania Via Santa Soa 64 Catania 95123, Italy(b) http://antares.in2p3.frPresenter: L. Caponetto (luigi.caponetto@ct.infn.it), ita-caponetto-L-abs1-og27-oralThe ANTARES Local Control Modules (LCMs) are electronic units achieving all the required functionalitiesinside a deep-sea submersed detector. LCMs sample, integrate, time stamp and digitise the analogue signalscoming from different sources to which they are connected, pack and send to shore and to other LCMs the readout data together with a slow control flow and a synchronising stream of commands. This document reports onthe LCM functionalities and on the construction of a dedicated test bench.1. The ANTARES Local Control ModulesThe ANTARES Collaboration is producing the first of 12 lines which will constitute a large undersea neutrinotelescope located  km south of Porquerolles Island (France) at a depth of  m [1]. The detector will bea three-dimensional array of photomultipliers distributed along 12 lines, each contained in a pressure resistantglass sphere called Optical Module (OM [2]). Three OMs including the PMTs looking downward at 45 degreesfrom the vertical constitute a storey: the front-end electronics is contained in a titanium cylinder acting as theLocal Control Module (LCM) of each storey. LCMs are grouped in sectors of 5 units: one out of them containsthe Ethernet switch which concentrates the data traffic coming from the other 4 and from itself. This particularLCM, called Master LCM (MLCM), transmits the Gigabit Ethernet data traffic to the String Control Module(SCM) located at the line base, using a Dense Waveform Division Multiplexer (DWDM) protocol. The mainfunctionalities of the LCM are reviewed in this work: a functional view of the module is presented togetherwith some of its design specifications. The production test bench, designed to detect manufacturing defects ofthe LCM assembly, is then described.The main purpose of a LCM is the digitisation of the data coming from the OMs triplet, yelding a raw datastream containing information on time, charge and pulse shape of the detected events. Besides this mainfunction, the LCM provides a set of features reported on Tab.1, where a decomposition of the LCM into itshigh level functional subsystems is also presented.Two software processes, the harnesses, implement the LCM’s DAQ/SC finite state machine. Each of them isdedicated to one particular data channel: OMs data acquisition (DAQ) and slow control (SC) commands andparameters read-out. Both channels share the same physical medium constituted by a monomode optical fibretransporting 	 BASE Ethernet data between each LCM and its sector’s MLCM1. The third data communi-cation channel is the clock (CLK) data link: its physical channel is separated from the DAQ/SC2. Unlike theDAQ/SC link case, two optical fibres are used to transport the clock channel in and out each LCM and MLCM.In more detail, the subsystem features presented in Tab.1 are:Power supply. The Local Power Box (LPB) provides the required DC voltages to the various loads presentin a storey: LCM’s boards, OMs and additional Beacons, hydrophones or marine instruments. It is fed by aA pair of monomode optical fibres transport the Gigabit Ethernet data link from the MLCM to the SCM and vice versa.The actuation of the commands transported by the clock data link has not to deal with the finite state machine implemented by thetwo harnesses.288 L. Caponetto on behalf of the ANTARES CollaborationTable 1. Overview of LCM subsystems and their features.LCM External features providedSubsystemPowerSupplyelectrical power to the external OMs and satellites together with a means to monitor andcontrol their switching state and the high voltage ramping of the PMTsFront end digitisation of the various signal features and packing into homogeneous data frames+DAQ/SCtransmission of the physical (OMs data acquisition) and parametrical data flow to the opticalfibre communication link using an Ethernet protocolprocessing of the slow control (SC) command and data flow monitoring internal electricalparameters as well as environmental physical conditions (internal-external temperatures andinternal humidity)handling of the information generated by the internal acoustic positioning system and by thecompass-tiltmeter systemmonitoring of the LED and Laser Beacons used for the calibration (see [4] for the use ofbeacons on ANTARES time calibration)CLK sub-nanosecond timing synchronisation with the reference clock (generated on shore) andreception-distribution of synchronised (on shore and with other LCMs) commandsMechanicalstructureremoval of the internal generated heat by conduction, avoiding hot air pockets inside thecylinder and reducing at the same time EMI propagation Vdc system, common to all  LCMs in the same sector, capable of supplying a maximum time limitedpower of  W. The LPB monitors and controls, via the SC, its own generated DC voltages and the switchingof  of its outputs to the OMs or other satellites connected to the LCM. The total output power of one LPB isabout  W with an overall efficiency greater than  %.Front-end. The LCM discriminates the OM signals in two categories: 1) single photo-electron (SPE) and 2)complex waveform shapes. Depending upon this discrimination, only the time and the integrated charge aremeasured and digitised (first case), or (second case) the signal is sampled and digitised. Both features areprovided, for each connected OM, by a dedicated board (ARS MB) containing two ARS chips [3]. Whenpresent, the external light Beacon monitor PMT, or a different satellite requiring digitisation of its output,is connected to another ARS: the maximum number of ARS chips digitising analogue signals is then of  .The configuration of each of the ARS chips may be changed via  internal digital registers setting all itsinternal thresholds and references, acquisition modes, and also controlling the chip behaviour. These bitstreamconfigurations are held in a central database after having been selected during the characterisation of the ARSchips. The optimised bitstream maximising the performances of each ARS is used to calibrate the overalltime, charge or amplitude transfer functions. These transfer functions, often approximated by a linear fit, arethen compared with the responses (offset and slopes) obtained during ARS MB and LCM level tests, and thesettings are readjusted. The calibration task will be completed by dark room testing of the complete sector andby in situ measurements.Clock (CLK). It provides a time reference and synchronous commands capabilities to the front end electronics.One digital  MHz clock signal is extracted from the CLOCK IN fibre incoming dataflow: the same dataflowalso carries the synchronous control signals using commercially available data transceivers (HOTLink systemdeveloped by Cypress Semiconductors). The time stability offered by this subsystem is better than  ns witha synchronisation precision with the GPS time stamp better than  ns.The ANTARES Local Control Modules and their functional test bench characterisation. 289Data acquisition and slow control (DAQ/SC). The scheduling of the two harnesses, the readout of the rawARSs physical data flow, its organisation in  ms long frames and their sending to the Ethernet linktogether with the slow control data flow are in charge of this subsystem. More precisely, the read-out and thecontrol of the front-end electronics are achieved by a Xilinx FPGA while the control of the I/O busses andports at board level, of the Ethernet link and of the LCM’s DAQ memory are in charge of a Motorola MPC860PowerPC.Mechanical structure. The aluminum crate has been designed to offer a complete cooling solution for allthe electronic boards populating the LCM: the hotspots of the high dissipating devices are glued with heat-conducting paste to cooling bases bolted to the crate; the crate itself holds two large hemicylindrical coolingplates spreading the heat, through an air gap, to the external titanium cylinder at seawater temperature. Eightshielding plates, thermically glued to the crate, divide it in 9 compartments for electronic boards: they increasethe rigidity of the structure and also help reducing EMI radiations. Great care has been put in offering a dedi-cated routing path for all the optical fibres traversing the interior of the crate, being prone to signal attenuationor ruptures in case of improper bending.2. LCM Test Bench OverviewBecause the detector will be inaccessible during operation, the reliability of all the components constitutes acrucial issue concerning its construction. A total number of  LCMs and  MLCMs must be assembledat three different production facilities and then sent to two different line integration facilities where the strings are built to be ready for deployment. All the electronics boards and the mechanical parts are producedby different companies and sent to the LCMs assembling sites after individual testing. The bench testing ofa large serial production of a complex electro-mechanical item like the LCM is, involves the use of variousbench equipment to trigger the module and measuring its responses. It needs to be highly automated: the largenumber of test settings and their configuration parameters together with the need to shorten the total testingtime (given that the schedule of the line deployment is already planned) put an upper limit to the number oftests which an human operator may perform. Furthermore, its ease of operation is a factor to be consideredon its own: involving the test of several subsystems and their known or supposed failure modes, the test benchmust provide its users with the largest possible flexibility in changing test strategies or applying different setsof parameters.The LCM Test Bench is based upon a set of LabVIEW3 virtual instruments which control both the bench andthe two harnesses processes running on the LCM Under Test. It offers a scripting language allowing the expertuser to fine tune the test flow, implementing two classes of tests: 1) functional, aimining at verifying all theexternal features reviewed above, and 2) physical, as part of the module calibration task. After its assembly, theLCM is connected to the bench and the operator chooses the test flow to be performed between a predefinedlist: different LCM configurations may in fact require different testing strategies. No cooling is provided duringthe test flow and the overall procedure (power on period for the LUT) has been contained within half an hour intime. The basic test flow verifies: 1) good general assembly (internal routing of optical fibres, internal/externalelectrical connections) 2) data channels (DAQ/SC and CLK) and 3) front end features (time, charge and shapeinformation). Besides that, the bench has been designed for being capable of running many production testsand supporting the three LCM production facilities. A strong effort has been put to offer the flexibility of amodular architecture as well as a minimal requirement on the overall instrumentation used.LabVIEW is a commercial graphical development environment developed by National Instruments.290 L. Caponetto on behalf of the ANTARES CollaborationFigure 1. Photographs showing various phases of the LCM manufacturing process: a) the 9 compartment aluminum crate;b) the LCM populated with all electronic boards, LPB, titanium endcap holding the connectors to the OMs (bottom side)and optical bre protection tube (top); c) the LCM closed with its hemi-cylindrical cooling plates; d) an opened LCMconnected to the Test Bench. On the foreground (right) the three optical bres exiting the LCM. On the background (left)the three submarine cables used to link the LCM with its satellites.3. ConclusionsThe main external features of ANTARES Local Control Modules have been presented together with its highlevel functional description and with the basic characteristics of the system which has been built to benchtesting its mass production. The LCM design has been proved robust and functional during its prototypingphase: its production is starting at the time of writing and the first batch of 25 modules will be completed bythe end of July  .The redactor thanks for their work in the TB construction: S. Trovato, D. Sciliberto, E. Falchini and E. Casto-rina; for the documentation provided and the expertise they have transmitted: all the designers and the develop-ers of LCM mechanics, electronics and software, particularly C. Olivetto, F. Rethore, T. Legou, A. Levansuu,P. Keller, M. Jaquet, J. Fopma, J.P. Pineau, C. Hoffman, F. Louis, H. Le Provost, S. Anvar, F. Druillole, J.Holgenbirk, L. Kruijer, E. Heine and P. Payre; for their precious help in the developing of the LCM TB: S.Loucatos, E. Kok, M. De Jong, M. Bouwhuis, J.M. Gallone and J. Serrano.References[1] E. Falchini et al. [ANTARES Collaboration], this conference.[2] P. Amram et al. [ANTARES Collaboration], Nucl. Instrum. Meth. A 484 (2002) 369.[3] F. Druillole, D. Lachartre, F. Feinstein, E. Delagnes, H. Lafoux, C. Hadamache and J. Fopma [ANTARESCollaboration], IEEE Trans. Nucl. Sci. 49 (2002) 1122.[4] F. Blanc et al. [ANTARES Collaboration], Presented by J.J. Hernandez-Rey on behalf of the ANTARESCollaboration, proceedings of 28th International Cosmic Ray Conferences (ICRC 2003), Tsukuba, Japan,31 Jul - 7 Aug 2003.

The ANTARES Local Control Modules and their functional test bench characterisation

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