NuclearInstrumentsandMethodsinPhysicsResearchA TheCOMPASSRICHreadoutsystem G
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NuclearInstrumentsandMethodsinPhysicsResearchA TheCOMPASSRICHreadoutsystem G

aum Rirsa radamante Aressan AChapiro ACicuttin PCiliberti AColavita c SCosta MCrespo c PCristaudo S allaTorre 0iaz Pauland ratnik MGiorgi Gobbo RIjaduola 05alinnikov M6amanna b2 AMartin GMenon PPagano PSchiavon Tessarotto A7anetti University of

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NuclearInstrumentsandMethodsinPhysicsResearchA TheCOMPASSRICHreadoutsystem G

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NuclearInstrumentsandMethodsinPhysicsResearchA502(2003)246250 TheCOMPASSRICH$%read$outsystem G.(aum )R.(irsa )+.(radamante )A.(ressan )A.Chapiro )A.Cicuttin P.Ciliberti )A.Colavita c)% )S.Costa )M.Crespo c) )% )P.Cristaudo )S. /allaTorre )0./iaz )P.+auland )+.+ratnik )M.Giorgi )(.Gobbo R.Ijaduola )0.5alinnikov )M.6amanna b)2 )A.Martin )G.Menon P.Pagano )P.Schiavon )+.Tessarotto )A.7anetti University of Bielefeld, Facult at f ur physik, D-33615, Bielefeld, Germany INFN, Sezione di Trieste and University of Trieste, Padriclano 99, I-34012, Trieste, Italy INFN, Sezione di

Trieste and ICTP, Via Beirut 31, 34100 Trieste, Italy INFN, Sezione di Torino and University of Torino, Via P. Giuria 1, I-10125, Torino, Italy Abstract This paper describes the reconfigurable read$out system for the :2;44 RICH$% channels of the COMPASS experiment(NA5:)atCERN.Thesystemisbasedon%;2identicallargefront$endboards((ORAboard).(ORAwas designedforacquiring)digitizing)thresholdsubtractingandtransmittingeventdata.Theoveralloperationoftheboard iscontrolledandsupervisedbya/SPtightlyinteractingwithan+PGAthatactsasaparallelco$processor.The/SP

allowscharacterizingeachanalogchannelbylocallycalculatingnoiseandpedestal.Each(ORAcommunicateswith theoutsideworldthroughtwoopticalfibersandthroughadedicated/SPnetwork.Oneopticalfiberisusedtoreceive event triggers) and the other one is used to transmit event data to subsequent processing stages of the acquisition system.The/SPnetworkallowsreconfiguringandreprogrammingthe/SPsand+PGAsaswellasacquiringsample eventstovisualizetheoveralloperationofthesystem.ThewholeRICHhaseight/SPnetworksworkinginparallel.

Thesenetworksarehandledby/O6INA)aPCresidentmultiprocessorboardcontainingeight/SPs.Eachnetworkis formedby24(ORA/SPsand%/O6INA/SP.Theread$outsystemcansteadilyworkuptoatriggerrateof@5kHz withmaximumpixeloccupancyof20A)reachingatransmissiondatarateof5.%3GbytesBs. 2003ElsevierScience(.0.Allrightsreserved. PACS: 2;.40.5aC0@.05. tC0@.05.Hd Keywords: RICHdetectorC/ataacquisitionC/SPC+PGA 1. Introduction The characteristics of new$generation RICH detectors represent challenging requirements for the read$out systemsC such as large number of channels) asynchronous triggering) high average trigger rates)

average data rates in the order of .Corresponding author. Tel.D E3;$040$224$;;30C faxD E3;$ 040$224$600. E-mailaddress: Onleaveofabsence)GniversidadNacionaldeSan6uis)San 6uis)Argentina. PresentlyonleaveofabsenceatCERN. 0%6:$;002B03BH$seefrontmatter 2003ElsevierScience(.0.Allrightsreserved. PIIDS 0%6:$;002(03)002:2$%
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several GbytesBs) reduced dead time) low power consumption and low noise. Moreover) since the experimentwilllastforyears)thesystemmustbe flexible enough in order to adapt itself to new experimentalconditions. COMPASS RICH$%

is a gas radiator RICH employing MWPCs with CsI photocathodes as photon detectors K%4L . The RICH$% photon detectors consist of eight identical chambers) and its total active area is about 5.5m . The photo$ cathodes are PC(s segmented in :mm :mm pads)resultingin:2);44pixelsforthetotalactive area K5L Allpixelsmustbeacquiredateverytrigger.The COMPASSRICH$%read$outsystemprocessesthe signals coming from the pixels. These signals are amplified) filtered) digitized in %0 bits) and temporarily stored at every asynchronous trigger. Subsequently) threshold subtraction is performed and all

resulting positive values) together with theirchannelidentification)arepackedintoadata frame and transmitted to the global data acquisi$ tion (/AM) system. The read$out system is also capable of measuring pedestal and noise of every single channel) and setting its corresponding threshold. Sparse sample events can be acquired) independently of the global /AM system) for monitoringpurposes. TheCOMPASSexperimentforeseesanaverage asynchronous trigger rate of %00kHz) which implies a /AM rate of %036:GbytesBs for the RICH$%.Themaximumexpectedpixeloccupancy for the RICH$% is 20A) which

generates a data transmissionrateofabout6.64GbytesBs. Inthefollowingsections)wedescribethegeneral architecture of the COMPASS RICH$% read$out system) and we give architectural details of the main boards as well as the functional description ofthem.Asummaryoftheachievedperformance ispresentedintheconclusions. 2. The general architecture The COMPASS RICH$% read$out system is based on %;2 identical large front$end boards) called (ORA K6L ) to acquire all the :2);44 channels.Theseboardsarepluggedontheexternal side of the photocathodes and connected to the pixels of the detector. There are 24 (ORAs

per chamber and each (ORA handles 432 analog channels.Eachboardisidentifiedbysettingan:$ bit dip switch) where three bits identify the chamber and the remaining five bits identify the (ORA within the chamber. This identification corresponds to a precise geographical position in theRICH$% K@L The overall operation of (ORA is controlled and supervised by a 32$bit /SP (A/SP$2%0656 K:L ). The board also has an +PGA (0IRTEN NC0%00 K;L )thatactsasaparallelco$processorof the /SP. The /SP configures the +PGA at reset time)andcanreconfigureitatanytime. The (ORA board

communicates with the out$ sideworldthroughtwoopticalfibersandthrough adedicated/SPnetwork.Oneopticalfiberisused toreceiveeventtriggers)andtheotheroneisused totransmitdatatosubsequentprocessingstagesof the acquisition system K%0L . The /SP network provides a slow connection with a PC(the RICH Control PC) where a high$level control application software runs. This application soft$ ware allows reconfiguring the +PGA and repro$ gramming the /SP. Programs) commands and data are transmitted through the /SP network betweena(ORAandtheRICH ControlPC. The whole RICH$% has eight /SP

networks working in parallel) one for each chamber. The RICH ControlPChasadedicatedmultiprocessor board)called/O6INA)tohandlethesenetworks. /O6INA has eight on$board /SPs. The 24 (ORA /SPsofachamber and%/O6INA /SP form each network. All (ORAs are optoisolated from /O6INA through eight specific optoisolat$ ing boards) one for each /SP network) avoiding this way grounding interference between the PC andthedetector. +ig.% showsthegeneralphysicalarchitectureof the read$out system. In the RICH$% box are displayed the eight chambers) each of them with its 24 connections (one per (ORA) to an

optoisolator board. The optoisolator boards are close to their corresponding chambers in the experimental area) and they are connected to /O6INA completing the eight /SP networks. G. Baum et al. / Nuclear Instruments and Methods in Physics Research A 502 (2003) 246250 24@
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/O6INA also distributes synchronization sig$ nals to the (ORAs. These signals) with explicit names) are start of run (SOR)) end of run (EOR)) start of burst (SO() and end of burst (EO(). SignalsSORandEORcomefromtheCOMPASS run control room)andsignalsSO(andEO(come from the Trigger Control System (TCS). As soon

as these signals arrive to the PC) /O6INA broadcaststhemtoall(ORAs. 3. The BORA board (ORA is the COMPASS RICH$% 432$channel front$endboard.Each(ORAisconnectedtothe pixels of the detector through a row of nine connectors. Each back$plane connector receives thesignalfrom4:pixels. The /AM in (ORA is divided into two independent stages. The first stage corresponds to the sample and hold of all channels at the peaking time) followed by the analog to digital conversion and temporary storage of the digital valuesintoon$board+I+Omemories.Thesecond stage corresponds to threshold subtraction and

datatransmission. Thefirst stage isaccomplished automatically after the arrival of every event trigger and takes about %.2 s per eventC the second stage is carried out later) under the command of the /SP) and requires about %3 per event. The difference in processing time between the two stages is absorbed by the +I+O memory capable of buffering %2: events. The durationofthefirststagedeterminestheminimum inter$trigger delay time (dead time)) while the duration of the second stage determines the maximumachievabletriggerrate. The/AMin(ORAstartsautomaticallyatthe

arrivalofeachtrigger)comingthroughoneofthe two optical fibers) or internally generated by the /SP. The signals enter into 2@ %6$channel COMPASS$GASSIP6EN K%%L front$end chips) which perform the analog amplification and filtering. The input pulse needs around %.%6 sto reach its peak at the output ( peaking time ). As soon as the +PGA receives a trigger) it waits a programmable delay before issuing all necessary signals for the first stage of acquisition. This programmabledelayisusedtosamplethesignals at the peaking time . When the output analog signals reach the maximum)

the GASSIP6EN chips hold the values of the signals) then the signalsareconvertedinto%0$bitsnumbersusing2@ A/Cs K%2L and written into %: %6$bit +I+O memories K%3L /uring the second stage of the acquisition the +PGA)underthecommandofthe/SP)readsand processesthecontentofthe+I+Omemories(three channels atthe same time). The +PGA compares thereadingsofeachchannelwiththecorrespond$ ingprogrammablethreshold)alreadystoredinthe +PGAmemory)andonlydataabovethresholdare packedintoeventframescontaining32bitsperhit channel. Each event frame contains the channel

valuesandidentifications)plusaheaderwordand a trailer word. The channel identification allows mapping a channel to a precise pixel. The +PGA transmits the event frames through the optical fiber to the global acquisition system at a data transmissionrateof400MbitBs K%4L (esides the regular /AM) the (ORA can be reconfiguredtoperformothertaskssuchasnoise Data to CATCHs (DAQ system) Triggers from CATCHs RICH-1 DSP networks 192 192 Optoisolator boards 24 24 24 24 24 24 24 24 EOB SOB From TCS EOR & SOR from Control Room Ethernet Card TCS Card DOLINA 24 BORAs per chamber

Experimental Area RICH CONTROL PC RICH barrack +ig.%. General physical architecture of the RICH$% read$out system. G. Baum et al. / Nuclear Instruments and Methods in Physics Research A 502 (2003) 246250 24:
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andpedestalmeasurement)thresholdssetting)and creation of engineering frames containing local temperatures and voltages. (ORA has four temperature sensors K%5L to monitor the tempera$ ture in different points of the board) and a multichannel analog to digital converter K%6L to monitorseveralon$boardpowersupplyvoltages. (ORA possesses built$in testing facilities in order

tocheck all analogchannels. (y mean ofa digitaltoanalogconverter)the/SPcanstimulate all analog channels simulating the signals coming fromthedetector.Thisallowscheckingtheboard independently of the detectors) and this feature can also be used to measure some characteristics likepeakingtimeandlinearity. The /SP configures the (ORA to work in differentmodes.TheseworkingmodesarecalledD OOeventPP) OOnoise and pedestalPP) OO/SP to /AMPP andOOthresholdPP. In OOeventPP mode) (ORA performs normal /AM. The /SP sends an event to the RICH Control PC) once in a while) to visualize

theoveralloperationofthesystem. InOOnoiseandpedestalPPmode)(ORAperforms /AMwithinternaltriggersgeneratedbythe/SP. Afterreceivinganinternaltrigger)the+PGAsaves a complete event frame (432 channels) without performing threshold subtraction.The /SP takes the values from the +PGA to calculate noise and pedestalofeverychannel)andsendstheresultsto the RICH Control PC or to the global /AM system. In OO/SP to /AMPP mode) the /SP transmits engineeringframes)thresholdvalues)andpedestal and noise measurements directly) through the opticalfiber)totheglobal/AMsystem. In OOthresholdsPP mode) the /SP

writes the threshold values) coming from the RICH Control PC)intothe+PGAmemorybefore/AM.The/SP can also read and send to the RICH Control PC thecurrentthresholdvalues)ifrequired. 4. The DOLINA board /O6INA is a PCresident multiprocessor PCI boardthatallowsthecommunicationbetweenthe RICH ControlPCandall(ORAs. /O6INA contains eight on$board /SPs iden$ ticaltothoseofthe(ORAS.Each/O6INA/SP handles a local time division multiplexed serial network formed by 24 (ORA /SPs and itself. /O6INAcommunicateswithall(ORAsthrough these eight networks) where each network works independently at one MbitBs. On

the other side each/O6INA/SPcommunicateswiththePCby writingtoandreadingfromanon$boarddualport memory(/PM) K%@L .The/PMisdividedintotwo logical regions. The reading region of the /SP is the writing region of the PCand conversely) the writingregionofthe/SPisthereadingregionof thePC.Oncethe/SPshavewrittensomethingfor the PC) the /SP writes into a /PM mail box to send an interrupt to the PCsignaling there is something to read. The PCuses the same mechanism to pass data to the /O6INA /SP. The two main functions of the /O6INA /SP are passing network packets between the PCand any of the (ORA boards)

and broadcasting synchronization commands (such as SO() EO() etc.)toall(ORAboards. Networkpacketshavebeendefinedforcommu$ nication amongst PC) /O6INA and (ORAs. ThesepacketsconveyanykindofdataDprograms) commands) generic data) and error and acknowl$ edge messages. The packet header contains the following information about the packetD source) destination) length) type) and packet number. /O6INA /SP analyses the header to process or passapacket. Synchronization commands have timing restrictionsbecausetheyareusedforsynchroniza$ tion with the global /AM systemC hence broad$ casting these

commands to all (ORAs is mandatory. Particularly) commands SO( and EO( have severe timing restrictionsC therefore) they come to /O6INA directly from the TCS board K%:L )andareimmediatelybroadcastedtoall (ORAs. 5. Conclusions ThereconfigurableRICH$%read$outsystemfor theCOMPASSexperimentatCERN(NA5:)has G. Baum et al. / Nuclear Instruments and Methods in Physics Research A 502 (2003) 246250 24;
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been proved to steadily work up to an asynchronous trigger rate of @5kHz with 20A maximum pixel occupancy. At these conditions) the /AM rate is @.@@GbytesBs and the data

transmission rate is 5.%3GbytesBs. The maximum achieved trigger rate is enough for the current COMPASS muon program (COMPASS Run 2002). +uture upgrades will push the acceptable trigger rate up to %00kHz) which is the initially foreseen trigger rate for the COMPASS experiment. The /SP$+PGA combination in the (ORAboard)withitsintrinsicparallelism)largely determines the high performance of the system. The local data processing capability in (ORA allows on$line threshold subtrac$ tion) as well as carrying out extensive statistical studies on all %0 channels in a reasonable time. The required

flexibility of the system) designed for adaptation to different experimental condi$ tionsorrequirementshasbeenachievedbytheuse of reprogrammable elements such as /SPs and +PGAs. The /SP networks allow reconfiguring and reprogramming these elements) as well as providing the communication between (ORAs and the RICH Control PC. These networks handled by /O6INA board provides the mean to manage and monitor the whole RICH$% read$ outsystem. Theuseofopticalfibersandadhocoptoisolator boards) has avoided grounding interference allowing to achieve excellent noise figures. The

RICH$% average noise level is about one A/Cchannel) which is close to the intrinsic A/Cnoise. Acknowledgements The design of the modified front$end chip COM$ PASS$GASSIP6EN would not have been possible withoutthegenerouscollaborationofC.Santiard. References K%L COMPASSCollaboration)Proposalforacommonmuon proton apparatus for structure and spectroscopy) CERN SPS6CBP2;@)CERN)March%;;6. K2L (aum)etal.)Nucl.Phys.(@:(%;;;)354. K3L (aum)etal.)Nucl.Instr.andMeth.A433(%;;;)20@. K4L Albrecht) et al.) COMPASS RICH$%) Nucl. Instr. and Meth.A4@:(2002)340. K5L

Albretch)etal.)COMPASSRICH$%)theseproceedings. K6L (aum)etal.)Nucl.Instr.Meth.A433(%;;;)426. K@L A.Colavita)Allyouwantedtoknowaboutdecodingthe RICH$%butwereafraidtoask)COMPASSnote200%$5. K:L Analog/evices)/SPmicrocomputerA/SP$2%0656data sheet. K;L NI6INN0IRTENNC0%00+PGAdatasheet. K%0L (raun)etal.)/esigningfront$endboardsforusewiththe CATCH$HOT6inkinterface.COMPASSNote%;;;$@. K%%L C. Santiard) et al.) GassiplexD a low noise analog signal Processor for readout of gaseous detectors) Presented at theSixthPisaMeetingonAdvanced/etector)6a(iodola) IsoladPElba)Italy)May%;;4. K%2L Analog /evices) /ual

channel %0$bit A/CA/;20% data sheet. K%3L CQPRESS)Sychronous+I+OCQ@C42350datasheet. K%4L CQPRESS) HOT6ink transmitterBreceiver CQ@(;23B;33 datasheet. K%5L MANIMB/allas semiconductor) SOT temperature sensor MAN65@5datasheet. K%6L MANIMB/allas semiconductor) :$channel :$bit A/C MAN%%@datasheet. K%@L CQPRESS)/ualPortMemoryCQ@C05@0datasheet. K%:L 5onorov) et al.) COMPASS TCS documentation. COM$ PASSNote. G. Baum et al. / Nuclear Instruments and Methods in Physics Research A 502 (2003) 246250 250