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PHOS Upgrade – how to cope with 50 kHz PbPb interction rate

PHOS Upgrade – how to cope with 50 kHz PbPb interction rate. LoI was submitted in 2012 – main points : Physics : improve capability for measuring prompt thermal radioation by better discrimination against hadrons ( mainly anti-neutrons ) using TOF cuts ;

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PHOS Upgrade – how to cope with 50 kHz PbPb interction rate

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  1. PHOS Upgrade – how to copewith 50 kHz PbPbinterction rate • LoIwassubmitted in 2012 – mainpoints: • Physics: improvecapability for measuring prompt thermalradioation by betterdiscriminationagainsthadrons (mainlyanti-neutrons) using TOF cuts; • Q: shouldthe PHOS TDR contain a (short) paragraphonthephysics arguments? Seemsthatthephysics arguments will becoveredin introductorychapter (?) • Read-out: replacecurrent GTL bus system withpoint-to-point (P2P) links; • Increase R/O bandwidthfor higherinteraction rate • Proposal to buildnew FEE cards (FECs) withintegrated TOF electronics • However, thisoption has beenabandoned due to insufficientengineeringresources; • An alternative under consideration is to add a TOF daughtercard to the FEC. However, such an add-on to the FEC must be prototyped and verified, and againthere is the question ofengineeringresourceswithinthe LS2 time horizon. • Bottom line: PHOS willusecommon ALICE solutionswhereverpossible! PHOS TDR run 3 - B.Skaali - Y. Kharlov / 31 May 2013

  2. PHOS: currenttopology and characteristics • PHOS detector: 4 modules x 3594 PbWcrystalswith APD photodetectors • The FEE/Trigger data/trigger/CTRL topology is the same as for EMCal/DCal • Per PHOS module: 4 RCUs x 2 R/O branches = 8 branches • RCU: TPC type, F/W configurable for TPC or PHOS • Branch: 14 FEE cards (FECs) + 1 Trigger Region Unit (TRU), interconnected by GTL bus • FEE card: 64 x 10-bit ALTRO channels, currently 64 samples at 10 MHz • ALTRO bus max R/O bandwidth = 260 MB/s • Setup time for onechannelreadout = 475 ns • 25 ns to readoutone 40 bit word • «Black event» 64 samples x 10 bits per eventgive 16 · 40 bit data words • FEC readout time = setup[64 · 475] · readout[64 · 16 · 25] = 30400 ns + 25600 ns ≈ 56 µs • Branch readout time = 14 · 56 ≈ 784 µs • Modulereadout time ≈ 784 µs, all branchescan be readout in parallell • Branch readoutwith ALTRO sparse data scan: ≈30µs + readoutof non-emptyFECs • TRU: the 1120 bits hit patterncan be readout as a «fake» ALTRO buffer • Special: detectormodulemechanics is gas tightstructure, FEE in N2 to avoidhumidity • Operating temperture for PbWcrystals and photodetectors: -25°C • RCU is placedonthemodulebottomplate • All power and data signals routedthroughthemodulebottom plate with gas-tight «feed-throughs» TRU ALICE CTP ALICE CTP TRU PHOS TDR run 3 - B.Skaali / 31 May 2013

  3. PHOS: LS2 electronicsupgrade • Baseline: keepcurrent FEE cards, upgradeTRUs to EMCal/Dcalversion • Therefore: nocontinousreadout, local trigger generation • Replace GTL bussedreadoutwith P2P links • Numberof links per module = 120 (112 FECs + 8 TRUs) • Type and functionality: TBD. (EMCal/DCal has an implementation, the Bergen areworkingon an implementation for TPC, seefollowingpages). Whateverthechoice, must co-existwith CRU. • DAQ / Control : CommonReadout Unit (CRU) • Q: how to interfaceP2P links to CRU? Electrical / fibre / protocol? • Q: or canoneuseseveral CRUs per modulewithXnumberof P2P inputs? • Q: or shouldoneforesee a PHOS specific MPX between P2P links and CRC(s)? • If so, can PHOS/EMCal/DCal have a commonsolution? EMCal/Dcal P2P nowbasedon H. Muller design. • Q: whatabout trigger ? • PHOS specific CRU capabilities: • Suppression: none • Data formatting: probably none • Trigger selection: none (assumingthat PHOS can send L0 / L1 decisions to CTP as now • CRU Project: see TB 25 April and also file «CRU_Project_23May2013.pdf» • Other: • L0/L1 decisions from all TRUsareOR’ed in a «TOR» unit for single L0/L1 signals to CTP • A BUSY Box controlsthe BUSY time ofthe PHOS PHOS TDR run 3 - B.Skaali - Y. Kharlov / 31 May 2013

  4. EMCal/DcalScalableReadout P2P The EMCal P2P adapter mountedon a PHOS FEC is shownbelow. Beforeanswering Werner I had a phonediscussionwith Hans Muller, whoindicatedthat a modificationofthe PHOS FEC could be necessary, possiblyalso for the TRU. However, to route 120 link cablesthroughthe PHOS bottom plate is (probably) outofthequestion, and there is (probably) not spaceinside PHOS for the SRU units. Photo onthe right shows setup in the EMCal lab. A 1U SRU unit has 40 P2P inputs, whichmeansthat3 units would be needed for a PHOS module. PHOS LS1 electronics tasks

  5. On-Detector Custom Electronics & Packaging Radiation Hard Off-Detector Commercial Off-The-Shelf (COTS) Custom Protocol • Point-to-pointtopology • Bidirectional link 3.2 Gbit/sec • Three logicalchannels: DAQ, DCS, Timing and Trigger GBT system

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