Upgrade of the ALICE readout and trigger system Technical Design report ALICE collaboration

146 Pages·2013·11.29 MB·English

Upgrade of the ALICE readout and trigger system
Technical Design report
ALICE collaboration
CERN
Geneva,
Switzerland
Document DRAFT Version 1.1
28th Oct 2013
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Changes in version 1.1: Tables cleaned up, Pierre and Torsten comments about O2
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implemented.
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Contents
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Contents 3
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Chapter 1. Introduction and executive summary 9
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1.1 Upgrade strategy 9
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1.2 System upgrade overview 10
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Chapter 2. Upgrade architecture 15
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2.1 Introduction 15
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2.2 System architecture 16
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2.3 Trigger system 17
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2.3.1 Heartbeat trigger 17
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2.3.2 Trigger, Timing and clock distribution System - TTS 18
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2.4 ALICE Detector Data Link - DDL 19
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2.5 The Common Readout Unit - CRU 19
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2.6 Readout of detectors not using the Common Readout Unit 24
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2.7 Data framing, aggregation and event building 24
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2.8 Detector overview 25
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Chapter 3. Radiation environment 29
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4 Contents
Chapter 4. Central Trigger Processor - CTP 35
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4.1 Introduction 35
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4.2 Trigger architecture 35
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4.3 Central Trigger Processor 37
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4.4 Local Trigger Unit - LTU 39
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4.5 Trigger and Timing distribution System - TTS 39
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4.5.1 TTS via GBT 39
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4.5.2 TTS via TTC 40
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4.6 Software triggers 41
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4.7 Funding and institutes 42
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Chapter 5. TPC/MCH readout ASIC - SAMPA 43
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5.1 System overview 44
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5.2 ASIC building blocks 45
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5.2.1 Front-end 47
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5.2.2 Digital signal processing 49
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5.3 Configuration and control 50
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5.4 Trigger and dead time 50
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5.5 Readout 51
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5.6 ASIC I/Os 51
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5.7 Schedule, funding and institutes 53
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Chapter 6. Muon tracking CHambers - MCH 57
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6.1 Introduction 57
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6.2 The present system 57
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6.3 Muon system upgrade 58
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6.3.1 Front-end electronics 58
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6.3.2 Readout electronics 59
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6.3.3 Data rate and format 60
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6.4 Schedule, funding and institutes 60
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Chapter 7. Muon Identifier - MID 63
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7.1 Overview 63
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7.2 Very Front-End electronics upgrade 64
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7.3 Front-end and readout electronics upgrade 67
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7.4 Schedule, funding and institutes 70
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Chapter 8. Transition Radiation Detector - TRD 71
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8.1 TRD upgrade strategy 71
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8.2 Frontend operation and readout 72
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8.2.1 Current FEE readout 72
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8.2.2 Readout with modified data formats 73
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8.3 TRD Performance with new data formats 75
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8.4 TRD readout and trigger 77
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8.4.1 TRD readout unit 77
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8.4.2 Trigger and busy handling 78
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8.4.3 Schedule, funding and institutes 79
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Chapter 9. Time Of Flight detector - TOF 81
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9.1 Introduction 81
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9.2 TOF present readout and limitations 82
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9.3 Upgrade implementation architecture 83
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9.4 Schedule, funding and institutes 87
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6 Contents
Chapter 10. Fast Interaction Trigger - FIT 89
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10.1 Introduction 89
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10.2 Performance of the current T0 detector 89
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10.3 Performance of the current V0 detector 91
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10.4 Required functionality for the FIT 93
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10.5 T0-Plus detector concept 94
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10.6 V0-Plus detector concept 103
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10.7 Common front-end and readout electronics for FIT 105
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10.8 Funding 107
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Chapter 11. Zero Degree Calorimeter - ZDC 109
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11.1 The present ZDC readout system 109
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11.2 Upgrade strategy 110
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11.2.1 Introduction 110
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11.2.2 DAQ and trigger architecture 111
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11.3 Schedule, funding and institutes 116
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Chapter 12. Electro Magnetic Calorimeter - EMC 119
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12.1 The EMCal detector 119
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12.2 The EMCal readout system 120
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12.2.1 Point to point links and SRU 120
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12.2.2 Suppression of low gain readout 121
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12.2.3 Implementation and test results 121
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Chapter 13. Photon Spectrometer - PHOS 125
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13.1 The PHOS detector 125
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13.2 The PHOS readout system 126
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13.3 Possible improvement of photon identification 128
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Contents 7
Chapter 14. High Momentum Particle Identification Detector - HMP 133
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14.1 Introduction 133
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14.2 Implementation architecture 134
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Chapter 15. Alice Cosmic Ray Detector - ACO 137
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Chapter 16. Cost summary 139
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References 141
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1 Introduction and executive summary 9
Chapter 1
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Introduction and executive
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summary
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1.1 Upgrade strategy
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ALICE (A Large Ion Collider Experiment) is the detector at the CERN LHC dedicated to
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the study of strongly interacting matter, in particular the properties of the Quark-Gluon
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Plasma (QGP). The ALICE collaboration plans a major upgrade of the detector during
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LongShutdown2(LS2),whichisatpresentforeseentostartinDec. 2017. Thescientific
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goals of this upgrade together with a basic description of the detector upgrade plans can
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be found in a Letter of Intent (LoI) [1], that was endorsed by the LHCC in September
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2012.
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The present ALICE detector is shown in Fig. 1.1, a detailed description of the detector
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can be found in [2] and the performance is summarised in [3]. ALICE will collect 1nb−1
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PbPb collisions before LS2, at peak luminosities of L=1027cm−2s−1, corresponding to a
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collision rate of 8kHz. Hardware triggers based on event multiplicity, calorimeter energy
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and track p provide event selectivity that allows sampling of the full luminosity. The
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maximumreadoutrateofthepresentALICEdetectorislimitedto500HzofPbPbevents.
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The physics objective of the upgrade is aimed at precision measurements of the QGP,
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which will be accessible through measurement of heavy-flavor transport parameters,
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quarkonia down to zero p and low mass di-leptons. Since these processes do not ex-
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hibit signatures that can be selected by hardware triggers, they can only be collected
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by a zero bias (minimum bias) trigger. Additional physics topics include studies of jet
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quenching and fragmentations as well as study of exotic heavy nuclear states.
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The ALICE upgrade strategy is therefore based on collecting > 10nb−1 of PbPb colli-
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sions at luminosities up to L=6×1027cm−2s−1 i.e. collision rates of 50kHz, where each
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collisionisshippedtotheonlinesystems,eitheruponaminimumbiastriggerorinaself-
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triggered or continuous fashion. The LoI considers in addition the collection of 6pb−1 of
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10 Introduction and executive summary
pp collisions at the equivalent PbPb nucleon energy as well as 50nb−1 of pPb collisions,
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both at a levelled collision rate of 200 kHz. With this program the statistics for the above
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mentioned physics topics will be increased by a factor 100 over the numbers achievable
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with the present ALICE detector up to LS2. In order to further enhance the sensitivity to
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charmed mesons and to make even the measurement of charmed baryons possible, an
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upgradeofthesilicontrackerwithsignificantlyincreasedsecondaryvertexresolutionand
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high standalone tracking efficiency will be implemented. Highly efficient triggering will be
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ensured by a new interaction trigger detector.
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The overall goal of the ALICE upgrade therefore consists of replacing the present sili-
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con tracker, upgrading the ALICE sub-detectors to read-out 50kHz PbPb collisions and
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200kHz pp and pPb collisions at nominal performance as well as implementing a new
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online system that is capable of receiving and processing the full detector information.
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Since the TPC drift time of 100µs is 5 times longer than the average time between in-
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teractions,thepresentlyemployedgatingoftheTPCwirechambersmustbeabandoned
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and continuously sensitive readout detectors using GEMs will be implemented.
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The idea of reading the full detector information, either upon a minimum bias trigger or
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in a continuous fashion, requires one single trigger level based on an interaction trigger
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detector only. However, in order to keep flexibility and to allow trigger contributions for
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theeliminationofpossiblebackgroundsignalsaswellastriggersforcalibrationandcom-
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missioning, a Central Trigger Processor (CTP) delivering several trigger signals will be
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employed.
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1.2 System upgrade overview
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The specification for the ALICE detector upgrade is set by the collision rate of 50kHz
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for PbPb and a collision rate of 200kHz for pp and pPb. The upgrade architecture is
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presented in Chap. 2 andin particular the Common Readout Unit (CRU) that willprovide
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the interface between the on-detector electronics and the online computing system. As
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a baseline the CRU units will sit in a counting room outside the radiation area and will
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receive data from the detectors through optical fibers via the GBT link.
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The radiation load for the upgrade program is discussed in Chap. 3. For the sensors
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closest to the beampipe we expect an ionizing dose up to 1MRad and a fluence of 1013
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hadrons/cm2 in units of 1MeV neutron equivalent.
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The central trigger processor (CTP) will be upgraded to accommodate the higher inter-
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action rate, providing trigger and timing distribution (TTS) to the upgraded detectors and
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backwards compatibility to detectors not upgrading their TTS interface. This upgrade is
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described in Chap. 4.
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ThepresentInnerTrackingSystem(ITS)isbasedontwolayersofSiliconPixelDetectors
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(SPD), two layers of Silicon Drift Detectors (SDD) and two Layers of Silicon Strip Detec-
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tors(SSD).Thisdetectorwillbereplacedby7layersofmonolithicsiliconpixeldetectors,
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as described in the ITS conceptual design report [4] and the ITS technical design report
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