: Thomas Owen James
: A Hardware Track-Trigger for CMS at the High Luminosity LHC
: Springer-Verlag
: 9783030319342
: 1
: CHF 85.40
:
: Atomphysik, Kernphysik
: English
: 133
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The work described in this PhD thesis is a study of a real implementation of a track-finder system which could provide reconstructed high transverse momentum tracks to the first-level trigger of the High Luminosity LHC upgrade of the CMS experiment. This is vital for the future success of CMS, since otherwise it will be impossible to achieve the trigger selectivity needed to contain the very high event rates. The unique and extremely challenging requirement of the system is to utilise the enormous volume of tracker data within a few microseconds to arrive at a trigger decision.

The track-finder demonstrator described proved unequivocally, using existing hardware, that a real-time track-finder could be built using present-generation FPGA-based technology which would meet the latency and performance requirements of the future tracker. This means that more advanced hardware customised for the new CMS tracker should be even more capable, and will deliver very significant gains for the future physics returns from the LHC.

Tom studied undergraduate physics Imperial College London, where he became involved in the High Energy Physics group. He graduated with an MSc in Physics in 2014, after completing a one year project on novel tracking techniques for the CMS experiment at the Large Hadron Collider. He remained at Imperial College London for his PhD studies, during which he spent 50% of his time based at CERN, Geneva. In 2018, he completed his PhD studies on the upgraded tracker and trigger of CMS, producing a thesis 'A Hardware Track-Trigger for CMS at the High Luminosity LHC', which was awarded the CMS thesis of the year. Tom now works as a research fellow in the CERN Experimental Physics department, where he continues to develop low-latency trigger algorithms for FPGA processing hardware.
Supervisor’s Foreword7
Abstract9
Acknowledgements10
Contents11
Acronyms14
1 Introduction17
1.1 Theory and Motivation17
1.2 The Large Hadron Collider18
1.3 The Compact Muon Solenoid18
1.3.1 Tracker19
1.3.2 Electromagnetic Calorimeter19
1.3.3 Hadronic Calorimeter21
1.3.4 Muon Detectors21
1.3.5 Trigger and Data Acquisition22
1.4 Field Programmable Gate Arrays23
References24
2 The CMS Phase II Upgrade26
2.1 The High-Luminosity LHC26
2.2 Motivation for an Upgraded CMS Tracker26
2.3 The Phase II Outer Tracker Design and Geometry27
2.4 The pT-Modules29
2.4.1 Front-End Electronics31
2.4.2 Sensor Type32
2.5 Module Prototyping and Beam Tests33
2.5.1 Test Beam Apparatus33
2.5.2 Test Beam Results34
2.6 Back-End Electronics36
References39
3 The Track Finder Demonstrator41
3.1 L1 Tracking Requirements41
3.2 Proposed Track Finder System Architecture42
3.2.1 A Time-Multiplexed Trigger42
3.2.2 Data Delivery and Regional Segmentation43
3.3 The Track Finder Demonstrator44
3.3.1 Overview of Firmware Architecture44
3.3.2 The Demonstrator Hardware46
References51
4 The Hough Transform53
4.1 The Hough Transform Algorithm53
4.2 Firmware Implementations57
4.2.1 Systolic Array Implementation57
4.2.2 Pipelined Implementation61
4.2.3 Daisy Chain Implementation63
4.3 Hough Transform Preprocessor68
4.3.1 HTP Mathematics Block69
4.4 Hough Transform Results73
4.4.1 Optimisations and Improvements78
4.5 Scaling to Ultrascale and Ultrascale+ FPGAs80
References82
5 The Kalman Filter83
5.1 The Kalman Filter Algorithm83
5.1.1 The Generic Kalman Filter83
5.1.2 The Kalman Track Fitter85
5.1.3 The Kalman State Updater89
5.1.4 The Kalman Filter Flow Control90
5.2 Resource Usage and Latency93
5.3 Potential for Improvements94
5.4 Seed Filter and Linear Regression Fit96
5.5 Duplicate Removal97
5.5.1 Algorithm97
5.5.2 Implementation98
References100
6 Demonstrator Results102
6.1 Demonstrator Configuration and Data Format102
6.2 Tracking Efficiency and Purity104
6.3 Track Parameter Resolution107
6.4 Data Rates and Limitations112
6.5 Tracking Robustness115
6.6 Track Finding Down to 2GeV116
6.7 Latency Measurements118
6.8 The Evolution of the Track Finder119
6.8.1 Rejected Ideas121
6.9 FPGA Resource Usage122
6.10 The Associative Memory Track Finder123
6.11 The Tracklet Track Finder125
References126
7 Outlook and Summary127
7.1 Demonstrator Scaling127
7.2 Projected Final System Technology130
7.2.1 Outer Tracker Data, Trigger and Control Board130
7.2.2 Track Finding Processor Board130
7.3 Summary132
References132