The ATLAS Trigger Upgrade

1. The ATLAS Trigger Upgrade Christian Bohm, Stockholm University for the L1 calorimeter collaboration • The ATLAS L1 calo upgrade discussions are still in an early stage • We had a first dedicated upgrade meeting in January • We are now in the process of formulating an EoI • Aiming at a R&D proposal late this year CMS Trigger Upgrade Workshop - Paris

2. The present L1 calo trigger is now operational • Few details remain • Much effort has gone into the production, installation and commissioning • Much work with cabling • Up to now the emphasis has been on the initial system operational • Upgrade work only started recently CMS Trigger Upgrade Workshop - Paris

3. ATLAS TDAQ Overview CALO MUON TRACKING calo muon Pipeline memories Level 1 trigger CTP Derandomizers Readout drivers (RODs) Region of interest Level 2 trigger Event builders Full event buffers and processor sub-farms Event filter Data recording CMS Trigger Upgrade Workshop - Paris

4. The upgrade plans are driven by • Physics - need for a non-trivial increase of the L1 trigger rejection rate with about a factor of 10, since the L1 accept rate can not be easily increased. • Technology - the availability of higher performance components such as larger and faster FPGAs, higher bandwidth transmission links and new backplane technologies • Machine parameters – bunch crossing rate, luminosity, … • Costs • Subdetector plans: possibility of full readout of all calorimeter data, track trigger, etc. • Experience from present trigger construction CMS Trigger Upgrade Workshop - Paris

5. Increasing the rejection rate • For a non-trivial increase of the rejection rate we need more information such as: • higher granularity and depth segmented ECAL data, • depth segmented HCAL data, • tracker information • We probably need topological trigger algorithms • We need a larger parameter space for the central TP – more threshold levels etc. • And we may get: • Digital inputdata extracted from the DAQ stream possibly with • Higher resolution • But first and foremost we need SIMULATIONS to guide our decisions CMS Trigger Upgrade Workshop - Paris

6. Changing design parameters • The calorimeter sample rate will probably stay the same which has a major impact on the design – the bunch crossing rate less so. • Longer latency allowing more complex algorithms – one ms in the L1 trigger doubles the available processing time • If full readout of all calorimeter data is chosen it requires high capacity trigger preprocessors probably near the Read-Out Drivers producing data streams to the L1 trigger and to the L2 and DAQ • Large # high capacity links needed – The GTB is one promising candidate for RO and DC but other alternatives exist CMS Trigger Upgrade Workshop - Paris

7. Possible future ATLAS TDAQ Overview CALO MUON TRACKING Pipeline memories Level 1 preprocessors calo muon Level 1 trigger CTP Readout drivers (RODs) Level 1.5 trigger Level 2 trigger Event builders Full event buffers and processor sub-farms Event filter Data recording CMS Trigger Upgrade Workshop - Paris

8. Technology considerations 1 • Decision to switch from ASICS to FPGAs has allowed many short and late design cycles - try to avoid unnecessary ASICs in SLHC L1 trigger as well • The use of multi purpose components (boards and backplanes) has proven successful - will be a guiding principle in the SLHC design • The higher FPGA complexity and higher clock rates will allow greater flexibility in choice of algorithms – but, this flexibility will be constrained by the chosen connectivity • If it is decided to bring all calo data to the counting room a huge total bandwidth is required – a large # of fast fiber links – present design 7klinks @400Mb/s, new design with full readout needs ~40klinks@4Gb/s CMS Trigger Upgrade Workshop - Paris

9. Technology considerations 2 • FPGAs SERDES allow ~ 6Gb/s but there are telecom components that deliver higher performance • Wavelength multiplexing techniques can greatly reduce # fibers – simplifies cabling • Clock distribution ´between modules a challenge – GBT one possibility • Many combinations to investigate CMS Trigger Upgrade Workshop - Paris

10. Logistics issues • Managing and sharing firmware designs between developers and institutes • Early development of complicated algorithms for future hardware • Evaluating new firmware design tools CMS Trigger Upgrade Workshop - Paris

11. Different Scenarios • Do nothing • Must be verified that present system is not adequate at SLHC • Small scale changes • Similar architecture but with digital transmission • Larger changes • Increased granularity depth segmentation • Radical redesigns • New trigger sources – e.g. track trigger CMS Trigger Upgrade Workshop - Paris

12. Possible R&D program • Stage 1 – generic – low cost and short time scale • Stage 2 – specific – higher costs and longer time scale • Evaluate new FADC front end processing • Faster generic processor module with current architecture • Small link technology test boards • Algorithm analysis for high granularity data • Build demonstrator system in new technology crate environment • Develop interface with calorimeter preprocessor CMS Trigger Upgrade Workshop - Paris

13. SLHC L1 collaborators From the L1 calo trigger: University of Birmingham, UK Contact: Dave Charlton University of Heidelberg, Germany Contact: Karlheinz Meier University of Mainz, Germany Contact: Stephan Tapprogge Queen Mary, University of London, UK Contact: Eric Eisenhandler Stockholm University Contact: Christian Bohm Rutherford Appleton Laboratory, UK Contact: Norman Gee New groups: Michigan State University, USA Contact: Maris Abolins Argonne National Laboratory, USA Contact: Bob Blair CMS Trigger Upgrade Workshop - Paris

14. SLHC Development projects • Multi-Gigabit links, Timing Distribution, Algorithm Firmware (Stockholm) • Clock Jitter reduction, JEM emulation, Offline simulation (Mainz) • High-speed design technologies, Algorithms, Architecture, Offline Simulation (Birmingham, QMUL, RAL) • Digitization and signal processing technologies (Heidelberg) • General purpose trigger evaluation board (Michigan) CMS Trigger Upgrade Workshop - Paris

15. Conclusions • A large design phase space • but many constraints • Close collaboration with calorimeters needed • Regular ATLAS – CMS trigger discussion may be useful (RD27) CMS Trigger Upgrade Workshop - Paris