Category: Theses Opportunities

DOMAIN: Technologies associated to the Portuguese participation at CERN and their transfer to society

SUPERVISOR: Patricia Conde Muino

HOST INSTITUTION: Laboratório de Instrumentação e Física Experimental de Partículas

DEGREE INSTITUTION: Universidade de Lisboa

ABSTRACT

The LHC is the highest energy particle accelerator ever built. The gigantic ATLAS experiment records proton and ion collisions produced by the LHC to study the most fundamental matter particles and the forces between them. At the nominal rate of the LHC, the proton bunches cross 40 million times per second, producing up to 40 collisions per bunch crossing. This event rate is processed in real time by the ATLAS Trigger and data acquisition system, that analyse the results of the collisions, as registered by the 10^8 electronic channels of the detector to select a maximum rate of about 1000 events/second for further offline storage and analysis. In 2025-26, the LHC will be upgraded to increase the LHC collision rate up to a factor 7, to allow acquiring a huge amount of data and pushing the limits of our understanding of Nature. The collision rate and data volume after the LHC upgrade will impose extreme demands on the ATLAS trigger system. The estimated increase in trigger rates and event size lead to larger data volume and much longer event reconstruction times, that are not matched by the slower expected growth in computing power at fixed cost. This requires a change in paradigm, increasing parallelism in computer architecture, using concurrency and multithreading and/or hardware accelerators, such as GPUs or FPGAs for handling suitable algorithmic code. The objective of this thesis program is develop novel calorimeter clustering and jet reconstruction algorithms using accelerators such as FPGAs or GPUs, for the Phase II Upgrade of the ATLAS Trigger system. The student will work in close collaboration with researchers from LIP computing center and particle physics groups, as well as with colleagues from CERN and other institutions involved in the ATLAS experiment. This work will be developed in an international environment. The student will contribute to the improvement of the jet trigger system of the ATLAS experiment at CERN. Presentations at ATLAS Collaboration meetings are expected, either by video-conferencing or at CERN.

DOMAIN: Technologies associated to the Portuguese participation at CERN and their transfer to society

SUPERVISOR: Guiomar Evans
CO-SUPERVISOR: Agostinho Gomes
HOST INSTITUTION: Laboratório de Instrumentação e Física Experimental de Partículas
DEGREE INSTITUTION: Universidade de Lisboa

ABSTRACT

This thesis proposal focus on the development, implementation and integration of a high voltage (HV) system to be used in the Tilecal calorimeter for the operation in the future High Luminosity LHC (HL-LHC) environment (upgrade Phase II). Tilecal, the ATLAS hadron calorimeter in the barrel region is a key sub-detector used for the measurement of jets energy, missing transverse energy, identification of muons with low transverse momentum and for other physics’ tasks. All the Tilecal electronics is being upgraded for the HL-LHC operation. The current HV system is based on a HV distributor system located in the detector that receives a single HV per module as input and regulates the individual voltages to be applied locally to each photomultiplier tube (PMT). This concept has been in use in the Tilecal, and it has the important advantage of not requiring (a large number of) 100-150 m long cables from the HV regulator to the PMTs. In the upgrade, the HV system will be replaced since it has two drawbacks: the radiation damage and the impossibility of replacement of boards if a problem occurs since access is difficult and is possible only at the LHC shutdowns. The new HV system for the upgrade Phase II is a remote one. The HV boards will fit in crates that provide low voltage and that are located outside the ATLAS main cavern. They use standard electronics components since they are not located in the areas exposed to radiation inside the detector but this solution has the drawback of requiring a large number of long cables. A new control and monitoring system is being developed. The HV regulation and the respective control system designs are being finalized and the prototypes will be tested in the calorimeter environment in setups similar to the one of the ATLAS detector, using beams of high energy pions, electrons and muons at CERN and likely also in a special module that will operate in the ATLAS detector. These tests will allow to access the performance of the new Tilecal electronics that is being developed for the HL-LHC. Linearity, stability and noise of the developed system will be measured in the tests with beams of high energy particles and whenever possible in the ATLAS detector during the LHC Run 3 that will start in 2021. A special prototype called demonstrator featuring the new electronics for Phase II will be produced and it is expected to be inserted in the ATLAS detector for regular operation during LHC operation in Run3. This full integration in ATLAS will allow to test the system in the normal conditions of operation before the Phase II upgrade takes place and will give useful information about the performance for the future operation in Phase II.