scholarly journals Space-point calibration of the ALICE TPC with track residuals

2020 ◽  
Vol 245 ◽  
pp. 01003
Author(s):  
Marten Ole Schmidt
Keyword(s):  
Tracking System ◽  
Radiation Detector ◽  
Drift Time ◽  
Calibration Procedure ◽  
Tracking Algorithm ◽  
Alice Experiment ◽  
Transition Radiation Detector ◽  
Online Tracking ◽  
Time Projection ◽  
Performance Results

In the LHC Run 3, starting in 2021, the upgraded Time Projection Chamber (TPC) of the ALICE experiment will record minimum bias Pb–Pb collisions in a continuous readout mode at an interaction rate up to 50 kHz. This corresponds to typically 4-5 overlapping collisions during the electron drift time in the detector. Despite careful tuning of the new quadruple GEM-based readout chambers, which fulfill the design requirement of an ion backflow below 1%, these conditions will lead to space-charge distortions of several centimeters that fluctuate in time. They will be corrected via a calibration procedure that uses the information of the Inner Tracking System (ITS), which is located inside, and the Transition Radiation Detector (TRD) and Time-Of-Flight system (TOF), located around the TPC, respectively. By using such a procedure the intrinsic track resolution of the TPC of a few hundred micrometers can be restored. The required online tracking algorithm for the TRD, which is based on a Kalman filter, is presented. The procedure matches extrapolated ITS-TPC tracks to TRD space-points utilizing GPUs. Subsequently these global tracks are refitted neglecting the TPC information. The residuals of the TPC clusters to the interpolation of the refitted tracks are used to create a map of spacecharge distortions. Regular updates of the map compensate for changes in the TPC conditions. The map is applied in the final reconstruction of the data. First performance results of the tracking algorithm will be shown.

scholarly journals GPU-based reconstruction and data compression at ALICE during LHC Run 3

2020 ◽  
Vol 245 ◽  
pp. 10005
Author(s):  
David Rohr
Keyword(s):  
Data Compression ◽  
Real Time ◽  
Tracking System ◽  
Radiation Detector ◽  
Data Rate ◽  
Transition Radiation Detector ◽  
Real Time Processing ◽  
The Status ◽  
Time Projection ◽  
Online Reconstruction

In LHC Run 3, ALICE will increase the data taking rate significantly to 50 kHz continuous read out of minimum bias Pb-Pb collisions. The reconstruction strategy of the online offline computing upgrade foresees a first synchronous online reconstruction stage during data taking enabling detector calibration, and a posterior calibrated asynchronous reconstruction stage. The significant increase in the data rate poses challenges for online and offline reconstruction as well as for data compression. Compared to Run 2, the online farm must process 50 times more events per second and achieve a higher data compression factor. ALICE will rely on GPUs to perform real time processing and data compression of the Time Projection Chamber (TPC) detector in real time, the biggest contributor to the data rate. With GPUs available in the online farm, we are evaluating their usage also for the full tracking chain during the asynchronous reconstruction for the silicon Inner Tracking System (ITS) and Transition Radiation Detector (TRD). The software is written in a generic way, such that it can also run on processors on the WLCG with the same reconstruction output. We give an overview of the status and the current performance of the reconstruction and the data compression implementations on the GPU for the TPC and for the global reconstruction.

scholarly journals DARMA - INFORMATION SYSTEM FOR ACCESSING LHC DATA WITHIN THE ALICE EXPERIMENT AT CERN

2020 ◽  
Vol 20 (4) ◽  
pp. 19-26
Author(s):  
Jan JADLOVSKÝ ◽  
◽  
Milan TKÁČIK ◽  
Slávka JADLOVSKÁ ◽  
Michal PÁNIK
Keyword(s):  
Information System ◽  
Historical Data ◽  
Transition Radiation ◽  
Radiation Detector ◽  
Failure Detection ◽  
Data Access ◽  
Alice Experiment ◽  
Transition Radiation Detector ◽  
International Laboratory ◽  
Detector Control System

The paper deals with the implementation of systems for remote data access in cooperation with the international laboratory CERN in Geneva. The first part discusses extensions of the DARMA information system for archive management. The main goal of this paper is to design and enhance the system with new functionalities and solve known shortcomings, and thus qualitatively increase the potential of the DARMA system in the context of the ALICE DCS (Detector Control System). The final part of the paper deals with the analysis of historical data and the design of a system for the anomaly and failure detection in the infrastructure of high voltage channels within the TRD detector (Transition Radiation Detector).

scholarly journals Production of (anti-)(hyper-)nuclei at LHC energies with ALICE

2018 ◽  
Vol 171 ◽  
pp. 14009 ◽  
Author(s):  
Maximiliano Puccio
Keyword(s):  
Time Projection Chamber ◽  
Tracking System ◽  
Quality Data ◽  
Alice Experiment ◽  
High Quality Data ◽  
Weak Decays ◽  
Inner Tracking System ◽  
Production Models ◽  
Time Projection ◽  
Deuteron Production

The ALICE experiment at the LHC has measured a variety of (anti-)(hyper-)nuclei produced in Pb–Pb collisions at [see formula in PDF] = 5.02 TeV and at 2.76 TeV. In addition, a large sample of high quality data was collected in pp collisions at √s = 7 TeV and 13 TeV and in p-Pb collisions at [see formula in PDF] = 5.02 TeV. These data are used to study the production of different (anti-)(hyper-)nuclei in the collisions, namely (anti-)deuteron, (anti-)3He, (anti-)alpha and (anti-)3ΛH. The identification of these (anti-)(hyper-)nuclei is based on the energy loss measurement in the Time Projection Chamber and the velocity measurement in the Time-Of-Flight detector. In addition, the Inner Tracking System is used to distinguish secondary vertices originating from weak decays from the primary vertex. New results on deuteron production as a function of multiplicity in pp, p–Pb and Pb–Pb collisions will be presented, as well as the measurement of 3He in p–Pb and Pb– Pb collisions. Special emphasis will be given to the new results of the (anti-)3ΛH in its charged-two-body decay mode. The large variety of measurements at different energies and system sizes constrains the production models of light flavour baryon clusters, in particular those based on coalescence and the statistical hadronisation approaches.

scholarly journals Deep neural network techniques in the calibration of space-charge distortion fluctuations for the ALICE TPC

2021 ◽  
Vol 251 ◽  
pp. 03020
Author(s):  
Sergey Gorbunov ◽  
Ernst Hellbär ◽  
Gian Michele Innocenti ◽  
Marian Ivanov ◽  
Maja Kabus ◽  
...  
Keyword(s):  
Neural Network ◽  
Space Charge ◽  
Uniform Electric Field ◽  
Alice Experiment ◽  
Electron Multiplier ◽  
System A ◽  
Novel Strategy ◽  
Time Projection ◽  
Readout Scheme ◽  
Further Development

The Time Projection Chamber (TPC) of the ALICE experiment at the CERN LHC was upgraded for Run 3 and Run 4. Readout chambers based on Gas Electron Multiplier (GEM) technology and a new readout scheme allow continuous data taking at the highest interaction rates expected in Pb-Pb collisions. Due to the absence of a gating grid system, a significant amount of ions created in the multiplication region is expected to enter the TPC drift volume and distort the uniform electric field that guides the electrons to the readout pads. Analytical calculations were considered to correct for space-charge distortion fluctuations but they proved to be too slow for the calibration and reconstruction workflow in Run 3. In this paper, we discuss a novel strategy developed by the ALICE Collaboration to perform distortion-fluctuation corrections with machine learning and convolutional neural network techniques. The results of preliminary studies are shown and the prospects for further development and optimization are also discussed.

scholarly journals Development of the Safety System for the Inner Tracking System of the ALICE Experiment

2021 ◽  
Vol 251 ◽  
pp. 04004
Author(s):  
Pascal Herve Blanc ◽  
Patricia Mendez Lorenzo ◽  
Xavier Pons
Keyword(s):  
Low Voltage ◽  
Tracking System ◽  
Industrial Applications ◽  
Safety System ◽  
Alice Experiment ◽  
Inner Tracking System ◽  
Scada System ◽  
Pixel Sensors ◽  
Control Application ◽  
Interlock System

During the LHC Long Shutdown 2, the ALICE experiment has undergone numerous upgrades to cope with the large amount of data expected. Among all new elements integrated into ALICE, the experiment counts with a new Inner Tracking System (ITS), with innovative pixel sensors that will substantially improve the performance of the system. The new detector is powered up through a complex Low Voltage (LV) distribution, increasing the power dissipated by the detector and requiring the installation of a large number of temperature measurement points. In 2020, a new safety system has been developed to distribute the ITS LV interlock system and to monitor the new temperature values. The safety system is based on a Siemens S7-1500 PLC device. The control application governing the PLC has been configured through the UNICOS-CPC infrastructure made at CERN for the standardisation of industrial applications. UNICOS-CPC enables both the automatisation of control tasks governing the PLC and the interface to the WinCC OA based SCADA system. This paper provides a complete description of the setup of this safety system.

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