Development And Data Quality Control Of The ITS2 Detector At LHC/ALICE Experiment

Beginning in the 6th century BC,ancient Greek philosophers began to explore the original of the world.They opposed the past myths and legends,and believed that the ori-gin of the world was some material elements,such as water,fire,and earth.With the devel-opment of philosophy,physics,electronics and other disciplines.Human’s understanding of matter has gradually shifted from elementary doctrine,to atoms and molecules,and then to today’s quark and leptons.In the history of development of human civilization,mankind has never given up the exploration of the deep structure of matter.Today,the most successful description of the particles that make up matter is the Standard Model（SM）.This model is a set of theories used to describe the three basic in-teractions of strong interaction force,weak interaction force and electromagnetic force.In order to verify this theory,since the 1960s,humans have built a series of complex large sci-entific devices,such as:Super Proton Synchrotron（SPS）,Relativistic Heavy Ion Collider（RHIC）,Large Hadron Collider（LHC）,etc.ALICE（A Large Ion Collider Experiment）is a general-purpose heavy ion collision detector on CERN LHC.The design purpose of the ALICE experiment is to use proton-proton,nucleus-nucleus,proton-nucleus collisions to study the strong interaction,and the properties of nuclear quark-gluon plasma（QGP）.Although the ALICE experimental group has achieved a large number of important physical results around this target,but the current detector and its electronic readout speed is not suitable for the request of the high luminosity in Run3/4.At the same time,the ALICE experiment also hopes to perform high-precision measurement of rare probes in a wider range of traverse momentum.Therefore,the ALICE detector is preparing to up-grade the detector and electronics during the LHC Long Shutdown 2（LS2）from 2018 to 2021 to meet the significant increase in beam luminosity and greatly improve the phys-ical performance of ALICE.In the ALICE upgrade,one of the most critical upgrade is to build a new,high-resolution,low-material Inner Tracking System（ITS2）to replace the current ITS.ITS2 uses the silicon pixel chip（ALice PXxel DEtector,ALPIDE chip）based on Monolithic Active Pixel Sensor（MAPS）technology.The chip has the characteristics of low power consumption,high resolution and high readout rate.This technology will greatly improve the position resolution and detection efficiency of ITS2 in the range of low traverse momentum.ITS2 is composed of 7 layers（3 Inner Barrel layers,4 Outer Barrel layers）of concen-tric barrel-shaped detectors.The effective detection area reaches 10 m²,with a total of 12 billion pixels.Our group undertook the development of one fifth of all ITS2 Outer Barrel module（Outer Barrel HIC,OB-HIC）.During the development of ITS2,the positioning accuracy of the chip,the fixed connection between the FPC（Flexible printed Circuit）and the chip,electrical performance of the chip and the assembly quality will directly affect the reliability,resolution,detection efficiency and service life of the ITS2.This article will introduce the development of ALICE Wuhan assembly point ITS2 in detail.The aim of Data Quality Control（QC）is to provide a prompt online feedback on the quality of the data during the data taking.QC can check the running status of the detector and the data collection situation most intuitively and quickly.At the same time,it can also provide relevant experts with information the fastest when the detector fails.This is extremely important for the maintenance of the detector,the reconstruction of the track and the subsequent data analysis.ITS2’s QC has been tested for Fake Hit Rate（FHR）,Threshold Scan（THS）,Front-End Electronics（FEE）,Cluster（Cluster）and Track（Track）Monitoring.These five aspects give the operating status information of the detector and its readout electronics.At present,the Outer Barrel Bottom of ITS2 has been installed inside the TPC,and the installation has completed in May 2021.The FHR and FEE of ITS2 data quality control have basically completed the development and used it during commissioning phase.The QC of THS,Clusters and Tracks are still under development.ITS2 QC plans to complete all development work before June 2021.ALICE plans to upgrade ITS again during LS3.The upgraded ITS（ITS3）will reach a material budget of 0.05%X₀,and the spatial resolution will also reach 5μm.