Abstract
HADES (High Acceptance Di-Electron Spectrometer) is located at the GSI (Helmholtzzentrum für Schwerionenforschung) Darmstadt. It is an experiment focused on the study of the hot and dense nuclear matter mainly via the detection of the di-lepton pairs. Electromagnetic CALorimeter (ECAL) was recently added to the HADES setup. This new subdetector allows measuring of photons from the decay of neutral mesons and resonances. It also allows to discriminate between electrons and pions in the high-momenta region over 400 MeV/c. ECAL follows same hexagonal geometry as HADES, i.e. it consists of six sectors in azimuth. The first four sectors were finished and commissioned in 2018. The first experiment with ECAL included in HADES setup took place on March 2019, investigating the Ag+Ag reaction at beam energy of 1.65 A GeV. During the commissioning, several issues popped up and they were addressed. The issues and their solution will be described in the article.
Highlights
It has almost full azimuthal coverage, between 18◦ and 85◦ of the polar angle. It consists of several subsystems: START and VETO systems which utilize diamond sensors, Ring Imaging Cherenkov detector (RICH) with gas radiator and pixel PMTs for read-out, four planes of Multiwire Drift Chambers (MDC) which provide tracking abilities, two layers are located before a two after the magnetic field, superconducting toroidal magnet with six coils which produces the magnetic field that allows measuring the momenta of charged particles, Time of Flight (TOF) wall and Resistive Plate Chambers (RPC) provide the time of flight and multiplicity information
The newest sub-system is the Electromagnetic Calorimeter (ECAL) which is discussed in more detail further
Magnetic shielding is made from MUMETALL R and is needed due to a residual magnetic field due to toroidal HADES superconducting magnet coils
Summary
After installation into the calorimeter frame, the modules were tested again. More precisely to the position and alignment between magnetic shielding and the PMT. When the magnetic shielding was nicely round and aligned with the PMT the issues did not occur.
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