The main goal of the NICA heavy-ion program at JINR is an experimental investigation into the properties of nuclear matter within the energy region of the maximum baryonic density.The Multi Purpose Detector (MPD) is one of the detectors at NICA collider, which is optimized for the study on properties of hot and dense matter in heavy-ion collisions and, in particular, the search for a manifestation of possible deconfinement and/or chiral symmetry restoration phase transitions, critical end-point and mixed quark-hadron phase. Electromagnetic calorimeter (ECal) is an important part of MPD. The particular goal of MPD-ECal is to measure position and energy of photons and electrons. Taking all factors (high energy resolution, high segmentation, large enough distance to the vertex, small Moliere radius, high magnetic field and high time resolution) into consideration, a shashlik-type electromagnetic calorimeter is selected. Therefore the tower consists of 220 layers of lead plates and scintillator plates whose thicknesses are namely 0.3mm/1.5mm. The tower cell is 4×4 cm 2 in size. To reduce the dead zones effect, all towers should be cut from four sides at small angles, which will significantly improve the position resolution and the performance homogeneity of the ECal. Currently, energy deposition, energy resolution and position reconstruction are studied through Monte Carlo simulations. A prototype of shashlik Ecal has been built and the cosmic test results show that the number of photoelectrons (Npe) is around 522. By comparing with the previous ECal experimental results and simulation results, it is indirectly considered that the energy resolution of the prototype has reached 5%/ √ E (GeV). Key technologies to increase light yield are being studied and will be used in the development of new prototypes.
A shashlik electromagnetic calorimeter will be produced in Hall A of Jefferson Laboratory for Solenoidal large Intensity Device (SoLID) to measure the energy deposition of electrons and hadrons, and to provide particle identification after the energy of the accelerator was upgraded to 12 GeV. Tsinghua University is the member of Hall A collaboration in charge of development and production of the large shashlik electromagnetic calorimeter of SoLID. One module of that calorimeter is composed by 194 layers. Each layer consists of a 1.5 mm thick plastic scintillator put on top of a 0.5 mm thick lead plate. Scintillation light is read out by wave-length shifter fibers penetrating through the calorimeter modules longitudinally along the direction of flight of the impact particle. This paper describes the design and construction of that module, as well as a few optimization studies meant to improve its performance. A detailed Geant4 simulation also shows that an energy resolution of 5%/√ E (GeV) and a good containment for electromagnetic showers can be achieved, as well as some basic electron identification. A prototype of that module will be tested soon with an electron beam at JLab.
SoLID (Solenoidal Large Intensity Device) is a large acceptance spectrometer which can handle very high luminosity, being planned for experimental Hall A at Jefferson Lab, USA. The shashlik-type sampling detector will be used for the electromagnetic calorimeter for SoLID. This calorimeter is 18 radiation-lengths long with 194 layers each of 1.5mm-thick plastic scintillators alternating with 0.5mm-thick lead plates. A few prototype of the calorimeter have been built at Shandong University. the light yield of these modules have been tested with cosmic ray. The assembling process of these prototypes and cosmic ray test results are presented.
A: Muon tomography system built by 2-D readout high spatial resolution Multi-gap Resistive Plate Chamber (MRPC) detector is a project in Tsinghua University. In 2013, we had developed a prototype of muon tomography system named TUMUTY, now we try to develop larger sensitive area and smarter structure MRPC detector to upgrade the system to a car detection system, which is used to detect high Z metal hidden in cars or other objects. For the system, 2 layers ×3 detectors are needed to get the incident particle's track, and the setting is the same for the outgoing track. Therefore, there will four layers containing twelve detectors in total, and its detection area will reach 1 × 3 m 2 . An encoding readout method is suggested to minimize the number of the readout electronics, which reduces the complexity and the cost of the system. In this paper, we measured the performance of 12 MRPCs used for the system.
A simulation program based on GEANT4 is developed to study the performance of the shashlik electromagnetic calorimeter, which is a part of the multi purpose detector at nuclotron-based ion collider facility (NICA-MPD) . The whole process is considered, including electromagnetic shower, scintillation process, wavelength shift (WLS) effect and photon transmission, which itself includes reflection, refraction, absorption and transport of optical photon. The program is used to analyse the factors affecting the number of photoelectrons (Npe) of the silicon photomultiplier (SiPM), e.g. the degree of polishing of optical surfaces, and the width of the gap between the reflective layer and the end surface of fibers. The simulation results show that the Npe is larger when the shashlik tower is wrapped with specular reflection material, instead of the diffuse reflective material used in the current design. Concerning the end of the fibers, we find that the encapsulation method, where the fiber is pulled to a specular layer, provides better performance than coating the end of fibers by diffuse reflective material.
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