On 23-24 July, specialists from the Central China Normal University (CCNU, Wuhan) and the University of Science and Technologies of China (USTC, Hefei) led by Prof. Xiangming Sun (CCNU) met with JINR colleagues at VBLHEP for the Seminar on the Chinese-Russian Cooperation within the NICA MPD-ITS Project. This was the second in-person meeting between the members of the international team engaged in the construction of the MPD-ITS Vertex Detector. At the event, the participants discussed the status and future steps of the project.

The project aims at producing the Inner Tracking System (ITS) of the MPD Experiment that will supplement the time projection chamber (TPC) for the precise tracking, momentum determination, and decay vertex reconstruction for hyperons (Λ, Ξ, Ω) and D-mesons. This detector will be built based entirely on a similar silicon Monolithic Active Pixel Sensor (MAPS) technology used for the upgrade of ALICE ITS2 at CERN, but with the MAPS and the related ASICs-based readout electronics designed and produced in China. This will ensure unrestricted access for JINR to this technology otherwise forbidden for importing to both Russia and China. MAPS was chosen due to its prospects for creating a tracking system integrating sensors and readout circuits on the same chip as well as high spatial resolution, minimal weight of the substance introduced into the path of particles, low power consumption, and low cost of the particle sensor. The MPD-ITS Detector will be assembled at different integration stages at JINR and CCNU in close collaboration with the USTC, Saint Petersburg State University (SPbSU, Russia), the Institute of Modern Physics (Lanzhou, China) and the Institute of High Energy Physics (Beijing, China).

The seminar took place three weeks after the announcement by the JINR-China Joint Coordination Committee on Cooperation that the project titled “Monolithic Si-Pixel Detector for Collider Experiments and Other Applications”, presented by the institutions participating in the MPD-ITS Project, was among the eight projects selected by the experts to be co-financed by JINR and the Ministry of Science and Technology of China.

Dmitry Peshekhonov, VBLHEP Deputy Director, made an opening speech emphasising that the China-JINR scientific cooperation is mutually beneficial.

The first day of the meeting was dedicated to reviewing the status and subsequent tasks of the main stages of the project under development. Prof. Valery Kondratiev (SPbSU) presented the results of the computer simulations for the quality assessment of the MPD Tracking System (TPC + ITS) in a configuration of six layers of MAPS sensors and a beampipe with a diameter of 40 mm for the reconstruction of charmed particles from Au-Au collisions at NICA energies. Simulation also shows the feasibility of D-mesons identification in central Bi+Bi collisions at √^SNN = 11 GeV, which opens up prospects for studying the heavy flavors physics at the NICA-MPD Facility.

Head of the VBLHEP JINR Scientific and Methodological Department of Silicon Tracking Systems Yuri Murin (JINR) presented the status of the production of the nine meter installation container that will be used to slide-in the thin-walled beryllium MPD beampipe, the ITS, and all its electrical and service components along with two reaction time detectors (FFD) into the TPC within a tolerance of 4 mm. The structure that is planned to be completed by the end of this year was shown at its current assembly place. The status of the corresponding stand-alone leakless cooling plant to be tested in the beginning of next year was also reported.

Le Xiao (CCNU) reported on the R&D works of the Chinese MAPS by the name of MICA chips of which the first 150 units of the first prototype have been recently produced on the CMOS 130 nm process and are currently under test. The full evaluation of the current version of the chip is expected to be completed by November this year.

Jianjun Qin (USTC) presented the status of the key milestones of the design and production of the readout electronics for the MPD-ITS Outer Barrel, including the FPGA-based readout unit (F-RU) and the power unit with the first prototype of both already produced and tested. His report also covered the R&D status of the NICA_ROC ASIC to be used for the production of the ASIC-based readout unit (A-RU). The major challenges for this readout electronics design are the high-speed data transmission, real-time pre-processing, and high reliability of operation in fields with increased radiation.

Di Guo (USTC) delivered an online report on the R&D of the other ASICs for the production of the A-RU chip, including the NICA_GBT for which the digital circuits (Encode, Decode functions) and Clock Phase control circuits are under design while the circuit with Data Phase Control (Phase Aligner) is currently being tested. The Transimpedance Amplifier (NICA_TIA) and the Laser Driver (NICA_LD) that conform the optical module of the readout for which the core design was completed and tested, is planned to be further optimised for their final version.

Dmitrii Dementev gave a talk about the possibilities of JINR participating in the tests of MICA Chips on beams of secondary light tagged fragments of projectile nuclei bombarding the BM@N targets and the irradiation with protons (200 MeV and 1 GeV) at the SC-1000 Facility at the Petersburg Nuclear Physics Institute (PNPI) in Gatchina. At PNPI, a recent test irradiation campaign of a combined telescope of MAPS and DSSD sensors was successfully conducted by JINR and SPbSU specialists, thus successfully testing of the MAPS Readout and dedicated software developed at JINR. This allows for the use of the same mechanics and DAQ system for the future in-beam tests of the MICA Chips.

Finally, the modules and supermodules assembly readiness at CCNU and JINR were reported by Yaping Wang (CCNU) and Aleksey Sheremetev (JINR) respectively. They also presented the challenges to be solved regarding the logistics for material interchange between JINR and CCNU, especially during the serial production phase.

The second day of the meeting was held as a round table discussion for defining future work plans with timelines and milestones. During this session, it was decided to organize the JINR-China cooperation as part of the MPD-ITS Projects as the NICA MPD-ITS Consortium that will last for 5 years. The CCNU will be the coordinator centre in China and JINR in the Russian Federation. The co-leaders of the projects and their deputies will be Dr. Yuri Murin (Leader for JINR), Cesar Ceballos Sanchez (Deputy Leader for JINR) while for CCNU the Leader and Deputy Leader will soon be decided. Each of the other institutions participating in the Consortium will have one representative on the project structure for decision making and control. At least once a year there will be an in-person meeting of the Consortium to review the status of the different work packages. The rules defining the paper authorship, conference presentation contributions, and personnel exchange were also discussed.

The last session of the meeting was devoted to field trips to the VBLHEP ITS Circuits assembly lab, the superconducting magnets factory, the assembling site of the TPC Detector and the MPD site, where all participants were introduced to the updates of the characteristics and status of those facilities.

These were two intense working days that all parties considered very useful and revealing the importance of conducting in-person meetings within international projects, providing an opportunity for many issues to be promptly yet detailed and accurately discussed and for relevant decisions to be duly taken. The first of these meetings took place on 15-16 June 2023 in Wuhan and the next one is to take place next year, once again in China.