Data acquisition system components of the SPD facility in the NICA accelerator complex
The electronic modules that facilitate precise synchronization of the SPD system’s data acquisition components, thereby ensuring accurate temporal measurements
Task
The NICA (Nuclotron-based Ion Collider fAcility) accelerator complex is one of six Megascience-class projects currently under construction in Russia at the Joint Institute for Nuclear Research in Dubna. The Superconducting Proton and Heavy Ion Collider is an international megaproject.
The collision of heavy ion bunches will facilitate the investigation of critical states of nuclear matter in extreme conditions that occurred subsequent to the Big Bang, in the nascent stages of the universe's evolution. The recreation of critical states of nuclear matter in laboratory conditions is achieved through the acceleration and collision of high-intensity heavy ion bunches in a collider. The processes involved will be the subject of study at the MPD (Multi-Purpose Detector) facility.
The spin structure of nucleons will be investigated through the interaction of polarized proton and deuteron bunches at the SPD (Spin Physics Detector) facility at the NICA collider.
In order to achieve high-precision synchronization of the collider and the data acquisition system of the SPD experiment, engineers from the Industrial Systems for Streaming Data Processing Laboratory at the SPbPU AES have been developing subsystems since 2020. These subsystems facilitate the linking of the time of bunch crossing within the SPD facility to the moment when the detectors register the changed particle characteristics with sub-nanosecond accuracy.
The precise synchronization of collider event times (corresponding to the moment of collision) and facility event times (associated with the recording of particle properties) represents a crucial element in the accuracy of data acquisition for the investigation of the spin structure of nucleons.
The SPbPU AES ISSDP Laboratory team forms part of the Polytechnic University scientific group, which has been engaged in official collaboration with JINR since 2018. The group is constituted by the scientific team of the Graduate School of Fundamental Physics Research of the SPbPU Physics and Mechanics Institute, which is headed by Yaroslav Berdnikov, Professor, Doctor of Physical and Mathematical Sciences. SPbPU scientists take part in experiments on two main collider facilities: MPD (Multi-Purpose Detector) and SPD (Spin Physics Detector).
Solution
Subsequent to the collision, the SPD electronics measure the signals from the particle detectors and transmit them to the DAQ (Data Acquisition System). The DAQ system is responsible for the collection, structuring, and recording of information to intermediate disc storage. Subsequently, high-performance online computers, utilizing machine learning algorithms, identify the requisite events within the data set for further analysis and record them in the storage facility.
One of the principal factors enabling the data to be collated into events is the ability to time them to the time of bunch crossing with nanosecond precision. For this to occur, two conditions must be met:
- Sufficient resolution of the reading electronics (Front-End Cards);
- Sufficient synchronization accuracy of all DAQ nodes.
In the SPD facility, the physical timestamp is defined as the moment of bunch crossing. It is therefore essential that the events recorded by the detectors are correlated with this reference point. The bunch crossing period is about 80 ns. The Monte Carlo method suggests that physical events will occur with a frequency of approximately every 3-4 bunch crossings. It is presumed that data regarding bunch crossing in the SPD facility will be conveyed by the collider control equipment. In order to facilitate an accurate comparison of detector and collider data, it is essential to synchronize the two systems with a high degree of precision, ideally to a level of less than 1 nanosecond (ns). This implies that the 'clock' of the SPD facility must remain in close alignment with the 'clock' of NICA throughout the data acquisition period.
The initial phase of work in the SPbPU AES ISSDP Laboratory entailed the re-engineering of the TCS (Trigger and Control System) synchronization and control subsystem, originally developed at the Technical University of Munich (TUM) for the COMPASS facility (CERN, Switzerland) between 2020 and 2023. The TCS module is a highly specialized device, and thus its computing core is a field-programmable gate array (FPGA). The module was re-engineered by experts from the ISSDP Laboratory, resulting in the creation of a new TCS module that meets the specifications required by the SPD facility. The TCS subsystem has been developed with the specific purpose of testing individual SPD detectors within the designated test area of the collider.
The next stage is the development of a high-precision TSS (Time Synchronization System) subsystem for use in SPD. The subsystem is implemented in accordance with a no-trigger data acquisition concept and the White Rabbit protocol. The TSS prototype has been developed on a field-programmable gate array (FPGA) and will be capable of functioning as both a terminator and a multi-port switch for the White Rabbit network. It will also guarantee the sub-nanosecond accuracy that is required for the SPD experiment.
Technologies
| Programming languages | C/C++, Tcl |
| Hardware description languages | Verilog, SystemVerilog |
| CAD | Xilinx Vivado, Altium Designer |
| Modeling tools | Icarus Verilog |
Project team
- Project manager: M.V. Bolsunovskaya, Head of the Industrial Systems for Streaming Data Processing Laboratory at SPbPU