Speaker
Description
For the upcoming high-luminosity LHC, the endcap calorimeters of the CMS experiment will be replaced by the high-granularity calorimeter (HGCAL), a sampling calorimeter using silicon sensors in the front and plastic scintillators read out by SiPMs in the back. After successfully integrating the SiPM-on-Tile sensors with the Serenity back-end hardware, we have conducted detailed system tests to validate the functionality and performance of the readout chain. In this contribution, we will describe our system validation setup and showcase results from bench-top tests and beam tests.
Summary (500 words)
The CMS high granularity calorimeter (HGCAL) is a sampling calorimeter that uses two different sensor technologies. Hexagonal silicon sensors are used in areas exposed to high radiation and pile-up, and the outer parts of the calorimeter endcap are instrumented with plastic scintillator tiles read out with SiPMs. Each endcap will contain roughly 200 m² of active area instrumented with plastic scintillators and 300 m² of silicon sensors, with more than 3 million readout channels.
HGCAL’s scintillator tile modules are readout PCBs with silicon photomultipliers (SiPMs) and plastic scintillator tiles placed directly on top of the SiPMs. Each tile module houses one or two readout chips (HGCROC) which digitize the SiPM signals. Up to five tile modules are connected to a scintillator motherboard which houses data concentrator ASICs, low power gigabit transceivers (lpGBT) for serialization of the data and optical transceivers (VTRx+) for communication with the back-end. The configuration, control, and readout interface of the HGCAL front-end is based on the Serenity FPGA boards [1, 2].
The commissioning of the SiPM-on-Tile readout chain with a Serenity back-end has been presented at TWEPP last year [3]. At the time of commissioning, a pre-series version of the motherboard was used that was equipped with data concentrators for the trigger path (ECON-T) but no DAQ data concentrator (ECON-D). Therefore, the DAQ data arrived in a different format so the system could not be tested with the latest version of the back-end (which expects data in ECON-D format) and a combined readout of scintillator and silicon sensors could only be demonstrated for the trigger path.
This year, motherboards with ECON-D have become available for system tests. Utilizing these new components, we have conducted a detailed validation of the SiPM-on-Tile readout chain.
The validation setup consists of 5 tile modules read out by one motherboard. The tile modules are mounted on a copper cooling plate to emulate a realistic installation and grounding environment. This system – resembling a slice of the HGCAL detector – allows for a range of tests: Firstly, the mechanical and electrical functionality of the system. Second, the distribution of clock signals and fast commands to all modules in the system, as well as the synchronicity of all counters. And finally, the scintillator system can be tested together with the silicon sensor readout.
In this contribution, we will describe our system validation setup and present the tests conducted to validate the system performance. Furthermore, we will showcase highlights from recent beam tests with the SiPM-on-Tile readout chain and report on the integration of the front-end with the latest Serenity-S1 hardware.
[1] A. Rose et al., PoS TWEPP2018 (2019) 115.
[2] T. Mehner et al 2024 JINST 19 C02018
[3] F. Hummer on behalf of the CMS collaboration 2025 JINST 20 C01015
