Performance improvement of a GEM readout module for J-PARC E16 experiment

Hadron mass spectra are expected to be modified in nuclei due to a partial restoration of chiral symmetry. The primary objective of the E16 experiment is to investigate origin of hadron mass by measuring the mass spectral modification of vector meson in nuclei. We aim to obtain definitive information of the mass origin through systematic data acquisition with high statistical precision, acquiring data with 100 times the statistics of the previous study, KEK-PS E325 experiment.

Commissioning runs were performed in 2020-21 at the high-momentum beam line in J-PARC, which is the newly-built primary beamline.Unexpected beam micro structure was found and it deteriorated DAQ performance: live-time was only 15% while the expected live-time is 76% for 1kHz trigger request.

To cope with the situation, we plan to improve the DAQ system, in parallel with the taking measures for the beam line. A current bottleneck of our DAQ system is the data transfer to PCs from SRS-ATCA(GEM readout module developed in CERN). We improved the firmware of SRS-ATCA by implementing a new data buffering function using the embedded DDR3 RAM. By using the spill off time for data transfer, we reduced dead time.

In this presentation, we present the improved performance of DAQ system using the new firmware, which was tested in the recent beamtime in June 2023.