Instrumentation R&D

Gamma-ray trigger for HERD

Gamma-ray trigger for HERD

The IFAE Gamma-ray group is responsible for designing, prototyping, and testing a new, advanced trigger system to detect gamma rays with energies as low as 100 MeV using HERD. In its original baseline design, the gamma-ray trigger relied on detecting energy deposition on the external layers of the calorimeter (CALO) and the absence of a signal in the anti-coincidence plastic scintillator detector (PSD). IFAE has proposed a new system that replaces the input from CALO with that from the fiber tracker (FIT) subsystem.

Our new system analyzes the FIT’s geometrical patterns of hits that are consistent with the passage of a gamma ray through the detector. This approach allows us to significantly lower the energy threshold for detecting gamma rays and increase the efficiency of detecting gamma rays with good reconstructed direction, thereby enhancing HERD’s scientific potential for Gamma-ray astronomy.

HERD trigger elecronics
For the CERN beam test in September 2023, we will be utilizing a setup based on a commercial evaluation board with a 136-channel FPGA to control and readout the ASIC in the FIT and PSD front-end electronics. The knowledge gained from this setup will inform the design of the engineering models for the FIT trigger and the PSD trigger+readout systems. Credit: IFAE

Meeting the tight latency constraints, which are in the order of a few tens of nanoseconds, is a key technological challenge in producing the FIT trigger signal and correlating it with the absence of a veto signal from the relevant PSD region of interest. This requires a highly precise and efficient trigger system that can operate with great speed and accuracy. Our team is addressing this challenge by developing innovative solutions and implementing advanced technologies for the FIT and PSD trigger and readout systems, ensuring that the HERD gamma-ray trigger system delivers the highest possible performance. We plan to test the first prototypes of these systems in fall 2023 using CERN’s proton and ion beams