Decoding Gamma Rays: How Advanced Detectors are Revolutionizing Nuclear Physics

The Advanced GAmma Tracking Array, known as AGATA, serves as a crucial tool for exploring the behavior of atomic nuclei under extreme conditions. Its primary function is to capture as much spatial and energy information as possible about gamma rays emitted from nuclear reactions. By meticulously analyzing signals from its segmented detectors, AGATA reconstructs the three-dimensional positions of interaction points, tracing the path of individual gamma rays to provide insights into the structure and dynamics of atomic nuclei. This detailed information is essential for advancing our understanding of nuclear structure and nuclear reactions. Other gamma ray detectors include segmented Ge detectors.

The Narval framework is a modular system that handles the data acquisition (DAQ) for AGATA. It processes data in a pipeline, initially managing each detector individually at the local level. This local processing is essential before the global-level processing, where detector events are assembled to construct actual events. The Narval framework also allows for offline actions through a Narval emulator, enabling replay of raw data. Each segment and the central contact are decoded by the Narval actor Producer. This step is crucial for ensuring data integrity and preparing it for subsequent analysis, such as Pulse Shape Analysis and Event Building. Narval enables offline recalibration of AGATA detector data.

Pulse Shape Analysis, or PSA, is a critical step in the AGATA data processing pipeline. Its main purpose is to determine the interaction position of gamma rays within the detector by comparing recorded signals with a set of reference signals. By analyzing the shape of the electrical pulses generated when a gamma ray interacts with the detector, PSA algorithms can pinpoint the precise location of the interaction. This information is vital for tracking the path of gamma rays and reconstructing the events that occurred within the nucleus. Following PSA, a PostPSA step makes all information accessible, including energy and time of the central contact and segment energies, allowing for recalibration if segment energy sums do not match the central contact's energy. Accurately determining the location of each interaction allows for more precise measurements of the gamma ray's energy and direction, ultimately leading to a more detailed understanding of nuclear structure.

The moving-window deconvolution technique is a digital algorithm used to access energy information from the sampled detector signal in AGATA. It employs trapezoidal filtering suitable for Germanium detectors. By applying this technique, scientists can correct for distortions and noise in the detector signal, leading to more accurate energy measurements. The Preprocessing filter can readily perform energy calibration by knowing the detector preamplifier features, such as rise-time and shaping-time. Linear combinations of recorded amplitudes correct the amplitude of the actual segment. This is particularly important when dealing with high-energy gamma rays or complex nuclear reactions, where precise energy measurements are essential for identifying specific nuclear states and transitions.

The source run measurements conducted during the PreSPEC-AGATA campaign at GSI (Helmholtzzentrum für Schwerionenforschung) are crucial for assessing and refining the performance of the AGATA array. These measurements, involving twenty-one 36-fold segmented AGATA crystals, help optimize data processing techniques and ensure reliable energy and position information for subsequent analysis. By analyzing data from known radioactive sources, scientists can calibrate the detectors, identify and correct for systematic errors, and fine-tune the tracking algorithms. This process ensures that AGATA provides the most accurate and reliable data possible, maximizing its potential for groundbreaking discoveries in radioactive ion beam research. Other radioactive ion beam facilities include ISOLDE at CERN.