Gamma-Ray Energy Tracking Research Articles

Data Acquisition and Trigger System of the Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA)

The Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA), capable of determining the energy and position (within 2 mm) of each gamma-ray interaction point and tracking multiple gamma-ray interactions, has been designed. GRETINA will be composed of seven detector modules, each with four highly pure germanium crystals. Each crystal has 36 segments and one central contact instrumented by charge sensitive amplifiers. Two custom designed modules, the Digitizer/Digital Signal Processing (DSP) and the Trigger Timing and Control, compose the electronics of this system. The digitizer/DSP converts the analog information with 14-bit analog to digital converters operating at 100 MS/s, and digitally processes the data to determine the energy and timing information of the gamma interactions with the crystal. Each Digitizer/DSP is controlled by and sends trigger information to the Trigger Timing & Control system through a bidirectional Gbit link. Presently four different trigger algorithms are planned for the trigger system and can be selected for trigger decision. In this paper the details of the electronics and algorithms of the GRETINA data acquisition and trigger system are presented and the performance is reviewed.

Gamma-ray tracking: Characterisation of the AGATA symmetric prototype detectors

Each major technical advance in gamma-ray detection devices has resulted in significant new insights into the structure of atomic nuclei. The next major step in gamma-ray spectroscopy involves achieving the goal of a 4pi ball of Germanium detectors by using the technique of gamma-ray energy tracking in electrically segmented Germanium crystals. The resulting spectrometer will have an unparalleled level of detection power for nuclear electromagnetic radiation. Collaborations have been established in Europe (AGATA) [J. Simpson, Acta Phys. Pol. B 36 (2005) 1383. [1]] and the USA (GRETA/GRETINA) to build gamma-ray tracking spectrometers. This paper discusses the performance of the AGATA (Advanced Gamma Tracking Array) symmetric prototype detectors that have been tested at the University of Liverpool. The use of a fully digital data acquisition system has allowed detector charge pulse shapes from a selection of well defined photon interaction positions to be analysed, yielding important information on the position sensitivity of the detector.

The AGATA project

Each major technical advance in gamma-ray detection devices has resulted in significant new insights into the structure of atomic nuclei. These advances have culminated in the construction of 4π arrays of escape-suppressed spectrometers that comprise a Ge detector and scintillation detector suppression shield. The next major step in gamma-ray spectroscopy involves achieving the ultimate goal of a 4π ball of just Ge detectors by using the technique of gamma-ray energy tracking in electrically segmented Ge crystals.The resulting spectrometer will have an unparalleled level of detection power for nuclear electromagnetic radiation. Its sensitivity for selecting the weakest signals from exotic nuclear events will be enhanced by a factor of up to 1000 relative to its predecessors. It will have an unprecedented angular resolution making it ideally suited for high-energy resolution even at recoil velocities up to 50% of the velocity of light. Therefore, it is ideally suited to be used in conjunction with the new generation of radioactive beam accelerators or existing stable beam facilities.A European collaboration has been established to construct a 4π tracking spectrometer called AGATA (Advanced Gamma Tracking Array). This collaboration is currently performing the research and development necessary to finalise the technology for gamma-ray tracking and hence fully specify the full 4π spectrometer. The status of this first phase of the AGATA project will be reported.

GRETINA: A gamma ray energy tracking array

A gamma-ray energy tracking array (GRETA) is a new concept for the detection of gamma radiation. In such an array, the individual interactions of all the gamma rays are identified by their energies and positions. Then, using tracking algorithms based on the properties of gamma ray interactions, the scattering sequences are reconstructed. GRETA will give high peak efficiency, peak-to-background ratio, and position resolution. Recent research and development efforts have demonstrated that the construction of a gamma ray tracking array is feasible, and a plan for constructing a US array GRETINA is in place.

Gamma-ray tracking: Utilizing new concepts in the detection of gamma-radiation

Gamma-ray tracking in a closed array of highly segmented HPGe detectors is a new concept for the detection of γ-radiation. Each of the interacting γ-rays is identified and separated by measuring the energies and positions of individual interactions and by applying tracking algorithms to reconstruct the scattering sequences, even if many γ-rays hit the array at the same time. The three-dimensional position and the energy of interactions are determined by using two-dimensionally segmented Ge detectors along with pulse-shape analysis of the signals. Such a detector will have new and much improved capabilities compared to current γ-ray spectrometer. One implementation of this concept, called GRETA (Gamma-Ray Energy Tracking Array), is currently being under development at LBNL.

GRETA: utilizing new concepts in γ-ray detection

We present a new concept for γ-ray detector arrays. An example, called GRETA (Gamma-Ray Energy Tracking Array), consists of highly segmented HPGe detectors covering 4π solid angle. The new feature is the ability to track the scattering sequence of incident γ-rays and in every event, this potentially allows one to measure with high resolution the energy deposited, the location (incident angle) and the time of each γ-ray that hits the array. GRETA will be of order of 1000 times more powerful than the best present arrays, such as Gammasphere or Euroball, and will provide access to new physics.

A γ-ray tracking algorithm for the GRETA spectrometer

Abstract We discuss a γ-ray tracking algorithm that has been developed for the proposed gamma-ray energy tracking array (GRETA). This algorithm has been designed so as to maximize the resolving power for detecting high-multiplicity γ-ray events. The conceptual basis for this algorithm will be presented. In addition, Monte Carlo simulated data will be used to assess performance over a large range of relevant parameters. A discussion of the potential γ-ray polarimeter performance of GRETA is also presented.

Gamma-ray cluster identification in a spherical shell of highly segmented germanium detectors

Research and development is proceeding on a new /spl gamma/-ray detector array for nuclear physics: the Gamma-Ray Energy Tracking Array (GRETA). This array will consist of a spherical shell of highly segmented Ge detectors. By obtaining the energy and position of each interaction point, high efficiency and peak-to-total ratios can be obtained as compared with existing arrays. Here we discuss the computer algorithms that are needed to process the raw data and maximize the performance of the array. The results of these algorithms on Monte Carlo simulated data are presented.