Developments in large gamma-ray detector arrays

Abstract

Gamma-ray spectroscopy was revolutionized with the introduction of high energy-resolution semiconductor germanium (Ge) detectors in the early 1960s. This led to the large increase in sensitivity realized by today's arrays of Compton-suppressed Ge detectors. A still larger increase in sensitivity is expected by implementing the new concept of tracking. A tracking array consists of highly segmented Ge detectors (that can cover the full 4π solid-angle) in which γ rays will be identified by measuring and tracking every γ -ray interaction. This article reviews the physics motivation for such detectors and the development of the new technologies involved. The concept of tracking is explained using the example of a proposed array called γ -ray energy tracking array (GRETA).

New Directions with Transfer Reactions

“…The time of flight (ToF) is shown as a function of detector number, which varies smoothly with angle, in Fig. 3 for the 16 O(d,n) measurement. As VANDLE is made of plastic scintillator, a γ ray background is present, including the prompt flash of γ's when the beam hits the target, and a second, more intense flash from the beamstop.…”

In-beam spectroscopy of the heaviest elements

“…At present the lowest cross section for meaningful in-beam -ray spectroscopy in an even-even transfermium nucleus is 17 nb, reached in the reaction of 50 Ti on 208 Pb targets [25]. Modern -ray tracking arrays such as AGATA [35] or GRETA/GRETINA [36,37] can push that limit down by at least one order of magnitude. They do this by tracking every -ray interaction in a full germanium shell and then reconstructing the number and energy of all simultaneously incoming rays using tracking algorithms.…”

Radioactive decay data: powerful aids in medical diagnosis and therapy, analytical science and other applications

“…The division of a Ge crystal into sections offers additional information identified with the γ interactions, referred to as γ -ray tracking expressed in terms of energy, time and location -the net result has been the twin achievements of unprecedented efficiency and energy resolution. The development and operational characteristics of single-crystal Ge detectors and more advanced Ge detector arrays can be found in the substantial review articles of Lee et al [22], and Eberth and Simpson [23]. Only a brief semi-historic summary is given below.…”

“…-GRETA (Gamma Ray Energy Tracking Array, USA [22]; geodesic configuration of 120 to 130 segmented HPGe detectors); -AGATA (Advanced GAmma Tracking Array, Europe [23,26]; geodesic configuration of 180 hexagonal and 12 pentagonal segmented HPGe detectors).…”

“…Assembled stacks of planar double-sided Ge strip detectors (DSSD) possess sufficient pixelation to achieve γ -ray positional resolution [22]. Possible drawbacks are envisaged, such as the existence of dead layers at the edge of each planar crystal and the need for mechanical structure to ensure the provision of sufficient cooling to the HPGe detectors.…”