GRI: focusing on the evolving violent universe

Abstract

The gamma-ray imager (GRI) is a novel mission concept that will provide an unprecedented sensitivity leap in the soft gamma-ray domain by All authors are on behalf of a large international collaborationThe GRI mission has been proposed as an international collaboration between (in alphabetical order) Belgium (CSR), China (IHEP, Tsinghua Univ.) using for the first time a focusing lens built of Laue diffracting crystals. The lens will cover an energy band from 200-1,300 keV with an effective area reaching 600 cm 2 . It will be complemented by a single reflection multilayer coated mirror, extending the GRI energy band into the hard X-ray regime, down to ∼10 keV. The concentrated photons will be collected by a position sensitive pixelised CZT stack detector. We estimate continuum sensitivities of better than 10 −7 ph cm −2 s −1 keV −1 for a 100 ks exposure; the narrow line sensitivity will be better than 3 × 10 −6 ph cm −2 s −1 for the same integration time. As focusing instrument, GRI will have an angular resolution of better than 30 arcsec within a field of view of roughly 5 arcmin-an unprecedented achievement in the gamma-ray domain. Owing to the large focal length of 100 m of the lens and the mirror, the optics and detector will be placed on two separate spacecrafts flying in formation in a high elliptical orbit. R&D work to enable the lens focusing technology and to develop the required focal plane detector is currently underway, financed by ASI, CNES, ESA, and the Spanish Ministery of Education and Science. The GRI mission has been proposed as class M mission for ESAs Cosmic Vision 2015-2025 program. GRI will allow studies of particle acceleration processes and explosion physics in unprecedented detail, providing essential clues on the innermost nature of the most violent and most energetic processes in the universe.

Proposal for a Laue lens relying on hybrid quasi-mosaic curved crystals

“…The results are shown in Fig. 9, which are in line with the sensitivity of the proposed Laue lens for the Gamma Ray Imager (GRI, Knödlseder et al 2009). Indeed, the smaller effective area of the QM-based Laue lens, which is intrinsic in the usage of QM crystals, is abundantly compensated for by the strong focusing exerted by QM effect.…”

“…It is conceived as an ensemble of many crystals arranged in such a way that as much radiation as possible is diffracted onto the lens focus over a selected energy band (Smither 1982;Lund 1992;von Ballmoos et al 2005;Knödlseder et al 2009). Perfect and flat mono-crystals diffract within a very narrow energy range, so that they are not adequate for a Laue lens.…”

Finding short GRB remnants in globular clusters: the VHE gamma-ray source in Terzan 5

“…The estimated flux values in the table are given for a mass of the respective nuclei of 10 −5 M , an age of the remnant of 10 4 , years and a distance to Terzan 5 of 5.9 kpc. Even for such an advantageous case, the line brightness would not exceed 10 −8 γ cm −2 s −1 , and detection would be challenging for the next generation of hard X-ray / soft gamma-ray instruments (e.g., Knödlseder et al 2009). …”

Gamma-ray polarization constraints on Planck scale violations of special relativity

“…Active Galactic Nuclei (AGN) will allow. This is of particular interest in the light of current experimental efforts to build X-ray polarimeters [14,15,16,17,18,19].…”