Niels Lund Danish National Space Center

1. The GRI Multilayer Telescope and Laue Lens - performance calculations Niels Lund Danish National Space Center

2. Multilayer vs Coded Mask for GRI • The concept of GRI is already well established within ESA • GRI is expected to be the mission by which Europe should make a major step forward in gamma-ray astronomy. • The GRI concept as it emerged from the Coimbra meeting can hardly be said to represent such a major step. The choice of the coded mask as the hard X-ray monitor reduces the available mass for the Laue Lens to the point where the gamma-ray part of the mission is severely constrained. • We emphasize that the technological readiness of the multilayer telescope of the size required for GRI is far ahead of the technological readiness of a 10 m2 Laue Lens. • We also amphasize that the multilayer offers much superior sensitivity in the energy range between a few keV and 250 keV compared to the coded mask. • We therefore strongly recommend that the multilayer telescope is considered as the baseline for GRI. GRI design meeting, London | June 12 2006 | page 2

3. ESA preparations for ML-developments for GRI/XEUS The Industrial Policy Committee is already now preparing or the next multilayer development contract for XEUS and GRI. The contract (600 kEuro) will come in competitive tender in 2007. GRI design meeting, London | June 12 2006 | page 3

4. 75 m focal length telescope. Several multilayer telescope configurations are under study. The telescope properties depends to the choice of focal length for the Laue lens. Si/W multilayer. F=75 m. W=41 kg. Ø=50 cm GRI design meeting, London | June 12 2006 | page 4

5. 100 m focal length telescope A focal length in excess of 100 m will allow the multilayer telescope to cover the energy range between 200 and 300 keV. SiC/W multilayer. F=100 m. W=65 kg. Ø=60 cm GRI design meeting, London | June 12 2006 | page 5

6. New Laue-lens performance calculations*) New developments since Coimbra. In my opinion we must emphasize that GRI is a gamma-ray mission. The sensitivity must be maximized for both continuum and lines above 500 keV. If we have to choose between sensitivity below and above 400 keV I strongly recommend that we go for the high energy range. This is where we will be unique. Other multilayer missions will easily beat the Laue lens below 300 keV. To allow easier comparisons of performance predictions I have adopted the same mini-mum crystal thickness (2 mm) as used by Nicolas. *) A cross check of the algorithms used within the GRI consortium for reflectivity and absorbtion calculations have revealed an error in my code which have led to an overestimate (of about 25 %) of the reflectivity for all chemical elements. This error has now been corrected. GRI design meeting, London | June 12 2006 | page 6

7. New lens calculations II Comparison of different Laue-lens options 361 kg 345 kg GRI : Laue lens (160-520 keV and 800-900 keV) 289 kg GRI design meeting, London | June 12 2006 | page 7

8. GRI design meeting, London | June 12 2006 | page 8

9. Lens Spacecraft Configuration Options: 1 • ”MAX”-configuration - limited lens area (10.5 m2) - high-E response limited by Rinner - spacecraft constrained (1 m diameter ?) • Single, rigid deployed disk + uncritical alignment after deployment + spacecraft unconstrained (3.8 m diameter) - limited lens area (11.5 m2) • Vertical mounted, rigid panel + large lens area (25 m2) + no deployment + spacecraft unconstrained (3.8 m diameter) • ”Flower” deployed lens + large lens area (40 m2 ?) -- very critical alignment after deployment - high-E response limited by Rinner - spacecraft constrained (1 m diameter ?) 2 3 4 GRI design meeting, London | June 12 2006 | page 9

10. Illumination of the focal spot • The focal spot from a Laue lens is a diffuse patch of light. It will be an important task to decide what fraction of the collected photons we should use and what part we better leave out because they will be associated with too much background. • The plot shows the effective area of one particular lens design contributing within circles 2, 4 , 6, 8 and 10 cm in diameter GRI design meeting, London | June 12 2006 | page 10