May 7, 2003University of Colorado The Off-Plane Option for the Reflection Grating Spectrometer Randy McEntaffer Webster Cash, Steve Osterman, Ann Shipley, Brian Gleeson University of Colorado

May 7, 2003University of Colorado Off-plane Mount In-plane Mount

May 7, 2003University of Colorado Radial Groove Gratings

May 7, 2003University of Colorado Grating Modules R450.0mm Inner Mirrors High Energy R151.4mm Off-plane Grating Module Locations on Envelope R770.0mm Outer Mirrors Grating Area

May 7, 2003University of Colorado Off-plane Tradeoffs Higher Throughput Higher Resolution Better Packing Geometry Looser Alignment Tolerances CON Higher Groove Density PRO

May 7, 2003University of Colorado Raytracing – Arc of Diffraction

May 7, 2003University of Colorado Raytrace – 35 & Å

May 7, 2003University of Colorado Resolution Energy (keV) ,000 E/  E Calorimeter – 2eV I-P n=1 I-P n=2 Primary Response ASSUMPTIONS: 5500g/mm 15” SXT 2” gratings 2” alignment <35% Response Extended CCD Mission Requirement Mission Goal O-P n=1 O-P n=2 O-P n=3 Mission Requirement

May 7, 2003University of Colorado Effective Area Energy (keV) cm 2 ASSUMPTIONS: Coverage 40% of outer envelope Off-Plane Groove Efficiency 80% of theoretical 85% Structure Transmission CCD thin Al filter only off-plane baseline  Goal Mission Requirement

May 7, 2003University of Colorado Off-Plane Program ● Optical Design – Projected Performance – Looks Attractive ● Engineering Requirements – Has Significant Advantages ● Grating Suppliers – Several Possible Suppliers – Holographic Techniques Look Better Than Mechanical ● Grating Efficiency – Test Gratings at Colorado Now ● Resolution Demonstration – Scheduled this Summer at Colorado ● TRL Development – Plan to Achieve TRL 6

May 7, 2003University of Colorado Grating Test Facility at CU Used for COS and FUSE

May 7, 2003University of Colorado Grating #1 Jobin-Yvon, radial grooves, 4246 g/mm, γ = 2º Absolute Efficiency: strongest order = 13% Sum orders = 29%

May 7, 2003University of Colorado Grating #2 Jobin-Yvon, radial grooves, 4246 g/mm, blazed γ = 2º Absolute Efficiency: strongest order = 6.4% Sum orders = 11% 30% (w/ scatter)

May 7, 2003University of Colorado Grating #3

May 7, 2003University of Colorado Grating #3 ● MIT, parallel rulings, 5000 g/mm, blazed 7º Groove eff. = Abs. eff./Reflectivity (a.k.a. Relative eff.)

May 7, 2003University of Colorado Conclusion ● Off-plane can significantly improve performance of Constellation-X RGS ● Gratings can be built to required efficiency and scatter specifications ● Resolution tests to be conducted this summer