Silicon Meta-Shell Optics for AXIS: High-Resolution, Light-Weight, and Low-Cost

Transcription

1 Silicon Meta-Shell Optics for AXIS: High-Resolution, Light-Weight, and Low-Cost William W. Zhang NASA Goddard Space Flight Center

2 Next Generation X-ray Optics (NGXO) Team K.D. Allgood 1, M.P. Biskach 1, J. Bonafede 1, K.W. Chan 2, M. Hlinka 1, J.D. Kearney 1, L.D. Kolos, J.R. Mazzarella 1, G. Matthews 3, R.S. McClelland, H. Mori 2, A. Numata 1, T. Okajima, L.G. Olsen, R.E. Riveros 2, T.T. Saha, P.M. Solly 1, and W.W. Zhang NASA Goddard Space Flight Center 1 also Stinger Ghaffarian Technologies, Inc. 2 also University of Maryland, Baltimore County 3 also ATA Aerospace, LLC Work supported & funded by NASA through GSFC/IRAD, ROSES/APRA, and ROSES/SAT. 2

3 A Brief History of the NGXO Team 2001: Established to develop X-ray optics for Con-X (IXO) : Funded by NASA s Con-X and IXO project offices present: funded by NASA through GSFC/IRAD, ROSES/APRA and ROSES/SAT : Built three mirror assemblies for NuSTAR. Teamed with Columbia Univ., DTU, and LLNL. Made 12,000, coated, and assembled 8,000 slumped glass mirror segments : Advanced glass slumping technology to enable ~10 X-ray telescopes. Built and tested modules and achieved ~7 HPD. Gave up glass slumping for several reasons Present: Developing polished silicon X-ray optics to meet three-fold requirement of future missions, including Lynx, AXIS, TAP, HEX-P, FORCE, STAR-X, & OGRE. High angular resolution, Large effective area, and Low production cost. NuSTAR Mirror Factory at GSFC NuSTAR Mirror Assembly 3

4 NGXO S Objective Develop an X-ray mirror technology that has the following characteristics compared to those of Chandra s: Higher Resolution Reaching ~0.3 (2 5 years). Reaching diffraction limit at 1 kev ~0.1 (5 10 years). Lighter Weight 30X lighter per unit effective are. Lower Cost 30X cheaper per unit effective area. 4

5 Conception of AXIS Mirror Assembly 0.3 m ID Secondaries 0.5 m Primaries Stray-light baffles Flexures Thermal Baffles Mounting flange X-rays 1.7 m OD 16,568 mirrors à 6 meta-shells à 1 assembly Mass: ~454 kg Heater Power: ~300 W Eff. Area@1keV: 0.77 m 2 with traditional Ir coating 5

6 Comparison of AXIS & Chandra Mirrors AXIS Chandra Comment Focal length 9,000 mm 10,000 mm Shorter focal length Outer (Inner) diameter 1,700 (300) mm 1,250 (650) mm Larger OD, Smaller ID Mass (kg) 450 kg 1,500 kg 3X lighter Mirror surface area (m 2 ) 168 m 2 19 m 2 8X mirror area Eff. Area@0.25; 5; 8 kev 8,180; 2,204; 908 cm 2 800; 400; 100 cm 2 PSF (0, 12 off-axis) 0.3 (0.4 ) 0.5 (16 ) Cost (full assembly) ~$170M (2020) 10X eff. area Better on-axis PSF 30X better off-axis PSF $1,423M (2020) 8X less expensive Cost per mirror area ($M/m 2 ) ~$1 $75 70X less expensive 6

7 Key Ingredients of Our Approach Precision polishing à good PSF The way to make the best optics, since Galileo. Tremendous advancement since the 1990s when Chandra was made. Mono-crystalline silicon à thin (or lightweight) mirrors Free of internal stress. Abundantly and inexpensively available. Nanofabrication à accurate & fast integration Fabrication of alignment and integration structures. Lowest possible costs for making precision structures. Mass production à low cost Industry standard equipment for making/processing wafers. Eliminate/minimize use of custom-designed and built equipment. Keep it simple à reliability. Simple to engineer, build, and test. 7

8 The Meta-Shell Approach Principle of the Approach Implementation of the Approach 8

9 Mono-crystalline Silicon Block Mirror Fabrication Process 15 hours of labor 1 week of time Finished Mirror Substrate Rough-Ground Block Block to be Recycled 9

10 Mirror Coating Process Bare Silicon Mirror 2 hours of labor 2 days of time Concave Side: Cr + Ir Convex Side: SiO 2 Coated Mirror Work done in collaboration with MIT: Y. Yao, B. Chalifoux, & M. L. Schattenburg. 10

11 Mirror Alignment & Bonding Four-point kinematic support Locations optimized to minimize gravity distortion and gravity release error. Use nanofabrication technology to make alignment combs ( scaffold ) Deterministic and efficient. Highly amendable to robotic operations. Use acoustics to settle the mirror Overcomes static friction and relaxes the mirror. X Gravity Y Circumferential Z Optical Axis 11

12 Entire Process Validated by X-ray Testing Secondary Mirror Primary Mirror Silicon Plate Two uncoated mono-crystalline silicon mirrors aligned and bonded on a silicon platform Full illumination with Ti-K X-rays (4.5 kev) Effective Area at Ti-K (cm 2 ): predicted, measured, agreeing within 2.3%. Acknowledgement: Thanks to Vadim Burwitz and his team at Panther who performed this measurement. 12

13 NGXO Progress over the Years NGXO Full Illumination (4.5 kev) X-Ray Test Results over Time Image Quality (acrsceonds HPD) 50 5 One pair of epoxy-replicated glass mirrors on 4 point temporary mount Slumped Glass Mirrors Polished Silicon Mirrors One pair slumped glass mirrors on mattress temporary mount One pair of Si mirrors 4P bonded bonded One pair of Si mirrors 4P bonded One pair of Si mirrors 4P bonded One pair of glass mirrors edge bonded Three pairs of glass mirrors edge bonded? 0.5 Jul-98 Apr-01 Jan-04 Oct-06 Jul-09 Apr-12 Dec-14 Sep-17 Jun-20 Time (Month-YY) 13

14 Single-Pair Modules TRL-4 In Pursuit of TRLs: Three Prongs Multiple-Pair Modules TRL-5 Meta-Shells TRL-6 Objectives: 1. Develop fabrication and coating processes. 2. Develop alignment & bonding procedures. Objectives: 1. Develop co-alignment and bonding processes. 2. Conduct environmental tests: vibration, thermal vacuum, and acoustic. Objectives: 1. Develop meta-shell production process 2. Validate mass production. 3. Validate schedule and cost estimates. 14

15 In Pursuit of TRLs: What s Happened and What s to Happen 10 TRL-4 (Single-pair) TRL-5 (Multi-Pair) TRL-6 (Meta-shell) Athena Requirement Image HPD (arc-second) 1 Done On-going AXIS Requirement 0.1 Dec-16 Dec-17 Dec-18 Dec-19 Dec-20 Dec-21 Dec-22 Dec-23 Dec-24 Dec-25 Time (Month-Year) 15

16 Summary The silicon meta-shell technology has the potential to meet the threefold requirements of future X-ray missions: High resolution, high throughput, and low cost. Three more years are needed to realize/demonstrate these potentials for Lynx, AXIS, and other missions that are currently on the drawing board. It is highly likely that we will be able to demonstrate its readiness for AXIS and Lynx by As the technology matures, two things will come as a matter of course: Performance will be more optimized, and Cost and schedule risks will go down. We are teaming up with others to develop advanced distortion-free coating to maximize effective area: Mark Schattenburg s group at MIT, and David Windt at Reflective X-ray Optics LLC 16

17 Silicon Meta-Shell Optics (SMO) Selected for Lynx DRM Three potential mirror technologies for Lynx Adjustable Optics (AO) by SAO and PSU, Full Shell Optics (FO) by OAB and MSFC, and Silicon Meta-shell Optics (SMO) by GSFC. The Lynx Mirror Architecture Trade (LMAT), consisting of more than 40 people with expertise in x-ray optics and other relevant areas, after 6 months of data gathering, evaluation and discussion, has recommended SMO to be the baseline for Lynx Design Reference Mission (DRM), FO and AO as viable alternates. 17