Paul B. Reid Harvard-Smithsonian Center for Astrophysics HEAD2013 April 8, 2013 Paul B. Reid Harvard-Smithsonian Center for Astrophysics HEAD2013 April 8, 2013 The Future of X-ray Optics

pbr 04/08/2013 2HEAD2013 Monterrey, CA

pbr 04/08/2013 3HEAD2013 Monterrey, CA

pbr 04/08/2013 4HEAD2013 Monterrey, CA Where do we need/want to be in 10 – 20 years?  Science goals drive what’s necessary  Imaging – high resolution –Chandra or better: 0.5 arc sec  AXSIO / Athena+ / N-Cal / SMART-X Collecting area – > 1 m 2 –Large area drives weight – lightweight –< 200 – 400 kg/m 2 for reasonable cost and launch vehicle options Chandra HRMA ~ 1600kg  20,000kg/m 2

pbr 04/08/2013 5HEAD2013 Monterrey, CA Imaging resolution vs. collecting area Area (square meters) Resolution (arc sec) Chandra XMM-Newton N-Cal/AXSIO Slope ~ 2 Slope ~ 1 Chandra XMM-Newton N-Cal/AXSIO/ Athena+ Area (square meters) Resolution (~HPD, arc sec) Promised Land

pbr 04/08/2013 6HEAD2013 Monterrey, CA Imaging resolution vs. collecting area Area (square meters) Chandra XMM-Newton N-Cal/AXSIO/ Athena+ Resolution (~HPD, arc sec) Promised Land

pbr 04/08/2013 7HEAD2013 Monterrey, CA Imaging resolution vs. collecting area Chandra XMM-Newton N-Cal/AXSIO/ Athena+ Area (square meters) Resolution (~HPD, arc sec) Promised Land Mass α t Area α Mass Distortion α 1/t 2 Resol. α Distortion so Resol. α Area 2 Chandra distortion budget = 0.16”

pbr 04/08/2013 8HEAD2013 Monterrey, CA Imaging resolution vs. collecting area Chandra XMM-Newton Area (square meters) Resolution (~HPD, arc sec) Promised Land Mass α t Area α Mass Distortion α 1/t 2 Resol. α Distortion so Resol. α Area 2 Chandra distortion budget = 0.16” N-Cal/AXSIO/ Athena+

pbr 04/08/2013 9HEAD2013 Monterrey, CA Imaging resolution vs. collecting area Chandra XMM-Newton N-Cal/AXSIO/ Athena+ Area (square meters) Resolution (~HPD, arc sec) Promised Land Mass α t Area α Mass Distortion α 1/t 2 Resol. α Distortion so Resol. α Area 2 Chandra distortion budget = 0.16”

pbr 04/08/ HEAD2013 Monterrey, CA The limiting factors:  Non-deterministic assembly strains limit resolution for thin shells –Chandra budget scaled for 1.5 mm thick shell ~ 15 arc sec RMSD  Don’t want to have to fabricate many mandrels to sub-arc sec accuracy –Chandra mirror surface area ~ 20 sq. meters –2 sq –m grazing incidence telescope ~ 400 – 500 sq-m surface area

pbr 04/08/ HEAD2013 Monterrey, CA Need to change paradigm regarding stiffness and resolution  Break the relationships between: –Thickness and resolution, or non-deterministic loads and resolution Assembly loads Thermal effects –Mirror polishing and resolution  Fortunately, some developmental technologies may do this –Adjustable grazing incidence optics (SAO + PSU + MSFC + JHU) –Differential deposition (MSFC, RXO), Magneto-strictive (NU) –Si-based optics (GSFC, MSFC) –Refractive/diffractive optics ( ? )  Precision low-force alignment and mounting (SAO, GSFC, MSFC) –Aiming at a couple of arc sec distortions, not 0.1  Possibility of combining approaches that separately might not work well enough, but together may be good enough.

pbr 04/08/ HEAD2013 Monterrey, CA Adjustable X-ray Optics X-ray reflective coatingGlass substrate Top and bottom electrodes 1-2um Piezo layer SiO2 layer Integrated on-cell strain gauges for remote feedback and on-orbit adjustment. Independently addressable piezo cells. Voltage across top electrode and bottom electrode produces strain in piezo in plane of mirror surface, resulting in localized bending. Optimizing the piezo voltages after mirror mounting enables correction of fabrication errors and mounting-induced deformations. Calibrated on-cell strain gauges provide feedback on cell strain/deformation, enable mirror figure corrections to be made on-orbit.

pbr 04/08/ HEAD2013 Monterrey, CA Adjustable X-ray Optics X-ray reflective coatingGlass substrate Top and bottom electrodes 1-2um Piezo layer ZnO layer Integrated piezo on-cell control electronics for row-column addressing Integrated on-cell strain gauges for remote feedback and on-orbit adjustment. Independently addressable piezo cells. Voltage across top electrode and bottom electrode produces strain in piezo in plane of mirror surface, resulting in localized bending. Optimizing the piezo voltages after mirror mounting enables correction of fabrication errors and mounting-induced deformations. Calibrated on-cell strain gauges provide feedback on cell strain/deformation, enable mirror figure corrections to be made on-orbit.

pbr 04/08/ HEAD2013 Monterrey, CA Adjustable X-ray Optics Cylindrical 10 x 10 cm 2 mirrors made. Models and measurements agree to 11 nm, rms. Metrology noise ~ 20 nm, rms. Final correction requirement ~ 4 nm, rms

pbr 04/08/ HEAD2013 Monterrey, CA Differential Deposition Differential deposition – inverse of computer controlled polishing. Image courtesy of B. Ramsey, NASA MSFC W.W. Zhang, private communication Can correct for mounting distortions but may be less time efficient Cannot correct on-orbit Can be used in combo with adjustable approach

pbr 04/08/ HEAD2013 Monterrey, CA Silicon Optics W.W. Zhang, private communication Figure low stress high quality Si wafer Machine/slice away back material Stress relieve Cannot correct post-mounting or on-orbit Can be used in combo with diff. deposition and/or adjustable approaches Image courtesy of W.W. Zhang, NASA GSFC

pbr 04/08/ HEAD2013 Monterrey, CA Diffractive-refractive X-ray lenses  van Speybroeck (2000), and independently, Skinner (2001): combine diffractive and refractive elements of opposite power, optimize to reduce chromatic aberration = expand energy bandwidth. –Low Z material G.F. Skinner, A.&A, 383, 352 (2002) Very large collecting area feasible. - Easy to imagine 1 – 4 sq meters Resolution ~ 10 micro arc sec. Very long focal lengths – 1 million km - LISA-like mission Very large focal planes for small FoV. Narrow energy bandwidth at high resolution: ΔE/E ~ 0.05

pbr 04/08/ HEAD2013 Monterrey, CA The future?  Thin, lightweight mirror technologies that break the thinness/resolution and mandrel/resolution couplings.  Major Advantage: Correct mounting related distortions –Adjustable optics –Differential deposition –Magneto-strictive optics  Major Advantage: Correct on-orbit (thermal, G-release, …) –Adjustable optics  Amenable to implement in combination with other technologies –Differential deposition –Silicon optics –Adjustable optics, magneto-strictive optics  Refractive/diffractive: bandwidth, focal length, focal plane – probably a long way off.

pbr 04/08/ HEAD2013 Monterrey, CA Summary/Closing  Several prospective technologies being actively worked and currently funded via APRAs, internal funds, etc. –No long term funding for long term development!  Message to NASA: “If you want to find a prince, you have to kiss a lot of frogs!”  Several technology posters – Gorenstein – diffractive/refractive – Zhang – Si – Reid - Adjustable – Vikhlinin – SMART-X – Schwartz – Wolter-I vs Wolter-Schwarschild for SMART-X  Go to PCOS X-ray SAG meeting, Friday 9 – 5:30