Paul B. Reid Harvard-Smithsonian Center for Astrophysics HEAD2013 April 8, 2013 Paul B. Reid...

Paul B. Reid

Harvard-Smithsonian Center for Astrophysics

HEAD2013 April 8, 2013

The Future of X-ray Optics

pbr 04/08/2013 2 HEAD2013 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 m2

– Large area drives weight – lightweight– < 200 – 400 kg/m2 for reasonable cost and launch vehicle options

• Chandra HRMA ~ 1600kg 20,000kg/m2


Imaging resolution vs. collecting area

Area (square meters)

Res

olut

ion

(arc

sec

)

Chandra

XMM-Newton

N-Cal/AXSIO

Slope ~ 2

Slope ~ 1

Chandra

XMM-Newton N-Cal/AXSIO/Athena+


Res

olut

ion

(~H

PD, a

rc s

ec)

PromisedLand




Chandra


Res

olut

ion

(~H

PD, a

rc s

ec)

PromisedLand



Chandra



Res

olut

ion

(~H

PD, a

rc s

ec)

PromisedLand

Mass α tArea α Mass

Distortion α 1/t2

Resol. α Distortionso

Resol. α Area2

Chandra distortionbudget = 0.16”



Chandra

XMM-Newton


Res

olut

ion

(~H

PD, a

rc s

ec)

PromisedLand


Distortion α 1/t2


Resol. α Area2


N-Cal/AXSIO/Athena+



Chandra



Res

olut

ion

(~H

PD, a

rc s

ec)

PromisedLand


Distortion α 1/t2


Resol. α Area2



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


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.


Adjustable X-ray Optics

X-ray reflective coating Glass substrate

Top and bottomelectrodes

1-2um Piezo layer

SiO2layer

Integrated on-cell straingauges for remote feedbackand 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.



X-ray reflective coating Glass substrate

Top and bottomelectrodes

1-2um Piezo layer

ZnOlayer

Integrated piezo on-cell controlelectronics for row-column

addressing

Integrated on-cell straingauges for remote feedbackand 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.



Cylindrical 10 x 10 cm2 mirrors made.

Models and measurements agree to 11 nm, rms.Metrology noise ~ 20 nm, rms.Final correction requirement ~ 4 nm, rms


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


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


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. - 100 – 1 million km - LISA-like mission •Very large focal planes for small FoV.

•Narrow energy bandwidth at high resolution: ΔE/E ~ 0.05


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 .


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 – 123.26 Gorenstein – diffractive/refractive – 123.27 Zhang – Si – 123.28 Reid - Adjustable– 123.29 Vikhlinin – SMART-X– 123.30 Schwartz – Wolter-I vs Wolter-Schwarschild for SMART-X

Go to PCOS X-ray SAG meeting, Friday 9 – 5:30

Paul B. Reid Harvard-Smithsonian Center for Astrophysics HEAD2013 April 8, 2013 Paul B. Reid...

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