X-ray SIG Session (APS April Meeting, 2020) William W. Zhang (NASA GSFC)

Silicon Meta-Shell X-ray Optics for Astronomy: High Resolution, Light Weight, and Low Cost

William W. Zhang

NASA Goddard Space Flight Center

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X-ray SIG Session (APS April Meeting, 2020) William W. Zhang (NASA GSFC) 2

Next Generation X-ray Optics (NGXO) Team

K.D. Allgood1, M.P. Biskach1, K.W. Chan2, T.A. DeVita1,M. Hlinka1, C.D. Hovis, J.D. Kearney1, J.R. Mazzarella1, R.S. McClelland, A. Numata1, R.E. Riveros2, T.T. Saha,

P.M. Solly1, and W.W. ZhangNASA Goddard Space Flight Center

1 also Stinger Ghaffarian Technologies, Inc. 2 also University of Maryland, Baltimore County

Developing X-ray optics technology of everhigher resolution, lighter weight, and lower cost.

X-ray SIG Session (APS April Meeting, 2020) William W. Zhang (NASA GSFC)

Lynx Mirror Assembly in Context

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Chandra (1999) NuSTAR (2012) Lynx (~2036)

1.2m diameter0.5” PSF19 m2 mirror area~1,200 kg mass

0.4m Diameter58” PSF44 m2 mirror area~40 kg mass

3.0m diameter0.5” PSF372 m2 mirror area~1,200 kg mass

X-ray SIG Session (APS April Meeting, 2020) William W. Zhang (NASA GSFC)

~0.01 kg ea. ~1.5 kg ea. ~80 kg ea. ~1,000 kg

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37,492Segments

611Modules

12Meta-shells

1Assembly

Major Steps to Build the Lynx Mirror Assembly

Technology Development Engineering Development

X-ray SIG Session (APS April Meeting, 2020) William W. Zhang (NASA GSFC)

Mirror Module

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Primary Mirror Segment:100 mm by 100 mm by 0.5 mm

Secondary Mirror Segment:100 mm by 100 mm by 0.5 mm

Central Plate:200 mm by 90 mm by 10 mm

Materials (relative proportions):• Silicon: 10,000,000. • Coatings (Cr, Ir, SiO2): ~1.• Epoxy: ~1.

Key Characteristics:• Athermal:• Easy to test on ground.• Easy thermal control on

orbit.• Verifiable on ground:• Science performance. • Spaceflight environment.

X-ray SIG Session (APS April Meeting, 2020) William W. Zhang (NASA GSFC)

Mirror Segment

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Front

Back

Ribs

Rib Thickness MirrorThickness

Optical Axis Direction

Two Precision Parts of a Mirror Segment:• Front surface: < 10 nm deviation from prescription.• Rib thickness: < 20 nm deviation from prescription.

X-ray SIG Session (APS April Meeting, 2020) William W. Zhang (NASA GSFC)

Process of Building a Module

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Interim Plate

Central Plate

X-ray SIG Session (APS April Meeting, 2020) William W. Zhang (NASA GSFC)

Image Quality Improvement Over Time

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0.1

1

10

100

Jul-98

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Imag

e Qu

ality

(acr

sceo

nds H

PD)

Time (Month-YY)

Full Illumination (4.5 keV) X-Ray Test Results over Time

One pair slumped glass mirrors on mattress temporary mount

One pair of glass mirrors edge bonded

One pair of Si mirrors 4P bonded

Three pairs of glass mirrors edge bonded

One pair of epoxy-replicated glass

One pair of Si mirrors 4P bondedOne pair of Si mirrors 4P bondedOne pair of Si mirrors 4P bondedOne pair of Si mirrors 4P bonded

One pair of Si mirrors 4P bonded

0.83” HPD4.5 keV X-rays

X-ray SIG Session (APS April Meeting, 2020) William W. Zhang (NASA GSFC)

Technology Status• We have devised and empirically validated an approach for

building high-resolution, lightweight X-ray optics. This approach has four basic technical elements– Substrate fabrication,

– Coating,

– Alignment, and

– Bonding

• We are in the process of building and testing mirror modules of ever higher level of integration to advance the technical readiness level.– More mirror segments,

– More stringent spaceflight environment requirements,

– More efficient process, in terms of both production time and cost.9

X-ray SIG Session (APS April Meeting, 2020) William W. Zhang (NASA GSFC)

Major Milestones (COVID-19 may force change to this timeline)

• TRL-3: Build and test 1-pair modules continually.– Reach and go beyond Lynx’s 0.5” HPD requirement, and

– Achieve structural robustness for spaceflight.

• TRL-4: Build and test 3-pair modules by March 2021.– Achieve images better than 0.5” HPD & structural robustness.

• TRL-5: Build and test many-pair modules by September 2023. – Meet 0.5” HPD image requirement, and

– Pass environmental tests: vibration, acoustic, thermal-vacuum, and shock.

• TRL-6: Build and test several Lynx modules by September 2027.– Ensure that Lynx mirror can be built on schedule and budget, and

– Meet all performance and spaceflight environment requirements.

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X-ray SIG Session (APS April Meeting, 2020) William W. Zhang (NASA GSFC)

Future Missions Requiring This Technology• Suborbital mission– OGRE (Off-plane Gratings Rocket Experiment),

PI: R. McEntaffer (PSU).• Explorer-class missions– STAR-X (Survey and Time-domain Astrophysical Research Explorer),

PI: W. Zhang (GSFC).– FORCE (Focusing on Relativistic universe and Cosmic Evolution),

PI: K. Mori (Miyazawa Univ., Japan).• Probe-class missions– AXIS (Advanced X-ray Imaging Satellite), PI: R. Mushotzky (Univ. of MD).– TAP (Transient Astrophysics Probe), PI: J. Camp (GSFC).– HEX-P (High Energy X-ray Probe), PI: F. Harrison (Caltech).

• Flagship mission– Lynx (formerly known as the X-ray Surveyor),

Study Scientist: J. Gaskin (MSFC).

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X-ray SIG Session (APS April Meeting, 2020) William W. Zhang (NASA GSFC)

Acknowledgements

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This work has been supported by NASA through

GSFC/IRAD, ROSES/APRA, and ROSES/SAT.