Dr. Julian Walker Profile

Dr. Julian Walker

at Pennsylvania State Univ

SPIE Involvement:

Author

Publications (6)

SPIE Journal Paper | 23 March 2019 Open Access

Thickness distribution of sputtered films on curved substrates for adjustable x-ray optics

Nathan Bishop, Julian Walker, Casey DeRoo, Tianning Liu, Mohit Tendulkar, Vincenzo Cotroneo, Edward Hertz, Vladimir Kradinov, Eric Schwartz, Paul Reid, Thomas Jackson, Susan Trolier-McKinstry

JATIS, Vol. 5, Issue 02, 021005, (March 2019) https://doi.org/10.1117/12.10.1117/1.JATIS.5.2.021005

KEYWORDS: Mirrors, X-ray optics, Sputter deposition, Finite element methods, Glasses, Ferroelectric materials, X-rays, Actuators, Prototyping, Mathematical modeling

Read Abstract +

Piezoelectric adjustable x-ray optics use magnetron sputtered thin film coatings on both sides of a thin curved glass substrate. To produce an optic suitable for a mission requiring high-angular resolution like “Lynx,” the integrated stresses (stress×thickness) of films on both sides of the optic must be approximately equal. Thus, understanding how sputtered film thickness distributions change for convex and concave curved substrates is necessary. To address this, thickness distributions of piezoelectric Pb0.995(Zr0.52Ti0.48)0.99Nb0.01O3 films are studied on flat, convex, and concave cylindrical substrates with a 220-mm radius of curvature. A mathematical model of the film thickness distribution is derived based on the geometric properties of the sputter tool and the substrate, and film thicknesses deposited with a commercially available sputtering tool are measured with spectroscopic ellipsometry. Experiment and modeled results for flat and convex curved substrates demonstrate good agreement, with average relative thickness distribution difference of 0.19% and −0.10% respectively, and a higher average difference of 1.4% for concave substrates. The calculated relative thickness distributions are applied to the convex and concave sides of a finite-element analysis (FEA) model of an adjustable x-ray optic prototype. The FEA model shows that, left uncorrected, the relative film thickness variation will yield an optic with an optical performance of 2.6 arc sec half power diameter (HPD) at 1 keV. However, the mirror figure can be corrected to diffraction-limited performance (0.3 arc sec HPD) using the piezoelectric adjusters, suggesting that the tolerances for applying a balanced integrated stress on both sides of a mirror are alleviated for adjustable x-ray optics as compared to traditional static x-ray mirrors. Furthermore, the piezoelectric adjusters will also allow changes in mirror figure over the telescope lifetime due to drift in the stress states of the x-ray surfaces to be corrected on orbit.

DOWNLOAD PAPER

Proceedings Article | 26 October 2018 Presentation + Paper

Progress in development of adjustable optics for x-ray astronomy

Vincenzo Cotroneo, Casey DeRoo, Thomas Jackson, Vladimir Kradinov, Tianning Liu, Vanessa Marquez, Paul Reid, Daniel Schwartz, Eric Schwartz, Mohit Tendulkar, Susan Trolier-McKinstry, Julian Walker

Proceedings Volume 10761, 1076109 (2018) https://doi.org/10.1117/12.2323283

KEYWORDS: Mirrors, Optics manufacturing, Ferroelectric materials, X-ray optics, Glasses, Prototyping, X-ray telescopes, Actuators, Crystals, Electronics

Read Abstract +

SPIE Journal Paper | 19 March 2018

Deterministic figure correction of piezoelectrically adjustable slumped glass optics

Casey DeRoo, Ryan Allured, Vincenzo Cotroneo, Edward Hertz, Vanessa Marquez, Paul Reid, Eric Schwartz, Alexey Vikhlinin, Susan Trolier-McKinstry, Julian Walker, Thomas Jackson, Tianning Liu, Mohit Tendulkar

JATIS, Vol. 4, Issue 01, 019004, (March 2018) https://doi.org/10.1117/12.10.1117/1.JATIS.4.1.019004

KEYWORDS: Mirrors, Iterated function systems, X-ray optics, Metrology, Glasses, Composites, Optics manufacturing, Finite element methods, Ferroelectric materials, X-rays

Read Abstract +

Proceedings Article | 19 September 2017 Presentation + Paper

Lynx Mission concept status

Jessica Gaskin, Ryan Allured, Simon Bandler, Stefano Basso, Marshall Bautz, Michael Baysinger, Michael Biskach, Tyrone Boswell, Peter Capizzo, Kai-Wing Chan, Marta Civitani, Lester Cohen, Vincenzo Cotroneo, Jacqueline Davis, Casey DeRoo, Michael DiPirro, Alexandra Dominguez, Leo Fabisinski, Abraham Falcone, Enectali Figueroa-Feliciano, Jay Garcia, Karen Gelmis, Ralf Heilmann, Randall Hopkins, Thomas Jackson, Kiranmayee Kilaru, Ralph Kraft, Tianning Liu, Ryan McClelland, Randy McEntaffer, Kevin McCarley, John Mulqueen, Feryal Özel, Giovanni Pareschi, Paul Reid, Raul Riveros, Mitchell Rodriguez, Justin Rowe, Timo Saha, Mark Schattenburg, Andrew Schnell, Daniel Schwartz, Peter Solly, Robert Suggs, Steven Sutherlin, Douglas Swartz, Susan Trolier-McKinstry, James Tutt, Alexey Vikhlinin, Julian Walker, Wonsik Yoon, William Zhang

Proceedings Volume 10397, 103970S (2017) https://doi.org/10.1117/12.2273911

KEYWORDS: X-rays, Astrophysics, Galactic astronomy, Environmental sensing, Stars, Planetary systems, X-ray optics, Observatories

Read Abstract +

Proceedings Article | 29 August 2017 Presentation + Paper

Design and fabrication of adjustable x-ray optics using piezoelectric thin films

J. Walker, T. Liu, M. Tendulkar, D. Burrows, C. DeRoo, R. Allured, E. Hertz, V. Cotroneo, P. Reid, E. Schwartz, T. Jackson, S. Trolier-McKinstry

Proceedings Volume 10399, 103991K (2017) https://doi.org/10.1117/12.2275351

KEYWORDS: Mirrors, Thin films, X-ray optics, Glasses, Ferroelectric materials, X-rays, Electrodes, Modulation, Coating, Radio optics

Read Abstract +

Proceedings Article | 29 August 2017 Presentation + Paper

Deterministic figure correction of piezoelectrically adjustable slumped glass optics

Proceedings Volume 10399, 103991M (2017) https://doi.org/10.1117/12.2275210

KEYWORDS: X-ray optics, Glasses, X-rays, Mirrors, Thin films, Actuators, Thermography, Optical fabrication, Metrology, Testing and analysis

Read Abstract +

Showing 5 of 6 publications

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Keywords/Phrases

Search In:

Publication Years