Karry Wong

Karry Wong

Visiting Researcher at Meta Reality Labs | ex-LLNL Postdoc | Geometry Enthusiast

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portfolio

publications

Application of mean curvature flow for surface parametrizations

Published in Proceedings of the John H. Barrett Memorial Lectures held at the University of Tennessee, 2018

This is an expository article describing the conformalized mean curvature flow, originally introduced by Kazhdan, Solomon, and Ben-Chen. We are interested in applying mean curvature flow to surface parametrizations. We discuss our own implementation of their algorithm and some limitations.

Recommended citation: K. Wong, Application of mean curvature flow for surface parametrization, Proceedings of the John H. Barrett Memorial Lectures held at the University of Tennessee, (May 29-June 1, 2018).

Conformal Parametrization of Surfaces of Genus Zero and 3D Reconstruction of Nuclear Fusion Hotspots

Published in University of California, Davis, 2021

The first part of this thesis is to study a modified version of mean curvature flow, the “conformalized mean curvature flow” (cMCF), developed by Kazhdan, Solomon, and Ben-Chen. The cMCF is a conformal mapping algorithm but it runs into numerical issues when it is applied on meshes with protrusions. We improve the cMCF with an initialization step which first maps the initial mesh onto a sphere. This initialization step is shown to improve the performance of cMCF such that it can be applied on meshes with long protrusions. More importantly, we give a new algorithm named “Sphericalized cMCF” to construct a homotopy from a degree one map to a homeomorphism from a unit sphere onto a unit sphere. The second part of this thesis focuses on my work in the limited view computer tomography at the Lawrence Livermore National Laboratory during a one year internship. This project is related to the inertial confinement fusion (ICF) experiments performed at the National Ignition Facility (NIF). Our work is to reconstruct the 3D x-ray emission distribution of the NIF-ICF hotspot from very limited number of 2D x-ray projection images. Such 3D x-ray reconstructions can help to characterize and compare the thermophysical states of the fusion plasma such its temperature. We apply and test the algebraic reconstruction technique (ART) to reconstruct the 3D x-ray emission distribution of the ICF hotspot. Subsequently, we infer the 3D hotspot electron temperature distribution from these 3D x-ray reconstructions in different energy channels.

Recommended citation: Ka Wai Wong, Conformal Parametrization of Surfaces of Genus Zero and 3D Reconstruction of Nuclear Fusion Hotspots, UC Davis Dissertation, (2021).

Three-dimensional Electron Temperature Measurement of Inertial Confinement Fusion Hotspots using X-Ray Emission Tomography

Published in Review of Scientific Instruments, 2022

We present a novel approach to reconstruct three-dimensional (3D) electron temperature distributions of inertially confined fusion plasma hotspots at the National Ignition Facility (NIF). Using very limited number of two-dimensional (2D) x-ray imaging lines-of-sight, we perform 3D reconstructions of x-ray emission distributions from different x-ray energy channels ranging from 20 to 30 keV. 2D time-integrated x-ray images are processed using the Algebraic Reconstruction Technique (ART) to reconstruct a 3D hotspot x-ray emission distribution that is self-consistent with the input images. 3D electron temperatures are computed using the energy channel ratios. We demonstrate the high accuracy and applicability of this method with different complex hotspot geometries in both synthetic and experimental results.

Recommended citation: Ka Wai Wong and Benjamin Bachmann, Three-dimensional electron temperature measurement of inertial confinement fusion hotspots using x-ray emission tomography, Review of Scientific Instruments 93, 073501 (2022) https://doi.org/10.1063/5.0097471

talks

3-D electron temperature and x-ray emission tomography of the ICF hotspot at the National Ignition Facility

Published:

A 3-D reconstruction of x-ray emission distribution of the inertial confinement fusion (ICF) hotspot can help to characterize and compare the thermophysical states of stagnated fusion plasmas. We apply and test the iterative algorithm, Algebraic Reconstruction Technique (ART), to reconstruct the 3-D x-ray distribution of the ICF hotspot from very limited number of two-dimensional x-ray projection images. Furthermore, we infer the 3-D hotspot electron temperature distribution by using the x-ray reconstructions from different x-ray energy channels ranging from 20 to 30 keV, where the ablator becomes optically thin. We will present our x-ray brightness and electron temperature reconstructions and compare results using two versus three lines-of-sight with synthetic and experimental data. Release Number LLNL-ABS-815375

teaching

Teaching experience 1

Undergraduate course, University 1, Department, 2014

This is a description of a teaching experience. You can use markdown like any other post.

Teaching experience 2

Workshop, University 1, Department, 2015

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