New Fabrication and Metrology Methods for Blazed, Radially-ruled Gratings
Open Access
- Author:
- Zhang, Ningxiao
- Graduate Program:
- Astronomy and Astrophysics
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- March 06, 2022
- Committee Members:
- Douglas Cowen, Outside Unit & Field Member
Fabien Grise, Major Field Member
Michael Eracleous, Major Field Member
Randy McEntaffer, Chair & Dissertation Advisor
Rebekah Ilene Dawson, Program Head/Chair - Keywords:
- X-rays
accretion disks
absorption lines
quasars
diffraction grating
customized groove patter
period
mapping
metrology - Abstract:
- AGN winds might be the key to solve the puzzle of the study of galaxy feedback. AGN winds have been observed in many X-ray observations. The large observed velocity of AGN winds might indicate large amounts of energy, which could be large enough to escape the gravitational potential of the host galaxy. However, it is hard to accurately measure the mass and density of the winds with current X-ray telescopes. A high efficiency and high spectral resolving power X-ray observatories, such as Lynx, is required to measure the recombination timescale and identify density sensitive emission lines for AGN winds' density estimation. Our group at Penn State University aims to explore fabrication of a blazed radially ruled grating array in the off-plane mount, which would allow next-generation telescopes to achieve high efficiency and high spectral resolving power over 5000 across the soft X-ray band. Traditional methods, such as mechanical method and interference lithography method, are designed for parallel grooves grating fabrication. Electron-Beam Lithography can generate radially ruled grooves in nanometer scale. However, it cannot be smoothly transferred to a mono-crystalline silicon substrate, which is required to generate a blazed profile by the wet etching process. This dissertation aims to search for a new fabrication method for blazed radially ruled gratings. This method first fabricates a PDMS stamp with blazed parallel grooves and then manipulates its groove distribution into a radial pattern by a new designed 2-D stretching tool. Meanwhile, I developed a new, inexpensive, bench-top method for measuring groove period and groove directions over large areas with high mapping resolution and high measurement accuracy, dubbed the grating mapper for accurate period (GMAP). The GMAP is used to guide the fine adjustment of the stretching distance during the stretching process. The test results confirm the stretching method can accurately control the groove period and generate a gradient of groove period. This work demonstrated a new fabrication method that has great potential for making the blazed, radial gratings that will be utilized in future observatories to observe AGN spectra in high resolution and determine critical characteristics of AGN and their winds.