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Title: High-speed digital holography for neutral gas and electron density imaging

Abstract

An instrument was developed using digital holographic reconstruction of the wavefront from a CO{sub 2} laser imaged on a high-speed commercial IR camera. An acousto-optic modulator is used to generate 1–25 μs pulses from a continuous-wave CO{sub 2} laser, both to limit the average power at the detector and also to freeze motion from sub-interframe time scales. Extensive effort was made to characterize and eliminate noise from vibrations and second-surface reflections. Mismatch of the reference and object beam curvature initially contributed substantially to vibrational noise, but was mitigated through careful positioning of identical imaging lenses. Vibrational mode amplitudes were successfully reduced to ≲1 nm for frequencies ≳50 Hz, and the inter-frame noise across the 128 × 128 pixel window which is typically used is ≲2.5 nm. To demonstrate the capabilities of the system, a piezo-electric valve and a reducing-expanding nozzle were used to generate a super-sonic gas jet which was imaged with high spatial resolution (better than 0.8 lp/mm) at high speed. Abel inversions were performed on the phase images to produce 2-D images of localized gas density. This system could also be used for high spatial and temporal resolution measurements of plasma electron density or surface deformations.

Authors:
 [1];  [2]; ;  [3]; ; ;  [4]
  1. Princeton University, Princeton, New Jersey 08540 (United States)
  2. Third Dimension Technologies, Oak Ridge, Tennessee 37831 (United States)
  3. Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)
  4. Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
Publication Date:
OSTI Identifier:
22598032
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 87; Journal Issue: 5; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; AMPLITUDES; BEAMS; CAMERAS; CARBON DIOXIDE LASERS; DEFORMATION; DENSITY; ELECTRON DENSITY; HOLOGRAPHY; IMAGES; LENSES; NOISE; NOZZLES; PLASMA; PULSES; REFLECTION; SPATIAL RESOLUTION; SURFACES; VALVES; VELOCITY; WINDOWS

Citation Formats

Granstedt, E. M., E-mail: egranstedt@gmail.com, Thomas, C. E., Kaita, R., Majeski, R., Baylor, L. R., Meitner, S. J., and Combs, S. K. High-speed digital holography for neutral gas and electron density imaging. United States: N. p., 2016. Web. doi:10.1063/1.4949505.
Granstedt, E. M., E-mail: egranstedt@gmail.com, Thomas, C. E., Kaita, R., Majeski, R., Baylor, L. R., Meitner, S. J., & Combs, S. K. High-speed digital holography for neutral gas and electron density imaging. United States. doi:10.1063/1.4949505.
Granstedt, E. M., E-mail: egranstedt@gmail.com, Thomas, C. E., Kaita, R., Majeski, R., Baylor, L. R., Meitner, S. J., and Combs, S. K. Sun . "High-speed digital holography for neutral gas and electron density imaging". United States. doi:10.1063/1.4949505.
@article{osti_22598032,
title = {High-speed digital holography for neutral gas and electron density imaging},
author = {Granstedt, E. M., E-mail: egranstedt@gmail.com and Thomas, C. E. and Kaita, R. and Majeski, R. and Baylor, L. R. and Meitner, S. J. and Combs, S. K.},
abstractNote = {An instrument was developed using digital holographic reconstruction of the wavefront from a CO{sub 2} laser imaged on a high-speed commercial IR camera. An acousto-optic modulator is used to generate 1–25 μs pulses from a continuous-wave CO{sub 2} laser, both to limit the average power at the detector and also to freeze motion from sub-interframe time scales. Extensive effort was made to characterize and eliminate noise from vibrations and second-surface reflections. Mismatch of the reference and object beam curvature initially contributed substantially to vibrational noise, but was mitigated through careful positioning of identical imaging lenses. Vibrational mode amplitudes were successfully reduced to ≲1 nm for frequencies ≳50 Hz, and the inter-frame noise across the 128 × 128 pixel window which is typically used is ≲2.5 nm. To demonstrate the capabilities of the system, a piezo-electric valve and a reducing-expanding nozzle were used to generate a super-sonic gas jet which was imaged with high spatial resolution (better than 0.8 lp/mm) at high speed. Abel inversions were performed on the phase images to produce 2-D images of localized gas density. This system could also be used for high spatial and temporal resolution measurements of plasma electron density or surface deformations.},
doi = {10.1063/1.4949505},
journal = {Review of Scientific Instruments},
number = 5,
volume = 87,
place = {United States},
year = {Sun May 15 00:00:00 EDT 2016},
month = {Sun May 15 00:00:00 EDT 2016}
}