University of Illinois Urbana-Champaign

DEVELOPMENT OF TWO-PHOTON PUMP POLARIZATION SPECTROSCOPY PROBE TECHNIQUE (TPP-PSP) FOR MEASUREMENTS OF ATOMIC HYDROGEN .

Satija, Aman

Content Files
1193.pdf
437831.pdf
437831.pptx

Permalink

https://hdl.handle.net/2142/79281

Description

Title
DEVELOPMENT OF TWO-PHOTON PUMP POLARIZATION SPECTROSCOPY PROBE TECHNIQUE (TPP-PSP) FOR MEASUREMENTS OF ATOMIC HYDROGEN .
Author(s)
Satija, Aman
Contributor(s)
Lucht, Robert P.
Issue Date
25-Jun-15
Keyword(s)
Instrument/Technique Demonstration
Date of Ingest
2016-01-05T20:06:08Z
Abstract
Atomic hydrogen (H) is a key radical in combustion and plasmas. Accurate knowledge of its concentration can be used to better understand transient phenomenon such as ignition and extinction in combustion environments. Laser induced polarization spectroscopy is a spatially resolved absorption technique which we have adapted for quantitative measurements of H atom. This adaptation is called two-photon pump, polarization spectroscopy probe technique (TPP-PSP) and it has been implemented using two different laser excitation schemes. The first scheme involves the two-photon excitation of 1S-2S transitions using a linearly polarized 243-nm beam. An anisotropy is created amongst Zeeman states in 2S-3P levels using a circularly polarized 656-nm pump beam. This anisotropy rotates the polarization of a weak, linearly polarized probe beam at 656 nm. As a result, the weak probe beam �leaks� past an analyzer in the detection channel and is measured using a PMT. This signal can be related to H atom density in the probe volume. The laser beams were created by optical parametric generation followed by multiple pulse dye amplification stages. This resulted in narrow linewidth beams which could be scanned in frequency domain and varied in energy. This allowed us to systematically investigate saturation and Stark effect in 2S-3P transitions with the goal of developing a quantitative H atom measurement technique. The second scheme involves the two-photon excitation of 1S-2S transitions using a linearly polarized 243-nm beam. An anisotropy is created amongst Zeeman states in 2S-4P transitions using a circularly polarized 486-nm pump beam. This anisotropy rotates the polarization of a weak, linearly polarized probe beam at 486 nm. As a result the weak probe beam �leaks� past an analyzer in the detection channel and is measured using a PMT. This signal can be related to H atom density in the probe volume. A dye laser was pumped by third harmonic of a Nd:YAG laser to create a laser beam at 486 nm. The 486-nm beam was frequency doubled to a 243-nm beam. Use of the second scheme simplifies the TPP-PSP technique making it more convenient for diagnostics in practical systems.
Publisher
International Symposium on Molecular Spectroscopy
Type of Resource
text
Genre of Resource
Conference Paper / Presentation
Language
English
Permalink
http://hdl.handle.net/2142/79281

Owning Collections

Abstracts & Presentations - 2015 International Symposium on Molecular Spectroscopy PRIMARY