Post on 25-Dec-2015
Project Overview
Laser Spectroscopy Group
http://laser-spectroscopy.ucc.ie
A. A. Ruth
Department of Physics, University College Cork, Cork, Ireland
(1) Optical trapping of spherical (droplet) particles (12 weeks)
(2) Establishment of a small weather station including the operation of a real-time wind shear LiDAR (6 weeks)
(3) Differential optical absorption spectroscopy (6 or 12 weeks)
(4) Laser induced breakdown spectroscopy (12 weeks)
Projects
Trap setup
Nebulizer
Trap chamber& illumination
Camera
Laser
M1
M2
M3
L1
L2
L3
BS
BS= beamsplitter
1064 nm
Objectives
· Optically trap droplet or transparent spherical solid.
· Measure radius of trapped particles.
· Study the time the particle can be trapped for as a function of particle size and trapping parameters.
· Measure scattering from the droplet/particle and check whether whispering gallery modes were formed.
· Compare mode frequencies with expectation based on particle size. Project is for 12 weeks
Project 2
Establishment of a small weather station
including the operation of a real-time wind
shear LiDAR
Weather Station
• Temperature • Atmospheric pressure• Humidity• Precipitation• Wind speed• Wind direction
Standard parameters measured by a weather station:
Cup Anemometer
LiDAR Principle / Set-up
Telescope
Receiver Optics
Filters
Detector
(B)
Signal Processing
Data Acquisitio
n
Data Analysis
(C)
(A) Transmitter
(B) Receiver
(C) Data Processing
(A)
Laser
Beam Steerin
g
Beam Expander
Power Measurement
(A)
Transm
itte
r
(C)
Data
Pro
cess
ing
(B)
Rece
iver
(A) (B) (C)
Aerosol drifting with the wind.
Doppler shift of elastically backscattered lightused to determinewind speed and direction.
Wind (Doppler) LiDAR
Objectives
• Establish weather station.
• Deploy wind LiDAR.
• Implement wireless data transmission to a central hub.
• Analyse and interpret collected data.
Collaboration withCivil, Environmental & Energy Engineering Department(Dr. P. Leahy)
Project is for 6 weeks
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Established method in trace gas detection:
Telescope
up to several kilometers
Lamp
Spectrometer
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Experiments in the project will take a little different approach.
Long-Path Differential Optical Absorption Spectroscopy
(LP-DOAS)
Different spectra
Steetlights of Cok observd during a merry knight after a kouple of white wine spritzerrrs.
Typical spectra of streetlights
Typical spectra of streetlights
Xe arc lamps ?
Typical spectra of streetlights
White LEDs ?
Typical spectra of streetlights
White LEDs ?
Typical spectra of streetlightsLow pressure Na lamp?
Typical spectra of streetlightsHigh pressure Na lamp?
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Long path differential optical absorption spectroscopy
Telescope
street light
Spectrometer
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aerosol, dust, particulate matter
molecular and radical trace species
Molecules exhibit structured spectra Aerosol spectra have broad extinctionfeatures
Inte
nsity
I0
IaerIaer+Imol
l
Difference spectra are being evaluated !
Objectives
Characterize streetlight spectra and select the most appropriate ones for DOAS experiments.
Measure spectra during the entire night and evaluate long term stability of the setup.
Evaluate spectra and check whether (a) retrieval of aerosol extinction is possible,(b) retrieval of molecular absorption is possible,
notably of H2O or NO2.
Check feasibility for automized 2D-DOAS study over Cork.
Project can be offeredas 12 weeks or 6 weeks
High powerlaser pulse
computer
filter
spectrometer
lensshutter
Nd:YAG laser(doubled, 532 nm)
oscilloscope(power monitor)
CCD fibre
vacuumcell
Different gases: air, N2, O2, Ar
Laser Induced Breakdown Exp.
100 ns
400 ns
1000 ns
4000 ns
wavelength
log
(em
issi
on in
tens
ity)
Laser pulse duration typically 10 ns !!Focus typically >10000 K.
High powerlaser pulse
computer
filter
spectrometer
lensshutter
Nd:YAG laser(doubled, 532 nm)
oscilloscope(power monitor)
CCD fibre
vacuumcell
Naphthalene
Laser Induced Breakdown Exp.
oscilloscope
PMT
computer
filter
vacuumcell
HR mirror
GPIB
shutter
Nd:YAG laser(doubled, 532 nm)
oscilloscope(power monitor)
High powerlaser pulse
Laser Induced Breakdown Exp.
lens
Objectives
· Set up LIBS experiment.
· Measure “breakdown spectra” of air for different pressures.
· Measure “breakdown spectra” of other inert gases, e.g. He, Ar, CO2.
· Trap laser plasma emission in an optical cavity and interpret the results.
Project is designed for 12 weeks
Absorbance (=optical density) A:
ln (I / I0) = d () = A
= absorption coefficient [cm-1], d = sample length [cm]
Light source.
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Detector
Absorbing sample (e.g. Gas)
Conventional absorption spectroscopy
d Intensity I