Andy Ruth - Physics Department - University College Cork

yakzephyrΤεχνίτη Νοημοσύνη και Ρομποτική

24 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

80 εμφανίσεις

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 i
nduced
b
reakdown spectroscopy
(12 weeks)

Projects

Project
1


Optical
trapping of
spherical (droplet) particles

Physical principle of optical trapping

Trap setup

N
ebulizer

Trap chamber

& illumination

Camera

Laser

M
1

M
2

M
3

L
1

L
2

L
3

BS

BS=
beamsplitter

1064 nm

Objective
lens

Beamsplitter

Particle chamber

Mirror

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
Acquisition

Data
Analysis

(C)

(A) Transmitter

(B) Receiver

(C) Data Processing

(A)

Laser

Beam
Steering

Beam
Expander

Power
Measurement

(A)

Transmitter

(C) Data
Processing

(B)

Receiver



(A)


(B)


(C)

Aerosol

drifting with

t
he wind.


Doppler shift

of elastically

backscattered light

u
sed to determine

w
ind 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 with

C
ivil
, Environmental &

Energy Engineering Department

(
Dr.

P. Leahy)

Project is for 6 weeks



Project 3



Differential Optical Absorption
Spectroscopy (DOAS)



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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 streetlights

Low pressure Na lamp?

Typical spectra of streetlights

High 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 extinction

features

Intensity

I
0

I
aer

I
aer
+
I
mol

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 H
2
O or NO
2
.





Check feasibility for
automized

2D
-
DOAS study

over Cork.


Project can be offered

as 12 weeks or 6 weeks


Project
4


Laser induced breakdown
spectroscopy

(LIBS)

High power

laser pulse

computer

filter

spectrometer

lens

shutter

Nd:YAG laser

(doubled, 532 nm)

oscilloscope

(power monitor)

CCD

fibre

vacuum

cell

Different gases: air, N
2
, O
2
,
Ar

Laser Induced Breakdown Exp.

100 ns

400
ns

1000
ns

4000
ns

wavelength


log (emission intensity)

Laser pulse duration typically 10 ns !!

Focus typically >10000 K.

High power

laser pulse

computer

filter

spectrometer

lens

shutter

Nd:YAG laser

(doubled, 532 nm)

oscilloscope

(power monitor)

CCD

fibre

vacuum

cell

Naphthalene

Laser Induced Breakdown Exp.

oscilloscope


PMT


computer

filter

vacuum

cell

HR mirror

GPIB

shutter

Nd:YAG laser

(doubled, 532 nm)

oscilloscope

(power monitor)

High power

laser 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
, CO
2
.



Trap laser plasma emission in an optical cavity and



interpret the results.

Project is designed for 12 weeks

Light source

Detector

No sample

Conventional absorption
spectroscopy

d

Intensity

I
0

Absorbance (=optical density)
A
:



ln

(
I / I
0
)
=

d

(
l
) =
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