cost action 529, mierlo, 31.03.06-2.04.06 g.revalde, asi light related activities at high resolution...

G.Revalde, G.Revalde, ASIASI

COST Action 529COST Action 529, , Mierlo, 31.03.06-2.04.06Mierlo, 31.03.06-2.04.06

Light related activitiesLight related activitiesat High resolution and light at High resolution and light

source technology laboratory,source technology laboratory,Institute of Atomic Physics Institute of Atomic Physics

and Spectroscopyand Spectroscopy, , RigaRiga



Institute of Institute of Atomic Atomic Physics Physics

and and SpectroscoSpectrosco

pypy



Laboratory is a part of the Institute of Atomic Laboratory is a part of the Institute of Atomic Physics and SpectroscopyPhysics and Spectroscopy

Members Dr. Atis Skudra (head) Dr. Imants Bersons Dr. Gita Rēvalde Eng. Juris Siliņš PhD students: Nataļja Zorina, Egils Bogans, Zanda Gavare, Mr. Mārtiņš Bērziņš

Collaboration partners:Collaboration partners:Institute of Institute of Theoretical and Applied Mechanics, Novosibirsk, Russia Theoretical and Applied Mechanics, Novosibirsk, Russia CPAT, Toulouse, FranceCPAT, Toulouse, FranceInstitute of Non-thermal plasma physics, Greifswald, GermanyInstitute of Non-thermal plasma physics, Greifswald, GermanyUniversity of St.Petersburg, RussiaUniversity of St.Petersburg, RussiaTomsk State University, RussiaTomsk State University, RussiaUniversity of Mainz, GermanyUniversity of Mainz, GermanyMoscow Kurchatov’s Institute, RussiaMoscow Kurchatov’s Institute, Russia



Research fieldsResearch fields Low-pressure discharge plasma studies, mainly, inductive/capacitatively

coupled; High frequency electrodeless discharge lamp technology and manufacturing Plasma/wall interaction Working life studies Radiation stability High-resolution emission spectroscopy, time and spatially resolved Spectral line shapes (resolution approx. 0.05 cm-1) (VUV-IR) Spectral line intensities - absolute and relative (VUV-IR) in dependence on

working conditions, pressure etc Ion trap spectroscopy Atomic absorption spectroscopy Zeeman spectroscopy Daylight measurements Mercury concentration detection in the environment Theoretical studies of the Ridberg atom interaction with half-cycle pulses



Atomic absorption and self-Atomic absorption and self-absorption method absorption method

The light from the unit volume can be absorbed by the rest of the plasma source

Unit volume

One can obtain the optical density by changing the length of the plasma source

Plasma source

0

)(

)(

1)(

de l



a b

l1 l2

mirror Discharge vessel

1. Method using a mirror

r

II

r

Ir

IIIrA b

ab

b

abbb

)1(

A – the “relative absorption”

Ia , Ib– the intensity of the plasma sources a and b

r – the reflection coefficient of the mirror

l1, l2 – the lengths of the plasma sources a and b



2. Method using a spectral light source

The precision of the method can be improved by placing the line spectra light source instead of the mirror.

L

PLPL

I

IIIA

A – the “relative absorption” IL – the intensity of the lamp (plasma is off)

IP– the intensity of the plasma (lamp is off)

IL+P– the intensity of the plasma and lamp

In this experimental work the high-frequency electrodeless discharge lamp (HFEDL) have been used



Determined concentrations for level sDetermined concentrations for level s55

using both methodsusing both methods

The concentrations for the metastable level s5 determined with two methods coincide within the experimental error.

0 20 40 60 80 100107

108

109

1010

Ar %

Level s5, lamp

Level s5, mirror

Ni/ (2J+1), cm-3

0,00

11,72

12,34

12,95

13,57

s5

s4

s3

s2

p10

p9

p8

p7

p6

p5

p4

p3

p2

p1

750.

4 nm

794.

8 nm

810.

4 nm

751.

5 nm

800.

6 nm

763.

5 nm

801.

5 nm

811.

5 nm

Ar I

, e

V

p = 0.5 mbar, P = 2.26 kWGas flow: 200 sccm

Ar/ H2 mixture (Ar % 10..100%)



Hg/Ar low pressure inductive Hg/Ar low pressure inductive coupled plasmascoupled plasmas

30 40 50 60 70Cold spot temperature, grad C

500

1000

1500

2000

2500

3000

Inte

nsi

ty,a

.u.

253.7nm

The intensity of the resonance line 253.7nm versus the cold spot temperature. Dashed line – numerical calculation, points – experimental data..

oeHTorrPAr 7.0,2 0

N. Denisova , G.Revalde, A. Skudra, G.Zissis, High-frequency electrodeless lamps in an argon-mercury mixture,

J.Phys.D.Appl.Phys. 38, 2005, 3275-3284.



Electrodeless discharge lampsElectrodeless discharge lamps Bright radiators in the broad spectral range (VUV - IR); Filled with gas or metal vapor+buffer gas like Sn, Cd, Hg, Zn, Pb, As, Sb, Bi, Fe, Tl, In, Se, Te, Rb, Cs, I2, H2, He, Ne, Ar, Kr, Xe, Dy,Tu(first samples) as well as combined Hg-Cd, Hg-Zn, Hg-Cd-Zn, Se-Te etc (also isotope fillings, as example Hg202) etc.No electrodes – long working life Inductive coupled/ capacitatively coupled; Hf, Rf Electromagnetic field excitation; Different designs and types in dependence on application

200 300 400 500 600 700 8000

1000

2000

3000

4000

Inte

nsity

, rel

. un.

Wavelength, nm

Hg



Line shape studiesLine shape studies

Capillary

Lamp

Capillary

Monochromator

Power supply

Fabry – Perrot interferometerPhotomultiplierComputer

LensLens

Vacuum chamberAmplifier

Spectral line shape measurements and modelling, to control self-absorption and to get important plasma parameters (such as gas temperature, lower state density, etc)

Zeeman Zeeman spectrometerspectrometer



Theoretical approachTheoretical approach

Observed spectral line profile:

(1)

where f ’(x) - real profile, f’’(x) - instrumental function, (x) - function characterizing random errors.

2 methods to find the real spectral line shape:

Line shape modeling – non-linear multi-parameter fitting of the model profile to an experimental spectral line profile by varying unknown parameters

Solving the inverse task using Tikhonov’s regularization method

f x f x y f y dy x( ) `̀ ( ) (̀ ) ( )



ModellingModelling

Model includes the basic factors causing the spectral line broadening in HF discharge: Doppler, natural, collision.. These effects are accounted by means of the Voigt profile.

Multiple overlapping lines are generated including hyperfine splitting and isotope shifts.

Self-absorption (one beam approximation) The resulting profile is a convolution of the manifold of self-absorbed

profiles and the instrument function. The resulting profile is fitted to the experimental lines by means of a

non-linear multi-parameter fitting procedure. Typically the following parameters are fitted: atom temperature,

collisional broadening, optical density, light source inhomogenity, width of the instrument function.



Solving the inverse problemSolving the inverse problem by by Tikhonov´s methodTikhonov´s method

To determine the real spectral line profile I(v) it is necessary to solve the inverse

problem (1). The problem (1) is known as the classic Rayleigh reduction problem and

can be described by the first kind of Fredholm integral equation:

' ' ' , ,b

a

A y d f c d (2)

where

'A - the kernel of the integral - the known instrument function;

f - the distribution function, which was registered by apparatus;

'y - the unknown real profile

a,b – the limits of the real profile;

c,d – the limits of the measured (experimental) profile.



We implemented the Tikhonov’s regularization method in our computations of Eq.

(2). This method is based on a transformation of the initial problem to a problem of

minimising the smoothing functional. The solution is the function that minimises the

smoothing functional (the Tikhonov’s functional):

2

' ' ' ,d b

c a

M y A y d f d

where Ω – the stabilising functional: 2 ' ' ,

b

a

y d

λ>0 – the regularisation’s parameter;

The instrumental function has to be known.

The reduction to ideal spectral device was performed in two stages:

1) the problem of the minimum searching of the Tikhonov’s functional was solved. So

we have got a regularized solution of the linear equations system depending on the

regularisation’s parameter λ.

2) In the second phase the parameter of the regularization λ. was determined.



Mercury 185 and 254 nm line examplesMercury 185 and 254 nm line examples in dependence on the Tcold spot (0oC-100oC)

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,00,0

0,2

0,4

0,6

0,8

1,0

Inte

nisi

ty, r

el. u

n.

Wavenumber, cm-1

Experimental Theoretical Real

Hg202+Ar

253.7 nm,i=160 mA,without cooling

Ar/Hg 202 (99.8 %) 253,7 nm line

0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4

0,0

0,2

0,4

0,6

0,8

1,0

Inte

nsity

, re.

un.

Wavenumber, cm-1

Experimental Theoretical Real

Hg202 - 90% +Ar (2 Torr)253.7 nm,i=140 mAwithout thermostabilisation

Optical density 6.8

dopl = 0,044 cm-1

(T=488 K)Reff= 0,84%

ModellingModelling



185 nm resonance line185 nm resonance line

i=200 mAi=200 mA

Reconstructed shapesReconstructed shapes



Hg 253.7 nm line intensity Hg 253.7 nm line intensity time dependancetime dependance

0 50 100 150 200 2500

2

4

6

8

10

12

14

Inte

nsity, re

l. u

n.

Time, hours

0,046 g 0,46 g 4,6 g

Plasma/wall interactionPlasma/wall interactionWorking life studiesWorking life studies



Blackening of the walls of the vessel in the Blackening of the walls of the vessel in the capillary lampcapillary lamp



12 nm z-range

X, Y range 3 m

Images of the vessel surfaces obtained by AFM: Images of the vessel surfaces obtained by AFM: a) without plasma treatment a) without plasma treatment b) after plasma treatmentb) after plasma treatment



Regular daylight study – 3 years Regular daylight study – 3 years experienceexperience

Relative daylight at 12:00 during 2004Relative daylight at 12:00 during 2004



Spectral changesSpectral changes

Wavelength, nmWavelength, nm

Daylight in the winter and summerDaylight in the winter and summer



Mercury concentration detection in Mercury concentration detection in air in real time with 2 ng precisionair in real time with 2 ng precision

GPS

• Riga’s city example



Mercury concentration Mercury concentration measurements in the criminalisticsmeasurements in the criminalistics



Mercury rest in cartridge cases Mercury rest in cartridge cases after the shotafter the shot

2

0

1

0

210

tttt

eAeAYY

Time after the shotTime after the shot

Hg

conc

entr

atio

nH

g co

ncen

trat

ion

cost action 529, mierlo, 31.03.06-2.04.06 g.revalde, asi light related activities at high resolution...

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