INVITED TALK

Simultaneous Estimations of Plasma Parameters using Quantitative Spectroscopy

(Plasma Devices LabMicrowave Tubes (MWT) Division,

CSIR-Central Electronics Engineering Research Institute (CEERI)Pilani-333031, Rajasthan, India

Ram Prakashramprakash@ceeri.ernet.in

Joint ICTP-IAEA Workshop on Modern Methods in Plasma Spectroscopy, ICTP, Italy, March 23-27, 2015

*

Home Town:Agra

Taj MahalCSIR-CEERI, Pilani

**

1.Semiconductor• Hybrid Microcircuits• IC Design• MEMS and Microsensors• Nanotechnology & Devices• Photonics & Optoelectronics

3.Microwave Tubes• Gyrotron• Klystron• Magnetron• TWT• Cathodes• Plasma Devices

2.Electronic Systems•Agri-Electronics• Embedded System• Digital System• Power Electronics

CSIR

CEERI

Foundation was laid on 1953.Around 425 Permanent Employees

Pioneer Research Institute in India in the Field of Electronics Devices Tech.

CSIR-CEERI, Pilani, India Plasma Devices Lab

Scientist/TO Project FellowsDr. Ram Prakash, Group Leader Ms.Pooja Gulati, SRFDr. U. N. Pal, Sr. Sci. Mr. R. P. Lamba, QHFDr. Hasib Rahman, Sci. Fellow Ms. Nalini Pareek, QHFMr. Niraj Kumar , Sci. Mr. Aditya Sinha, PFMr. Mahesh Kumar, STO Mr. Varun Pathania, PFMr. B. L. Meena, STO Mr. Arvind Jadon, PF

AcknowledgementsPlasma Devices Group members

Plasma Devices Technology Activities

• VUV/UV Excimer Sources based on DBD Biomedical Applications (UV-B)Surface Treatment (VUV, UV-A)Water Purification (VUV, UV-C)

• High Power Plasma SwitchesThyratrons (25kV/1kA, 40kV/3kA) & Pseudospark (25kV/5kA, 20kV/20kA)

• Plasma Cathode Electron GunElectron Beam Sources (22kV/200A/cm2), (Sheet beam 20kV/1kA/cm2)

• Plasma Assisted Microwave Sources: PASOTRON (0.5MW) • Penning Discharge Devices

Ion Beam Sources (25keV Xe+ ion) and VUV Spectrometer-detector -system Calibration (22-106 nm)

Outline of the Presentation

Plasma Spectroscopy!

Why simultaneous plasma parameter measurements?

Simultaneous plasma parameter measurements usingCR-model

Least squire analysis

Opacity and diffusion analysis

Development of Penning Plasma Discharge Device forVUV-spectrometer calibration

Conclusion

Wavelength (Ao)

CII

HeI

Plasma Spectroscopy: Comment

This was due to the fact that it remains difficult to establish thelocal plasma conditions needed for the evaluation of passiveemission spectra.

“The Plasma Spectroscopy at some stage in its history had sufferedfrom misleading reputation of being primarily a subject, which hasits main goal of the identification of impurity species and respectivewavelengths” M. G. von Hellermann JET-P (94) 08

In most cases~ accurate knowledge of atomic properties, like emitted wavelength,transition probabilities, collisional cross-sections etc are required.

Spectrum Rich in information content

Ne Te Ti plasmamotion

concentration of different impurity species

4550 4600 4650 4700 4750 4800 4850 4900

1x1012

2x1012

3x1012

4x1012

5x1012

6x1012

7x1012

8x1012

shot no= 10015

Abso

lute p

hoton

inten

sity (

photo

ns. c

m-2.se

c-1. s

r-1)

Wavelength (A0)

Cumulative efforts CR model based codes ADAS, ALADDIN and CHIANTI etc.

Spectrum and Quantitative Plasma Spectroscopy

dxAN41I 2

1

x

x uluul

n=3

n=4

n=5n=6

n=�Ionization level

Hydrogen likeground state

Doubly excitedlevels

Helium like ground state

Continuum

1s2 (1S)

1s

1s2s (1S)

1s2s (3S)

1s2p (1P)1s2p (3P)

2p2 (1D) 2p2 (3P)

2s 2p (1P) 2s 2p (3P)

-- Photons cm-2 sec-1 sr-1

Spectrum and Quantitative Plasma Spectroscopy

1

uldeie

ullulue puNuNNAlNXlNN

tuN )()()()()()(

ulul

ululee AXNuSNuN )()(

The local temporal relaxation of the density N(u) of level u is described by,

Populating term

Depopulating term

For Simplifications: One can take some valid assumptions

Radialtransport:1D

urrr1

u

uu

NsourceK )(

Nu can be solved at various degrees of sophistications judged to be relevant.

Spectrum and Quantitative Plasma Spectroscopy

2). To a desired accuracy there is always some level above which theeffect of the radiative processes may be neglected.

4.) Compared with the relaxation time for the ground level populationthese others may regarded as instantaneous

3). Dominant population~ Ground state atoms, ions and metastablesand their some is constant

1). Electrons are Maxwellian

uldeie

ullulue puNuNNAlNXlNN

tuN )()()()()()(

ulul

ululee AXNuSNuN )()(

Main rate equation

will reduce to -----------------

Collisional Radiative (CR)-model and assumptions

Simplification in CR-model

]ANX)[u(R)1(N)1()1( 1u1u

e1u0edCR

])[(1)1( 11

111

1 uu

euu e

uCR ANXuRN

XSS

geie NNuRNNuRuN )()()( 10

and egCReiCRig NNSNN

dtdN

dtdN

from u=1 condition

Ng+Ni =Constant=NS,TotalFrom III appr.

From I, II & IV appr.

From IV appr.

Collisional Radiative (CR)-model solution

The quasi-steady-state solution for the dominant ground states will be,

Here R0 (u) and R1 (u) are the relative population coefficients and are complex functionof S, A, X, , , d which are function of electron temperature and density only.

The ADAS, ALADDIN, CHIANTI etc are few well-known codes to be used for rate coefficients

From u>1 condition

With an assumption of average electron density and temperature in an emissionlength 1 cm, the photon intensity from the CR-model,

)N~(N~CPE)N~(N~CPE)N~(N~CPE41)(I~ Memetastablegeexcitationiegrecombininul

where grecombininCPEexcitationCPE

represents the effective photon emission coefficients (photons cm3 sec-1).

The ADAS code derives PEC values for particular line ul after calculatingthe population distribution of levels.

Note: PEC’s are complicated functions of electron densities and temperatures.

Finding Ne, Te, Ni, Ng and Nm simultaneously

metastableCPEand,

Simultaneous plasma parameter measurements using CR-model

For VUV spectrometer-detector system calibration

Such calibrations are possible by branching ratio method or bysynchrotron radiation sources

A simple laboratory based method to calibrate a VUV spectrometerdetector systemRam Prakash et al. “Calibration of a VUV spectrograph by Collisional-Radiative modeling of a discharge plasma” J.Phys. B: At. Mol. Opt. Phys. 5 July 43 (2010) 144012(5pp). (Nominated for ENI International Award, Italy, 2011)

In this method, on the basis of experimentally observed intensities ofa number of spectral lines of helium in the visible region from aPenning discharge (PD) source , a large number of plasma parameters,such as, Ne, Te, Ni, Ng and Nm (2 3S) simultaneously estimated usingcollisional-radiative (CR) model of ADAS database.

These are used to obtain the absolute intensities of a few lines in thevacuum ultraviolet (VUV) region, which were compared with observedVUV spectrometer-detector system to obtain calibration factors.

Why simultaneous plasma parameter measurements?

A standard 1cm penning plasma source (VUV Source SD-01 from Jobin-Yvon,France) for wavelength calibration (i.e. from 100 Ǻ to 1700 Ǻ)Helium gas plasma was characterizedBoth visible and VUV spectra were recorded simultaneously.

Our model understanding

VUV spectrometer (Jobin-Yvon TGS 300, f 300 mmused with 290 g mm−1

grating, resolution 5 Ǻ)

Princeton Instrumentvisible spectrometer(resolution 2.5 Ǻ) fittedwith a CCD camera, whichhad been calibrated forabsolute intensitymeasurements.

Measured helium spectral lines from the 1 cm penning plasma source

Visible Vacuum Ultra Violet

He I He II He I He II

3889.7 Ǻ (2s3S-3p3P0) 4685 Ǻ 522.2 Ǻ 303.9 Ǻ

3965.7 Ǻ (2s1S-4p1P0) 537 Ǻ

4714.8 Ǻ (2p3P0-4s3S) 584.4 Ǻ

4923.2 Ǻ (2p1P0-4d1D)

5049.0 Ǻ (2p1P0-3s1S)

5877.5 Ǻ (2p3P0-3d3D)

6680.0 Ǻ (2p1P0-3d1D0)

7067.6 Ǻ (2p3P0-3s3S)

7283.3 Ǻ (2p1P0-3s1S)

Our model understanding

Absolute intensities of visible spectrahas been obtained from Visiblespectrometer-detector system.

)N~(NC~PE)N~(NC~PE)N~(NC~PEI Memetageexctierecotexp 1111 41

)N~(NC~PE)N~(NC~PE)N~(NC~PEI Memetageexctierecotexp 2222 41

)N~(NC~PE)N~(NC~PE)N~(NC~PEI Memetageexctierecotexp 3333 41

)N~(NC~PE)N~(NC~PE)N~(NC~PEI Memetageexctierecotexp 4444 41

)N~(NC~PE)N~(NC~PE)N~(NC~PEI Memetageexctierecotexp 5555 41

)N~(NC~PE)N~(NC~PE)N~(NC~PEI Memetageexctierecotexp 6666 41

)N~(NC~PE)N~(NC~PE)N~(NC~PEI Memetageexctierecotexp 7777 41

)N~(NC~PE)N~(NC~PE)N~(NC~PEI Memetageexctierecotexp 8888 41

)N~(NC~PE)N~(NC~PE)N~(NC~PEI Memetageexctierecotexp 9999 41

where index 1-9 is used for nine different wavelengths of the observed He lines

This procedure gives unique solutions for Ng and Nm at given Ne and Te.

Calculated Ng and Nm corresponding to following nine spectral lines for each Neand Te using SVD technique under the quasi-neutral approximation . .

Simultaneous plasma parameter measurements using CR-model

ie NN ~~

Simultaneous plasma parameter measurements using CR-model

Created grid of Te and Ne.. The grid for Te was kept between 3 eV to150 eV at the step size of 0.5 eV and for density it was in between1x109 to 1x1013 cm-3.

Example: Grid points of PECexcitation from He I 7283.3 A0 line

Simultaneous plasma parameter measurements using CR-model

We then estimated the absolute intensities of He I 3889.7 , He I 3965.7 , He I4714.8 , He I 4923.2 , He I 5049.0 , He I 5877.5 , He I 6680.0 , He I 7067.6and He I 7283.3 lines at every positive values of , , , and .eN eTiN

~gN~

MN~

A mismatch parameter,

9

1

2

91i exp

calexp

III

The index ‘i ’ is summed over all the used wavelengths, here it is nine.

The minimum in the sigma shows the best fit values of experimentallyobtained intensities with the theoretically predicted intensities at certainvalues of , , , and .eN eT iN

~gN~

MN~

Variation of mismatch parameter ( ) for different Ne and Te values

Simultaneous plasma parameter measurements using CR-model

Simultaneous plasma parameter measurements using CR-model

Diff. pressures and fixed 40 mA discharge current

Sigma

3 x 10-2 mbar 0.20

1 x 10-2 mbar 0.16

7 x 10-3 mbar 0.16

4 x 10-3 mbar 0.20

1 x 10-3 mbar 0.23

4 x 10-4 mbar 0.41

Diff. currents and fixed 4 x 10-3 mbar pressure

Sigma

20 mA 0.20

50 mA 0.23

64 mA 0.15

80 mA 0.14

90 mA 0.15

100 mA 0.12

Simultaneous plasma parameter measurements using CR-model

Densities for varying discharge currentsat constant pressure of 4x10-3 mbar

Densities for varying dischargepressures at constant dischargecurrent 40 mA.

Simultaneous plasma parameter measurements using CR-model

Inferences:•The estimation of electron density is quite similar to the previousreporting's [P. X. Feng et al. Plasma Source Sci. Technol.12 (2003)p. 142-147].

•Though the temperature prediction is poorly determined, theabsolute intensity calculations and their fit with the all-experimental values were very good at different pressures anddischarge conditions. This gives us confidence to synthesizethe spectrum in the VUV region also.

•Imperfect estimation of temperature could be due to the nature ofthe PEC coefficients and their poor dependence on temperature forspecific case or due to re-absorption or diffusion problems.

VUV spectrometer calibration scheme

Simultaneous plasma parameter measurements using CR-model

Typical VUV spectrum for discharge current 100 mA and workingpressure 4x10-3 mbar

Simultaneous plasma parameter measurements using CR-model

Comparison of observed VUV spectrum and theoretical spectrum fordischarge current 100 mA and working pressure 4x10-3 mbar .

The apparent calibration factors at 584, 537 and 522 Å lines can be inferred as ~3x1010,~2 x1011 and ~1x1012 per count

Sensitivity Curve

Obtained calibration factors for different wavelengths in the VUV region atdifferent discharge currents and constant pressure.

Simultaneous plasma parameter measurements using CR-model

Further Cross-CheckCalculated intensities change with Te in the range of 20-60 eV when the otherparameters are kept fixed.

There is no significant change in the intensities and their ratios in the VUV region forlarger range of temperatures.

Simultaneous plasma parameter measurements using CR-model

FFFurthththe CCCr Cross CChChChe kkck

Least Square Calculations qLeast Square Calculations

To simplify the problem recombination process is neglected above 3 eVIt is a good approximation for plasma to be taken purely ionizing above 3 eV

The SVD produces a solution that is the best approximation in the leastsquire sense

To cross-checked these results we used least squire fit procedure also

Least Square Calculations

The intensity equation can be written as

Memetastablegeexcitationtheor N~NC~PEN~NC~PEI41

where Itheor gives the theoretically estimated intensities for allnine lines. Now we can define a merit function,

9

1

2

___exp

9

1

2__exp

~~~~41

jMejmetastablegejexcitationjt

jjtheorjt NNCPENNCPEIIIS

where Iexpt_j represents the corresponding experimental intensities for all ninelines. If

jej_excitation ANC~PE jej_metastable BNC~PEand

The above equation will reduce to,

9

1

2

41

jMjgjj_texp N~BN~AIS

Least Square Calculations

The merit function S should be minimum with respect to Ng and Nm for thebest-fit values. This could be achieved by,

0gNS 0

iNS

and

After simplification, we gotdcccbcaNm

12

2

1121~

221

211

cdccbdaN~g

where,9

11 4

1j

j_texpj IAa9

11 4

1j

j_texpj IBb9

1

21 4

1j

jAc9

12 4

1j

jj BAc9

1

2

41

jjBd

Again we derived the values of and for the set values of the grid points for Tebetween 3 eV - 150 eV at the step size of 0.5 eV and for Ne in between 1 x 10 9 - 1 x 1013 cm-3.

gN~

MN~

Used same mismatch technique to find the plasma parameters

For discharge current 100 mA and pressure 4x10-3 mbar

The obtained results are exactly similar to the SVD technique

Least Squire Calculations

Jalaj Jain, Ram Prakash, et al., J. Theo. & Appl. phys. Vol 9 (2015) 25-31

Opacity and Diffusion Analysis

Optically thin plasma model: Very near homogeneous along the line-of-sight and remainsin steady-state for the duration of the observation.

Optically thick plasma: The re-absorption (opacity) of the photons may cause the wronginformation about the estimated plasma parameters [K Behringer and U Fantz, New J. Phys. 2, 23 (2000)]

Used ADAS database to calculate opacity affected photon emissivity coefficientson the basis of escape factor methodology.

Basically inclusion of escape factors causes a net reduction in Einstein’s A coefficients, i.e., itmodifies the atomic transition probability values. The effect of self-absorption not onlychanges the net emergent flux but also changes the population of excited states and hencethe effective rate coefficients.

A diffusion time scale ~10-4 sec is also taken into account in order to introduce the diffusionof metastable states to the wall. The diffusion time scale was estimated for our geometryusing radius of the cylinder (0.5 cm), zero order Bessel's function and the diffusion coefficientfor helium.

Opacity and Diffusion Effects on Spectral Lines

Inclusion of opacity in the observed spectral lines through PECs and addition of diffusion ofneutrals and metastable state species in the CR-model code improves the electrontemperature estimation in the simultaneous measurement.

Jalaj Jain, Ram Prakash, et al., J. Theo. & Appl. phys. Vol 9 (2015) 25-31

Penning Plasma DischargeSourcePennnnnnnSouuuuuuu

niiiiiing PlPlPlPlPlPlasma DiDiDiDiDiDischhhhhhargennnning Plasma Dischargerning Plasma Dischargerce

Ram Prakash, Gheesa lal Vyas, Jalaj Jain, JitendraPrajapati, Udit Narayan Pal, Malay Bikas Chowdhuri andRanjana Manchanda Rev. Sci. Instrum, Vol. 83, 4December (2012) 123502(1-7).

Neodymium (Nd2Fe14B)

Development of Penning Plasma Discharge Device

Device Specifications

Stainless Steel (304L) Vacuum ChamberThe chamber dimensions 200 mm x 200 mm x 450 mmPlasma size approximately 50 mm x 50 mm x 50 mmDeveloped in three different anode configurations,

1. Single Anode Ring2. Double Anode Ring3. Rectangular Anode

Vacuum Base Pressure: 1x10-6 mbarWorking Pressure: 10-5 mbar to 10-2 mbar.Used Gases: Helium, Argon, Neon.Power: 2.5 kV, 1 A DC power supplyAxial magnetic field: 1kGThe discharge and VUV emission is made for steady operation

(Continuous source)

Double anode ring configuration has beenobserved & optimized as efficient sourceof visible and VUV light radiation simultaneously.

X-axis length = 50 mmY-axis cross section 30 mm 50 mmZ-axis cross section 18 mm 50mm

12 mm is aligned on x-axis

Anode optimization (Diagnostics)

(Visible spectroscopy) Langmuir ProbeVUV spectroscopy

At fixed pressure 6X10-3mbar and fixeddischarge current 5 mA.

At fixed pressure 6X10-3mbar

At fixed pressure 6X10-3mbar

Discharge Current 15 mA

Double Ring Single Ring Rectangular Anode

Working gas pressure (mbar)

9.0x10-4 1.0x10-3 9.0x10-4 1.0x10-3 9.0x10-4

(He I 667.81nm/He I 728.13nm)

1.40 1.26 1.05 1.03 1.21

Predicted density (cm-3)

~2 x1011 ~1x1011 ~2 x1010 ~2x1010 ~9 x1010

Predicted density (cm-3) LP

~2.5 x1011 ~1.2x1011 ~2.1 x1010 ~2.6x1010 ~9.5 x1010

Studies on Penning Plasma Discharge Device

AMAZE Simulation Software VORPAL PIC Simulation

After 1 sec

Anode Optimization (Simulations)

VORPAL PIC SimulationAfter 1 sec

Observed Spectra

Working pressure 2x10-3 mbar and applied voltage 400 V

Observed VUV Spectral Range: 20 nm - 110 nm

Visible and VUV Spectra of pure helium at working pressure 7x10-3 mbar, applied voltage 1.0kV

Observed Visible Spectral Range: 400 nm - 750 nm

501.

56H

eI

VUV spectral range useful for calibration

At working pressure 7x10-3 mbar, applied voltage 1.5kV &discharge current 13 mA in the double anode ring penningdischarge arrangement

200 250 300 350 400 450 500 550 600107

108

109

1010

1011

VU

V C

alib

ratio

n Fa

ctor

s

VUV Wavelengths (Angstrom)

Ne~Ni=3x1011 cm-3

Ng~2.90x1013 cm-3

Nm = 5.66x107 cm-3

Appl. V0=1.5kV, Pressure=7x10-3 mbarTe=3.0 eV, Gas=Helium,

Application of simultaneous measurements in Tokamak Divertor Plasma

Simultaneous fit of the deuterium Balmer series D , D , D , D line intensities with ADAScollisional-radiative (CR) model data in ASXED upgrade tokamak during ohmic dischargeshas been used

During detached divertor conditions, the plasma becamerecombining and temperature dropped from 7-10 eV to ~1.5 eV inthe outer divertor region

Ram Prakash et al., IPP 10/31 Sep, 2006

485.5 486.0 486.5 487.0

0

1x1020

2x1020

3x1020

4x1020

5x1020

6x1020

7x1020

(g)

AUG21249Time=2.254-2.354 s VOL2

Inte

nsity

(Ph

m n

m s

)

Wavelength (nm)

D

H 486.15

418 420 422 424 426 428 430 432 434 4360.0

5.0x1019

1.0x1020

1.5x1020

2.0x1020

(j)

AUG21249Time=2.254-2.354 s VOL2

BII 419.48

Inte

nsi

ty (

Ph

m-2

nm

-1 s

-1)

Wavelength (nm)

D +H 433.94

CII 426.73

BIII triplet424.29,424.35424.37

Ca I 422.67CIIIOII BD 1-1BD 0-0

CD 400 402 404 406 408 410 412 414

0

1x1020

2x1020

3x1020

(l)

AUG21249Time=2.254-2.354 s VOL2

C III 406 .794C III 406 .891

O II 407 .586O II 407 .215

C III 407 .030

Mo I 4 05.1 2

BII 412.19

Inte

nsity

(Ph

m-2

nm

-1 s

-1)

Wavelength (nm)

D +H 410.06

CII 402.11

ShotNo.

Te(eV)

error%

Ne (m-3) error %

(m-2)

error%

(m-2)

error%

21258 7.87 10.8 7.86x1019 13.6 3.03x1016 10.6 4.54x1018 150.0

21279 7.33 29.9 6.21x1019 21.5 1.60x1016 31.1 3.82x1018 176.3

21320 10.3 21.5 7.72x1019 21.6 1.43 x1016 24.1 1.20x1018 Independent

21322 1.54 15.2 1.26x1020 16.6 2.63 x1019 106.5 4.69x1018 28.0

21325 1.62 8.9 2.06x1020 14.9 1.73 x1019 57.2 2.87x1019 23.2

21327 1.56 4.4 2.47x1020 6.6 3.39 x1019 28.3 5.41 x1019 10.8

xN~ ixN~ g

Estimated plasma parameters in the ohmic series discharges along with low-density H-mode discharge

Table V: Obtained recombining and ionizing terms in the ohmic series discharges

ShotNo.

photons m3

sec-1Ionizing term (Ph. m-2 sec-1)

21258 2.83x10-18 6.74 x1018

21279 2.94x10-18 2.92 x1018

21320 4.49x10-18 4.96 x1018

21322 6.39 x10-21 2.12 x1019

21325 6.74 x10-21 2.40 x1019

21327 4.61 x10-21 3.86 x1019

excitationCPE )xN~(N~CPE geexcitation grecombininCPE

photons m3

sec-1Recombining term (Ph. m-2 sec-1)

1.01 x10-21 3.59 x1017

1.13 x10-21 2.69 x1017

6.64 x10-22 6.15 x1016

1.51 x10-20 8.94 x1019

1.39 x10-20 8.23 x1019

1.49 x10-20 1.99 x1020

)xN~(N~CPE iegrecombinin

Ram Prakash et al., IPP 10/31 Sep, 2006

Further application of simultaneous measurements Conclusion

A simple method to infer large number of plasma parameterssimultaneously from a Penning Plasma discharge (PPD) source has beendeveloped.

The electron density, electron temperature, ground-state atom and iondensities and also the triplet metastable state (2 3S) density are theparameters estimated.

The derived plasma parameters are then used to obtain the absoluteintensities of a few lines in the vacuum ultraviolet (VUV) region.

This has been compared with the observed VUV spectral lines for whichintensity calibration was not available which facilitates to determine thecalibration factors for a few VUV spectral lines.

It is seen that the inclusion of opacity in the observed spectral lines throughCR-model based photo emission coefficients (PECs) and addition of diffusionof neutrals and metastable state species in the CR-model code improves theelectron temperature estimation in the simultaneous measurement.

Multi-gases analysis and Non-Maxwellian electron consideration need to bestudied further for large data point calibration curve.

Students:Mr. G. L. Vyas, Mr. Jalaj Jain, Ms. Bishu Agarwal

Colleagues:Dr. Vinay Kumar, IPR, GandhinagarDr. P. Vasu, IPR, GandhinagarDr. M. B. Chowdhuri, IPR, GandhinagarMrs. R. Manchanda, IPR, GandhinagarDr. Udit Narayan Pal, CSIR-CEERI, Pilani

Collaborators:Prof. R. Dux & Prof. Kurtz Behringer IPP, GermanyProf. H. P. Summers & Prof. Martin O'Mullane, JET, UKDr. R-E-H Clark, IAEA, AustriaDr. M. Goto, NIFS, Japan

Acknowledgements

Thanks