1. Study of laser produced plasma of limiter of the aditya tokomak for detection of molecular bands
A. K. RAI
Department of Physics, Allahabad University,
Allahabad
International Symposium on Molecular Spectroscopy, Champaign-Urbana, Illinois
June 20‐24, 2016

2. History of research in Spectroscopy at University of Allahabad
The Department of Physics of Allahabad University started its journey in the field of spectroscopy with the pioneering work of Prof. Meghnad Saha. He brought Spectroscopy Laboratory of Allahabad University at the fore front in the world by his brilliant research work on spectral emission from extremely hot atoms and molecules. The glorious tradition of Professor Saha continues in our laboratory and today I will talk about the development and applications of the technique of Laser Induced Breakdown Spectroscopy (LIBS).

3. Laser Induced Breakdown Spectroscopy (LIBS)
LIBS is relatively new laser based Spectroscopic technique which has wide applications starting from the alphabet “A” which stands for Archeology to the alphabet “Z” which stands for Zoology.
We can just imagine the importance of the LIBS technique by the fact that this technique is not only being used on the earth to study the elemental composition of targets in environments but this technique is also being used on another planet (Mars) to study its geological layers.
NASA’s Curiosity rover, which landed on Mars in the first week of August 2012, carries a LIBS equipment for exploring the geological layers of the Red Planet.

4. We have develop the experimental facility of LIBS in the Department of Physics, University of Allahabad and started multidisciplinary research work. Here in the present talk I will discuss some interesting problems which we have carried out in Allahabad.

5. Study of Biomaterials
A. K. Patrhak, Rohit Kumar, V. K. Singh, R. Agarawal and A. K. Rai, (2012), Assessment of LIBS for spectrochemical analysis: A review. Applied Spectroscopy Reviews, 47, 14-40,
V. K.Singh and A.K. Rai (2011), Prospects of Laser Induced Breakdown Spectroscopy for Biomedical Applications: A Review, Laser in Medical Science, 26, Issue 5,
A.K. Pathak and A.K. Rai, (2010), In-vivo analysis of human nail using LIBS, Assian Journal Spectroscopy Special Issue,
A. K. Pathak, V. K. Singh, N. K. Rai, A. K. Rai, Pradeep K Rai, Promod K Rai, S. Rai and G. D. Baruah, (2011), Study of different concentric rings inside gallstones with LIBS" Lasers in Medical Science, 26, ,
V. K. Singh and A. K. Rai, (2011), Potential of laser induced breakdown spectroscopy for the rapid identification of carious teeth, Lasers Med Sci, 26, 307–315, .
  V. K. Singh, N. K. Rai, S. Pandhija, A. K. Rai, and P. K. Rai, (2009), Investigation of common Indian edible salts suitable for Kidney disease by Laser Induced Breakdown Spectroscopy, Laser Med Scie., 24, ,
V. K. Singh, Vinita Rai and A.K. Rai, (2009), Variational study of the constituents of cholesterol stones by LIBS, Lasers in Medical Science, 24,
V. K. Singh, P. K. Rai, P. K. Jindal, and A. K. Rai,(2009) “Cross-sectional study of kidney stones by laser induced breakdown spectroscopy, Lasers Medical Science, 24,
V.K. Singh, Vinita Singh, A. K. Rai, S. N. Thakur, P K. Rai and J. P. Singh, (2008) Quantitative analysis of Gallstone by laser - induced breakdown spectroscopy, Appl. Opt., 47, G

6. Study of Energetic Materials
Shikha Rai and A. K. Rai, (2011), Characterization of Organic Materials by LIBS for exploration of correlation between molecular and elemental signals, AIP Advances (Vol 1, Issue 4), DOI /
Shikha Rai, A. K. Rai, I. M. L. Das and K. C. Tripathi, (2011), Implementation of statistical methods on LIBS data for classification of residues of energetic materials (nitro compounds), Adv. Mat. Lett. 2011, 2(1), DOI: /amlett
Shikha Rai and A. K. Rai, (2010), PCA: an intuitive approach for classification of nitro compounds with LIBS, Assian Journal Spectroscopy Special Issue,
Shikha Rai, A. K. Rai and S. N. Thakur, (2008), Identification of nitro-compounds with LIBS. Appl. Phys. B, 91,

7. Detection and quantification Toxic metals in solid and liquid wastes
R. Kumar, D. Alamelu, R. Acharya and A. K. Rai, (2014), Determination of concentrations of chromium and other elements in soil and plant samples from leather tanning area by Instrumental Neutron Activation Analysis, J Radional Nucl Chem, DOI /s
R. Kumar, D. K. Trpathi, D. Alamelu, D. K. Chauhan and A. K. Rai, (2014)"In Situ Monitoring of Chromium Uptake in Different Parts of the Wheat Seedling (Triticum aestivum) using LIBS" Spectroscopy Letter, 47, 1-10
S. Pandhija, N. K. Rai, A. K.r Pathak and A.K.Rai, (2013)Calibration curve with improved limit of detection for Cadmium in soil: An approach to minimize the matrix effect in LIBS analysis,, Spectroscopy Letter (Accepted)
R. Kumar, A. K. Rai, D. Alamelu and S. K. Aggarwal,(2013) Monitoring of toxic elements present in sludge of industrial waste using CF-LIBS, Environ. Monit. Assess., 185, , DOI: /s
S. Pandhija, N. K. Rai1, A. K. Rai and S. N. Thakur (2010) Contaminant concentration in environmental samples using LIBS and CF-LIBS" by, App. Phys. B 98, 231–241, DOI /s x.
S. Pandhija & A. K. Rai (2009) In-Situ Multielemental Monitoring in Coral Skeleton by CF-LIBS, App. Phys. B 94, 545–552, DOI /s
S. Pandhija & A. K. Rai (2009), Screening of brick-kiln area soil for determination of heavy metal Pb using LIBS, J. Environmental Monitoring and Assessment 148,
N. K. Rai, A. K. Rai, A. Kumar and S. N. Thakur (2008), Detection Sensitivity of LIBS for Cr II in liquid sample, Appl. Opt., 47, G105 – G111.
N. K. Rai and A. K. Rai, (2008) LIBS-An Efficient Approach for the Determination of Cr in industrial wastewater, Journal of hazardous material, 150,
 S. Pandhija & A. K. Rai (2008), Laser Induced Breakdown Spectroscopy: A versatile tool for monitoring of traces in materials, Pramana-Journal of Physics 70,

8. Study of Food Materials
Effect of processing on the magnesium content of Green Leafy Vegetables”, Deepti Rai, R. Agrawal, R. Kumar, A. K. Rai and G.. K. Rai, (2013) J. Applied Spectroscopy, 80, Number 6.
"LIBS: Surveillance on carcinogenic colors in crushed ice-ball" Rahul Agrawal, A. K. Pathak, A. K. Rai and G. K. Rai, (2013), ISRN Analytical Chemistry, (Accepted)
Manju Tiwari. R. Agrawal, A. K. Pathak, A. K. Rai and G. K. Rai, (2012) Laser Induced Breakdown Spectroscopy: An Approach to Detect Adulteration in Turmeric, Spectroscopy Letters DOI: /
 Rahul Agrawal, Rohit Kumar, Shikha Rai, A. K. Pathak, A. K. Rai, and G. K. Rai, (2011), LIBS:A Quality Control Tool For Food Supplements, Food Biophysics, DOI: /s y
Rahul Agrawal, A.K.Pathak, A.K.Rai, and G.K.Rai, (2010) Classification of Milk of different origin using LIBS, Assian Journal Spectroscopy Special Issue,

9. Study of Some Medicinal plants
Shikha Mehta, Prashant Kumar Rai, Nilesh Kumar Rai, A. K. Rai, Dane Bicanic & Geeta Watal, (2011), Role of Spectral Studies in Detection of Antibacterial Phytoelements and Phytochemicals of Moringa oleifera" , Food Biophysics, DOI /s
D.K. Chauhan, D.K. Tripathi, N. K. Rai, and A.K. Rai, (2011) Detection of Biogenic Silica in Leaf blade, Leaf sheath and Stem of Cynodon dactylon Using LIBS and Phytolith Analysis, Food Biophysics, 6, 416–423,
Shikha Mehta, P. K. Rai, D. K. Rai, N. K. Rai, A. K. Rai, Dane Bicanic, B. Sharma, and Geeta Watal (2010) LIBS Based Detection of Antioxidant Elements in Seeds of E. officinalis, Food Biophysics, (DOI /s z).
P. K. Rai, Sanjukta Chatterji, N. K. Rai, A. K. Rai, Dane Bicanic, and Geeta Watal (2010) The Glycemic Elemental Profile of Trichosanthes dioica: A LIBS-Based Study Food Biophysics, 5, 17–23
P. K. Rai, Dolly Jiaswal, N. K. Rai Shiwani Pandhija, A. K. Rai and G. Watal, (2009) “New Strategies of LIBS Based Validation of Glycemic Elements for Diabetes Management", Food Biophysics 4, 260–265
N. K. Rai, P. K. Rai, Shiwani Pandhija, G. Watal, A. K. Rai & Dane Bicanic, (2009) “Application of LIBS in Detection of Antihyperglycemic Trace Elements in Momordica charantia, Food Biophysics 4, 167–171
P. K. Rai, Dolly Jiaswal, N. K. Rai, S. Pandhija, A. K. Rai and G. Watal, (2009), Role of glycemic elements of Cynodon dactylon and Musa paradisiaca in diabetes management, Lasers Med Sci, (2009) 24,7 61–768,   

10. Three Parts

11. Atomic emission spectroscopic technique based on elemental analysis of material.
High power pulsed laser beam is focused on target material (solid, liquid, gas etc.)
The temperature of locally heated region rises rapidly up to vaporization temperature of material
Plasma is formed at the surface of the sample
The plasma contains the emission spectra of the elements.
Collection of the light from the plasma,permits identification of the elements via their unique spectral signatures.

12. Plasma Generation Plasma Expansion Laser Beam Some 100 ns UnspecificEK E1
Unspecific
ff-or fb-emission E0
Some µs E1
Sample E1 EK E1
Emission of excited
atoms and ions E0
Sample
Pulsed Laser
(Typically
5 ns Pulse,
1064 nm)
Plasma Expansion
into
2л Steradians
Plasma Plume

13. UNIQUE ADVANTAGES OF LIBS
Powerful laser-based analytical technique.
Simplicity & quick (The results may be obtained within microseconds)
Minimum sample preparation.
Versatile sampling of sample of any kind & in any phase.
Permit analysis of extremely hard materials & refractory materials & also of non-conducting materials.
Minimally invasive (minimally destructive).
Point detection capability
Simultaneous analysis of many elements
Quantitative measurements of minor elements
Remote Analysis Capabilities
Capability to in-situ analysis and real time analysis

14. Experimental Setup of LIBS
Photograph of LIBS experimental set up

15. Photograph of the LIBS system

16. Creation of Plasma on coins using Laser-induced Breakdown spectroscopy

18. Gated titanium spectra of a LIBS plasma illustrating the development of the spectra as a function of the time after the plasma initiation. The time intervals are; (a) 0-.5 µs (b) µs and © µs

19. Motivation behind the present work
Windows, Mirrors and Limiters are essential components in devices used for the study of controlled thermonuclear fusion (Tokamak). The lifetime of these components unprotected from reactor grade plasmas is reduced because of intensive contamination. Due to plasma-wall interaction, some material from the wall is eroded and mixes with the plasma and finally deposited on other cooler area of the vacuum vessel like the optical window and other view ports. Therefore, to protect and maintain the optimum quality of the components of the tokamak, it is essential to identify the impurities deposited on the components of the tokamak. We have tried to identify the impurities deposited on the limiter of Aditya Tokamak, IPR, Ahmedabad using LIBS..

20. Study of major and minor components on surface of the Limiter
Limiters are used to protect the Tokamak wall from the hot plasma.
Tokamak Limiter

21. (a) b Curved Surface 1st scan 2nd 4th 6th 9th scan 8th
For spatial and depth profile analysis of the impurity layer of the limiter, laser was focused on the curved surface of the limiter and the single laser shot LIBS spectra were recorded by focusing 15 successive number of laser shots at the same point. Total of 15 such point have been considered in the same scan line as shown in the figure. b
1st scan
9th scan
Curved Surface
(a)
6th
2nd
4th
8th
(a) Block diagram of the limiter and (b)Actual photograph of Limiter

22. Single shot LIBS spectra of the limiter of the tokomak
LIBS. LIBS spectra show the presence of spectral signature of Fe, Cr, Ni, Mo, Mn, Cu, C, Ca and Mg on the surface of limiter.
Typical LIBS spectra of exposed surface of the limiter

23. Intensity variation of spectral lines (a) Cr(428. 9 nm) and (b) Fe(371
Intensity variation of spectral lines (a) Cr(428.9 nm) and (b) Fe(371.9 nm) in contaminated surface of the tokamak limiter with successive number of laser shots in 1st scan

24. Similar type of behavior is also observed for 2nd scan, 3rd scan and further scans lines
Intensity variation of spectral lines (a) Cr(428.9 nm) and (b) Fe(371.9 nm) in contaminated surface of the tokamak tile with successive number of laser shots in different laser scans

25. Relative intensity variation of C(247
Relative intensity variation of C(247.8 nm) with impurity elements have been calculated for different successive number of laser shot. It is observed that relative intensity increases with increasing laser shots and after some laser shot it becomes constant.

26. Spatial distribution of impurities on the limiter surface
For spatial analysis of the impurity elements, the single shot LIBS spectra have been recorded by focusing the laser beam at different scan lines starting from one end of curvature to the other end with distance(mm) mm
This result represents that deposition of impurity is greater at two scan lines (at around 15 mm and 40 mm from one end). The probable explanation for the above trend is due to its arrangement in the tokamak

27. Concentration (%) at Fe Cr Ni Mo Cu Mn Ca Mg C 1st laser shot
Concentration of elements present in the impurity layer of the limiter using CF- LIBS method
Concentration (%) at Fe Cr Ni Mo Cu Mn Ca Mg C
1st laser shot
±2.12
±1.08
±0.97
2.3 ±0.09
2.24 ±0.19
2.93 ±0.05
9.02 ±0.27
2.71 ±0.03
0.82 ±0.01
3rd laser shot
±3.14
±0.94
9.76 ±0.53
2.16 ±0.06
1.81 ±0.03
1.68 ±0.03
5.05 ±0.2
2.03 ±0.08
±1.4
5th laser shot
±1.67
9.3 ±0.63
±0.48
1.63 ±0.34
1.4 ±0.09
1.09 ±0.07
1.04 ±0.93
1.89 ±0.08
±1.56
8th laser shot
±1.11
±0.24
±0.21
---
±2.57

28. Variation of spectral line intensity of C (2478 nm) with increasing gate delay

29. Variation of spectral lines of CN band related to ΔV=0

30. Variation of spectral lines of CN band related to ΔV=-1

31. Variation of spectral lines of CN band related to ΔV=+1

32. Variation of spectral lines of C2 band related to ΔV=-1 to ΔV=+1

33. Conclusion
Depth profile analysis of the impurity layer on different vertical lines of the limiter surface has been performed.
Spatial analysis of the impurity elements on the limiter surface show the pattern of impurity deposition.
Relative spectral intensity of carbon increases with increases no. of laser shots and becomes constant after some laser shots.
Laser induced plasma was studied at Different gate delay to get different sequence of CN and C2 band at different gate delay.

34. Publications related to the topic
1.Proof-of-concept experiment for On-line LIBS Analysis of Impurity Layer Deposited on ptical Window and Other Plasma Facing Components of Aditya Tokamak Gulab Singh Maurya, Rohit Kumar, Ajai Kumar and Awadhesh Kumar Rai, Rev. Sci. Instrum. 2015, 86,123112
2. Analysis of deposited impurity material on the surface of optical window of the Tokamak using LIBS, (2014) Gulab S. Maurya, Aradhana Jyotsana, Rohit Kumar, Ajai Kumar and Awadhesh K. Rai, Physica Scripta 89,
3. Gulab Singh Maurya, Aradhana Jyotsana, Ajai kumar and Awadhesh Kumar Rai, Spatial analysis of impurities on the surface of flange and optical window of the Tokamak using Laser Induced Breakdown Spectroscopy, , (2014), Optics and Lasers in Engineering, 56, 13–18
4. Gulab Singh Maurya, Aradhana Jyotsana, Ajai kumar and Awadhesh Kumar Rai,In-situ analysis of impurities deposited on the Tokamak flange using Laser Induced Breakdown Spectroscopy, (2014), J. Nucl. Mater., 444 (2014), pp
DOI information: /j.jnucmat
5. Gulab Singh Maurya, Aradhana Jyotsana, Ajai kumar and Awadhesh Kumar Rai,I, Analysis of the impurities on the contaminated surface of the tokomak limiter using Laser Induced Breakdown Spectroscopy, Spectro Chimica Acta (comunicated)

35. Acknowledgement
Prof. Ajai Kumar, Institute for plasma Research is gratefully acknowledged for his help and support for providing the tokamak samples. I want to express my thanks to my research student Mr. Gulab Singh Maurya who has done all work presented in this talk.
Board of Research in Fusion Science and Technology (NFP/DIAG/F11/03), Institute for Plasma Research, Gandhinagar, Gujarat, and UGC are gratefully acknowledged for financial assistance.

36. THANK YOU…