ICPSA Singapore Dec Laser Produced Colliding Plasmas: Diagnostics and Potential for Applications in LIBS. John T. Costello

Transcription

1 ICPSA Singapore Dec Laser Produced Colliding Plasmas: Diagnostics and Potential for Applications in LIBS John T. Costello National Centre for Plasma Science & Technology (NCPST)/ School of Physical Sciences, Dublin City University

2 ICPSA Singapore Dec Focus of this talk will be on the effects of target geometry (specifically the attitude of the colliding plumes) on the plasma parameters of the stagnation layer formed at the collision plane..

3 DCU Laser Plasmas / Atomic Physics Laser NCPST - 6 laboratory areas focussed on pulsed laser matter interactions (spectroscopy/ imaging) Research Domains: 1. Colliding Laser Produced Plasmas 2. Optical Particle Diagnostics of Laser Produced Plasmas 3. Laser Induced Breakdown Spectroscopy (LIBS) in the Vacuum-UV 4. Pulsed Laser Deposition (PLD) of Materials 5. Photoionization of Atoms and Ions with Laser Plasma and Free Electron Laser Light Sources Some Current Projects: 1. UV-Vis imaging, spectroscopy and interferometry of colliding laser produced plasmas [with and without laser reheating] 2. Double Pulse VUV-LIBS for Elemental Characterisation in Steel 3. Ion emission from single and colliding laser plasmas 4. PLD and in-situ P-type doping of ZnO nanostructures 5. 2 photon and 2 colour photoionization of atoms with EUV FEL

4 DCU Laser Plasmas / Atomic Physics Laser NCPST - 6 laboratory areas focussed on pulsed laser matter interactions (spectroscopy/ imaging) Academic Faculty (5): John T. Costello, Eugene T. Kennedy, Jean-Paul Mosnier, Paul van Kampen & Lampros Nikolopoulos (T) Current Postdocs (2): Dr. Colm Fallon and Dr. Mossy Kelly Current PhD students (10): D Middleton, Cathal O Broin, Nichola Walsh, Brian Sheehy, Ben Delaney, Stephen Davitt, Lu Hu, Getasew Admasu, William Hanks, Paul Grimes Recent Nat l / Int l Interns: Ricarda Laasch (Univ. Hamburg), Nadia Gambino (Univ. Catania, Sicily), Julien Witz (Ecole Polytechnique, Palaiseau, Paris Sud), K. Nishant. R. Tejaswi, (LNMIIT, Jaipur), Conor Hand, (NUIM) Recent PhD Grads ( ): Padraig Hough, Conor McLoughlin, Rick O Haire, Vincent Richardson, Dave Smith, Tommy Walsh, Jack Connolly, Jiang Xi, Leanne Doughty, Eanna MacCarthy, Colm Fallon, Mossy Kelly Recent Postdocs ( ): Paddy Hayden (UCD) Satheesh Krishnamurthy (OU UK), Pat Yeates (Elekta Oncology UK), Subhash Singh (U. Allahabad).

5 CP People (incl. NSF-PIRE) DCU Eugene Kennedy, Ben Delaney, Stephen Davitt, Lu Hu, Getasew Admasu & William Hanks DCU Colliding Plasma Alumni: Kevin Kavanagh, John Dardis, Padraig Hough, Colm Fallon, Mossy Kelly, Hugo de Luna, Jofre Pedragosa, Paddy Hayden, Pat Yeates & Subhash Singh Purdue Ahmed Hassanein, Sivanandan Harilal & Justin Freeman Osaka Kazuo A Tanaka, T. Yabuuchi et al.

6 Colliding Plasma Collaboration NSF PIRE Int l Exchange: (PI Purdue) Purdue, School of Nuclear Engineering, January 2013 December 6th 2013

7 Outline of the Talk Colliding Plasmas - Orientation Target Geometrical Effects A Perspective on CP-LIBS

8 Colliding Plasmas - Orientation Making Stagnation Layers d = γf ( n 1) Laser Pulse Energy: mj/ beam Laser Pulse duration: 170 ps, 6 ns, 15 ns Focal Spot Size: ~ µm Irradiance: W.cm -2

9 Colliding Plasmas - Orientation Not a new idea! Seed Plasmas Stagnation Layer When plasma plumes collide there are two extreme scenarios: 1. Interpenetration - interactions are mostly via binary collisions 2. Stagnation - plumes decelerated at collision plane, rapid accumulation of material, kinetic energy converted into excitation energy (glow), rapid growth of dense (stagnated) layer,

10 Colliding Plasmas - Orientation Time Evolution: Tight point focus on each Ca face: 15 ns/ 120 mj per beam 4 mm ICCD: 5 ns gate 10 ns interval Ca - Emission 423 nm

11 Colliding Plasmas - Orientation From the very BIG' NGC Planetary Nebula Distance - 2,000 light years Extent ~ 0.4 light years Result of the collision of two stars believed that one became a red giant and started to swallowed its partner in the binary system. NGC 2346 Credit: Hubble Wide Field & Planeary Camera - Massimo Stiavelli (NASA)

12 Colliding Plasmas - Orientation To the very small' Hohlraums Fusion energy generation' Multiple laser plasmas formed inside a single high-z cavity e.g., Au) which provide an array of extremely bright X-ray sources. The fuel pellet is compressed by the X-ray radiation pressure. Advantage is more uniform compression with concomitant amelioration of instabilities

13 Colliding Plasmas - Orientation Plasma - Plasma Separation Collisionality Parameter: ξ = D λ ii Ion - Ion Mean Free Path (mfp) For collisions between opposing plumes (1, 2) λ ii >> D Interpenetration λ ii ~ D Soft Stagnation λ ii << D Hard Stagnation λ ii 1 2 ( ) = m 2 4 i v 12 4πe 4 Z 4 n e ln( Λ ) 12 Slow moving and dense plumes are more likely to stagnate!

14 Colliding Plasmas - Orientation Plasma - Plasma Separation Collisionality Parameter: ξ = D λ ii Ion - Ion Mean Free Path (mfp) For collisions between opposing plumes (1, 2) λ ii 1 2 ( ) = m 2 4 i v 12 4πe 4 Z 4 n e ln( Λ ) 12 Key point: One can engineer stagnation layer characteristics; hardness, density, temperature, shape, etc. by varying geometry (D) and laser-target interaction physics (mfp, λ ii ) - application specific..

15 Diagnostics Used to Characterise Colliding Laser Plasmas Stagnation layer evolution/parameterisation 1. Fast Photography - all phases ( ns) 2. Interferometry - usable early phase (0 100 ns) 3. Spectroscopy - usable mid phase ( ns) 4. Faraday Cup (TOF) - Ions and electrons 5. Others: Shadowgraphy, Moire deflectometry, LIF, etc, (potentially useful for stagnation layer formation in ambient gas experiments)

16 Diagnostics Part 2. Diagnostic Used to Investigation Characterise of Colliding Laser Plasmas Colliding Plasma Laboratory Imaging, Spectroscopy, Interferometry, Shadowgraphy, Ion TOF, (Q LIF)

17 Colliding Plasmas - Photography ICCD Photography: Time and angle resolved.

18 Colliding Plasmas-Spectroscopy ICCD Spectroscopy: Time and space resolved.

19 Colliding Plasmas - Spectroscopy Stagnation layer temperature (Boltzmann Plot / Line Ratio) and density (Stark Broadening) determination Cu stagnation layer spectrum, nm

20 Colliding Plasmas - Spectroscopy Copper stagnation layers Temperatures (Boltzmann Plot)! Ln Iλ $ # & = E " ga % kt e

21 Colliding Plasmas - Spectroscopy Copper stagnation layers - electron density (Stark Analysis)

22 Imaging - effect of seed collision angle ξ = D λ ii λ ii ( 1 2) = m 2 4 i v 12 ( ) 4πe 4 Z 4 n e ln Λ 12

23 Stagnation Colliding Plasmas Layer Atom/Ion -- Spectroscopy Photography Tracking Sn target under vacuum 50mJ seed energy λ = 532nm wedge angle = D =1.3mm 645 nm Sn + line

24 Colliding Plasmas - Spectroscopy Results Distribution of Cu Atoms & Ions Cu + Cu

25 Results Electron Density Distributions

26 Results Electron Temp. Distributions

27 Results Comparison with Single Plume Density and temperature of single plume plasma are initiated with relatively high values that decrease sharply as time proceeds Stagnation layers maintain both temperature and density at relatively high values for longer this a key potential advantage for applications..

28 Target Geometrical Variations - Summary Ion/ neutral atom velocity ratio generally >3 More than one process determines species transport in SL Velocities of SL species drop as the wedge angle decreases Both temperatures and densities increase as wedge angle decreases, i.e. both can be controlled by target geometry Compared to single plume the duration of self emission from atoms and ions is longer Densities and temperatures remain at higher values for longer in stagnation layers Of course lots of other laser and geometrical parameters can be varied under investigation currently

29 Re-excitation of SLs towards a DP LIBS 4 Wedges 485 nm line - Sn 2+ - time & space integrated

30 Re-excitation of SLs towards a DP LIBS 4 Wedges 485 nm line - Sn 2+ - time & space integrated No Reheat Inter-pulse Delay 80 ns Reheat Sn 2+ peak is typ. 170% brighter (Factor of 2 for a Sn + line) 120 ns reheat 120 ns 180 ns 240 ns Acquisition Delay Time

31 Support Higher Education Authority Programme for Research in Third Level Institutes (IV and V) Science Foundation Ireland Investigator Programme 12/IA/1742 & 07/IN.1/I1771 Irish Research Council (PhD Scholarships / Postdoctoral Fellowships) EU FP7 Erasmus Mundus Joint Doctorate EXTATIC EUV and X-ray Technology and Training for Interdisciplinary Cooperation Grant No. FPA

32 Associated Diagnostic Papers 1. Plasma parametrization by analysis of time-resolved laser plasma image spectra, D Doria, K D Kavanagh, J T Costello and H Luna, Meas Sci Technol 17, 670 (2006) 2. Analysis of Time-Resolved Laser Plasma Ablation using an Imaging Spectra Technique, H Luna, J Dardis, D Doria, and J T Costello Brasil. J. Phys (2007) 3. Particle Diagnostics Of A ZnO Laser Ablation Plume For Nanostructured Material Deposition, C McLoughlin, P Hough, J T Costello and J-P Mosnier, Appl. Surf. Sci (2009) 4. Time Resolved Nomarski Interferometery of Laser Produced Plasma Plumes, P Hough, C McLoughlin, T J Kelly, S S Harilal, J-P Mosnier and J T Costello, Appl. Surf. Sci (2009) 5. Characterization of a high-pressure laser ion source with dc and pulsed extraction, P Yeates, J T Costello and E T Kennedy, Plasma Sources Sci. Technol. 19 Art No (2010) 6. Perveance and ion bunch structure from a compact, high-pressure laser ion source, P Yeates, J T Costello and E T Kennedy, Physics of Plasmas 17 Art No (2010) 7. Charged particle dynamics in a high-pressure laser ion source, P Yeates, J T Costello and E T Kennedy, J. Phys. D: Appl. Phys (2011) 8. Enhanced shock wave detection sensitivity for laser produced plasmas in low pressure ambient gases using interferometry, P Hough, T Kelly, C Fallon, C McLoughlin, P Hayden, E Kennedy, J Mosnier, S Harilal and J T Costello, Meas. Sci. Technol (2012)