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John T. Costello

Laser Generated Plasmas - ( Stars with a Bright Future ). John T. Costello National Centre for Plasma Science & Technology (NCPST) and School of Physical Sciences, Dublin City University www.physics.dcu.ie/~jtc & john.costello@dcu.ie. Astronomy/Phys Society, NUI-Maynooth, Feb 17th, 2004.

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John T. Costello

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  1. Laser Generated Plasmas - (Stars with a Bright Future) John T. Costello National Centre for Plasma Science & Technology (NCPST) and School of Physical Sciences, Dublin City University www.physics.dcu.ie/~jtc & john.costello@dcu.ie Astronomy/Phys Society, NUI-Maynooth, Feb 17th, 2004

  2. Outline of Talk Part I - Laser Plasma Fundamentals • Laser Plasmas: Generation, Properties & Scales Part II - Laser Plasma UV - X-ray Light Sources Part III - Absorption Imaging of Laser Plasmas Part IV - Into the future Laser Plasmas & Extreme Physics Ultraintense (Petawatt) Laser Generated Plasmas - RAL A New Laser, 'VUV/X-Ray Free Electron Laser' - DESY-FEL

  3. Collaborators & Contributors to the Talk Laser Plasma Sources RAL - Edmund Turcu& Waseem Shaikh QUB - Ciaran Lewis and A MacPhee DCU - Oonagh Meighan & Adrian Murphy Absorption Imaging Padua - Piergiorgio Nicolosi and Luca Poletto DCU - John Hirsch, Kevin Kavanagh& Eugene Kennedy DESY Extreme-UV & X-ray Free Electron Laser Hasylab- Josef Feldhaus, Elke Ploenjes, Kai Tiedke et al. Orsay- Michael Meyer & Patrick O'Keefe, Lund- Jorgen Larsson et al. MBI- Ingo Will et al. DCU- Eugene Kennedy & John Hirsch Padua- Piergiorgio Nicolosi Petawatt VULCAN Laser VUV/EUV Science & Technology RAL - Colin Danson U. Berkeley - David Attwood

  4. NCPST - CLPR The CLPR node comprises 6 laboratories focussed on PLD (2) & photoabsorption spectroscopy/ imaging (4) Staff: John T. Costello, Eugene T. Kennedy, Jean-Paul Mosnier and Paul van Kampen Post Doctoral Fellows: John Hirsch (ETK/JC) Deirdre Kilbane (PVK/JC) -2004 Jean-Rene Duclere (JPM) - 2004 Incoming - Hugo de Luna (JC) - Easter 2004 Vacancy (ETK) PGs: Kevin Kavanangh, Adrian Murphy (JC) Jonathan Mullen (PVK) + Vacancy (PVK/JC) Alan McKiernan, Mark Stapleton, Rick O'Hare (JPM), Eoin O’Leary & Pat Yeates(ETK) MCFs:Jaoine Burghexta(Navarra) and Nely Paravanova (Sofia) Michael Novotny (CZ - incoming)

  5. NCPST/ CLPR - What do we do ? DCU Pico/Nanosecond Laser Plasma Light Sources VUV, XUV & X-ray Photoabsorption Spectroscopy VUV Photoabsorpion Imaging VUV LIPS for Analytical Purposes ICCD Imaging and Spectroscopy of PLD Plumes Orsay/Berkeley Synchrotrons Photoion and Photoelectron Spectroscopy Hamburg - FEL Femtosecond IR+XUV Facility Development

  6. Part I - Table Top Laser-Plasmas

  7. Plasma & The 4 Phases of Matter Greek Philosophers Physicists Earth Solid Water Liquid Wind Gas FirePlasma Plasma: Fluid (gas) of electrons and ions

  8. Why study plasmas ? NGC 4676 START ? Plasma Process

  9. 'Table-Top' Pulsed Lasers Q-switched Nd-YAG: DCU 1J in 10 ns = 100 MW, (1012 W.cm-2 in 100 mm spot) SBS Compressed Nd-YAG: DCU 0.5J in 150 ps ~ 3 GW, (1014 W.cm-2 in 30 mm spot) Modelocked Ti-Sapphire: Coherent (QUB-PLIP) 0.03 mJ in 30 fs = 1 GW, 1 x 1015 W.cm-2 in a 10 mm spot

  10. How do you make a laser plasma ? Vacuum or Background Gas Target Plasma Assisted Chemistry Laser Pulse 1064 nm/ 0.01 - 1 J/ 5ps - 10 ns Lens Spot Size = 50 mm (typ.) F: 1011 - 1014 W.cm-2 Te : 10 - 1000 eV Ne: 1021 cm-3 Vexpansion 106 cm.s-1 Emitted - Atoms, Ions, Electrons, Clusters, IR - X-ray Radiation

  11. How is a laser plasma formed ? • Seed electrons are liberated by single (or multi) photon ionization from the surface forming a tenuous plasma • These electrons absorb laser photons by Inverse Bremssstrahlung (IB) and are raised to high energies - e (T1) + ng + (Zn+)  e (T2) + (Zn+), T2 = T1+nЋw • These energetic electrons collide with the target surface causing futher ablation and ionization. • The electron density close to the target surface rises rapidly until a 'critical density layer' is formed where the 'plasma frequency' becomes comparable to the laser frequency, wP = wLaser - wP =(4pe2ne/me)1/2, wLaser =(4pe2nc/me)1/2 - nc (cm-3) = 1.1 x 1021 (1 mm/lLaser)2 • At this point the plasma becomes reflecting and the laser light cannot penetrate through ot the target. • The Plasma plume expands, ne drops below nc, the laser light penetrates through to the surface and the process cycle continues.

  12. Intense Laser Plasma Interaction S Elizer, “The Interaction of High Power Lasers with Plasmas”, IOP Series in Plasma Physics (2002)

  13. What does a Laser Plasma look like ?

  14. Video - Air Breakdown with 150 picosecond laser pulses

  15. Video - Air Breakdown with 150 picosecond laser pulses - EKSPLA 312P

  16. Laser Plasmas - Some Fundamentals The state of a plasma is characterised by e.g., electron temperature, average ion stage, etc. Plasma temperatures, expansion velocities, etc. all easily estimated from simple scaling laws - See Shalom Elizer,' 'The interaction of high power lasers with plasmas' IOP Publishing, 2002 Reviewed by J Costello in 'Contemporary Physics', Vol 44, pp373-374 (2003)

  17. Laser Plasmas  Electron Temperatures D Colombant & G F Tonon, J.Appl.Phys Vol 44, pp3524-3537 (1973) Plasma Electron Temperature Te- dependence on laser wavelength & intensity

  18. Laser-Plasmas  Extreme Plasma Fields

  19. Laser-PlasmasExtreme Plasma Pressure

  20. How highly charged can the ions get ?

  21. Laser Plasmas  Plume Velocity

  22. Plasma plume expands rapidly  need fast (nanosecond) time resolved probes and detectors Solution: Intensified CCD - (ICCD) Essentially a fast framing camera - Nanosecond shutter time & synchonised to laser with low (<ns) jitter !

  23. Time Resolved (gated) ICCD imaging I ICCD Delay-Gate Gen. Nd-YAG 0.5 J/ 15 ns Dt

  24. ICCD Framing Photography (P Yeates, DCU) Video 1 Video 2 Videos of plume emission of laser plasma expanding into vacuum. Each frame is 10 ns wide/ 50 ns delay between frames

  25. Video 1 - Laser Plasma formed on flat Al metal surface

  26. Video 2 - Laser Plasma formed in slot (confined)

  27. So, in summary we know that:Laser Produced Fireballs are-Hot: Te = 105 - 108 KelvinDense: ne= 1021 e/cm3Transient: ps - msRapid: 106 - 107 cm/secDublin to Cork in 3 seconds !!!

  28. Laser - Astrophysical Plasmas - Solar Interior So now we know that laser plasmas are hot & dense ! We can tune temperature, density etc. so that they produce spectra to be compared with spectra from other laboratory and astrophysical sources !! Figure - David Attwood, U C Berkeley

  29. Part II- UV to X-ray Light Sources Generally Extreme-UV Science & Technology is Growing Rapidly Industry: Lithography Bio-Medical: Microscopy Basic Research: Astronomy

  30. Laser Plasmas as VUV to X-ray Light Sources - I Since a laser plasma is HOT - (Te= 10 - 1000 eV) and (say) you consider it to be a black (or grey) body, then most emission should be at photon energies also in the 10 - 1000 eV range, i.e., at Vacuum Ultraviolet (VUV),Extreme-Ultraviolet (EUV)and Soft X-ray (SXR) wavelengths !! Figure from lectures notes of David Attwood, U Calif.-Berkeley

  31. Laser Plasmas as VUV to X-ray Light Sources - II Lots of activity right now driven by prospects for reducing feature sizes in semiconductor lithography - diffraction limit Lithography Slides from David Attwood - Berkeley

  32. EUV- SXR astronomy TRACE Image sunland.gsfc.nasa.gov/smex/trace/ EUV Solar Image using a Multilayer Mirror based Cassegrain Mount Arthur B C Walker: Born: Aug.24, 1936 Died: Apr.29, 2001 From Lectures Notes of Prof. David Attwood, U Calif.-Berkeley

  33. But back to laser-plasma EUV Sources

  34. Our Major Objective: We want to probe matter with wavelength tuneable UV-SXR radiation so that we can study photoabsorption/ photo-ionization. Ergo we need a laser plasma source that emits a 'continuum' from the UV to the soft X-ray: We need a table-top 'synchrotron'

  35. Laser Produced ‘Rare Earth’ Continua Physical Origin, History & Update P K Carroll et al., Opt.Lett 2, 72 (1978)

  36. What is the Origin of the Continuum ? Continua emitted from laser produced rare-earth (and neighbouring element) plasmas are predominantly free-bound in origin Bound - Free Transitions - Recombination/Photoionization* A(n+1)+ + e An+ + h Where have all the lines gone ?

  37. Ultrafast Laser Plasma Continua - I Picosecond LPLS (DCU, QUB & RAL, UK) Meighan, Costello et al., Appl.Phys.Lett 70, 1497 (1997) & J.Phys.B 33, 1159 (2000)

  38. Ultrafast Laser Plasma Continua - II Picosecond EUV Emission Spectra Streak Camera Trace from a W plasma

  39. Summary - LP Continuum Light Sources Table-top continuum light source now well established Covers Deep-UV to soft X-ray spectral range Pulse duration can be < 100 ps ! Continuum flux ~ 1014 photons/pulse/sr/nm Low cost laboratory source Next step - Working on (100 ps) + (6ns) Pre-plasma source - we already see a flux gain of up to X4 with Cu- A Murphy et al., Proc SPIE, 4876, 1202 (2003)

  40. Now we can probe matter with photoionizing radiation from this Fast-Pulsed, Laser Plasma Continuum Light Source

  41. BUT !!! Laser plasmas are also are a source of atoms, ions, clusters, etc. Ergo not only should we be able to develop laser plasmas into light sources but also into samples of atoms and ions to be probed. Result - DUAL LASER PLASMA (DLP) PHOTO-ABSORPTION EXPERIMENTS

  42. DUAL LASER PLASMA (DLP) EXPERIMENTS UV - Xray Source Absorbing Sample

  43. Why Photoabsorption ?  Access to ground/ metastable state (Dark) species  Electric dipole excitation yields tractable spectra

  44. Photoabsorption/ ionization data are relevant to-  Astrophysical spectra and models  Laboratory plasma modelling  Fundamental many-body theory  X-ray laser schemes  ICF

  45. DLP Studies on C Ions (Padua)- I VUV Photoabsorption -Absolute Cross-sections ! Motivation: Ions of astrophys. interest, tests of databases (Opacity, etc.) P Recanatini, P Nicolosi & P Villoresi, Phys. Rev. A 64, Art. No. 012509 (2001) Spaced resolved emission from a W plasma in the VUV around (a) 49 nm and (b) 69 nm Normal Incidence DLP Setup

  46. DLP Studies on Ions (Padua) - II, C+ 2.1 mm 3.3 mm 1.2 J on target in line focus: 9 mm X 0.01 mm Absorption spectra of C+ taken at an inter-plasma delay of 58 ns and at 2.1 and 3.3 mm above the carbon target surface

  47. Summary - Padua Work centres low-Z ions of astrophysical interest All isonuclear sequences of Be, B and C measured. Designed and built DLP systems to work from VUV to Soft X-ray (Carbon K) Have determined absolute photoabsorption cross sections using DLP Group have designed and built many VUV and EUV spectrometers and optical systems for NASA

  48. Dublin Have published upwards of 100 papers on DLP photoabsorption experiments on selected atoms and ions from all rows of the periodic table. Motivation - almost always exploration of some 'quirk' of the photoionization process in a many electron atom ! Recent Examples “Trends in Autoionization of Rydberg States converging to the 4s Threshold in the Kr-Rb+-Sr2+ Series: Experiment and Theory” Amit Neogi, John T Costello et al., Phys.Rev.A 67, Art. No. 042707 (2003) “EUV Ionising Radiation and Atoms and Ions: Dual Laser Plasma Investigations”, E T Kennedy, J T Costello, J-P Mosnier and P van Kampen, Radiat. Phys. Chem. (in press 2004)

  49. BUT NO TIME TO TALK ABOUT THAT RIGHT NOW BECAUSE I WANT TO TALK ABOUT.....................

  50. Part III VUV Photoabsorption Imaging Collaboration between DCU & Univ. Padua Key paper: J Hirsch, E Kennedy, J T Costello, L Poletto & P Nicolosi Rev.Sci. Instrum. 74, 2992 (2003)

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