X-VUV Spectroscopy: A role for laser plasma light sources ?

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X-VUV Spectroscopy A role for laser plasma
light sources ?

• John T. Costello
• National Centre for Plasma Science Technology
  (NCPST) and School of Physical Sciences, Dublin
  City University

RAL-CLF Workshop on Applications Laser Plasma
Generated X-rays, Jan 14 - 2003
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The Remit

• Contribute to the discussion on a new (laser
  plasma) X-ray (X-VUV) source for the CLF

Related question - Where do LPLS fit in the
todays source value chain ?
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Presentation Structure

• The Centre for Laser Plasma Research (CLPR) Node
  of the NCPST What do we do ?
• DCU and the CLF What have we done at RAL why
  are we here today ?
• Whats hot in At.Mol.Phys ?
• Next generation experiments in photoionization
• A new LPLS for (photoionization) at the CLF

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NCPST/ CLPR - Who are we ?

• NCPST established with Irish Government funding
  (Euro 8M) in 1999. Now EU Training Site.
• Consortium of new and existing laboratories in
  plasma physics, chemistry and engineering
• Fundamental and Applied Scientific Goals
• CLPR node is divided into 4(6) laboratories
  focussed on PLD and photoabsorption spectroscopy/
  imaging

Staff John T. Costello, Eugene T. Kennedy,
Jean-Paul Mosnier and Paul van Kampen Postdocs Dr
. Amit Neogi, Dr. Mohamed Khater - 1 new EU and
1 new SFI Fellow PGs John Hirsch, Kevin
Kavanangh, Adrian Murphy (JC) Jonathan Mullen
(PVK), Alan McKiernan, Mark Stapleton (JPM),
Eoin OLeary Pat Yeates (ETK)
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V-UV Photoabsorption Imaging Laboratory
Project Title VUV Photoabsorption
Imaging Project Aim To develop VUV
photoabsorption imaging as a diagnostic of
expanding plasma plumes (and other dynamic
samples) Key Reference J. Hirsch et al., JAP
88, 4953 (2000) Rev.Sci.Instrum (submitted) DCU
Personnel John Hirsch, Kevin Kavanagh John T.
Costello Collaborators Giorgio Nicolosi and Luca
Poletto (Univ. Padua) First Experiment RAL-CLF
X-ray Laboratory 1999
Project Title VUV Thin Film Imaging (DCU - AC
Fellowship) Project Aim Use the VPIF to perform
transmission and reflection imaging and
spectroscopy of thin films. DCU Personnel
Jonathan Mullen and Paul van Kampen
Key Words Plasma, Laser, Spectroscopy, Imaging,
VUV
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X-UV Spectroscopy Laboratory
Project Title Controlled Generation of Laser
Plasmas Project Aim Optical diagnostics of
plasmas formed on non-planar target
configurations (e.g., confined in
capilliaries) in magnetic fields CLPR
Personnel Pat Yeates and Eugene T Kennedy
Collaborators J Lunney (TCD)
Project Title Dual Laser Plasma
Absorption Aim Study of fundamentals of
photoabsorption by simple ions e.g., recently
Kr-like ions (Rb and Sr2) Key Reference A
Neogi et al., Phys.Rev.A (Submitted Dec. 02)
CLPR Personnel J T Costello, E Kennedy, J-P
Mosnier and P van Kampen Collaborators Gerry
OSullivan (UCD) and Victor Sukhorukov (State
Univ. Rostov)
Key Words Plasma, Laser, Probe, Spectroscopy, XUV
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V-UV Spectroscopy Laboratory
Project Title Analytical Characterisation of
Steel Alloys Project Aim VUV Laser Induced
Plasma Spectroscopy Technique (VUV-LIPS) Record
detection limits for C in Steel ( 2ppm !!) Key
Reference M A Khater, J T Costello and E
Kennedy, Appl.Spec. 56, 970 (2002) CLPR
Personnel E OLeary, M Khater, E T Kennedy and
J T Costello,
Key Words Plasma, Laser, Analytical
Spectroscopy, LIPS, VUV
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Soft X-ray (SXR) Spectroscopy Laboratory (new)
Project Title SXR Absorption Spectroscopy Pro
ject Aim To extend the current Dual Laser Plasma
Photoabsorption technique (XUV/ 20 ns) into the
X-ray (0.2 - 2nm) and picosecond time
domains. DCU Personnel Adrian Murphy, Eugene
Kennedy and John T. Costello Collaborators
Padraig Dunne/Gerry OSullivan (UCD) and Ciaran
Lewis (QUB) First Experiment RAL-CLF ASTRA 2002
Key Words Plasma, Laser, Point Projection
Imaging, X-ray,
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Pulsed Laser Deposition Laser Ablation
Diagnostics Lab(s)
Project Title Pulsed Laser Deposition Project
Aim PLD of GaN and ZnO. Laser Plasma
Spectroscopy and Imaging is carried out at DCU to
characterize the ablation mechanisms. Films
are grown in TCD (soon DCU) and tested in DCU
using 10K laser induced photoluminescence
technique. Key Reference K Mah et al., Appl.
Phys. Lett 80, 3301 (2002) CLPR Personnel Mark
Stapleton, Alan McKiernan and Jean-Paul
Mosnier Collaborators D OMahony J Lunney
(TCD) / E McGlynn M Henry (DCU)
VUV CCD
Key Words PLD, Laser Ablation, Spectroscopy,
Imaging
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DCU and the CLF _at_ RAL

• Collaborated on 4 x EU-LSF Access Projects since
  1995 3 in the XR Lab and 1 at ASTRA
• Work centred on development/ characterisation of
  picosecond XUV LPLS and their application in
  absorption spectroscopy/ imaging of LP plumes
• CLF provides opportunities to access fast and
  ultrafast lasers in a flexible environment
• Pathfinder experiments, performed at the CLF,
  have underpinned success in levering Irish
  Government funds for new facilities at DCU

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Whats hot in at. mol. physics ?

• Ultra-cold
• Atomic BEC
• Ultracold Molecules and Collisions
• Atoms and Molecules in Laser Fields
• 1. Attosecond pulse generation/ HHG
• 2. Photoionization of state prepared species
• (a) Weak Optical Weak X-VUV
• (b) Intense Optical Weak X-VUV
• (c) Intense Optical Intense X-VUV
• 3. Atoms, Molecules, Cluster Ions in Intense
  Fields (Multiple-Photo and Optical
  Field-Ionization)

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Experiment Type I
(a) Weak Optical Weak X-VUV
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Photoionization of Laser Excited Species (Weak
Optical Weak X-VUV)
Investigation of Na 2p53s3p resonances using
angle resolved photoelectron spectroscopy of
laser excited-aligned sodium atoms, S Baier, M
Schulze, H Staiger, P Zimmermann, C Lorenz, M
Pahler, J Ruder, B Sonntag, J T Costello and L
Kiernan, J.Phys.BAt.Mol.Opt.Phys 27, 1341 (1994)
Experimental Setup
Level Scheme
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CIS (expt. theor.)
Angle Resolved PES
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Can it be done at the XR Lab ?
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Picosecond Dual Laser Plasma Photoionization at
the CLF
O Meighan, C Danson, L. Dardis, C L S Lewis, A
MacPhee, C McGuinness R ORourke, W Shaikh, I C
E Turcu and J T Costello, J.Phys.BAt.Mol.Opt.Phy
s 33, 1159 (2000)
OPO/DYE
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So type I (weak laser excitation) experiments
appear straightforward with current laser
technology
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Experiment Type II
(b) Intense Optical Weak X-VUV
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Photoionization of Atoms in Intense Fields -
(Intense Optical Weak X-VUV)
1. Bathe an atom in resonant X-VUV and optical
fields e.g., He, Li (Hollow), Ca, Ca, Ba,
Ba,.. He - 1s2 (1S) hnXUV-gt 2s2p (1P)
(intense)hnLaser lt-gt 2s3d (1D) 2. hnLaser
3.574 eV (2 - 4 eV typ.) 3. Proposal around for
a long time (Lambropoulos on He in1986) 4. No
(?) experiments to date 5. Precursor to such
experiments at VUV and X-FELs
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Hollow Li (Field Free)
1s22s(2S) (weak) hnXUV-gt 2s22p (2P)
Satellite to 1st member of the famous Madden
Codling 2e series in He 1s2(1S) (weak) hnXUV-gt
2s2p (1P)
First Observation of a Photon Induced Triply
Excited State in Atomic Lithium L Kiernan, J-P
Mosnier E T Kennedy, J T Costello and B F
Sonntag, Phys.Rev.Lett 72 2359 (1994)
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Laser-Excited Hollow Li
1s22s(2S) (weak)hnLaser-gt 1s22p (2P)
(weak)hnXUV -gt 2s2p2 (2D)
Experiment - D Cubannes et al. PRL 77, 2194,
(1996)
Hollow Li in an intense laser field
1s22s(2S) hnXUV-gt 2s22p (2P)
(intense)hnLaser lt-gt 2s23d (2D)
Theory- L Madsen, P Schlagheck and P
Lambropoulos, PRL Vol 85, pp42-45 (2000)
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Photoionization of Atoms in Intense Fields -
Predictions
L Madsen, P Schlagheck and P Lambropoulos, PRL
Vol 85, pp42-45 (2000)
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This is not an easy experiment !
In principle you just cross the sample with
intense laser and weak XUV beams BUT The
Sample must be dilute - other wise RLDI will
dominate and drive it into an ionized state
Sample dilute gt DLP photoabsorption experiment
is unsuitable Can still use a laser plasma X-VUV
source BUT Need wavelength selection and high
(average) X-VUV intensity More sophisticated
Photoion (or electron) spectroscopy needed Count
rate low - 1 ion/laser shot for He with Vint
10 -3 cm-3 !
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But - the Ca Ca 3p-3d resonances have 1.
Cross sections up to 3000 MB .vs. lt 1MB for Li 2.
An excitation widths up to 100s meV 3. A VUV
(normal incidence) excitation energy (31 eV)
Scheme- Ca 3p64s (2S) hnXUV-gt 3p53d4s (2P)
hnLaser lt-gt 3p53d4p (2D)
Possible collaboration with QUB on ion beam/TOF
? Many other possibilities - Ca, Ba, Sr, Na, K
and their ions
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What about the X-VUV source and tunable laser
needed ?
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A Laser-Plasma X-Ray Source for Photoionization
at the CLF ?
Wanted ! Reliable, Economical, Accessible,
Flexible, 10 ps, High Rep. Rate, High Fluence/
High Average Power (tuneable)VUV - X-ray
Source Synchronised, high flux, tuneable (UV -
IR) laser source (OPG ?)
Desirable ! Good laser and plasma optical
diagnostics suite Full time laser support
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Laser Specifications
Laser (Plasma) Source 1. PRF 1 - 1000 Hz
(selectable) 2. Pulse energy 500 mJ - 1 mJ
(selectable) 3. Pulse duration lt10 ps - 50 ps
(selectable) 4. Intensity 1012 - 1015 W.cm-2
(thermal X-rays) 5. X-VUV duration lt 100 ps 6.
X-VUV tuning Continuous, 0.1 - 100 nm
What might approaching this spec. right now ? A
pulse-train laser driven XUV source for
picosecond pump-probe experiments in the water
window M Beck, U Vogt, I Will, A Liero, H Stiel,
W Sandner and T Wilhelm, Opt. Comm. 190,
pp317-326 (2001)
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LP Source Details
2 trains per second/ 25 - 400 Micro-Pulses per
train 15 mJ - 0.5 mJ per micropulse 25 ps pulse
duration XUV Pulse Duration (44 ps - Cu and 73 ps
- PET)
Experimental Setups
Laser and XUV Pulse Trains
1011 Ph./1/sr/train !!
All Solid State !
XUV Spectra (line and continuum)
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What about ASTRA ?

• 1. Ideal for super-intense laser matter
  interactions - Up to 1019 W.cm-2 and really
  useful for testing ideas before full Vulcan PW
  experiments.
• 2. Generates HXR (Bremsstrahlung K-alpha
  radiation) and HE particles - Many high end
  applications e.g., X and p- Radiography,
  relativistic effects in plasmas, ...
• 3. Pre-compression (600 psec) beam (500 mJ) could
  be used to generate thermal X-rays. However
  EKSPLA 312P (1064 nm/ 500 mJ in 150 psec) costs lt
  75K and so calls into question whether this
  would be making best use of ASTRA ?
• 4. ASTRA PRF limited to 10 Hz - problem for ion
  counting!

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Optical Source to Bathe Atoms in Intense
Resonant Fields
Parameters Wavelength Range 300 nm - 600
nm Pulse Duration gt X-VUV Duration Threshold
(He/Li) lt1010 W.cm-2 Footprint 0.03 cm x 0.03
cm Peak Power 0.1 GW
Tuneable Lasers Getting There ? OPO/DYE e.g.,
Continuum Panther - 100 mJ in 4 ns gt 0.025 GW
or Continuum ND6000 (Powerlite 8010/532 nm) 200
mJ in 5 ns gt 0.04 GW
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But what about..
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(c) Intense Optical Intense X-VUV ?
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X-VUV FELs Femtosecond OPAs- The Ultimate
Photoionization Expt ?

• Tuneable NOW! 80 - 110 nm (20 - 60 nm in 2004)
• Ultrafast 100 fs pulse duration
• High PRF 1 - 10 bunch trains/sec with up to
  11315pulses/bunch
• Energy Up to 1 mJ/bunch
• Intense 100 mJ (single pulse) /100 fs /1 mm gt
  1017 W.cm-2
• Moving to XUV (2004) and X-ray (2010)
• Need a Linac insertion devices gt Fraction of a
  GigaEuro !!
• Project Title Pump-Probe with DESY-VUV-FEL
  (EU-RTD)
• Aim FEL OPA synchronisation with sub ps
  jitter
• Key Reference http//tesla.desy.de/new_pages/TDR_
  CD/start.html
• Personnel MBI, DESY, CLPR-DCU, LURE, LLC, BESSY

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Why the CLF XR Lab and not Diamond or 4 GLS ?
1. 105 - 108 ph./micropulse at G3 synchrotrons 2.
Sci. Tech. Transfer 3. Access (particularly
FELs)
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Before I forget ! Many thanks to all
collaborators at the CLF XR Lab at ASTRA TA2
for their commitment, advice, support and
interest over the past years
Summary coming up
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Conclusions

• Need VUV/XUV/X-ray source with shortest possible
  pulse width commensurate with providing high
  flux/pulse and high average power (continuously
  tunable) radiation
• Must be flexible on pulse repetition rate x
  energy per pulse product !
• Combining with a high peak power tunable source
  opens up possibilities to study photoionization
  of a whole range of atoms, ions, etc. in weak and
  intense resonant fields for the first time
• Good laser, laser plasma source and photoion
  diagnostics highly desirable