Transcript X-VUV Spectroscopy and Imaging: A role for laser plasma

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
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 today’s ‘source value chain’ ?
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 ?

What’s hot in At.Mol.Phys ?

Next generation experiments in photoionization

A new LPLS for (photoionization) at the CLF
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 O’Leary & Pat Yeates (ETK)
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:
DCU Personnel:
Collaborators:
First Experiment:
J. Hirsch et al., JAP 88, 4953 (2000) & Rev.Sci.Instrum (submitted)
John Hirsch, Kevin Kavanagh & John T. Costello
Giorgio Nicolosi and Luca Poletto (Univ. Padua)
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
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 O’Sullivan (UCD) and Victor Sukhorukov (State Univ. Rostov)
Key Words: Plasma, Laser, Probe, Spectroscopy, XUV
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 O’Leary, M Khater, E T Kennedy and J T Costello,
Key Words: Plasma, Laser, Analytical Spectroscopy, LIPS, VUV
Soft X-ray (SXR)
Spectroscopy Laboratory (new)
Project Title: SXR Absorption Spectroscopy***
Project 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 O’Sullivan (UCD) and Ciaran Lewis (QUB)
First Experiment: RAL-CLF ASTRA 2002
Key Words: Plasma, Laser, Point Projection Imaging, X-ray,
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
VUV
laser induced photoluminescence technique.
CCD
Key Reference:
CLPR Personnel:
Collaborators:
Key Words:
K Mah et al., Appl. Phys. Lett 80, 3301 (2002)
Mark Stapleton, Alan McKiernan and Jean-Paul Mosnier
D O’Mahony & J Lunney (TCD) / E McGlynn & M Henry (DCU)
PLD, Laser Ablation, Spectroscopy, Imaging
DCU and the CLF @ 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
What’s 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)
Experiment Type I
(a) Weak Optical + Weak X-VUV
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.B:At.Mol.Opt.Phys 27, 1341 (1994)
Experimental Setup
Level Scheme
CIS (expt. & theor.)
Angle Resolved PES
Can it be done at the XR Lab ?
Picosecond Dual Laser Plasma Photoionization at the CLF
O Meighan, C Danson, L. Dardis, C L S Lewis, A MacPhee, C McGuinness R O’Rourke,
W Shaikh, I C E Turcu and J T Costello, J.Phys.B:At.Mol.Opt.Phys 33, 1159 (2000)
OPO/DYE
So type I (weak laser excitation)
experiments appear straightforward
with current laser technology
Experiment Type II
(b) Intense Optical + Weak X-VUV
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-> {2s2p (1P) + (intense)hnLaser <-> 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
Hollow Li (Field Free)
1s22s(2S) + (weak) hnXUV-> 2s22p (2P)
Satellite to 1st member of the famous
Madden & Codling 2e series in He:
1s2(1S) + (weak) hnXUV-> 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)
Laser-Excited Hollow Li
1s22s(2S) + (weak)hnLaser-> 1s22p (2P) + (weak)hnXUV -> 2s2p2 (2D)
Experiment - D Cubannes et al. PRL 77, 2194, (1996)
Hollow Li in an intense laser field
1s22s(2S) + hnXUV-> {2s22p (2P) + (intense)hnLaser <-> 2s23d (2D)}
Theory- L Madsen, P Schlagheck and P Lambropoulos, PRL Vol 85, pp42-45 (2000)
Photoionization of Atoms
in Intense Fields - Predictions
L Madsen, P Schlagheck and P Lambropoulos, PRL Vol 85, pp42-45 (2000)
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 => 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 !
But - the Ca & Ca+ 3p-3d resonances have:
1. Cross sections up to 3000 MB .vs. < 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-> {3p53d4s (2P) + hnLaser <-> 3p53d4p (2D)}
Possible collaboration with QUB on ion beam/TOF ?
Many other possibilities - Ca, Ba, Sr, Na, K and their ions
What about the X-VUV source
and tunable laser needed ?
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
Laser Specifications
Laser (Plasma) Source
1. PRF:
2. Pulse energy:
3. Pulse duration:
4. Intensity:
5. X-VUV duration:
6. X-VUV tuning:
1 - 1000 Hz (selectable)
500 mJ - 1 mJ (selectable)
<10 ps - 50 ps (selectable)
1012 - 1015 W.cm-2 (thermal X-rays)
< 100 ps
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)
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
All Solid State !
1011 Ph./1%/sr/train !!
XUV Spectra (line and continuum)
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 pRadiography, 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 < $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!
Optical Source to Bathe Atoms
in Intense Resonant Fields
Parameters
Wavelength Range:
Pulse Duration:
Threshold (He/Li):
Footprint:
Peak Power:
300 nm - 600 nm
> X-VUV Duration
<1010 W.cm-2
0.03 cm x 0.03 cm
0.1 GW
Tuneable Lasers Getting There ?
OPO/DYE
e.g., Continuum Panther - 100 mJ in 4 ns
=> 0.025 GW or
Continuum ND6000 (Powerlite 8010/532 nm)
200 mJ in 5 ns => 0.04 GW
But what about……..
(c) Intense Optical + Intense X-VUV ?
X-VUV FELs + Femtosecond OPAsThe Ultimate Photoionization Expt ?
Tuneable:
Ultrafast:
High PRF:
Energy:
Intense:
NOW! 80 - 110 nm (20 - 60 nm in 2004)
100 fs pulse duration
1 - 10 bunch trains/sec with up to 11315pulses/bunch
Up to 1 mJ/bunch
100 mJ (single pulse) /100 fs /1 mm => 1017 W.cm-2
•Moving to XUV (2004) and X-ray (2010):
•Need a Linac + insertion devices => Fraction of a GigaEuro !!
Project Title: ‘Pump-Probe’ with DESY-VUV-FEL (EU-RTD)
Aim:
Key Reference:
Personnel:
FEL + OPA synchronisation with sub ps jitter
http://tesla.desy.de/new_pages/TDR_CD/start.html
MBI, DESY, CLPR-DCU, LURE, LLC, BESSY
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)
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
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