LASERMATTER INTERACTION STUDIES FOR XRAY PRODUCTION AND CONTROL

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LASER-MATTER INTERACTION STUDIES FOR X-RAY
PRODUCTION AND CONTROL
33rd European Physical Society Conference on
Plasma Physics Rome, June 19 - 23, 2006

• Leonida A. Gizzi

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Outline and Aknowledgements

• X-RAYS FROM LASER-PLASMAS and APPLICATIONS
  in collaboration with C.
  Bellecci, M. Francucci, P. Gaudio, S.
  Martellucci, M. Richetta (Univ. Tor Vergata
  Roma) A. Faenov and T. Pikuz (MISDC of VNIIFTRI,
  Russia) F.Flora (ENEA, Frascati).
• ULTRAFAST LASER INTERACTIONS WITH SOLIDS for
  X-ray studies and production of high-energy
  particles in collaboration with F.
  Zamponi, T. Kämpfer, I. Uschmann, E. Förster, R.
  Sauerbrey (IOQ, Univ. Jena, Germany) A.
  Mackinnon (LLNL, USA), D. Batani, A. Antonicci
  (Univ. Milano Bicocca, Italy) V.R. Albertini
  (ISM-CNR, Italy).

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The ILIL GROUP

• People
• Antonio GIULIETTI (CNR)
• Danilo GIULIETTI (Univ. Pisa)
• Leonida A. GIZZI (CNR)
• Paolo TOMASSINI (CNR)
• Marco GALIMBERTI (CNR)
• Luca LABATE (CNR)
• Petra KOESTER (CNR Univ. of Pisa)
• Tadzio LEVATO (CNR Univ. of Pisa)
• Andrea GAMUCCI (CNR Univ. of Pisa)
• Walter BALDESCHI (CNR)
• Antonella ROSSI (CNR)
• Also associated with INFN, the Nat. Institute
  of Nuclear Physics

http//ilil.ipcf.cnr.it
Area della ricerca CNR, Pisa
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Ultrafast Interactions TOC

• Fast electron propagation
• Main technique X-ray single-photon detection
• Analysis of forward emitted electrons
• First results of oonochromatic X-ray imaging
• Conclusions and perspectives

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Laser-plasma interaction
- plasmas produced by laser intensities above
1018 W/cm2 - expected current of several MA
Application in fusion research (fast ignitor)
RAL Report, J.S.Green et al., et al.,
Need to investigate pattern and divergence of
fast electron beam inside the material
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Ka radiation mechanisms
High energy electron
K
L
M
Laser
Ewald Europhys Lett Vol.60
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Experimental technique
Optical spectroscopy on reflected and diffused
radiation
SP-PHC
10 Hz rep rate fs laser pulse 1-10 TW
Main issue for single photon detection Reduce
unwanted X-ray photons!
Use lots of shielding and magnets!
IOQ, Univ. Jena
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Single-Photon X-ray Spectroscopy (SPS)
Spectral analysis of X-rays generated by
femtosecond laser-plasma interactions is
performed by using a low noise CCD array to
measure the charge produced by each photon
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CCD Calibration set-up (lt2 keV)
NdYLF laser
focusing lens
PIN diode()
Al filter
crystal
Al target
The total crystal to CCD camera distance is about
1m in order to
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Algorithm
Event identification
Subtraction of local background
Sum of charge over pixels of each event
Histogram of events for each class (one pixel,
two pixels etc. )
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Calibration histograms
Response of CCD to monochromatic X-ray photons at
low (lt2keV) photon energy
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CCD Calibration curve for SPS
Calibration at higher (gt2keV) energy was
performed using radioactive sources
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Experiments with high contrast at ILIL
Optical spectroscopy on reflected and diffused
radiation
10 Hz rep rate fs laser pulse 1-10 TW
IOQ, Univ. Jena
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ILIL Laser
TiSa 2TW main beam 0.1 TW probe beam.
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Laser pulse contrast
Autocorrelation trace after second amplifier stage
Measurement carried out by Amplitude Tech. using
a SEQUOIA autocorrelator
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Fast electron generationat low laser intensity
IL1017 W/cm2
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High-energy continuum emission
KTe1.5keV
KTe10keV
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K-alpha emission from Titanium target
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Polarization dependence
K-alpha emission as a function of the
polarisation angle (using wave-plate)
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FORWARD-EMITTED ELECTRONS
Dose is released along the axis perpendicular to
the target.
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Laser
Laser intensity on target 2 x 1017 W/cm2
Dose-sensitive radiation detector (radio-chromic
film)
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FORWARD-EMITTED ELECTRONS
Spectral distribution of forward emitted
electrons are modelled using PIC simulations
Results are consistent with interaction with a
steep (lt ?) density gradient.
Labate et al., submitted
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DETECTING PROPAGATION IN MULTI-LAYER TARGETS
Higher intensity with precursor plasma
Optical spectroscopy
Charged particle detector
100 fs 0.6 J
1019 W/cm2
Laser
Ni
Fe
Cr
Rear pin hole camera
Front pin hole camera
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X-ray Tunable Monocromatic Imaging

• X-ray imaging M11,
• spatial resolution 5 µm
• energy resolution 150 eV
• Stack electron spectrometer (SHEEBA, Galimberti
  RSI 76)
• 3/2 w and 2 w observation
• proton detection

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The signal
Signal must be single photon, to be able to use
the CCD as a spectrometer. mylar foils were used
to attenuate the signal
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2300 eV
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4200 eV
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6400 eV
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11300 eV
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22000 eV
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50000 eV
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Full image (all photons)
Observed on the front side of the target
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Front vs. Rear emission
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Imaging of front and rear side
LASER
250µm
10µm
Cr
Back CCD
10µm
Ni
Front CCD
10µm
Fe
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Lineout of source
FWHM33µm 28µm 47µm
FWHM25µm
LASER
Cr
Ni
Fe
Lineout over 10 pixel
Front CCD
Back CCD
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The geometry

• 2 points of view
• cylindrical geometry
• reconstruction
• of the electron path is possible

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Forward emitted electrons
Target
Radiochromic film layers
Laser
Forward emitted charged Particles (electrons)
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Electron spectrometer
Target
Radiochromic film layers
Laser
Spectrum is obtained matching dose reseased in
each layer with predictions of MC (GEANT4)
through an iterative process.
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Forward emitted electrons
Target
Radiochromic film layers
Laser
Forward emitted charged Particles (electrons)
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Electron acceleration in laser-solid interactions
Target
Narrow e-beam production
Radiochromic film layers
Laser
Forward emitted charged Particles (electrons)
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Electron spectrum
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Electron spectrum at E lt 1MeV
CrNiFe target
Fit with a relativistic Maxwellian
Yields a fast electron temperature of 160 keV
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Modification of electron distribution
Measured energy distribution of forward emitted
electrons includes the electrons that generate
most K-a inside the material
Bethe-Bloch calculation in the three layers
assuming 100 keV rel Maxwellian

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Conclusions

• EXTENSION OF THE SINGLE PHOTON DETECTION
  TECHNIQUE
• TO ENABLE µm-RESOLUTION, MONOCHROMATIC X-RAY
  IMAGING
• TECHNIQUE APPLIED TO DETECTION OF Ka EMISSION
• TO INVESTIGATE FAST ELECTRON PROPAGATION IN
  MULTI-LAYER TARGETS
• INTERACTION OF RELATIVISTIC PULSES WITH
  MULTI-LAYER METALLIC TARGETS show collimated
  propagation of fast electrons inside the material
• ELECTRONS PRODUCING K-a INSIDE THE MATERIAL CAN
  BE CORRELATED with forward emitted electrons
• NEXT STEP IS TO INVESTIGATE PROPAGATION IN
  DIELECTRICS (in progress)