In view of their properties, laser-driven ion beams have the potential to be employed in innovati... more In view of their properties, laser-driven ion beams have the potential to be employed in innovative applications in the scientific, technological and medical areas. Among these, a particularly high-profile application is particle therapy for cancer treatment, which however requires ...
Ion acceleration resulting from the interaction of ultra-high intensity (2 × 1020 W/cm2) and ultr... more Ion acceleration resulting from the interaction of ultra-high intensity (2 × 1020 W/cm2) and ultra-high contrast (~1010) laser pulses with 0.05-10 mum thick Al foils at normal (0°) and 35° laser incidence is investigated. When decreasing the target thickness from 10 mum down to 0.05 mum, the accelerated ions become less divergent and the ion flux increases, particularly at normal
O Tresca 1, DC Carroll 1, XH Yuan 1, 7, B Aurand 2, V Bagnoud 2, CM Brenner 1, 3, M Coury 1, J Fi... more O Tresca 1, DC Carroll 1, XH Yuan 1, 7, B Aurand 2, V Bagnoud 2, CM Brenner 1, 3, M Coury 1, J Fils 2, RJ Gray 1, T Kühl 2, C Li 4, YT Li 4, XX Lin 4, MN Quinn 1, RG Evans 5, B Zielbauer 2, M Roth 6, D Neely 3 and P McKenna 1
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2011
A novel design of a 1-D imaging X-ray spectrometer is implemented, using a high efficiency HOPG (... more A novel design of a 1-D imaging X-ray spectrometer is implemented, using a high efficiency HOPG (highly oriented pyrolitic graphite) Bragg crystal and a double-entrance-slit. The double slit provides self-calibration of the imaging magnification. The spatial and spectral resolutions and dispersion are characterised both analytically and by ray tracing simulations. A key feature of this approach is that it enables the X-ray spectrum to be measured over different regions of the plasma source. The application of this instrument is demonstrated in high intensity laser–foil interaction experiments.
The propagation of fast electrons produced in the interaction of relativistically intense, picose... more The propagation of fast electrons produced in the interaction of relativistically intense, picosecond laser pulses with solid targets is experimentally investigated using Kα emission as a diagnostic. The role of fast electron refluxing within the target, which occurs when the electrons are reflected by the sheath potentials formed at the front and rear surfaces, is elucidated. The targets consist of a Cu fluorescence layer of fixed thickness at the front surface backed with a propagation layer of CH, the thickness of which is varied to control the number of times the refluxing fast electron population transits the Cu fluorescence layer. Enhancements in the Kα yield and source size are measured as the thickness of the CH layer is decreased. Comparison with analytical and numerical modelling confirms that significant refluxing occurs and highlights the importance of considering this phenomenon when deriving information on fast electron transport from laser-solid interaction experiments involving relatively thin targets.
We report on the transverse refluxing of energetic electrons in mass-limited foil targets irradia... more We report on the transverse refluxing of energetic electrons in mass-limited foil targets irradiated with high intensity (1 × 1019 W cm-2), picosecond laser pulses. It is shown experimentally that the maximum energies of protons accelerated by sheath fields formed at the rear and at the edges of the target increase with decreasing target size. This is due to the modification of the sheath field by the energetic electrons which spread laterally along the target surface and reflect from the edges. In addition, it is shown that this transverse refluxing of energetic electrons can be used to tailor the spatial-intensity distribution of the proton beam by engineering the shape and size of the target.
Ion acceleration resulting from the interaction of ultra-high intensity (2 × 1020 W/cm2) and ultr... more Ion acceleration resulting from the interaction of ultra-high intensity (2 × 1020 W/cm2) and ultra-high contrast (~1010) laser pulses with 0.05-10 μm thick Al foils at normal (0°) and 35° laser incidence is investigated. When decreasing the target thickness from 10 μm down to 0.05 μm, the accelerated ions become less divergent and the ion flux increases, particularly at normal (0°) laser incidence on the target. A laser energy conversion into protons of ~6.5% is estimated at 35° laser incidence. Experimental results are in reasonable agreement with theoretical estimates and can be a benchmark for further theoretical and computational work.
The propagation of fast electrons produced in the interaction of relativistically intense, picose... more The propagation of fast electrons produced in the interaction of relativistically intense, picosecond laser pulses with solid targets is experimentally investigated using Kα emission as a diagnostic. The role of fast electron refluxing within the target, which occurs when the electrons are reflected by the sheath potentials formed at the front and rear surfaces, is elucidated. The targets consist of a Cu fluorescence layer of fixed thickness at the front surface backed with a propagation layer of CH, the thickness of which is varied to control the number of times the refluxing fast electron population transits the Cu fluorescence layer. Enhancements in the Kα yield and source size are measured as the thickness of the CH layer is decreased. Comparison with analytical and numerical modelling confirms that significant refluxing occurs and highlights the importance of considering this phenomenon when deriving information on fast electron transport from laser–solid interaction experiments involving relatively thin targets.
The propagation of fast electrons produced in the interaction of relativistically intense, picose... more The propagation of fast electrons produced in the interaction of relativistically intense, picosecond laser pulses with solid targets is experimentally investigated using Kα emission as a diagnostic. The role of fast electron refluxing within the target, which occurs when the electrons are reflected by the sheath potentials formed at the front and rear surfaces, is elucidated. The targets consist of a Cu fluorescence layer of fixed thickness at the front surface backed with a propagation layer of CH, the thickness of which is varied to control the number of times the refluxing fast electron population transits the Cu fluorescence layer. Enhancements in the Kα yield and source size are measured as the thickness of the CH layer is decreased. Comparison with analytical and numerical modelling confirms that significant refluxing occurs and highlights the importance of considering this phenomenon when deriving information on fast electron transport from laser–solid interaction experiments involving relatively thin targets.
Next generation intense, short-pulse laser facilities require new high repetition rate diagnostic... more Next generation intense, short-pulse laser facilities require new high repetition rate diagnostics for the detection of ionizing radiation. We have designed a new scintillator-based ion beam profiler capable of measuring the ion beam transverse profile for a number of discrete energy ranges. The optical response and emission characteristics of four common plastic scintillators has been investigated for a range of proton energies and fluxes. The scintillator light output (for 1 MeV > Ep < 28 MeV) was found to have a non-linear scaling with proton energy but a linear response to incident flux. Initial measurements with a prototype diagnostic have been successful, although further calibration work is required to characterize the total system response and limitations under the high flux, short pulse duration conditions of a typical high intensity laser-plasma interaction.
Radiation pressure acceleration with ultraintense laser pulses presents an exciting new scheme fo... more Radiation pressure acceleration with ultraintense laser pulses presents an exciting new scheme for obtaining energetic protons from a gas jet target. One of the advantages conferred by using a gaseous laser and target is the potential for a fast (1 Hz) repetition rate. This requires diagnostics which are not only comprehensive for a single shot, but also capable of repeated use. We consider several scintillators as candidates for an imaging diagnostic for protons accelerated to MeV energies by a CO2 laser focused on a gas jet target. We have measured the response of chromium-doped alumina (Chromox), CsI:Tl, and a polyvinyl toluene (PVT) screen to protons in the 2-12 MeV range using a CCD camera. We have calibrated the luminescent yield in terms of photons emitted per incident proton for each scintillator. We also discuss photon scattering in each and determine its impact on their respective resolutions. In addition, we consider the impact of radiation intensity on the materials, inc...
ABSTRACT Typical laser acceleration experiments probe the interaction of intense linearly-polariz... more ABSTRACT Typical laser acceleration experiments probe the interaction of intense linearly-polarized solid state laser pulses with dense metal targets. This interaction generates strong electric fields via Transverse Normal Sheath Acceleration and can accelerate protons to high peak energies but with a large thermal spectrum. Recently, the advancement of high pressure amplified CO2 laser technology has allowed for the creation of intense (10^16 Wcm^2) pulses at λ˜10 μm. These pulses may interact with reproducible, high rep. rate gas jet targets and still produce plasmas of critical density (nc˜10^19 cm-3), leading to the transference of laser energy via radiation pressure. This acceleration mode has the advantage of producing narrow energy spectra while scaling well with pulse intensity. We observe the interaction of an intense CO2 laser pulse with an overdense hydrogen gas jet. Using two pulse optical probing in conjunction with interferometry, we are able to obtain density profiles of the plasma. Proton energy spectra are obtained using a magnetic spectrometer and scintillating screen.
ABSTRACT Laser energy absorption to fast electrons during the interaction of an ultra-intense (10... more ABSTRACT Laser energy absorption to fast electrons during the interaction of an ultra-intense (1020 W cm−2), picosecond laser pulse with a solid is investigated, experimentally and numerically, as a function of the plasma density scale length at the irradiated surface. It is shown that there is an optimum density gradient for efficient energy coupling to electrons and that this arises due to strong self-focusing and channeling driving energy absorption over an extended length in the preformed plasma. At longer density gradients the laser filaments, resulting in significantly lower overall energy coupling. As the scale length is further increased, a transition to a second laser energy absorption process is observed experimentally via multiple diagnostics. The results demonstrate that it is possible to significantly enhance laser energy absorption and coupling to fast electrons by dynamically controlling the plasma density gradient.
2012 Abstracts IEEE International Conference on Plasma Science, 2012
ABSTRACT form only given. The physics of the transport of large currents of fast (relativistic) e... more ABSTRACT form only given. The physics of the transport of large currents of fast (relativistic) electrons in dense matter underpins many topics in high intensity laser-solid interactions, including warm dense matter, ion acceleration and the fast ignition approach to inertial confinement fusion. The propagation of fast electrons within the target is subject to transport instabilities (e.g. resistive instabilities) which give rise to filamentation of the beam.
In view of their properties, laser-driven ion beams have the potential to be employed in innovati... more In view of their properties, laser-driven ion beams have the potential to be employed in innovative applications in the scientific, technological and medical areas. Among these, a particularly high-profile application is particle therapy for cancer treatment, which however requires ...
In view of their properties, laser-driven ion beams have the potential to be employed in innovati... more In view of their properties, laser-driven ion beams have the potential to be employed in innovative applications in the scientific, technological and medical areas. Among these, a particularly high-profile application is particle therapy for cancer treatment, which however requires ...
Ion acceleration resulting from the interaction of ultra-high intensity (2 × 1020 W/cm2) and ultr... more Ion acceleration resulting from the interaction of ultra-high intensity (2 × 1020 W/cm2) and ultra-high contrast (~1010) laser pulses with 0.05-10 mum thick Al foils at normal (0°) and 35° laser incidence is investigated. When decreasing the target thickness from 10 mum down to 0.05 mum, the accelerated ions become less divergent and the ion flux increases, particularly at normal
O Tresca 1, DC Carroll 1, XH Yuan 1, 7, B Aurand 2, V Bagnoud 2, CM Brenner 1, 3, M Coury 1, J Fi... more O Tresca 1, DC Carroll 1, XH Yuan 1, 7, B Aurand 2, V Bagnoud 2, CM Brenner 1, 3, M Coury 1, J Fils 2, RJ Gray 1, T Kühl 2, C Li 4, YT Li 4, XX Lin 4, MN Quinn 1, RG Evans 5, B Zielbauer 2, M Roth 6, D Neely 3 and P McKenna 1
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2011
A novel design of a 1-D imaging X-ray spectrometer is implemented, using a high efficiency HOPG (... more A novel design of a 1-D imaging X-ray spectrometer is implemented, using a high efficiency HOPG (highly oriented pyrolitic graphite) Bragg crystal and a double-entrance-slit. The double slit provides self-calibration of the imaging magnification. The spatial and spectral resolutions and dispersion are characterised both analytically and by ray tracing simulations. A key feature of this approach is that it enables the X-ray spectrum to be measured over different regions of the plasma source. The application of this instrument is demonstrated in high intensity laser–foil interaction experiments.
The propagation of fast electrons produced in the interaction of relativistically intense, picose... more The propagation of fast electrons produced in the interaction of relativistically intense, picosecond laser pulses with solid targets is experimentally investigated using Kα emission as a diagnostic. The role of fast electron refluxing within the target, which occurs when the electrons are reflected by the sheath potentials formed at the front and rear surfaces, is elucidated. The targets consist of a Cu fluorescence layer of fixed thickness at the front surface backed with a propagation layer of CH, the thickness of which is varied to control the number of times the refluxing fast electron population transits the Cu fluorescence layer. Enhancements in the Kα yield and source size are measured as the thickness of the CH layer is decreased. Comparison with analytical and numerical modelling confirms that significant refluxing occurs and highlights the importance of considering this phenomenon when deriving information on fast electron transport from laser-solid interaction experiments involving relatively thin targets.
We report on the transverse refluxing of energetic electrons in mass-limited foil targets irradia... more We report on the transverse refluxing of energetic electrons in mass-limited foil targets irradiated with high intensity (1 × 1019 W cm-2), picosecond laser pulses. It is shown experimentally that the maximum energies of protons accelerated by sheath fields formed at the rear and at the edges of the target increase with decreasing target size. This is due to the modification of the sheath field by the energetic electrons which spread laterally along the target surface and reflect from the edges. In addition, it is shown that this transverse refluxing of energetic electrons can be used to tailor the spatial-intensity distribution of the proton beam by engineering the shape and size of the target.
Ion acceleration resulting from the interaction of ultra-high intensity (2 × 1020 W/cm2) and ultr... more Ion acceleration resulting from the interaction of ultra-high intensity (2 × 1020 W/cm2) and ultra-high contrast (~1010) laser pulses with 0.05-10 μm thick Al foils at normal (0°) and 35° laser incidence is investigated. When decreasing the target thickness from 10 μm down to 0.05 μm, the accelerated ions become less divergent and the ion flux increases, particularly at normal (0°) laser incidence on the target. A laser energy conversion into protons of ~6.5% is estimated at 35° laser incidence. Experimental results are in reasonable agreement with theoretical estimates and can be a benchmark for further theoretical and computational work.
The propagation of fast electrons produced in the interaction of relativistically intense, picose... more The propagation of fast electrons produced in the interaction of relativistically intense, picosecond laser pulses with solid targets is experimentally investigated using Kα emission as a diagnostic. The role of fast electron refluxing within the target, which occurs when the electrons are reflected by the sheath potentials formed at the front and rear surfaces, is elucidated. The targets consist of a Cu fluorescence layer of fixed thickness at the front surface backed with a propagation layer of CH, the thickness of which is varied to control the number of times the refluxing fast electron population transits the Cu fluorescence layer. Enhancements in the Kα yield and source size are measured as the thickness of the CH layer is decreased. Comparison with analytical and numerical modelling confirms that significant refluxing occurs and highlights the importance of considering this phenomenon when deriving information on fast electron transport from laser–solid interaction experiments involving relatively thin targets.
The propagation of fast electrons produced in the interaction of relativistically intense, picose... more The propagation of fast electrons produced in the interaction of relativistically intense, picosecond laser pulses with solid targets is experimentally investigated using Kα emission as a diagnostic. The role of fast electron refluxing within the target, which occurs when the electrons are reflected by the sheath potentials formed at the front and rear surfaces, is elucidated. The targets consist of a Cu fluorescence layer of fixed thickness at the front surface backed with a propagation layer of CH, the thickness of which is varied to control the number of times the refluxing fast electron population transits the Cu fluorescence layer. Enhancements in the Kα yield and source size are measured as the thickness of the CH layer is decreased. Comparison with analytical and numerical modelling confirms that significant refluxing occurs and highlights the importance of considering this phenomenon when deriving information on fast electron transport from laser–solid interaction experiments involving relatively thin targets.
Next generation intense, short-pulse laser facilities require new high repetition rate diagnostic... more Next generation intense, short-pulse laser facilities require new high repetition rate diagnostics for the detection of ionizing radiation. We have designed a new scintillator-based ion beam profiler capable of measuring the ion beam transverse profile for a number of discrete energy ranges. The optical response and emission characteristics of four common plastic scintillators has been investigated for a range of proton energies and fluxes. The scintillator light output (for 1 MeV > Ep < 28 MeV) was found to have a non-linear scaling with proton energy but a linear response to incident flux. Initial measurements with a prototype diagnostic have been successful, although further calibration work is required to characterize the total system response and limitations under the high flux, short pulse duration conditions of a typical high intensity laser-plasma interaction.
Radiation pressure acceleration with ultraintense laser pulses presents an exciting new scheme fo... more Radiation pressure acceleration with ultraintense laser pulses presents an exciting new scheme for obtaining energetic protons from a gas jet target. One of the advantages conferred by using a gaseous laser and target is the potential for a fast (1 Hz) repetition rate. This requires diagnostics which are not only comprehensive for a single shot, but also capable of repeated use. We consider several scintillators as candidates for an imaging diagnostic for protons accelerated to MeV energies by a CO2 laser focused on a gas jet target. We have measured the response of chromium-doped alumina (Chromox), CsI:Tl, and a polyvinyl toluene (PVT) screen to protons in the 2-12 MeV range using a CCD camera. We have calibrated the luminescent yield in terms of photons emitted per incident proton for each scintillator. We also discuss photon scattering in each and determine its impact on their respective resolutions. In addition, we consider the impact of radiation intensity on the materials, inc...
ABSTRACT Typical laser acceleration experiments probe the interaction of intense linearly-polariz... more ABSTRACT Typical laser acceleration experiments probe the interaction of intense linearly-polarized solid state laser pulses with dense metal targets. This interaction generates strong electric fields via Transverse Normal Sheath Acceleration and can accelerate protons to high peak energies but with a large thermal spectrum. Recently, the advancement of high pressure amplified CO2 laser technology has allowed for the creation of intense (10^16 Wcm^2) pulses at λ˜10 μm. These pulses may interact with reproducible, high rep. rate gas jet targets and still produce plasmas of critical density (nc˜10^19 cm-3), leading to the transference of laser energy via radiation pressure. This acceleration mode has the advantage of producing narrow energy spectra while scaling well with pulse intensity. We observe the interaction of an intense CO2 laser pulse with an overdense hydrogen gas jet. Using two pulse optical probing in conjunction with interferometry, we are able to obtain density profiles of the plasma. Proton energy spectra are obtained using a magnetic spectrometer and scintillating screen.
ABSTRACT Laser energy absorption to fast electrons during the interaction of an ultra-intense (10... more ABSTRACT Laser energy absorption to fast electrons during the interaction of an ultra-intense (1020 W cm−2), picosecond laser pulse with a solid is investigated, experimentally and numerically, as a function of the plasma density scale length at the irradiated surface. It is shown that there is an optimum density gradient for efficient energy coupling to electrons and that this arises due to strong self-focusing and channeling driving energy absorption over an extended length in the preformed plasma. At longer density gradients the laser filaments, resulting in significantly lower overall energy coupling. As the scale length is further increased, a transition to a second laser energy absorption process is observed experimentally via multiple diagnostics. The results demonstrate that it is possible to significantly enhance laser energy absorption and coupling to fast electrons by dynamically controlling the plasma density gradient.
2012 Abstracts IEEE International Conference on Plasma Science, 2012
ABSTRACT form only given. The physics of the transport of large currents of fast (relativistic) e... more ABSTRACT form only given. The physics of the transport of large currents of fast (relativistic) electrons in dense matter underpins many topics in high intensity laser-solid interactions, including warm dense matter, ion acceleration and the fast ignition approach to inertial confinement fusion. The propagation of fast electrons within the target is subject to transport instabilities (e.g. resistive instabilities) which give rise to filamentation of the beam.
In view of their properties, laser-driven ion beams have the potential to be employed in innovati... more In view of their properties, laser-driven ion beams have the potential to be employed in innovative applications in the scientific, technological and medical areas. Among these, a particularly high-profile application is particle therapy for cancer treatment, which however requires ...
Uploads
Papers by olivier tresca