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Laser- driven generation o f intense ion beams for fusion-related applications Jan Badziak

Laser- driven generation o f intense ion beams for fusion-related applications Jan Badziak Institute of Plasma Physics and Laser Microfusion, Warsaw, Poland. Tenth Kudowa Summer School „Towards Fusion Energy”, June 14 – 18, 2011. Outline.

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Laser- driven generation o f intense ion beams for fusion-related applications Jan Badziak

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  1. Laser-driven generation of intense ion beams for fusion-related applications Jan Badziak Institute of Plasma Physics and Laser Microfusion, Warsaw, Poland Tenth Kudowa Summer School „Towards Fusion Energy”, June 14 – 18, 2011

  2. Outline • Fast ignition of a fusion target and requirements for an ion ignitor • Generation of ion beams using the target normal sheath acceleration mechanism • Acceleration of ions by ponderomotive (radiation) pressure • proton beams from an insulator target • the short-wavelength laser driver • the laser driver with circular light polarization • ion acceleration in the LICPA accelerator • Summary

  3. Conventional Inertial Confinement Fusion MEGAJOULE LASER FACILITIES FOR ICF Ignition and energy gain ispredicted to be demonstrated in 2012 - 2013

  4. Fast Ignition Approach to ICF i i • Fast Ignition (FI) decouples the compression driver from the ignitor • FI approach offers: • lower compression driver energy (5 – 10x) • reduced susceptibility to parasitic hydrodynamic effects • flexibility in compression drivers • higher energy gain Tabak et al., PoP 1994;

  5. Fast Ignition – General Concepts The originalconcept of Tabak et al., assumes that the ultra-intense ps laser pulsepenetrates to the dense fuel through a channel bored in the plasma by a preceding 100-ps laser pulse. The relativistic electron beam produced at the interaction of the ultra-intense pulse with the dense plasma ignites the fuel The ultra-intense ps laser pulse penetrates close to the dense fuel through a hollow cone. The particle beam generated at the interaction of the laser pulse with the cone, or the target placed inside the cone, ignites the fuel Tabak et al., PoP 1994 Hatchett et al., 2000; Norreys et al., PoP 2000, Kodama et al., Nature 2001, 2002

  6. Fast Ignition – General Concepts Ignitors Compression drivers • driven by a PW laser • electron beam • proton beam • light ion beam • others • heavy ion beam • ultrafast macroparticle (impact ignition) • ? • laser • (direct or indirect drive) • heavy ion accelerator • (indirect drive) • Z-pinch machine • (indirect drive) The most studied FI schemes employ a multi-PW laser-drivenelectron or proton/ion beam as a fuel ignitor and a high-energy laser as a compression driver

  7. Electron Beam Ignitor vs Ion Beam Ignitor • Ion beam • Advantages: • high efficiency of the ion beam energy deposition to the fuel • more effective control of the ion beam parameters • more stable, ballistic transport • Drawbacks: • lower laser-ions energy conversion efficiency • more complex target • necessity for the ion beam focusing (?) • Electron beam • Advantages: • high laser-electrons energy conversion efficiency (up to 40%) • relatively simple target • Drawbacks: • difficulties with controlling the electron beam parameters (angular divergence, spectrum, ...) • complex electron transport from the source to the fuel • lower efficiency of the electron beam energy deposition to the fuel

  8. Ion Fast Ignition • Requirements for an ion beam: • (at  300 g /cm3) • beam energy 15 – 20 kJ • mean ionenergy 10 – 40 MeV/amu • beam intensity  1020 W/cm2 • ion current density  1012A/cm2 • pulse duration 5 – 20 ps • beam power 1 – 4 PW • beam size40 m • ion production efficiency  15% LHC proton bunch: 125 kJ 7 TeV 2 x1020 W/cm2 3 x107A/cm2 250 ps 0.5 PW 20 m Scheme for IFI • Two laser methods of ion beam generation seem to have potential to meet these requirements: • Target Normal Sheath Acceleration (TNSA) • Skin-Layer Ponderomotive Acceleration (SLPA)/ Radiation Pressure Acceleration (RPA) Atzeni et al.; NF 2002; Temporal et al., PoP 2002; Badziak et al., PPCF 2007

  9. Generation of Ion Beams by TNSA Requirements and characteristic features The requirements: • a metal target, typically of LT 2 - 50mm (light ions are produced from contaminants) • a short (<10ps) laser pulse • relativistic or subrelativistic laser intensity • moderate preplasma scale length Ln 1 – 10 lL The features: • ionsare produced and accelerated at the rear target surface, mostly along the surface normal • focusing of the ion beam by curving the rear surface is possible; • the ion source area Ss >>SL(absorbed laser energy is dispersed in the target volume) • the ion density at the source is moderate:ni ~ 1019cm-3high-intensity ion beams can be produced only at high (multi-MeV) ion energies • the areal ion density is relatively smal si≤ 1017 cm-2 high-power (high-current) ion beams can be produced only from the ion source of a large area • the ion energy spectrum is broad (quasi-maxwellian)

  10. Target: 15µm Au • N = 1.4 E12 protons • T = 3.0 MeV • E = 670 mJ • = 2% laser energy Divergence 1-20deg 3.8MeV 6.5MeV 11MeV 14MeV 17MeV 20MeV Proton Beams Produced by TNSA TNSA proton beam generation and focusing – experimental results E= 37J 0.7ps 5x1019Wcm-2 High-quality MeV proton beams are routinely generated using TNSA The laser-protons conversion efficiency of 10% was achieved Proton beam focusing and isochoric heating of the solid by protons were demonstrated Key et al., FST 2006 MacKinnon et al., FIW 2006; Patel et al., PRL 2003

  11. Proton Beams Produced by TNSA TNSA laser-protons energy conversion efficiency as a function of laser energy (for 1ps pulse) and the laser pulse duration (at 8 1019 W/cm2). The VULCAN PW experiment The conversion efficiency for protons of energy > 4 MeV exceeds 6% for laser energy 300J and intensity ~ 6 1020W/cm2. The conversion efficiency increases more slowly than linearly with laser energy (intensity). Robson et al., Nature Phys. 3, 58 (2007)

  12. Proton Beams Produced by TNSA Maximum proton energy as a function of laser intensity (for 1ps pulse) and the laser pulse duration (at 8 1019 W/cm2). The VULCAN PW experiment At laser intensity IL 6 1020 W/cm2 the maximum proton energy attains 55 MeV. Above 100 MeV can be achieved at IL>21021W/cm2. The maximum energy increases roughly as with laser intensity. Robson et al., Nature Phys. 2007

  13. Proton Beams Produced by TNSA Possible ways to improve proton beam parameters • To increase the conversion efficiency: • using a double-layer target (eg. Au/CH) (Badziak et al., PRL 2001, JAP 2008) • employing a double laser pulse(Markey et al., PRL 2010) • using a micro-structured target(Kawata et al., IEEE TPS 2009) • ? • To narrow the energy spectrum: • using a double-layer target with a proton dot (small proton number)(Schwoerer et al., Nature 2006) • using a sofisticated two-component target (low conversion efficiency)(Hegelich et al., Nature 2006) • ?

  14. TNSA-driven Ions for Fast Ignition Summary • Advantages: • excellent quality of the ion (proton) beam transverse distribution • very low transverse emittance of the beam • moderate requirements for the laser beam quality • experimentally confirmed properties • Drawbacks: • the laser-protons energy conversion efficiency (for the required proton /ion energies) probably limited to ~ 10 – 15% and to yet smaller value for heavier ions the laser driver of energy > 100 kJ is needed, • small areal proton/ion density ( 1017 cm-2) the area of the proton/ion source has to be large (>2 - 5 mm2)  high (>100PW)laser power is needed •  strong focusing of the beam is necessary to increase the proton/ion density by a factor 103 – 104 • broad (quasi-maxwellian) proton/ion energy spectrum lower efficiency of the beam transport and the beam energy deposition to the fuel •  the proton/ion source has to be very close to the fuel • high sensitivity of the proton/ion parameters and the conversion efficiency on the target rear surface quality an effective protection of the rear surface aqainst radiation emited from the fuel and mechanical deformations is necessary.

  15. SLPA employes strong ponderomotive forces induced at the interaction of a short laser pulse with a thin and densepreplasma layercreated by the laser pulse leading edge in front of a target. The (main) laser pulse interacts with the preplasma near the critical plasma surface producing two opposite ponderomotive forces. These forces drive two plasma (ion) bunchesmoving in forward and backward direction. At high plasma density gradient and relativistic laser intensity the forward-directed ponderomotive force (the ponderomotive/radiation pressure) clearly prevails the backward-directed one and, actually, only a high-density forward-accelerated ion bunch is generated. Two stages can be distinguished in the (forward) acceleration process: - the hole boring stage, when ion (plasma) bunch is formed, compressed and accelerated by the ponderomotive (radiation) pressure inside the target, - the light sail stage, when the ion (plasma) bunch (or the target as a whole) is accelerated by the ponderomotive pressure after leaving the target initial position. Exemplary references: Denavit, PRL 1992; Badziak et al., PPCF 2004, APL 2006; Macchi et al., PRL 2005; Robinson et al., NJP 2008.

  16. Generation of Forward-Accelerated Ion Beams by SLPA Requirements and characteristic features The requirements: • an insulator target (for linearly polarized light) or a circularly polarized laser beam or a short-wavelength laser beam • a short (≤ 10ps) laser pulse • relativistic laser intensity • a small preplasma scale length Ln < ~ lL The features: • ions are produced and accelerated in front of the target,mostly along the laser beam axis • the ion source area Ss SL • focusing of the ion beam by curving thefront target surfaceis possible • the ion density at the source ishigh:ni > 1021- 1022cm-3  high-intensity ion beams can be produced even at moderate ion energies • the areal ion density is high : si 1017 – 1020 cm-2 high-power (high-current)ion beams can be produced from the ion source of a small area

  17. Generation of Ion Beams by SLPA The ways to reach the fast ignition requirements • to optimize the target structure (eg. insulator double-layer target) • to use a short-wavelength laser beam • to use a circularly polarized laser beam • to combine the advantage of short wavelength with that of circular polarization • to employ the LICPA accelerator

  18. Production of Intense Proton Beams Using an Insulator Target The 100TW LULI experiment – experimental set-up and basic parameters • Laser beam • pulse duration L = 0,35 ps • energy EL = 0.5 – 15 J • intensity IL = 5 × 1016 – 2 × 1019 W/cm2 • focal spot diameter dL = 10 – 50 m • prepulse intensity Ipre≤1010 – 2 × 1012 W/cm2 • wavelength L = 1.05 m or 0.53 m • linear polarization • Target • polystyrene (PS) of the thickness LT = 0.6 – 5 m • double-layer Au/PS of LT = 1 – 3 m • (PS covered by 0.05 – 0.2 m Au front layer) The laser-target interaction conditions approach the SLPA requirements

  19. Production of Intense Proton Beams Using an Insulator Target The proton beam intensity at the source and the laser-protons energy conversion efficiency as a function of the 1w laser beam intensity for moderate-energy (0.1 – 3 MeV) protons For MeV protons, the beam intensity approaches 1018 W/cm2 and the conversion efficiency is nearly 4% at 2 x 1019 W/cm2. These parameters are remarkably higher when sub-MeV protons are also taken into account Badziak et al., J. Appl. Phys. 2008

  20. Production of Intense Proton Beams Using an Insulator Target The proton beam intensity at the source as a function of the preplasma density gradient scale length experiment: Both 1D PIC simulations and the momentum-conservation model result in the proton beam intensity value ~1018W/cm2, in agreement (within a factor 2) with the value estimated from the measurements (assuming the SLPA model of proton acceleration) Badziak et al., J. Appl. Phys. 2008

  21. Production of Intense Proton Beams Using an Insulator Target A comparison of the proton beam intensity at the source and the laser-protons energy conversion efficiency for Au/PS and PS targets for protons of energy Ep< 3MeV IL= 2 x 1018 W/cm2 , lL= 1.05 mm The proton beam intensity and the conversion efficiency for Au/PS target are twice as high as those for PS target Badziak et al., J. Appl. Phys. 2008

  22. Production of Intense Proton Beams Using an Insulator Target A comparison of the proton energy spectrum in the high-energyrange for PS and Au/PS targets at different laser intensities of the 1w beam Au/PS target produces a high-energy proton beam of higher intensity and temperature for both moderate and high laser intensity. A high-temperature component can be seen for both laser intensities Badziak et al., J. Appl. Phys. 2008

  23. Production of Intense Proton Beams Using an Insulator Target Summary • Using an insulator target enables us to increase the contribution of the SLPA mechanism to the ion acceleration process and to produce a moderate-energy (1 – 3 MeV) proton beam of intensity at the source approaching 1018 W/cm2. • The proton beam intensity and the laser-protons conversion efficiency can be increased by a factor 2 using a double-layer (Au/PS) target.

  24. Proton Beams Driven by a Short-Wavelength Laser Parameters of proton beams driven by laser pulses of different wavelengths as a function of the target thickness. IL2 = 5  1019 Wcm-2m2, L = 1ps Parameters of proton beams at ILl2 = const are the higher the shorter is the wavelength of the laser driver. For the 3w-driver the laser-protons energy conversion efficiency attains the values  15% for a broad range of the target thicknesses. J. Badziak and S. Jabłoński, Phys. Plasmas 2010

  25. Proton Beams Driven by a Short-Wavelength Laser Spatial distributions of the electron (Ne) and proton (Ni) density as well as the proton beam intensity (Ii) and current density (ji) at different t for the case of 1w (a) and 3w (b) driver. IL2 = 5  1019 Wcm-2m2, L = 1ps The ponderomotive force of the short-wavelength (3w) driver produces an ultraintense (~1021 W/cm2) and very dense (5  1022 cm-3 ) proton beam of mean proton energy ~ 20MeV. The 3w-driven proton beam is much more intense and dense than that produced by the long-wavelength (1w) driver. J. Badziak and S. Jabłoński, Phys. Plasmas 2010

  26. Proton Beams Driven by a Short-Wavelength Laser Temporal shapes of proton pulses driven by the 1w, 2w or 3w laser beam of IL= 21020 W/cm2 and L=1ps The strong compression of the proton bunch by the ponderomotive pressure results in the production of extremely short ( 100 fs) proton pulses at the short distances (~ 20 – 30mm) from the target. The contrast ratio of proton pulses driven by the short-wavelength (2w, 3w) laser is much higherthan that of the proton pulse produced by the long-wavelength (1w) driver. J. Badziak and S. Jabłoński, Phys. Plasmas 2010

  27. Proton Beams Driven by a Short-Wavelength Laser A comparison of the angular distributions of protons generated by the 1w and 2w laser beam 2D hydro simulations Experiment The proton beam generated by the 2w beam is more homogeneous than that driven by the 1w beam Badziak et al.,Las. Part. Beams 2010

  28. Proton Beams Driven by a Short-Wavelength Laser A comparison of parameters of moderate-energy (1 – 3MeV) and high-energy (>3 MeV) proton beams generated by the 1w and 2w laser beam The intensity of a proton beam generated by the 2w laser beam is significantly higher than that produced by the 1w beam with the same value of ILl2, while these intensities are comparable when Badziak et al.,Las. Part. Beams 2010

  29. Proton Beams Driven by a Short-Wavelength Laser The proton beam intensity at the source and the laser-protons energy conversion efficiency as a function of the preplasma thickness – a comparison of results of 1D PIC simulations for the 1w and 2w laser beam. ILl2 = 2.25 x 1018W/cm2. The intensity of a proton beam generated by the 2w laser beam is significantly higher than that produced by the 1w beam with the same value of ILl2while the conversion efficiencies are comparable for both drivers (for Ln(2w) < 1mm)– in agreement with the results of measurements Badziak et al.,Las. Part. Beams 2010

  30. Proton Beams Driven by a Short-Wavelength Laser Summary • Shortening the laser wavelength causes a growth of the contribution of the SLPA mechanism to the ion acceleration process and at the fixed value of IL2 it results in an increase in almost all ion beam parameters and in the shifting the optimum target thickness towards greater values. • Even at moderate values of IL2 1020Wcm-2m2, a short-wavelength ( 0.5m) ps/subps laser driver makes it possible to produce ultrashort ( 100fs), multi-MeV proton bunches of intensity and current density in excess of 1021W/cm2 and 1014A/cm2, respectively.

  31. Ponderomotive Acceleration of Ions by a Laser Pulseof Circular Polarization Snapshots of the proton (ni) and electron (ne) distributions in the (z, x) plane for various times. IL= 6.3  1022 W/cm2 ,  60 fs, LT = 0.35 m High-density proton bunch is accelerated up to relativistic velocities within a short time period ~ 100fs. Qiao et al., Phys. Rev. Lett. 2009

  32. Proton Beams Driven by a Multi-ps Laser Pulse of Circular Polarization Snapshots of the proton density (ni), electron density (ne) and longitudinal electric field (Ex) distributions for proton beams driven by a laser pulse of moderate (a, b) and high (c, d) laser intensity. l = 1.05mm, L=5ps, LT = 45 m,  3.3 fs. All the electrons and protons stored in the target (of 45m thick) are accelerated forward by the piston of the longitudinal electric field produced at the skin layer by the laser-induced ponderomotive force SLPA clearly dominates over TNSA. The proton (plasma) bunch density is close to the hydrogen solid density. Badziak et al., Phys. Plasmas 2011

  33. Proton Beams Driven by a Multi-ps Laser Pulse of Circular Polarization The temporal shape of intensity (It) and current density (jt) of the proton beam recorded at lCP = 90m for various laser intensities. l = 1.05mm, L=5ps, LT = 45m. Both for high and moderate laser intensities the proton pulse duration is  1ps and its peak intensity and current density is above 1020 W/cm2 and 1013A/cm2, respectively, as required for FI. Badziak et al., Phys. Plasmas 2011

  34. Proton Beams Driven by a Multi-ps Laser Pulse of Circular Polarization The proton energy spectra recorded at lCP = 90m for two different laser intensities. l = 1.05mm,L=5ps, LT = 45m. The final proton energy spectrum has a two-peak structure in the energy range required for FI. Badziak et al., Phys. Plasmas 2011

  35. Proton Beams Driven by a Multi-ps Laser Pulse of Circular Polarization The laser-protons energy conversion efficiency as well as the proton beam energy fluence, peak intensity and peak current density as a function of the target thickness. lCP = 90m, l = 1.05mm,IL = 21020 W/cm2, L=5ps In a broad range of the target thicknesses the conversion efficiency is above 20%. Badziak et al., Phys. Plasmas 2011

  36. Proton Beams Driven by a Multi-ps Laser Pulse of Circular Polarization Summary • At circular light polarization SLPA clearly dominates over TNSA and a compact, high-density proton bunch can be accelerated up to subrelativistic velocities • Using a multi-ps circularly polarized laser pulse of relativistic, but moderate intensity ((2 – 5) x 1020 W/cm2) enables us to produce proton beams of parameters suitable for fast ignition with the conversion efficiency about 20%.

  37. Acceleration of a Deuteron Beam by a Short-Wavelength Laser Beam of Circular Polarization Snapshots of the deuteron (ni) and electron (ne) density distributions for deuteron beams driven by KrF and Nd:glass laser. IL2 = 41020 Wcm-2m2, L = 2ps, LT = 10mm, circular polarization KrF laser 1w Nd:glass laser KrF laserproduces a solid-density deuteron beam much faster than that generated by the Nd:glass laser beam of the same value of IL2. Parameters of the KrF laser-driven deuteron beam (intensity, energy fluence, mean ion energy, ...) approach those required for fast ignition of a DT fuel.

  38. Acceleration of a Deuteron Beam by a Short-Wavelength Laser Beam of Circular Polarization The energy spectrum of deuterons driven by a KrF (= 0.248m) and 1 Nd:glass(1.06m) laser.IL2 = 41020 Wcm-2m2, L = 2ps, LT= 10mm, circular polarization Both KrF and Nd:glass laser produces a deuteron beam of a narrow energy spectrum but the mean deuteron energy forKrF is a hundred times higherthan for Nd:glass (at IL2 fixed).

  39. Acceleration of a Deuteron Beam by a Short-Wavelength Laser Beam of Circular Polarization A comparison of PIC simulations with the „Light Sail” model of SLPALT= 10mm, tL = 2ps, circular polarization KrF laser 1w Nd:glass laser An excellent agreement between the PIC simulations and the model can be seen for laser intensities above 1020 W/cm2, in spite of a complex internal structure of the accelerated plasma bunch.

  40. Acceleration of a Deuteron Beam by a Short-Wavelength Laser Beam of Circular Polarization Summary • Using a laser beam of short wavelength (UV range) and circular polarization allows for a further improvement of the ion beam parameters. In particular, a deuteron beam of a narrow energy spectrum and other parameters fulfilling the FI requirements can be produced with a high (~20%) conversion efficiency. • In spite of a complex internal structure of the accelerated ion (plasma) bunch its motion is very well described by the „Light Sail” model of SLPA.

  41. Laser- Induced Cavity Pressure Acceleration (LICPA) In the LICPA scheme, a projectile placed in a cavity is irradiated by a laser beam introduced into the cavity through a hole and accelerated along a guiding channelby the thermal pressure created in the cavity by the laser-produced plasma or by the photon pressure of the ultraintense laser radiation trapped in the cavity. The cylindrical accelerator The conical accelerator LICPA using the thermal pressure(ns/subns pulses):vp<5 x 108cm/s (e.g. for impact FI) LICPA using the photon pressure(ps/subps pulses):vp> 109cm/s (e.g. for proton/ion FI) A common feature of both the LICPA regimes is very high acceleration efficiency, much higher than for the schemes without the cavity Badziak et al., Appl. Phys. Lett. 2010

  42. Ion Acceleration in the LICPA Accelerator with Photon Pressure Snapshots of the carbon ion (Qi) and electron (Qe) charge density distributions for carbon ion beams produced in the LICPA accelerator and in the conventional scheme with a planar target. LT= 2mm, IL = 2.5 x 1021 W/cm2, tL= 2ps, circular polarization, Rc = 0.64 A fast solid-density plasma (ion) bunch is produced in both the conventional and the LICPA scheme but the LICPA-produced bunch is clearly faster.

  43. Ion Acceleration in the LICPA Accelerator with Photon Pressure The energy spectrum of carbon ions accelerated in the LICPA accelerator and in the conventional scheme with a planar target LT= 2mm, IL = 2.5 x 1021 W/cm2, tL= 2ps, circular polarization, Rc = 0.64 The laser-ions conversion efficiency, the mean ion energy and the ion energy fluence in the LICPA scheme is more than a factor 2 higher than the ones in the conventional scheme even at the conservative assumption (Rc = 0.64) that only 2/3 of laser energy is confined in the cavity. The carbon ion beam produced in the LICPA accelerator meets very well the requirements for ion fast ignition of a DT fuel.

  44. Ion Acceleration in the LICPA Accelerator with Photon Pressure The energy spectrum of various ions accelerated in the LICPA accelerator as well as a comparison of the mean ion energy and the laser-ions energy conversion efficiency for LICPA and the conventional scheme with a planar target. IL= 2.5 1021 W/cm2 , tL=ps, circular polarisation; the areal mass density sH  sBe sC sAl. For all considered ions the mean ion energy and the conversion efficiency for LICPA are a factor 2 higher than those for the conventional scheme in spite of the conservative assumptions on the cavity parameters. In the LICPA accelerator the conversion efficiency attains about 40% and the ion beam parameters (the mean energy, intensity, fluence) meet the FI requirements.

  45. Ion Acceleration in the LICPA Accelerator with Photon Pressure Summary • LICPA is a fundamentally new, highly efficient scheme of acceleration of dense matter which can also be used for production of ultraintense ion beams. • The LICPA accelerator makes it possible to produce ion beams with parameters and with the energy conversion efficiency significantly higher than in the case of conventional scheme with a planar target. • In particular, even at relatively low cavity parameters the LICPA accelerator can produce ion beams of parameters fulfilling the fast ignition requirements with the conversion efficiency approaching 40%.

  46. SLPA-driven Ions for Fast Ignition Summary • Advantages: • high (> 20%) laser-ions energy conversion efficiency  the laser driver of energy 50 – 100 kJ can meet the FI requirements • high areal ion density ( 1020 cm-2) the area of the ion source can be small ( 0.01mm2) •  the laser power can be moderate ( 50 PW) •  only slight focusing or no focusing of the ion beam is needed • quasi-monoenergetic ion energy spectrum high efficiency of the beam transport and energy deposition to the fuel • heavier ions can be efficiently accelerated like protons  flexibility in use of most suitable ions • lower sensitivity of the ion beam parameters and the conversion efficiency on the target disturbance by the radiation emited from the fuel • Drawbacks: • circularly polarized or short-wavelength laser beam is required • the transverse homogeneity of the laser beam must be high • Rayleigh-Taylor – like instabilities can occur and destroy the ion beam • experiments with laser beams of suitable parameters are only in an initial stage

  47. General Summary • Both TNSA and SLPA/RPA have a potential to produce ion beams of parameters required for fast ignition • The TNSA main advantages: • excellent quality of the spatial beam characteristics • moderate requirements for the laser beam quality and intensity • and main drawbacks: • small areal ion density • relatively low laser-ions energy conversion efficiency ( 15%) • broad ion energy spectrum • The SLPA/RPA main advantages: • high areal ion density • high laser-ions energy conversion efficiency ( 20%) • relatively narrow ion energy spectrum • flexibility in production of ions of various atomic numbers • and main drawbacks: • high requirements for the laser beam parameters (polarization, homogeneity, fluence) • possible transverse instabilities of the ion beam

  48. General Summary • The LICPA accelerator seems to be a highly promising tool for a production of ultraintense ion beams with a very high energetic efficiency but its investigation is in a very initial stage • The main properties of ion beams revealed by numerical simulations (especially those of the beams produced by SLPA/RPA) have to be confirmed by experiments with kJ and multi-kJ short-pulse lasers which have just been lunched (USA, Japan) or are under development (Europe, USA , China) • The laser-driven intense ion beams developed for fusion-related applications have a potential to be also used in other domains, in particular, in nuclear physics, high energy-density physics or medicine (hadron therapy, radioisotopes production)

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