Laser-induced Cavity Pressure Acceleration Research Articles

Neutron production in cavity pressure acceleration of plasma objects

The laser-induced Cavity Pressure Acceleration (CPA) scheme [S. Borodziuk et al., Appl. Phys. Lett. 95, 231501 (2009)] allows for effective transformation of the laser energy into the kinetic energy of plasma streams and dense plasma objects. It has been proven that using long-wavelength laser beams, with relatively low energies (up to 500 J for λ1 = 1.315 µm and FWHM = 350 ps), it is possible to accelerate macroparticles to very high velocities (above 107 cm/s). The study of neutron yield showed the benefit of CPA in delivering ion temperatures and density sufficient to reach the thermonuclear region.

Enhancement of proton collimation and acceleration by an ultra-intense laser interacting with a cone target followed by a beam collimator

A special method is proposed of a laser-induced cavity pressure acceleration scheme for collimating, accelerating and guiding protons, using a single-cone target with a beam collimator through a target normal sheath acceleration mechanism. In addition, the problems involved are studied by using two-dimensional particle-in-cell simulations. The results show that the proton beam can be collimated, accelerated and guided effectively through this type of target. Theoretically, a formula is derived for the combined electric field of accelerating protons. Compared with a proton beam without a beam collimator, the proton beam density and cut-off energy of protons in the type II are increased by 3.3 times and 10% respectively. Detailed analysis shows that the enhancement is mainly due to the compact and strong sheath electrostatic field, and that the beam collimator plays a role in focusing energy. In addition, the simulation results show that the divergence angle of the proton beam in type II is less than 1.67 times that of type I. The more prominent point is that the proton number of type II is 2.2 times higher than that of type I. This kind of target has important applications in many fields, such as fast ion ignition in inertial fusion, high energy physics and proton therapy.

Generation of sub-gigabar-pressure shocks by a hyper-velocity impact in the collider driven by laser-induced cavity pressure

The generation of high-pressure shocks in the newly proposed collider in which the projectile impacting a solid target is driven by the laser-induced cavity pressure acceleration (LICPA) mechanism is investigated using two-dimensional hydrodynamic simulations. The dependence of parameters of the shock generated in the target by the impact of a gold projectile on the impacted target material and the laser driver energy is examined. It is found that both in case of low-density (CH, Al) and high-density (Au, Cu) solid targets the shock pressures in the sub-Gbar range can be produced in the LICPA-driven collider with the laser energy of only a few hundreds of joules, and the laser-to-shock energy conversion efficiency can reach values of 10 – 20 %, by an order of magnitude higher than the conversion efficiencies achieved with other laser-based methods used so far.

Efficient acceleration of a dense plasma projectile to hyper velocities in the laser-induced cavity pressure acceleration scheme

AbstractThe experimental study of the plasma projectile acceleration in the laser-induced cavity pressure acceleration (LICPA) scheme is reported. In the experiment performed at the kilojoule PALS laser facility, the parameters of the projectile were measured using interferometry, a streak camera and ion diagnostics, and the measurements were supported by two-dimensional hydrodynamic simulations. It is shown that in the LICPA accelerator with a 200-J laser driver, a 4-μg gold plasma projectile is accelerated to the velocity of 140 km/s with the energetic acceleration efficiency of 15–19% which is significantly higher than those achieved with the commonly used ablative acceleration and the highest among the ones measured so far for any projectiles accelerated to the velocities ≥100 km/s. This achievement opens the possibility of creation and investigation of high-energy-density matter states with the use of moderate-energy lasers and may also have an impact on the development of the impact ignition approach to inertial confinement fusion.

Production of sub-gigabar pressures by a hyper-velocity impact in the collider using laser-induced cavity pressure acceleration

AbstractProduction of high dynamic pressure using a strong shock wave is a topic of high relevance for high-energy-density physics, inertial confinement fusion, and materials science. Although the pressures in the multi-Mbar range can be produced by the shocks generated with a large variety of methods, the higher pressures, in the sub-Gbar or Gbar range, are achievable only with nuclear explosions or laser-driven shocks. However, the laser-to-shock energy conversion efficiency in the laser-based methods currently applied is low and, as a result, multi-kJ multi-beam lasers have to be used to produce such extremely high pressures. In this paper, the generation of high-pressure shocks in the newly proposed collider in which the projectile impacting a solid target is driven by the laser-induced cavity pressure acceleration (LICPA) mechanism is investigated using two-dimensional hydrodynamic simulations. A special attention is paid to the dependence of shock parameters and the laser-to-shock energy conversion efficiency on the impacted target material and the laser driver energy. It has been found that both in case of low-density and high-density solid targets, the shock pressures in the sub-Gbar range can be produced in the LICPA-based collider with the laser energy of only a few hundreds of joules, and the laser-to-shock energy conversion efficiency can reach values of 10–20%, by an order of magnitude higher than the conversion efficiencies achieved with other laser-based methods used so far.

Laser-driven accelerator of intense plasma beams for materials research

A concept and a laboratory model of the laser-driven accelerator of plasma beams for materials research is presented. The accelerator is based on the laser-induced cavity pressure acceleration (LICPA) scheme and enables us to control the plasma beam parameters and change values of these parameters within a few orders of magnitude. It is predicted that the accelerator employing a commercial nanosecond laser of energy ∼3J would be capable of producing a plasma beam of controlled composition and the beam fluence up to 200J/cm2, the beam peak intensity up to 10GW/cm2 and the beam duration within the 20ns–10μs range. A laboratory model of the accelerator with a 0.5J/4ns Nd:YAG laser driver was built and tested. A CH plasma beam of the fluence >10J/cm2 and the peak intensity >100MW/cm2 at the accelerator channel outlet was produced with the laser-to-beam energy conversion efficiency approaching 15%. A strong surface damage of various metal samples by the beam was observed.The proposed accelerator is a novel tool for materials research which seems to be particularly useful for testing materials proposed for future fusion reactors both the MCF and ICF ones.

The LICPA-driven collider—a novel efficient tool for the production of ultra-high pressures in condensed media

Generation of strong shock waves for the production of Mbar or Gbar pressures is a topic of high relevance for contemporary research in various domains, including inertial confinement fusion, laboratory astrophysics, planetology and material science. The pressures in the multi-Mbar range can be produced by the shocks generated using chemical explosions, light-gas guns, Z-pinch machines or lasers. Higher pressures, in the sub-Gbar or Gbar range are attainable only with nuclear explosions or laser-based methods. Unfortunately, due to the low efficiency of energy conversion from a laser to the shock (below a few percent), multi-kJ, multi-beam lasers are needed to produce such pressures with these methods. Here, we propose and investigate a novel scheme for generating high-pressure shocks which is much more efficient than the laser-based schemes known so far. In the proposed scheme, the shock is generated in a dense target by the impact of a fast projectile driven by the laser-induced cavity pressure acceleration (LICPA) mechanism. Using two-dimensional hydrodynamic simulations and the measurements performed at the kilojoule PALS laser facility it is shown that in the LICPA-driven collider the laser-to-shock energy conversion efficiency can reach a very high value ∼ 15–20 % and, as a result, the shock pressure ∼ 0.5–1 Gbar can be produced using lasers of energy ⩽ 0.5 kJ. On the other hand, the pressures in the multi-Mbar range could be produced in this collider with low-energy (∼ 10 J) lasers available on the market. It would open up the possibility of conducting research in high energy-density science also in small, university-class laboratories.

Generation of ultra-intense ion beams by a short-pulse laser

This paper summarizes briefly the main experimental and numerical results of the IPPLM team studies on the generation of ultra-intense ion beams by a short (≤1 ps) laser pulse. Basic laser-driven ion acceleration schemes capable of generating such ion beams are described including the target normal sheath acceleration (TNSA) scheme, the skin-layer ponderomotive acceleration (SLPA) scheme and the laser-induced cavity pressure acceleration (LICPA) scheme. It is shown that an efficient way for achieving high ion beam intensities and fluencies lies in using a short-wavelength laser driver of circular light polarization. In such a case, SLPA clearly dominates over TNSA, and dense and compact ion bunch is generated with high energetic efficiency. The LICPA scheme operating in the photon (radiation) pressure regime can be even more efficient than SLPA. As it is demonstrated by particle-in-cell simulations, the LICPA accelerator with a picosecond, circularly polarized laser driver of intensity ∼ 1021 W/cm2 can produce sub-picosecond light ion beams of intensity ∼ 1022 W/cm2 and fluence > 1 GJ/cm2 with the energetic efficiency of tens of percent. Laser-driven ion beams of such extreme parameters could open up new research areas in high-energy-density science, inertial fusion or nuclear physics.

Generation of ultra-high-pressure shocks by collision of a fast plasma projectile driven in the laser-induced cavity pressure acceleration scheme with a solid target

A novel, efficient method of generating ultra-high-pressure shocks is proposed and investigated. In this method, the shock is generated by collision of a fast plasma projectile (a macro-particle) driven by laser-induced cavity pressure acceleration (LICPA) with a solid target placed at the LICPA accelerator channel exit. Using the measurements performed at the kilojoule PALS laser facility and two-dimensional hydrodynamic simulations, it is shown that the shock pressure ∼ Gbar can be produced with this method at the laser driver energy of only a few hundred joules, by an order of magnitude lower than the energy needed for production of such pressure with other laser-based methods known so far.

Enhanced efficiency of plasma acceleration in the laser-induced cavity pressure acceleration scheme

Among various methods for the acceleration of dense plasmas the mechanism called laser-induced cavity pressure acceleration (LICPA) is capable of achieving the highest energetic efficiency. In the LICPA scheme, a projectile placed in a cavity is accelerated along a guiding channel by the laser-induced thermal plasma pressure or by the radiation pressure of an intense laser radiation trapped in the cavity. This arrangement leads to a significant enhancement of the hydrodynamic or electromagnetic forces driving the projectile, relative to standard laser acceleration schemes. The aim of this paper is to review recent experimental and numerical works on LICPA with the emphasis on the acceleration of heavy plasma macroparticles and dense ion beams. The main experimental part concerns the research carried out at the kilojoule sub-nanosecond PALS laser facility in Prague. Our measurements performed at this facility, supported by advanced two-dimensional hydrodynamic simulations, have demonstrated that the LICPA accelerator working in the long-pulse hydrodynamic regime can be a highly efficient tool for the acceleration of heavy plasma macroparticles to hyper-velocities and the generation of ultra-high-pressure (>100 Mbar) shocks through the collision of the macroparticle with a solid target. The energetic efficiency of the macroparticle acceleration and the shock generation has been found to be significantly higher than that for other laser-based methods used so far. Using particle-in-cell simulations it is shown that the LICPA scheme is highly efficient also in the short-pulse high-intensity regime and, in particular, may be used for production of intense ion beams of multi-MeV to GeV ion energies with the energetic efficiency of tens of per cent, much higher than for conventional laser acceleration schemes.

Efficient acceleration of dense plasma bunches for fusion-related applications in the LICPA accelerator

The results of particle-in-cell simulations of acceleration of carbon ions and a heavy (0.5 μg) gold micro-projectile in the laser-induced cavity pressure acceleration (LICPA) scheme at the conditions relevant to fast ignition of deuterium-tritium (DT) fusion are presented. It is shown that the LICPA accelerator employing a picosecond 100 kJ laser driver can produce quasi-monoenergetic carbon ion beams of parameters significantly higher than those achieved in the conventional radiation pressure acceleration (RPA) scheme and the beam parameters meet the ion fast ignition requirements fairly well. The LICPA accelerator can also efficiently accelerate the heavy micro-projectile to high velocities (> 5 × 108 cm s−1) required for the impact ignition of DT fusion and the acceleration efficiency for LICPA is almost an order of magnitude higher than that for RPA.

Two-dimensional relativistic particle-in-cell code for simulation of laser-driven ion acceleration in various acceleration schemes

Results of a new relativistic two-dimensional particle-in-cell code for simulation of laser-driven ion acceleration are presented. It is shown that a complex electric field structure arose during the laser–target interaction as well as the evolution of the ion and electron concentration for the laser-induced cavity pressure acceleration scheme took place. During computation the influence of parameters such as target thickness and width, target starting position inside cavity and its atomic composition, as well as laser pulse length and beam width are examined. Values adopted for the calculation reflect the experimental conditions.

The LICPA accelerator of dense plasma and ion beams

Laser-induced cavity pressure acceleration (LICPA) is a novel scheme of acceleration of dense matter having a potential to accelerate plasma projectiles with the energetic efficiency much higher than the achieved so far with other methods. In this 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 channel by 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. This paper summarizes briefly the main results of our recent LICPA studies, in particular, experimental investigations of ion beam generation and heavy macroparticle acceleration in the hydrodynamic LICPA regime (at moderate laser intensities ~ 1015W/cm2) and numerical, particle-in-cell (PIC) studies of production of ultraintense ion beams and fast macroparticles using the photon pressure LICPA regime (at high laser intensities > 1020 W/cm2). It is shown that in both LICPA regimes the macroparticles and ion beams can be accelerated much more efficiently than in other laser-based acceleration scheme commonly used and the accelerated plasma/ion bunches can have a wide variety of parameters. It creates a prospect for a broad range of applications of the LICPA accelerator, in particular in such domains as high energy density physics, ICF research (ion fast ignition, impact ignition) or nuclear physics.

Generation of high-energy ion bunches via laser-induced cavity pressure acceleration at ultra-high laser intensities

AbstractIn this paper, a new method for efficient generation of high-energy ion bunches via laser-induced cavity pressure acceleration (LICPA) is examined using one-dimensional particle-in-cell code PIC1D. It is found that for high laser beam intensities of the order of 1022 W/cm2 and for circular light polarization, a substantial increase in parameters of the accelerated ions is obtained when the target is placed inside a special cavity, into which the laser beam is introduced by a small hole. As compared to the pure radiation pressure acceleration scheme, the LICPA scheme leads to an increase in ion energies and the laser-to-ions energy conversion efficiency while the width of the ion energy spectrum are similar for both the schemes. Such a tendency was observed for all carbon targets (from 2 µm to 0.2 µm thick) investigated in the paper. The results of PIC1D simulations agree very well with predictions of the suitably generalized light sail model.

Improved generation of ion fluxes by a long laser pulse using laser-induced cavity pressure acceleration

Generation of ion fluxes in the laser-induced cavity pressure acceleration (LICPA) scheme is investigated by the time-of-flight method and compared with the one in the conventional laser-planar target interaction scheme. It is shown that the ion current density and intensity of the ion flux produced in the LICPA scheme from CD2 foil target irradiated by a 0.3-ns laser pulse of intensity ∼1014–1015 W/cm2 are by an order of magnitude higher and the mean and maximum ion energies by a factor 4–5 higher than those for the conventional scheme.

Highly efficient generation of ultraintense high-energy ion beams using laser-induced cavity pressure acceleration

Results of particle-in-cell (PIC) simulations of fast ion generation in the recently proposed laser-induced cavity pressure acceleration (LICPA) scheme in which a picosecond circularly polarized laser pulse of intensity ∼1021 W/cm2 irradiates a carbon target placed in a cavity are presented. It is shown that due to circulation of the laser pulse in the cavity, the laser-ions energy conversion efficiency in the LICPA scheme is more than twice as high as that for the conventional (without a cavity) radiation pressure acceleration scheme and a quasi-monoenergetic carbon ion beam of the mean ion energy ∼0.5 GeV and the energy fluence ∼0.5 GJ/cm2 is produced with the efficiency ∼40%. The results of PIC simulations are found to be in fairly good agreement with the predictions of the generalized light-sail model.

Highly efficient accelerator of dense matter using laser-induced cavity pressure acceleration

Acceleration of dense matter to high velocities is of high importance for high energy density physics, inertial confinement fusion, or space research. The acceleration schemes employed so far are capable of accelerating dense microprojectiles to velocities approaching 1000 km/s; however, the energetic efficiency of acceleration is low. Here, we propose and demonstrate a highly efficient scheme of acceleration of dense matter in which a projectile placed in a cavity is irradiated by a laser beam introduced into the cavity through a hole and then accelerated in a guiding channel by the pressure of a hot plasma produced in the cavity by the laser beam or by the photon pressure of the ultra-intense laser radiation trapped in the cavity. We show that the acceleration efficiency in this scheme can be much higher than that achieved so far and that sub-relativisitic projectile velocities are feasible in the radiation pressure regime.