A new laser-driven ion acceleration mechanism has been identified using particle-in-cell (PIC) simulations. This mechanism allows ion acceleration to GeV energies at vastly reduced laser intensities compared with earlier acceleration schemes. The new mechanism, dubbed “Laser Break-out Afterburner” (BOA), enables the acceleration of carbon ions to greater than 2 GeV energy at a laser intensity of only 10 21 W/cm 2 , an intensity that has been realized in existing laser systems. Other techniques for achieving these energies in the literature rely upon intensities of 10 24 W/cm 2 or above, i.e., 2–3 orders of magnitude higher than any laser intensity that has been demonstrated to date. Also, the BOA mechanism attains higher energy and efficiency than target normal sheath acceleration (TNSA), where the scaling laws predict carbon energies of 50 MeV/u for identical laser conditions. In the early stages of the BOA, the carbon ions accelerate as a quasi-monoenergetic bunch with median energy higher than that realized recently experimentally.

http://absimage.aps.org/image/DPP06/MWS_DPP06-2006-000896.pdf

GeV Laser Ion Acceleration from Ultrathin Targets: The Laser Break-Out Afterburner

Intense heavy ion beams from the Gesellschaft fur Schwerionenforschung ~GSI, Darmstadt, Germany! accelerator facilities, together with two high energy laser systems: petawatt high energy laser for ion experiments ~PHELIX! and nanosecond high energy laser for ion experiments ~NHELIX! are a unique combination to facilitate pioneering beam-plasma interaction experiments, to generate and probe high-energy-density ~HED! matter and to address basic physics issues associated with heavy ion driven inertial confinement fusion. In one class of experiments, the laser will be used to generate plasma and the ion beam will be used to study the energy loss of energetic ions in ionized matter, and to probe the physical state of the laser-generated plasma. In another class of experiments, the intense heavy ion beam will be employed to create a sample of HED matter and the laser beam, together with other diagnostic tools, will be used to explore the properties of these exotic states of matter. The existing heavy ion synchrotron facility, SIS18, deliver an intense uranium beam that deposit about 1 kJ0g specific energy in solid matter. Using this beam, experiments have recently been performed where solid lead foils had been heated and a brightness temperature on the order of 5000 K was measured, using a fast multi-channel pyrometer that has been developed jointly by GSI and IPCP Chernogolovka. It is expected that the future heavy ion facility, facility for antiprotons and ion research ~FAIR! will provide compressed beam pulses with an intensity that exceeds the current beam intensities by three orders of magnitude. This will open up the possibility to explore the thermophysical and transport properties of HED matter in a regime that is very difficult to access using the traditional methods of shock compression. Beam plasma interaction experiments using dense plasmas with a G-parameter between 0.5 and 1.5 have also been carried out. This dense Ar-plasma was generated by explosively driven shockwaves and showed enhanced energy loss for Xe and Ar ions in the energy range between 5.9 to 11.4 MeV.

Present and future perspectives for high energy density physics with intense heavy ion and laser beams

At the Helmholtz center GSI, PHELIX (Petawatt High Energy Laser for heavy Ion eXperiments) has been commissioned for operation in stand-alone mode and, in combination with ions accelerated up to an energy of 13 MeV/u by the heavy ion accelerator UNILAC The combination of PHELIX with the heavy-ion beams available at GSI enables a large variety of unique experiments Novel research opportunities are spanning from the study of ion–matter interaction, through challenging new experiments in atomic physics, nuclear physics, and astrophysics, into the field of relativistic plasma physics

/pdf/commissioning-and-early-experiments-of-the-phelix-facility-1vuqpf4nfh.pdf

Commissioning and early experiments of the PHELIX facility

Stopping of heavy ions in plasmas at strong coupling

Results of theoretical calculations and experimental measurements of the equation of state (EOS) at extreme conditions are discussed and applied to aluminum. It is pointed out that the available high pressure and temperature information covers a broad range of the phase diagram, but only irregularly and, as a rule, is not thermodynamically complete; its generalization can be done only in the form of a thermodynamically complete EOS. A multi-phase EOS model is presented, accounting for solid, liquid, gas, and plasma states, as well as two-phase regions of melting and evaporation. The thermodynamic properties of aluminum and its phase diagram are calculated with the use of this model. Theoretical calculations of thermodynamic properties of the solid, liquid, and plasma phases, and of the critical point, are compared with results of static and dynamic experiments. The analysis deals with thermodynamic properties of solid aluminum at T = 0 and 298 K from different band-structure theories, static compression experiments in diamond anvil cells, and the information obtained in isentropic-compression and shock-wave experiments. Thermodynamic data in the liquid state, resulting from traditional thermophysical measurements, “exploding wire” experiments, and evaluations of the critical point are presented. Numerous shock-wave experiments for aluminum have been done to measure shock adiabats of crystal and porous samples, release isentropes, and sound speed in shocked metal. These data are analyzed in a self-consistent manner together with all other available data at high pressure.The model's results are shown for the principal shock adiabat, the high-pressure melting and evaporation regions and the critical point of aluminum. New experimental and theoretical data helped to improve the description of the high-pressure, high-temperature aluminum liquid. The present EOS describes with high accuracy and reliability the complete set of available information.

Multi-phase equation of state for aluminum

The energy loss in a plasma target was measured for different heavy-ion species, ranging from $^{40}\mathrm{Ca}$ to $^{238}\mathrm{U}$ at an energy of 1.4 MeV/u. A discharge tube was used to generate a hydrogen plasma with a high degree of ionization and temperatures between 1 and 2 eV. An on-line diagnostic of the plasma was performed to measure the free-electron density and the electron temperature. Compared to neutral hydrogen of the same particle density, the plasma target shows an enhanced stopping power due to the increased energy transfer to the free plasma electrons, and a higher effective charge of the projectiles inside the plasma target. Theoretical predictions based on the Bethe-Bohr-Bloch stopping theory are in good agreement with the experimental results.

Energy loss of heavy ions in a plasma target.

Stopping of Heavy Ions in a Hydrogen Plasma

The interaction of energetic multicharged ion beams with separately produced target plasmas is investigated within a projectile-ion-target-electron bin

Ion beam-plasma interaction: A standard model approach

Interaction processes of heavy ions and ionized matter have been investigated experimentally. A Monte Carlo code to simulate charge exchange and energy loss processes in a plasma environment has been developed to plan the experiments, to analyze the results, and to investigate the influence of magnetic fields on the particle trajectories inside the plasma target. The first results of the beam plasma interaction experiments are: — The stopping power of ionized matter is increased compared to that of cold, non-ionized matter. This effect is especially pronounced at low ion energies (E 1MeV/u) this effect is less dramatic, but is still on the order of 2–3, depending on the ion species. — The charge state of ions traversing a fully ionized plasma is increased due to reduced capture cross sections of free plasma electrons. — It is possible to focus intense heavy ion beams of high magnetic rigidity using a plasma lens. This ideal focusing device achieves a high focusing power for ion beams almost comparable to optical systems for intense beams from high power lasers. — Energetic ion beams are very well suited to heat cylindrical target volumes and to create a dense plasma. The characteristic inner-shell target and projectile X-rays provide a tool to analyze the hydrodynamic behavior of beam heated targets with space and time resolution.

K. Weyrich

Papers

Present and future perspectives for high energy density physics with intense heavy ion and laser beams

Energy loss of heavy ions in a plasma target.

Stopping of Heavy Ions in a Hydrogen Plasma

Ion beam-plasma interaction: A standard model approach

Energy loss of fast heavy ions in plasmas