P. V. Nickles

Radiation-Pressure Acceleration of Ion Beams Driven by Circularly Polarized Laser Pulses

We present experimental studies on ion acceleration from ultrathin diamondlike carbon foils irradiated by ultrahigh contrast laser pulses of energy 0.7 J focused to peak intensities of 5x10(19) W/cm2. A reduction in electron heating is observed when the laser polarization is changed from linear to circular, leading to a pronounced peak in the fully ionized carbon spectrum at the optimum foil thickness of 5.3 nm. Two-dimensional particle-in-cell simulations reveal that those C6+ ions are for the first time dominantly accelerated in a phase-stable way by the laser radiation pressure.

High-repetition-rate chirped-pulse-amplification thin-disk laser system with joule-level pulse energy

We are reporting on the development of a diode-pumped chirped-pulse-amplification (CPA) laser system based on Yb:YAG thin-disk technology with a repetition rate of 100 Hz and output pulse energy in the joule range. The focus lies with the first results of the preamplifier--a regenerative amplifier (RA) and a multipass amplifier (MP). The system consists of a front end including the CPA stretcher followed by an amplifier chain based on Yb:YAG thin-disk amplifiers and the CPA compressor. It is developed in the frame of our x-ray laser (XRL) program and fulfills all requirements for pumping a plasma-based XRL in grazing incidence pumping geometry. Of course it can also be used for other interesting applications. With the RA pulse energies of more than 165 mJ can be realized. At a repetition rate of 100 Hz a stability of 0.8% (1sigma) over a period of more than 45 min has been measured. The optical-to-optical efficiency is 14%. The following MP amplifier can increase the pulse energy to more than 300 mJ. A nearly bandwidth-limited recompression to less than 2 ps could be demonstrated.

Transition of proton energy scaling using an ultrathin target irradiated by linearly polarized femtosecond laser pulses.

Particle acceleration using ultraintense, ultrashort laser pulses is one of the most attractive topics in relativistic laser-plasma research. We report proton/ion acceleration in the intensity range of 5x1019 W/cm2 to 3.3x1020 W/cm2 by irradiating linearly polarized, 30-fs, 1-PW laser pulses on 10- to 100-nm-thick polymer targets. The proton energy scaling with respect to the intensity and target thickness was examined. The experiments demonstrated, for the first time with linearly polarized light, a transition from the target normal sheath acceleration to radiation pressure acceleration and showed a maximum proton energy of 45 MeV when a 10-nm-thick target was irradiated by a laser intensity of 3.3x1020 W/cm2. The experimental results were further supported by two- and three-dimensional particle-in-cell simulations. Based on the deduced proton energy scaling, proton beams having an energy of ~ 200 MeV should be feasible at a laser intensity of 1.5x1021 W/cm2.

The Photon Collider at Tesla

High energy photon colliders (γγ,γe) are based on e-e- linear colliders where high energy photons are produced using Compton scattering of laser light on high energy electrons just before the interaction point. This paper is a part of the Technical Design Report of the linear collider TESLA.1 Physics program, possible parameters and some technical aspects of the photon collider at TESLA are discussed.

Fusion neutron yield from a laser-irradiated heavy-water spray

The fusion neutron yield from a laser-irradiated heavy-water (D2O) spray target was studied. Heavy-water droplets of about 150nm diameter in the spray were exposed to 35fs laser pulses at an intensity of 1×1019W∕cm2. Due to the 10–50 times bigger size of the spray droplets compared to usual cluster sizes, deuterons are accelerated to considerably higher kinetic energies of up to 1MeV. Neutrons are generated by the deuterons escaping from the plasma and initiating a fusion reaction within the surrounding cold plume of the spray jet. For each 0.6J of laser pulse energy, 6×103 neutrons are produced by about 1011 accelerated deuterons. This corresponds to a D(d,n) reaction probability of about 6×10−8. Compared to cluster targets, the reaction probability in the spray target is found to be two orders of magnitude larger. This finding apparently is due to both the considerably higher deuteron energies and the larger effective target thickness in the spray target. The measured neutron yield per accelerated deute...

Review of ultrafast ion acceleration experiments in laser plasma at Max Born Institute

New perspectives have been opened up in the field of laser–matter interactions due to recent advances in laser technology, leading to laser systems of high contrast and extreme intensity values, where the frontier of maximum intensity is pushed now to about 1022 W/cm2. Many striking phenomena such as laser-acceleration of electrons up to the GeV level, fast moving ions with kinetic energies of several 10s of MeV, as well as nuclear physics experiments have already actuated a broad variety of theoretical as well as experimental studies. Also highly relativistic effects like laser induced electron-positron pair production are under discussion. All these activities have considerably stimulated the progress in understanding the underlying physical processes and possible applications. This article reviews recent advances in the experimental techniques as well as the associated plasma dynamics studies at relativistic intensities performed at the Max-Born-Institute (MBI). Interactions of a laser pulse at intensities above 1019 W/cm2 with water- and heavy-water droplets, as well as, with thin foils are discussed. Rear and front side acceleration mechanisms, particle dynamics inside the dense target, proton source characteristics, strong modulations in proton and deuteron emission spectra, and finally generation of quasi-monoenergetic deuteron bursts are the topics covered in the article.

Quasi-mono-energetic ion acceleration from a homogeneous composite target by an intense laser pulse

The paper presents an analytical model and particle-in-cell simulations of the quasi-mono-energetic ion acceleration by an intense laser pulse in a multispecies target and the corresponding experimental observations. Homogeneous and heterogeneous targets are considered, and it is shown that the formation of the energy spectrum proceeds in three stages: (1) the initial light ion acceleration in the sheath electric field, (2) the ion species separation followed by the electrostatic shock formation, and (3) the interaction of spatially separated ion bunches accompanied by electron cooling. The field ionization of heavy ions and interaction between the heavy and light species play an important role in the formation and preservation of the energy spectrum of light ions. The simulation results are compared with the theoretical predictions and the experiments.

TESLA Technical Design Report, Part VI, Chapter 1: The Photon Collider at TESLA

High energy photon colliders (γγ,γe) are based on e-e- linear colliders where high energy photons are produced using Compton scattering of laser light on high energy electrons just before the interaction point. This paper is a part of the Technical Design Report of the linear collider TESLA.1 Physics program, possible parameters and some technical aspects of the photon collider at TESLA are discussed.

Pulse-front control of 15-TW pulses with a tilted compressor, and application to the subpicosecond traveling-wave pumping of a soft-x-ray laser

We have implemented an adjustable traveling-wave method of excitation for the transverse pumping of laser media based on tilting one of the gratings of the compressor of a chirped pulse amplification [Opt. Commun.56, 219 (1985)] (CPA) laser chain. We show that the only requirement to obtain the best locally compressed pulse is to slightly tilt and translate one of the gratings from its original position. Exact and approximate expressions of these two motions are derived, allowing an easy reconfiguration of any CPA laser. An experimental validation is performed with the first observation of a unidirectional soft-x-ray lasing when subpicosecond pumping pulses are used.

Time resolved corpuscular diagnostics of plasmas produced with high-intensity femtosecond laser pulses

Ion acceleration dynamics from a water microdroplet target driven by intense (about 1019 W cm−2) femtosecond laser pulses has been investigated. A gated Thomson-parabola spectrometer with a temporal resolution of a few hundreds of picoseconds allows one to measure the temporal development of the ion acceleration process for different charge states and energies. It was found, within the resolution of the measurement, that all ion species are accelerated simultaneously in the same built-up electric field. The ion acceleration during a very short time period results in a very broad instantaneous energy (velocity) spread. The measured time-resolved ion spectra are in good agreement with calculated ones. It shows that the ion acceleration created by a highly intense femtosecond laser pulse can be described in the frame of a model, where the acceleration starts simultaneously for all ions.The temporally resolved ion spectra, measured on the basis of the elaborated diagnostics, show great potential for studies of ion acceleration processes in femtosecond laser pulse driven plasmas.