Search

We present optimization of laser plasma x-ray experimental conditions for ultrafast x-ray absorption spectroscopy measurements on broad range of transition metal oxides. First, the x-ray flux generated from a laser plasma source was optimized with an emphasis on the Bremsstrahlung by investigating the influence of the angle of the incidence of laser beam on a Cu tape target. The x-ray flux emitted in both the front and transmitted side of the target was found to be optimal at the incident angle of 15 ~ 25 degrees. Moreover the manipulation of the Bremsstrahlung peak energy by the laser focus distribution was discussed. In addition to the source optimization, we present a scheme to find the time-delay zero position in a pump-probe experiment together with a normalization scheme for x-ray source fluctuations. As a feasibility check, we present the transmitted spectra of two materials, Ni and NiO.

Laser-driven proton/ion acceleration is a rapidly developing research field attractive for both fundamental physics and applications such as hadron therapy, radiography, inertial confinement fusion, and nuclear/particle physics. Laser-driven proton/ion beams, compared to those obtained in conventional accelerators, have outstanding features such as low emittance, small source size, ultra-short duration and huge acceleration gradient of ∼1 MeV μm−1. We report proton acceleration from ultrathin polymer targets irradiated with linearly polarized, 30-fs, 1-PW Ti:sapphire laser pulses. A maximum proton energy of 45 MeV with a broad and modulated profile was obtained when a 10-nm-thick target was irradiated at a laser intensity of 3.3 × 1020 W/cm2. The transition from slow (I1/2) to fast scaling (I) of maximum proton energy with respect to laser intensity I was observed and explained by the hybrid acceleration mechanism including target normal sheath acceleration and radiation pressure acceleration in the acceleration stage and Coulomb-explosion-assisted free expansion in the post acceleration stage.

Physical processes in laser–matter interaction used to be determined by generation of fast electrons resulting from efficient conversion of the absorbed laser radiation. Composite materials offer the possibility to control the absorption by choice of the host material and dopants. Reported here strong absorption of ultrashort laser pulse in a composite carbon-based nanomaterial including single-walled carbon nanotubes (SWCNTs) or multilayer graphene was measured in the intensity range between 1012 and 1016 W cm−2. A protein (lysozyme) was used as the host. The maximum absorption of femtosecond laser pulse has reached 92–96 %. The optical damage thresholds of the coatings were registered at an intensity of (1.1 ± 0.5) × 1013 W cm−2 for the embedded SWCNTs and at (3.4 ± 0.3) × 1013 W cm−2 for the embedded graphene. Encapsulated variant of the dispersed nanomaterial was investigated as well. It was found that supernatant protein in the coating material tends to dominate the absorption process, independently of the embedded nanomaterial. The opposite was observed for the encapsulated material.

A tabletop, short-pulse laser-based hard X-ray (Kα) source equipped with an advanced X-ray optics and dedicated for high-resolution spectroscopy and time-resolved diffraction is described. Operation of the source together with a high-resolution spectrometer containing a large-aperture highly annealed pyrolytic graphite gave a resolution E/ΔE of ~1,800 for the spectral range around Kα line of Cu. The estimated total flux of the 8.05-keV photons was equal to 5.9 × 1010 ph/s in 4π sr. Performance boost of the source caused by X-ray optics relied on the significant increase in the Cu-Kα photon flux on both, the sample (4.7 × 106 ph/s) and the detector (3.4 × 103 ph/s). A spectral brightness of 1.4 × 107 ph/s/mm2/mrad2 was derived from the source parameters for the Kα line. Better performance due to high collecting power and reflectivity of the spectrometer enabled application of the cross-correlation technique with an Ni foil. An upper bound of emission duration of 323 ± 47 fs was obtained in this measurement. X-ray absorption near-edge spectroscopy on an Ni sample with an acquisition time of only 15 min confirmed the increased capability of the setup also for continuous spectrum (bremsstrahlung).

Advancement of ion acceleration by intense laser pulses is studied with ultra-thin nanometer-thick diamond like carbon and micrometer-thick Titanium target foils. Both investigations aim at optimizing the electron density distribution which is the key for efficient laser driven ion acceleration. While recently found maximum ion energies achieved with ultra-thin foils mark record values micrometer thick foils are flexible in terms of atomic constituents. Electron recirculation is one prerequisite for the validity of a very simple model that can approximate the dependence of ion energies of nanometer-thick targets when all electrons of the irradiated target area interact coherently with the laser pulse and Coherent Acceleration of Ions by Laser pulses (CAIL) becomes dominant. Complementary experiments, an analytical model and particle in cell computer simulations show, that with regard to ultra-short laser pulses (duration ~45 fs at intensities up to 5 × 1019 W/cm2) and a micrometer-thick target foil with higher atomic number a close to linear increase of ion energies manifests in a certain range of laser intensities.

In this paper we report on an experimental study of high harmonic radiation generated in nanometer-scale foil targets irradiated under normal incidence. The experiments constitute the first unambiguous observation of odd-numbered relativistic harmonics generated by the v × B component of the Lorentz force verifying a long predicted property of solid target harmonics. Simultaneously the observed harmonic spectra allow in-situ extraction of the target density in an experimental scenario which is of utmost interest for applications such as ion acceleration by the radiation pressure of an ultraintense laser.

A new technique to investigate laser driven ion acceleration with fully isolated, mass-limited glass spheres with a diameter down to 8 μ m is presented. A Paul trap was used to prepare a levitating glass sphere for the interaction with a laser pulse of relativistic intensity. Narrow-bandwidth energy spectra of protons and oxygen ions have been observed and were attributed to specific acceleration field dynamics in case of the spherical target geometry. A general limiting mechanism has been found that explains the experimentally observed ion energies for the mass-limited target.

In this paper the route towards the current optimum of laser generated ion beams by subsequently changing the important parameters such as target thickness, laser pulse contrast, angle of incidence and laser pulse polarization is sketched. Beginning with parameters of isothermal target normal sheath acceleration (TNSA), we reached the regime where the plasma expansion can be described adiabatically and results in a symmetric ion acceleration. Further we demonstrated a way to phase match the accelerating electron population with the ions, namely coherent acceleration of ions by laser pulses (CAIL), which finally lead to radiation pressure acceleration (RPA) if the laser polarization was changed from linear to circular. These findings of ion acceleration with transparent solid targets are additionally supported by analyzing the optical properties of the transmitted laser pulse (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The complex dynamical behavior of the electron sheath in laser driven ion acceleration leads to variations in ion beam pointing and ion energy modulation. These processes are derived from high resolution particle spectroscopy and 2D-PIC simulations. The phenomena arise from ion source movement if laser irradiation occurs at oblique incidence. Different laser absorption processes act in dependence on laser parameter which determines the ion acceleration.

Laser produced ion beams have a large divergence angle and a wide energy spread. To our knowledge, this is the first demonstration of collimation and monochromatisation of laser accelerated proton beams, using a permanent quadrupole magnet lens system. It acts as a tunable band pass filter by collimating or focusing the protons with the same energy. Because it gathers nearly the whole proton emission, a strong enhancement of the beam density appears. For the collimated beam, an increase of the proton density in the (3.7 ± 0.3) MeV energy band up to a factor of ~30, from possible 40, relative to the non-collimated beam is demonstrated. With the help of this simple, reliable, and well established technique new perspectives will be opened for science and technology, monoenergetic ion beams can be attained in any lab, where a source of laser accelerated ions exist. This finding enables to apply afterward well known beam steering techniques to the formed ion beam, which are applied in conventional accelerators to manipulate the beam parameters or to transport the beams and make them use in many application.

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.

Intense and stable laser operation with Ni-like Zr and Ag was demonstrated at pump energies between 2 J and 5 J energy from the PHELIX pre-amplifier section. A novel single mirror focusing scheme for the TCE x-ray laser (XRL) has been successfully implemented by the LIXAM/MBI/GSI collaboration under different pump geometries. This shows potential for an extension to shorter XRL wavelength. Generation of high quality XRL beams for XRL spectroscopy of highly charged ions is an important issue within the scientific program of PHELIX. Long range perspective is the study of nuclear properties of radioactive isotopes within the FAIR project.

The high-energy high-power laser system PHELIX (Petawatt High Energy Laser for heavy Ion eXperiments) [1] is currently under construction at the Gesellschaft fuer Schwerionenforschung mbH (GSI) Darmstadt. With PHELIX GSI will offer the unique combination of a high-current, high-energy (GeV/u) heavy-ion beam with an intense laser beam. This will open the door to a variety of fundamental science issues in the field of atomic physics, plasma physics and nuclear physics. The project will gain further interest in the near future by the dramatic increase of the accelerator performance with the starting FAIR project at GSI [2]. This paper reports the current status of the project as well as the laser architecture. The proposed physics program and a first experiment carried out with PHELIX, the realization of a transient collisionally excited x-ray laser [3], will also be reviewed briefly.

A third-order correlator suitable for detailed shape measurements of picosecond laser pulses has been developed. The working principle in both the single shot and the scanning mode is based on detection of the phase-matched difference frequency non-collinear generated signal in a non-linear crystal. This third-order OPA correlator was applied for the characterization of the specifically shaped picosecond laser pulses from the MBI CPA Nd: glass laser system.

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.

We present a laser produced plasma (LPP) source optimized for metrology and the results of its radiometric characterization. The presented (LPP) source can be used for reflectometry and spectroscopy in the soft x-ray range. For these applications, stable operation with high spectral photon yields high reliability in continuous operation and, to reach high spectral resolution, a small source size and high source point stability is necessary. For the characterization of the source, special instruments have been designed and calibrated using the soft x-ray radiometry beamline of the Physikalisch-Technische-Bundesanstalt at BESSY. These instruments are an imaging spectrometer, a double multilayer tool for in-band power measurements, a transmission slit grating spectrograph, and a pinhole camera. From the measurements a source size of 30 μm×55 μm (2σ, horizontal by vertical) and a stability of better than 5 μm horizontally and 9 μm vertically were obtained. The source provides a flat continuous emission in the...

Terawatt laser systems are affected by the problem that optical components, typically installed in vacuum, get contaminated with carbon. In this paper, we describe an “on-line” cleaning system, based on a radiofrequency discharge, to avoid carbon production or to clean optical components if carbon is already deposited. The advantage of such a cleaning system is the direct installation along the beam line which not only allows a fast and reproducible cleaning of the components without removing them from the beam line, but also allows a preventive treatment of the most sensitive optics from further contamination.

Highly energetic negative ions have been observed by irradiating water and heavy water micro droplets with ultrashort (35 fs) and highly intense ((0.8–1.2) × 1019 W cm−2) laser pulses. The creation of negative hydrogen (H−), deuterium (D−) as well as oxygen (O−) ions is suggested due to a process in which first their formation takes place in the hot plasma followed by an acceleration together with the positive ions. The negative ions are pulled by the energetic positive ions and propagate with them contributing to the quasineutrality of the beam. The observed phenomenon is discussed on the basis of possible formation and acceleration mechanisms of negative ions.

X-ray lasers (XRLs) belong to the brightest existing short-wavelength sources. The development trends are discussed from the point of view their suitability for applications. A detailed analysis of the output parameters of the XRL with transient inversion proves that this type of laser has become sufficiently mature to be applied in practice.

Propagation of a high intensity (∼1019 W/cm2) ultrashort (∼35 fs) laser pulse through a cloud of water spheres (150 nm diameter) results in hot electron driven proton acceleration up to 1 MeV. It is suggested that during the propagation of the short pulse through the low density wing of the cloud, the leading pulse pedestal is reduced owing to absorption by the preplasma created. Then, the high-intensity peak of the pulse propagates through this underdense plasma and interacts with the high-density inner part of the cloud, which has not been transformed into an underdense plasma so that a sheath acceleration process at each individual microsphere can take place. The observed proton spectra show strong modulations, which are interpreted within the framework of a known fluid-expansion model incorporating two hot-electron populations with significantly different densities and temperatures.

Structured proton spectra and a two-temperature electron distribution were simulated using a 1D3V particle-in-cell code for a plasma created by 35-fs laser pulses with an intensity of I≥1019 W/cm2. Such a two-temperature electron distribution was used as a prerequisite for a fluid dynamical model allowing us to describe the experimentally measured deep dips in the proton energy spectra of laser-produced plasmas from water-droplet targets.

We studied extreme ultraviolet (EUV) emission from Xe cluster jet targets irradiated with high repetitive ps and ns laser pulses in the intensity range between 10(11) and 10(15) W/cm(2). It was fou ...

A simple model of dynamics of a collisional X-ray laser is given applying Maxwell-Bloch equations in a uniform approximation. The main considered parameters include polarization and coherence of the emitted radiation. Speckle pattern, typical for a radiation source of partial coherence, especially, if involving process of the amplified spontaneous emission (ASE), are used as an alternative source of information on the processes occurring in the active medium of an X-ray laser. A level of partial coherence is deduced by statistical analysis of the speckle pattern generated in the output beam of the laser. It is shown that plasma fluctuation and non-Gaussian character of the statistics are needed to reproduce the transverse coherence values reported in the experiment.

If regions of localized strong fields at plasma-vacuum interfaces are probed longitudinally with laser accelerated proton beams their velocity distribution changes sensitively and very fast. Its measured variations provide indirectly a higher temporal resolution as deduced from deflection geometries which rely on the explicit temporal resolution of the proton beam at the position of the object to probe. With help of reasonable models and comparative measurements changes of proton velocity can trace the field dynamics even at femtosecond time scale. In longitudinal probing, the very low longitudinal emittance together with a broad band kinetic energy distribution of laser accelerated protons is the essential prerequisite of the method. With a combination of energy and one-dimensional spatial resolution, we resolve fast field changes down to 100 fs. The used pump probe setup extends previous schemes and allows discriminating simultaneously between electric and magnetic fields in their temporal evolution.

We present the design of a titanium–sapphire Ti : Sa laser system for generating 100TW laser pulses. The main aspects of the multiterawatt Ti : Sa laser architecture which can allow to reach the focusable intensity exceeding 10 20 W / cm 2 are discussed.

The satellite structure accompanying the Al Lyα emission from plasma regions close to the surface of the laser-irradiated targets is studied. In spectra produced at constant laser energy but variable pulse duration we identify the situations where the resonance line is suppressed and only the emission from long-wavelength satellites is observed. The experimental data are compared with results of calculations based on two-dimensional hydrodynamics and multilevel collisional-radiative codes. Simulations indicate that these spectra originate from cold dense plasma created inside the crater several tens of micrometers under the surface of the solid target.

While huge progress has been achieved for EUVL system design and multilayer optics during the last years the decision on the best suited source is still open. In a German basic research cooperation on short-wavelength plasma based sources some key issues also relevant for EUVL are addressed: the comparison of existing sources, investigations on the scalability of source concepts and the demonstration of key features. Preliminary results of investigations on parameters for best conversion efficiency of laser produced plasmas, concepts for high-power lasers and scalability of gas discharge based sources are presented. Comparability of results is assured by calibrated metrology tools which are cross checked with ASML’s flying circus.

We describe an experiment demonstrating XUV amplification following collisional excitation in a discharge-created plasma waveguide irradiated by a picosecond optical laser pulse. A capillary discharge was used to generate a plasma radiation pipe with a radially concave electron density profile. Temporally resolved transmission characteristics and guiding effect have been measured. An intense short laser pulse rapidly heated the electrons, producing amplification in the 3p 1 S 0 -3s 1 P 1 transition of Ne-like S at 60.84 nm. The integrated gain-length product obtained within a 3 cm active medium with a laser energy of 0.46 J was -6.8. The pump energy depletion has been analysed as well. This new, hybridly pumped soft X-ray laser with the transient gain offers a new way towards efficient tabletop coherent XUV sources.

Using 50 fs ( ∼ 2×1018 W/cm2) and 2 ps ( ∼ 5×1016 W/cm2) pulses from a Ti:Sa multi-TW laser at 800 nm wavelength large Xe-clusters ( 105...106 atoms per cluster) have been excited. Absolute yield measurements of EUV-emission in a wavelength range between 10 nm and 15 nm in combination with cluster target variation were carried out. The ps-laser pulse has resulted in about 30% enhanced and spatially more uniform EUV-emission compared to fs-laser excitation. Circularly polarized laser light instead of linear polarization results in enhanced emission which is probably caused by electrons gaining higher energies by the polarization dependent optical field ionization process. An absolute emission efficiency at 13.4 nm of up to 0.8% in 2π sr and 2.2% bandwidth has been obtained.

Results from particle-in-cell simulations of the three-dimensional regime of proton acceleration in the interaction of laser radiation with a thin spherical target are presented. It is shown that the density of accelerated protons can be several times higher than that in conventional accelerators. The focusing of fast protons created in the interaction of laser radiation with a spherical target is demonstrated. The focal spot of fast protons is localized near the center of the sphere. The conversion efficiency of laser energy into fast ion energy attains 5%. The acceleration mechanism is analyzed and the electron and proton energy spectra are obtained.

For laser plasma diagnostic purposes, a specific Thomson spectrometer with a multi-pinhole array at the entrance aperture is proposed. The ion beam under investigation is thus divided into small beamlets and the obtained spectral image combines the recorded spectra of the ions, which are emitted under different angles of the source. This resembles a simultaneous measurement with many independent spectrometers. Thereby, the emission characteristic of the ion source can be reconstructed. The quantitative analysis of the ion emission spectra allows one to gain detailed information about the accelerating sheath field profile and dynamics.

We describe an experiment demonstrating XUV amplification following collisional excitation in a capillary discharge plasma irradiated by a picosecond IR laser pulse. Guiding and temporally resolved transmission of the pump laser beam are also demonstrated and analysed. The short pump laser pulse heated rapidly the electrons producing amplification in the 3 p 1 S 0 –3 s 1 P 1 transition of Ne-like sulphur at 60.84 nm. The estimated gain–length product was equal to 6.8, while the beam divergence reached 2.5 mrad for 30 mm capillary. This new, hybridly pumped collisional soft X-ray laser with the transient gain offers a new way towards efficient table-top XUV sources.

Seit der Demonstration der ersten Rontgenlaser im Jahre 1985, die damals nur mittels groser und hochenergetischer Laser fur die Fusionsforschung moglich war, sucht man nach neuen effizienten Pumpmethoden. In der letzten Dekade sind viele wichtige Experimente durchgefuhrt und enorme Fortschritte in Richtung kompakter, so genannter Tabletop-Rontgenlaser mit einer hohen Brillanz erzielt worden, sodass man uber konkrete Anwendungen nachdenken kann.

Novel X-ray laser sources driven by short-pulse high power lasers can provide intense beams of radiation at fixed energy. In combination with the Doppler-tuning possible at the ESR storage ring, this can be utilized for precision spectroscopy of highly charged ions. The sensitivity should be sufficient to apply this technique to lithium-like radioactive ions.

Simulations are presented for the collisionally pumped germanium X-ray laser working in the transient gain scheme. The influence of the shape, length, intensity and energy of the preforming pulse on the gain and X-ray output are analysed. The hydrodynamics simulations post-processed with 3D raytracing give additional information about the effective gain and the output signals determined by the refraction due to the plasma density gradients. The modelling presented shows to what extent the plasma preforming plays a deciding role for the improvement of the lasing conditions. Dependence on the main pulse delay is tested as well. There are indications that significant gain and output signal could be created with a subpicosecond main driving pulse of reduced total energy provided the preforming pulse is optimised.

The energy distribution and yield of electrons and hard x-ray photons were investigated by irradiating tungsten and tantalum targets with ~ 30 fs pulses in the intensity range 1018 — 1019 W cm-2 by using the Laboratoire d'Optique Appliquee (LOA) as well as the Max Born Institut (MBI) multiterawatt Ti:sapphire lasers. For the measurement of the hard x-ray emission in the energy range from 15 keV to 700 keV at the LOA a 9-channel spectrometer of calibrated thermoluminescence detectors (TLD) was used. The scaling of the hard x-rays was studied by varying the incident laser energy within one order of magnitude and the pulsewidth by a factor of 5. The hot electron output was investigated in the range 300 keV — 1 MeV with the new MBI Ti:sapphire laser by using a time-of-flight spectrometer. The results indicate a sensitive interplay between the temporal laser shape and laser intensity.

The collisionally excited transient inversion scheme is shown to produce exceptionally high gain coefficients and gain-length products. Data are presented for the Ne-like titanium and germanium and Ni-like silver X-ray lasers (XRL's) pumped using a combination of nanosecond and picosecond duration laser pulses. This method leads to a dramatic reduction of the required pump energy and makes down-sizing of XRL's possible, an important prerequisite if they are to become commonly used tools in the long-term.

We report the polarization measurement of a very high order (59th and 61st order, $\ensuremath{\sim}$17 nm) harmonic. A Mo-Si multilayer mirror is used as a polarizer with reflectivity of 60% and polarization analyzing power close to unity around a wavelength of 17 nm. We observe that for these high harmonics in Ne there is no rotation of the polarization ellipse with respect to the fundamental laser polarization, even though the harmonics are in the plateau. For linear and slightly elliptical laser polarization the harmonics still remain linearly polarized. These findings are supported by a full theoretical simulation, which includes spatiotemporal integration and phase matching of the emitted harmonic radiation.

We have measured the absolute photon number of single-shot high-order harmonic spectra generated by focusing intense short pulsed laser radiation into a gas target with a calibrated extreme ultraviolet (EUV) spectrometer. For the calibration, we used a compact hollow-cathode source as a radiometric transfer standard providing radiation from rare gas plasma emission lines of known radiant intensity in the spectral range from 13.1 nm to 58.4 nm. The photon number measurement is based on the comparison of the detected signals of the high-order harmonics and the hollow-cathode emission lines with nearly identical spectrometer set-ups. This technique provides a measurement of the harmonics photon number with a relative uncertainty of less than 50% (1σ).

Information about the energy distribution of hot electrons generated by the interaction of short-pulse (0.7 ps pulse duration at laser wavelength) and high-intensity laser beams with solid targets is derived from measurements of the spectral and angular distribution of hard x-rays with energies above 10 keV. The measurements were carried out with thermoluminescence dosemeters and a nine-channel spectrometer. A comparison of experimental data and model calculations shows that under the conditions of our experiment the hot-electron distribution deviates significantly from a Maxwell - Boltzmann shape with a single-electron temperature parameter.

Lasing in a titanium XII plasma at 32.6 nm and ∼ 30 nm as well as in vanadium XIII at 30.4 nm using a short pulse driven transient inversion population has been realized. Gain performances and temporal characteristics of the X-ray signal output at only few Joules of pump energy are described.

An investigation was made of an eight-pass amplifier based on titanium-doped sapphire, pumped by the second harmonic of a YAG laser and intended for terawatt femtosecond laser systems. The gain reached 2×107 for a pump energy density of 3.2 J cm-2.

A novel two-step excitation scheme for an efficient table-top x-ray laser has been realized for the first time. A nanosecond pulse creates a plasma of neonlike ions of titanium, followed by a subpicosecond pulse which excites a nonstationary population inversion. With only a few joules of pump energy, a compact x-ray laser at 32.6 nm with a very high gain coefficient of $g\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}19{\mathrm{cm}}^{\ensuremath{-}1}$ and a gain-length product of $gL\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}9.5$ was achieved.

A hybrid Ti:Sa Nd:glass laser is described delivering two synchronized laser pulses with duration of 0.7 ps and 1.2 ns and output energies of 4 J in the short pulse and 8 J in the long pulse. The system was successfully used to drive efficiently a transient inversion XUV laser on [Ne]-like ions [see Nickles et al., SPIE Vol. 2520].

Particle acceleration using ultraintense, ultrashort laser pulses is one of the most attractive topics in relativistic laser-plasma research. We report proton and/or ion acceleration in the intensity range of 5×10(19) to 3.3×10(20) W/cm2 by irradiating linearly polarized, 30-fs laser pulses on 10-to 100-nm-thick polymer targets. The proton energy scaling with respect to the intensity and target thickness is examined, and a maximum proton energy of 45 MeV is obtained when a 10-nm-thick target is irradiated by a laser intensity of 3.3×10(20) W/cm2. The proton acceleration is explained by a hybrid acceleration mechanism including target normal sheath acceleration, radiation pressure acceleration, and Coulomb explosion assisted-free expansion. The transition of proton energy scaling from I(1/2) to I is observed as a consequence of the hybrid acceleration mechanism. The experimental results are supported by two- and three-dimensional particle-in-cell simulations.

Ultrafast X-ray absorption spectroscopy (UXAS) offers the opportunity to investigate function-structure relationships of complex organic molecules or biological functional subunits without the need of crystallization. Of special interest from the viewpoint of structural biology is the region of K-edges of transition metals between 5 and 10 keV. Regardless of successful application of time-resolved diffraction techniques to investigations of crystal dynamics using synchrotron and laboratory based sources there are only very few examples for application of UXAS to revealing the structural dynamics in biomolecular systems. This is mainly caused by the lack of broadband ultrafast x-ray sources as well as of appropriate optics adapted to these sources. Due to the long-data-recording time in UXAS experiments the sample integrity is mainly determined by the average power of the pump pulses inducing the structural changes. Using a fixed energy of the pump pulse the latter one is determined by the repetition rate of the pump laser. In this paper we discuss the prospects of UXAS comparing fs laser plasma sources with different repetition rates in combination with tailor-made optics based on highly annealed pyrolytic graphite (HAPG).

We have developed a 0.1-Hz-repetition-rate, 30-fs, 1.5-PW Ti:sapphire laser system for the research on high field physics. In this paper, we describe the design and output performance of the PW Ti:sapphire laser and its applications in the generation of relativistic high order harmonic generation and the acceleration of charged particles (protons and electrons). In the experiment on relativistic harmonic generation, the harmonic order dramatically extended up to 164 th that corresponds to 4.9 nm in wavelength, and the dramatic extension was explained by the oscillatory flying mirror model. Recently, we could accelerate protons up to 45 MeV from a 10-nm polymer target and show the change in the acceleration mechanism from target normal sheath acceleration to radiation pressure acceleration. The femtosecond high power laser system is a good candidate for developing a compact electron accelerator as well. The generation of multi-GeV electron beam was observed from an injection scheme when a PW laser pulse was focused by a long focal length spherical mirror.

Calibrated thermoluminescence dosimeters have been used to measure the angular and spectral dependence of hard x‐ray emission produced from intense subpicosecond laser irradiation of solid targets. A dosimeter detector set with nine filter channels (13.5–400 keV) has been tested successfully. Total bremsstrahlung conversion up to 0.23% and conversion of 8×10−5 from laser energy to Ta Kα line emission (photon energy ≊57 keV) was determined. The scaling of the hard x‐ray yield with laser intensities ranging from 3×1016 to 3×1018 W/cm2 was investigated.

We present a compact FROG system for determination of both pulse shape and phase of sub-picosecond pulses in a single-shot measurement. The system utilizes third-order auto-correlation due to the induced optical Kerr effect in heavy flint glass (SF6). The optical layout allows to use single Calcite wedges as high-contrast polarizers. Instead of using a separate spectrgraph, we incorporated a grating and appropriate imaging optics directly into the optical scheme. The FROG system has proven to be a convenient measurement tool to optimally align the grating compressor of CPA laser systems.

New excitation channels for the explanation of the strong emission of Li-like and Be-like satellite transitions in numerous picosecond and subpicosecond laser-produced plasma experiments are proposed. `Blue Li-like satellites' of the He-like resonance line W are predicted. Corresponding spectral simulations exploiting new calculated atomic data for these mechanisms are in rather good agreement with experimental single-shot spectra of plasma produced at the intensities up to and recorded by means of a high-resolution spherically bent mica crystal technique.