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All-dielectric gratings are ideal for high average power laser pulse compressors due to their low loss and high diffraction efficiencies. However, they have not been utilized in petawatt-class lasers with pulse durations below 100 fs due to a variety of challenges. We present a resonance-free design for low-dispersion (1480 lines/mm) diffraction gratings made of dielectric materials resistant to femtosecond laser damage (SiO 2 /HfO 2 ). A 14 cm diameter sample was fabricated resulting in a mean diffraction efficiency of 99.1% at λ = 810 nm with high spatial uniformity using equipment which can produce gratings up to 1 m diagonal. The implementation of these gratings in the compression of 30 fs pulses in an out-of-plane geometry can result in compressor efficiencies approaching 95%. The measured laser absorption is 500× lower than current ultrafast petawatt-class compressor gratings enabling a substantial increase in average power handling capabilities of these laser systems.

The advanced radiographic capability (ARC) laser system, part of the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, is a short-pulse laser capability integrated into the NIF. The ARC is designed to provide adjustable pulse lengths of ∼ 1 − 38 p s in four independent beamlets, each with energies up to 1 kJ (depending on pulse duration). A detailed model of the ARC lasers has been developed that predicts the time- and space-resolved focal spots on target for each shot. Measurements made to characterize static and dynamic wavefront characteristics of the ARC are important inputs to the code. Modeling has been validated with measurements of the time-integrated focal spot at the target chamber center (TCC) at low power, and the space-integrated pulse duration at high power, using currently available diagnostics. These simulations indicate that each of the four ARC beamlets achieves a peak intensity on target of up to a few 10 18 W / c m 2 .

European physical journal special topics 229(24), 3675 - 4284 (2020). doi:10.1140/epjst/e2020-000127-8, This report presents the conceptual design of a new European research infrastructure EuPRAXIA. The concept has been established over the last four years in a unique collaboration of 41 laboratories within a Horizon 2020 design study funded by the European Union. EuPRAXIA is the first European project that develops a dedicated particle accelerator research infrastructure based on novel plasma acceleration concepts and laser technology. It focuses on the development of electron accelerators and underlying technologies, their user communities, and the exploitation of existing accelerator infrastructures in Europe. EuPRAXIA has involved, amongst others, the international laser community and industry to build links and bridges with accelerator science — through realising synergies, identifying disruptive ideas, innovating, and fostering knowledge exchange. The Eu-PRAXIA project aims at the construction of an innovative electron accelerator using laser- and electron-beam-driven plasma wakefield acceleration that offers a significant reduction in size and possible savings in cost over current state-of-the-art radiofrequency-based accelerators. The foreseen electron energy range of one to five gigaelectronvolts (GeV) and its performance goals will enable versatile applications in various domains, e.g. as a compact free-electron laser (FEL), compact sources for medical imaging and positron generation, table-top test beams for particle detectors, as well as deeply penetrating X-ray and gamma-ray sources for material testing. EuPRAXIA is designed to be the required stepping stone to possible future plasma-based facilities, such as linear colliders at the high-energy physics (HEP) energy frontier. Consistent with a high-confidence approach, the project includes measures to retire risk by establishing scaled technology demonstrators. This report includes preliminary models for project implementation, cost and schedule that would allow operation of the full Eu-PRAXIA facility within 8—10 years., Published by Springer, Heidelberg

ARC is a kilojoule petawatt-class laser system which generates high energy x-ray and particle sources for radiography of experiments on the National Ignition Facility. We present recent progress on laser performance measurements and system modeling.

Figure 20.1 was not correct in the published article. The original article has been corrected. The published apologizes for the inconvenience.

We present a study of the temporal pre-pulse contrast degradation of high focused intensity pulses produced in CPA laser systems due to imperfections in amplifier design, alignment of amplifier components, and crystal inhomogenity. Using a measurement technique we have developed, we demonstrate the presence of multiple crystal domains inside Ti:sapphire slabs with ≈10 cm diameter. The results of our numeric calculations show that crystalline c-axis orientation inhomogenity caused by these crystal domains can lead to generation of pre-pulses with relative contrast >10-10 within several picoseconds before the main pulse. In a multiple-slab amplifier head configuration sometimes used in high repetition rate systems, the misalignment of the amplifier slabs crystalline c-axes with respect to each other can lead to the generation of pre-pulses with relative contrast as high as 10-6, depending on the magnitude of misalignment.

Petawatt laser applications, such as laser plasma acceleration, EUV generation, neutron generation, and materials processing are average-power limited. However, the highest average-power petawatt-class laser to date has an average power of less than 1 kW. Scaling Petawatt-class lasers beyond 10 kW of average power requires a paradigm shift in laser design. To date, average power scaling has been accomplished by increasing the repetition rate of single-shot lasers, in which each shot represents a complete pump/extraction cycle. We propose an alternative scheme, multipulse extraction, in which the gain medium is pumped continuously and the upper state population is extracted over many pulses. This method has two primary benefits: First, because efficient extraction is not necessary in a single pulse, the extraction fluence (and hence the B-integral) can be much lower than in a single pulse design. Second, there isn’t a need to pump within a single inverse lifetime, and therefore less expensive, less complex, and more efficient CW pump sources can be used. Multipulse extraction requires that the gain material have an inverse lifetime significantly less than the desired repetition rate. The design and optimization two multipulse extraction amplifiers, a 10 kHz-100 fs-30J amplifier and a 200 Hz-240 fs-240 J amplifier, will be presented. These point designs have applications in laser plasma acceleration and neutron generation, respectively

Novel architectures of Petawatt-class, high peak power laser systems that allow operating at high repetition rates are opening a new arena of commercial applications of secondary sources and discovery science. The natural path to higher average power is the reduction of the total heat load induced and generated in the laser gain medium and eliminating other inefficiencies with the goal to turn more energy into laser photons while maintaining good beam quality. However, the laser architecture must be tailored to the specific application and laser parameters such as wavelength, peak power and intensity, pulse length, and shot rate must be optimized. We have developed a number of different concepts tailored to secondary source generation that minimize inefficiencies and maximize the average power. The Scalable Highaverage- power Advanced Radiographic Capability (SHARC) and the Big Aperture Thulium (BAT) laser are examples of two such high average power laser concepts; SHARC is designed for production of ion beams and x-rays, and exploration of high energy density physics at 1.5 kW average power, and BAT is envisioned for driving laser-based electron accelerators at 300 kW average power.

New short-pulse kilojoule, Petawatt-class lasers, which have recently come online and are coupled to large-scale, many-beam long-pulse facilities, undoubtedly serve as very exciting tools to capture transformational science opportunities in high energy density physics. These short-pulse lasers also happen to reside in a unique laser regime: very high-energy (kilojoule), relatively long (multi-picosecond) pulse-lengths, and large (10s of micron) focal spots, where their use in driving energetic particle beams is largely unexplored. Proton acceleration via Target Normal Sheath Acceleration (TNSA) using the Advanced Radiographic Capability (ARC) short-pulse laser at the National Ignition Facility in the Lawrence Livermore National Laboratory is demonstrated for the first time, and protons of up to 18 MeV are measured using laser irradiation of >1 ps pulse-lengths and quasi-relativistic (∼1018 W/cm2) intensities. This is indicative of a super-ponderomotive electron acceleration mechanism that sustains acceleration over long (multi-picosecond) time-scales and allows for proton energies to be achieved far beyond what the well-established scalings of proton acceleration via TNSA would predict at these modest intensities. Furthermore, the characteristics of the ARC laser (large ∼100 μm diameter focal spot, flat spatial profile, multi-picosecond, relatively low prepulse) provide acceleration conditions that allow for the investigation of 1D-like particle acceleration. A high flux ∼ 50 J of laser-accelerated protons is experimentally demonstrated. A new capability in multi-picosecond particle-in-cell simulation is applied to model the data, corroborating the high proton energies and elucidating the physics of multi-picosecond particle acceleration.

High power laser science and engineering 7, e54 (2019). doi:10.1017/hpl.2019.36, Published by Cambridge Univ. Press, Cambridge

New control techniques are required to utilize the full potential of next generation high-energy high-repetition-rate pulses lasers while ensuring their safe operation. During automated optimization of an experiment, the control system is required to identify and reject unsafe laser configurations proposed by the optimizer. Using conventional physics codes render impossible when applied to a high energy laser system with 1ms or less time between shots, and also including laser fluctuations and drift. To mitigate this, we are using a deep Bayesian neural network to map the laser’s input power spectrum to its output power spectrum and demonstrate the speed of this approach. The Bayesian neural network can provide an estimate of its own uncertainty as a function of wavelength. A recently developed algorithm enables the uncertainty to be calculated inexpensively using multiple dropout layers inserted into the model. The uncertainty estimates are used by an active learning algorithm to improve the accuracy of the model and intelligently explore the input domain.

Evolving discovery science to deliver a continuous flux of secondary radiation for applications necessitates a new perspective on laser systems design to achieve robust operational capability at high average power.

Large laser systems that deliver optical pulses with peak powers exceeding one Petawatt (PW) have been constructed at dozens of research facilities worldwide and have fostered research in High-Energy-Density (HED) Science, High-Field and nonlinear physics [1]. Furthermore, the high intensities exceeding 1018W/cm2 allow for efficiently driving secondary sources that inherit some of the properties of the laser pulse, e.g. pulse duration, spatial and/or divergence characteristics. In the intervening decades since that first PW laser, single-shot proof-of-principle experiments have been successful in demonstrating new high-intensity laser-matter interactions and subsequent secondary particle and photon sources. These secondary sources include generation and acceleration of charged-particle (electron, proton, ion) and neutron beams, and x-ray and gamma-ray sources, generation of radioisotopes for positron emission tomography (PET), targeted cancer therapy, medical imaging, and the transmutation of radioactive waste [2, 3]. Each of these promising applications requires lasers with peak power of hundreds of terawatt (TW) to petawatt (PW) and with average power of tens to hundreds of kW to achieve the required secondary source flux.

Overview of progress in construction and testing of the laser systems of ELI-Beamlines, accomplished since 2015, is presented. Good progress has been achieved in construction of all four lasers based largely on the technology of diode-pumped solid state lasers (DPSSL). The first part of the L1 laser, designed to provide 200 mJ

We have demonstrated the world's highest average power, fully diode-pumped, petawatt-class peak power laser, the High-repetition-rate Advanced Petawatt Laser System (HAPLS) [1-3]. These first commissioning results at 16J (stretched) at 3%Hz fully validate projected performance of 30J/30fs (>1PW) at 10Hz. The laser has been operated at this intermediate level at Lawrence Livermore National Laboratory to demonstrate integrated performance of all subsystems and provide benchmarking data to laser performance models before further increasing energy and peak power. Data was obtained during multiple campaigns, exceeding several hours of run time, and a snapshot of 60min of data is shown in Fig. 1. The average pump laser 1ω (1053nm) energy was 97J with an rms stability of 0.7%, 2ω (527nm) energy at the Ti:sapphire power amplifier was 62J, and the average stretched short pulse energy was 16J. A full-aperture diagnostic suite allows simultaneous, single-shot measurement of energy, spectrum, beam quality, and pulse duration at full repetition rate. Single-shot SPIDER retrieved pulse shapes (Fig. 1 inset) with an average pulse duration over 12000 consecutive shots of 28.6fs (rms=1.4fs). The mean pulse duration is consistent with the measured spectral bandwidth and is ∼1.2× the transform limit. All results shown are raw data without filtering or averaging, demonstrating the exceptional pulse characteristics, repeatability, and stability of the entire laser system.

This talk will provide an overview of high power laser research at Lawrence Livermore National Laboratory (LLNL). It will discuss the status of the National Ignition Facility (NIF) laser. In addition, the talk will describe other laser development activities such as the development of high average power lasers and novel fiber lasers. The National Ignition Facility (NIF) has been in service since 2007 and operating with > 1 MJ energies since 2009. During this time the facility has transitioned to become an international user facility and increased the shot rate from ~150 target shots per year to greater than 400 shots per year. Today, the NIF plays an essential role in the US Stockpile Stewardship Program, providing data under the extreme conditions needed to validate computer models and train the next generation of stockpile stewards. Recent upgrades include the Advanced Radiographic Capability (ARC), a high energy short pulse laser used to do high resolution radiography. In addition to the NIF, this talk will include an overview of progress on the high average power laser development, recent results from fiber laser development activities and improvements to laser design and computational capabilities.

Laser energy absorption and subsequent heat removal from diffraction gratings in chirped pulse compressors poses a significant challenge in high repetition rate, high peak power laser development. In order to understand the average power limitations, we have modeled the time-resolved thermo-mechanical properties of current and advanced diffraction gratings. We have also developed and demonstrated a technique of actively cooling Petawatt scale, gold compressor gratings to operate at 600W of average power - a 15x increase over the highest average power petawatt laser currently in operation. Combining this technique with low absorption multilayer dielectric gratings developed in our group would enable pulse compressors for petawatt peak power lasers operating at average powers well above 40kW.

We have developed a high-efficiency (∼90%), broad-bandwidth low-absorption pulse compressor suitable for high energy pulses. This technology is a significant step in enabling high peak power laser systems to operate at high repetition rates.

The HAPLS laser system has been commissioned to its first integrated performance milestone, delivering laser pulses with 16J sub-30fs duration at a 3⅓Hz repetition rate. This first all-diode-pumped petawatt-class laser offers the average powers required for secondary source applications.

An entirely reflective slit spatial filter is proposed to provide spatial filtering, gain isolation, and ASE mitigation for high-energy laser systems. The traditional circular pinhole is replaced by two orthogonal slits, which lowers the intensity at the spatial filter plane by up to two orders of magnitude, and by using reflective optics we reduce spatial dispersion and eliminate B-integral effects. A ray trace model of the spatial filter shows excellent transmitted wavefront, but also indicates aberrations at the foci from using cylindrical optics at 45°. It is expected that the use of off-axis parabolic mirrors would mitigate this issue but comes at the cost of more complicated, expensive optics and more complex alignment. We created a numerical model based on Fourier optics to explain this effect and guide design requirements to mitigate it. High-quality imaging and filtering capabilities are demonstrated experimentally.

Initial performance ramping of the HAPLS pump laser, a high-energy DPSSL based on Nd:glass, produced 70J at 1053nm from a single aperture and 39J at 527nm using LBO frequency converter all at 3.3Hz repetition rate.

Phase 1 performance ramping of the HAPLS pump laser, a high-energy DPSSL based on Nd:glass, successfully produced 70J at 1053nm from a single aperture and 39J at 527nm using LBO frequency converter running at 3.3Hz repetition rate.

A new generation of high power lasers is enabled by recent advancement of optical materials and processing techniques, laser performance modeling and laser control systems, diode technology and new laser architectures. One of the most remarkable and promising opportunities of these light sources is the combination of high peak intensity, high energy, short pulses, and high repetition rate that allow experiments of unprecedented fidelity and new commercial applications.

We have developed preliminary conceptual laser system designs for the Laser ICF (Inertial Confinement Fusion) Fission Energy (LIFE) application. Our approach leverages experience in high-energy Nd:...

Laser-induced damage threshold (LIDT) testing was performed on commercially-available multilayer dielectric coatings to qualify for use in the High Repetition-Rate Advanced Petawatt Laser System (HAPLS) for Extreme Light Infrastructure Beamlines. Various tests were performed with uncompressed pulses (150 ps) from a 780 nm-centered Ti:Sapphire regenerative ampliflier, and the raster scan method was used to determine the best-performing coatings. Performance varied from 2–8 J/cm 2 across samples from 6 different manufacturers.

Precise assessment of the high fluence performance of pulse compressor gratings is necessary to determine the safe operational limits of short-pulse high energy lasers. We have measured the picosecond laser damage behavior of multilayer dielectric (MLD) diffraction gratings used in the compression of chirped pulses on the Advanced Radiographic Capability (ARC) kilojoule petawatt laser system at the Lawrence Livermore National Laboratory (LLNL). We present optical damage density measurements of MLD gratings using the raster scan method in order to estimate operational performance. We also report results of R-on-1 tests performed with varying pulse duration (1-30 ps) in air, and clean vacuum. Measurements were also performed in vacuum with controlled exposure to organic contamination to simulate the grating use environment. Results show sparse defects with lower damage resistance which were not detected by small-area damage test methods.

Industrial and Scientific High Energy Laser Systems with output energies in the Joule to Megajoule range typically rely on flash lamps to energize the gain media. Especially in rep rated laser systems the advantage of low capital cost per lamp is outweighed by many disadvantages, such as low pump efficiency, heating of the gain medium, frequent maintenance requirement, significant capital cost for its pulsed power system, and laser performance stability. Diode Pumped Solid State Laser (DPSSL) systems represent a viable alternative. In this paper we will present an efficient, integrated power conditioning system developed for the High-Repetition-Rate Advanced Petawatt Laser System (HAPLS) that is being developed by LLNL for deployment in the international user facility Extreme Light Infrastructure Beamlines (ELI-Beamlines) in Czech Republic [1]. The High Energy Pump Laser of HAPLS is energized by 4 High Peak Power Laser Diode Arrays with total peak power of 3.2 MW that were developed by Lasertel and LLNL. The diode arrays deliver ∼1kJ at repetition rate 10Hz. Each diode array is comprised of 40 individual diode tiles where every tile generates >20 kilowatts of peak power. Each tile is driven by a single pulser that contains its own energy storage, control and high current drive circuitry. As part of the HAPLS laser the pulsers are operated at approximately 520A, a pulse width of 300μs at 10Hz. In another LLNL laser system basically identical pulsers are operated at 315A, 300us at 120Hz. The pulsers were designed to be operated in a support frame called a pulser crate. Each crate is designed to hold up to 45 pulsers in a volume similar to a desktop computer. Communication with the pulsers is by means of a one-way digital optical link which greatly simplifies the internal wiring. Each crate contains a “Brain Box” which in turn contains the front end processor (FEP), machine safety system (MSS) and energy storage dump subsystems. Providing flexibility and system balancing capability each pulser can be tailored to the diode tile: it has an internal Arbitrary Waveform Generator (AWG) on board that controls the shape of the diode current pulse. The AWG can vary the pulse shape in any combination of programmable increments with resolutions 1A and 1μs up to maximums of 1kA and 350μs. Under command of the crate controller each pulser can create its own distinct waveform and deliver that waveform when triggered.

The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory is the first of a kind megajoule-class laser with 192 beams capable of delivering over 1.8 MJ and 500TW of 351nm light [1], [2]. It has been commissioned and operated since 2009 to support a wide range of missions including the study of inertial confinement fusion, high energy density physics, material science, and laboratory astrophysics. In order to advance our understanding, and enable short-pulse multi-frame radiographic experiments of dense cores of cold material, the generation of very hard x-rays above 50 keV is necessary. X-rays with such characteristics can be efficiently generated with high intensity laser pulses above 1017 W/cm² [3]. The Advanced Radiographic Capability (ARC) [4] which is currently being commissioned on the NIF will provide eight, 1 ps to 50 ps, adjustable pulses with up to 1.7 kJ each to create x-ray point sources enabling dynamic, multi-frame x-ray backlighting. This paper will provide an overview of the ARC system and report on the laser performance tests conducted with a stretched-pulse up to the main laser output and their comparison with the results of our laser propagation codes.

We investigate the laser damage resistance of multilayer dielectric (MLD) diffraction gratings used in the pulse compressors for high energy, high peak power laser systems such as the Advanced Radiographic Capability (ARC) Petawatt laser on the National Ignition Facility (NIF). Our study includes measurements of damage threshold and damage density (ρ(Φ)) with picosecond laser pulses at 1053 nm under relevant operational conditions. Initial results indicate that sparse defects present on the optic surface from the manufacturing processes are responsible for damage initiation at laser fluences below the damage threshold indicated by the standard R-on-1 test methods, as is the case for laser damage with nanosecond pulse durations. As such, this study supports the development of damage density measurements for more accurate predictions on the damage performance of large area optics.

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.

Dynamic wave front correction is applied before each shot on a 100 TW, 30 J/300 fs high power laser facility using an adaptive optics system. This system allows one to increase the repetition rate of high-energy lasers while maintaining excellent and constant beam focusability with a Strehl ratio >0.75 despite the amplifiers not being in thermal equilibrium. Best results in terms of highest Strehl ratio and intensities are obtained when locking the system on wave front sensing after pulse recompression.

Recent advances in the average-power capabilities of lasers with petawatt peak powers are enabling new science and applications in industry, biomedicine and security.

To predict in-vacuum optical damage performance of Advanced Radiographic Capability Petawatt final optics we have developed a ps-damage test station to measure damage density and compare results to R-on-1 tests.

Laser-produced energetic protons via target normal sheath acceleration are deteriorated by amplified spontaneous emission (ASE). Here we test a new method of reducing ASE and increasing proton energy by relativistic self-guiding in the plasma.

A transient collisionally excited X-ray laser has been put into operation using the front end of the PHELIX laser system as a pump laser. Strong lasing at 22 nm has been observed in nickel-like zirconium.

Dispersion balancing in complex, high-intensity, chirped-pulse-amplification, laser systems is critical for optimizing temporal pulse fidelity. We demonstrate a method for dispersion management of the eight-beam, Petawatt Advanced Radiographic Capability Laser being built at the National Ignition Facility utilizing the phase shift technique.

A novel high-dynamic-range cross-correlator is presented that enables single-shot characterization of pulse contrast for ultrahigh intensity lasers in the temporal region up to 200 ps.

The use of chirped-pulse amplification (CPA) in high-energy systems allows the generation of high-peak power and ultrahigh intensity, and has led to intensities greater than 1020 W · cm−2 [1]–[3]. These systems are of especially high interest for exploring high-energy dense plasma physics and for fast ignition in inertial confinement fusion [4]. In these systems the control of the prepulses is crucial as their intensity might perturb the target before the main pulse arrives. Plasma generation thresholds of solid targets are generally of the order of 1010 W · cm−2 and hence require a contrast ratio exceeding 1010 for a 1020 W · cm−2 system. Optical parametric chirped-pulse amplification (OPCPA), a CPA technique which relies on the three-wave mixing process in a nonlinear crystal, has received much attention due to its superior characteristics for broadband amplification in high-power laser system front-ends. In fact, OPCPA operated near degeneracy and thus providing high gain while maintaining broad spectral bandwidth is increasingly replacing Ti:sapphire front-ends in Nd:glass short-pulse lasers [5]–[8]. With respect to the prepulse contrast ratio, an OPCPA system offers enormous advantages. High-gain regenerative amplifiers usually produce a train of prepulses caused by the cavity leakage due to the limited extinction ratio of the intracavity polarizer, and they thus require additional postamplification temporal pulse cleaning techniques (e.g. [9],[10]). OPCPA amplifies only a single pulse out of the oscillator pulse train resulting in a prepulse contrast enhancement equal to the total saturated gain, provided that the pump pulse duration is sufficiently short so that there is no temporal overlap of the pump pulse with preceding or subsequent pulses.

Dynamic wave-front correction is applied before each shot on a 100-TW, 30-J/300-fs high-power laser facility by use of an adaptive-optics system. This system allows us to increase the repetition rate of high-energy lasers while maintaining excellent and constant beam focusability with a Strehl ratio of >0.75 despite the amplifiers’ not being in thermal equilibrium. The best results in terms of the highest Strehl ratio and intensities are obtained when locking the system on wave-front sensing after pulse recompression.

We demonstrate the wave-front correction of the LULI 100TW, 300 fs/30 J high power laser facility for a sequence of shots. Excellent beam focusability close to diffraction limit has been obtained using an adaptive optic system, composed of a large aperture dielectric coated deformable mirror and a home-made shearing interferometer. This correction allows to produce reproducible focal spots with Strehl ratios close to 0.9 at a repetition rate of a shot every 20 minutes, despite of wave front distortions generated by cumulative thermal effects in the large disc amplifiers.

The Gesellschaft fuer Schwerionenforschung (GSI, Society for Heavy Ion Research) is currently the leading facility in the production of radioactive isotopes. Nuclear properties like charge radii, spin, and magnetic moments of exotic nuclei provide important data for testing of nuclear models. These properties are usually accessed by laser spectroscopy, which requires photon energies of around 100 eV in the case of lithium-like ions. We propose to use a transient gain X-ray laser (XRL) at the experimental storage ring (ESR) to perform this kind of spectroscopy. In this article we describe the planned experiments and give an overview of the current construction at GSI.

The unique combination of an intense heavy ion beam accelerator and a high energy laser opens the possibility of exploring new physics taking advantage of the synergy of both facilities. A variety of new fields can be addressed with this combination in plasma physics, atomic physics, nuclear- and astro-physics as well as material research. In addition, using CPA-technology, laser pulses with a pulse power of up to a petawatt opens the door to explore the regime of fully relativistic plasmas. Therefore the Gesellschaft fuer Schwerionenforschung is augmenting the current high intensity upgrade of the heavy ion accelerator facility with the construction of PHELIX. Designed with two pulse-generating front ends and send to multiple experimental areas PHELIX will serve as a highly versatile laser system for various applications. In this report, we present the design of the laser system and some key experiments that can be performed with this combination for the first time.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In order to achieve the highest intensities possible with the short-pulse Advanced Radiographic Capability beamline at the National Ignition Facility (NIF), it will be necessary to phase the individual ARC apertures. This is made especially challenging because the design of ARC results in two laser beams with different dispersions sharing the same NIF aperture. The extent to which two beams with different dispersions can be phased with each other has been an open question. This paper presents results of an analysis showing that the different dispersion values that will be encountered by the shared-aperture beams will not preclude the phasing of the two beams. We also highlight a situation in which dispersion mismatch will prevent good phasing between apertures, and discuss the limits to which higher-order dispersion values may differ before the beams begin to dephase.