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We present a stable supercontinuum (SC) generated in a bulk YAG crystal, pumped by 3 ps chirped pulses at 1030 nm. The SC is generated in a loose focus geometry in a 13 cm long YAG crystal, allowing for stable and robust single-filament generation. The SC energy stability exceeds that of the pump laser by almost a factor of 3. Additionally, we show that the SC spectrum has long-term stability and that the SC is coherent and compressible by compressing the portions of SC spectra close to the corresponding Fourier limit. This makes the picosecond-pulse-driven SC a suitable stable seed for OPCPA amplifiers.

We report on the design and performance of a fiber-based, multi-channel laser amplifier seed pulse distribution system. The device is designed to condition and distribute low energy laser pulses from a mode-locked oscillator to multiple, highly synchronized, high energy amplifiers integrated into a laser beamline. Critical functions such as temporal pulse stretching well beyond 100 ps/nm, pulse picking, and fine control over the pulse delay up to 300 ps are all performed in fiber eliminating the need for bulky and expensive grating stretchers, Pockels cells, and delay lines. These functions are characterized and the system as a whole is demonstrated by seeding two high energy amplifiers in the laser beamline. The design of this system allows for complete computer control of all functions, including tuning of dispersion, and is entirely hands-free. The performance of this device and its subsystems will be relevant to those developing lasers where reliability, size, and cost are key concerns in addition to performance; this includes those developing large-scale laser systems similar to ours and also those developing table-top experiments and commercial systems.

We present a stable supercontinuum generation in a YAG crystal, driven by 3 ps pulses at 1030 nm. The supercontinuum is demonstrated to be coherent and compressible by Dazzler and prism compressor to below 15 fs.

We report on a broadband OPCPA system, pumped at 515 nm by frequency doubled Yb:YAG thin disk lasers. The system delivers 11.3 mJ pulses at a central wavelength of 800 nm with a spatial beam quality of Msup2/sup= 1.25 and25% pump-to-signal conversion efficiency. The broadband pulses were demonstrated to be compressible to 12 fs using a chirped mirror compressor.

We report on a frequency-doubled picosecond Yb:YAG thin disk regenerative amplifier, developed as a pump laser for a kilohertz repetition rate OPCPA. At a repetition rate of 1 kHz, the compressed output of the regenerative amplifier has a pulse duration of 1.2 ps and pulse energy of 90 mJ with energy stability of σ < 0.8% and M2 < 1.2. The pulses are frequency doubled in an LBO crystal yielding 42 mJ at 515 nm.

We present a high-energy picosecond Nd:YAG-amplification system seeded with pulses of a femtosecond Yb:KGW oscillator. The Nd : YAG amplifier is intended to pump an optical parametric chirped-pulse amplification (OPCPA) system. Generation of high contrast pulses with energy of 600 mJ and pulse duration of 100 ps is demonstrated.

We investigated thermal-lensing effects in a diode end-pumped Yb:KGW laser with slab shaped active element. Performance and thermal lensing properties for Ng cut Yb:KGW and Yb:KGW cut for athermal propagation direction are presented. It is found that crystal cut along athermal direction provides weaker thermal lens than Ng cut active element, however, due to anisotropic Yb:KGW characteristics, thermal lens is highly astigmatic. End bulging contribution to thermal lensing under intense pump was measured (for Ng cut active element). Keywords: Yb:KGW, thermal lens, diode-pumped, athermal orientation

We report the high beam quality diode end-pumped Q-switched Yb:YAG laser operating at 1030 nm wavelength with elliptical cavity mode conguration operating at 1n100 kHz repetition rates. We have performed measurements of highly astigmatic thermal lens in laser active element by means of ShacknHartmann wavefront sensor that provides necessary data for laser cavity design. With optimized laser cavity the output beam quality parameter M 2 does not exceed 1.2 value even at maximum pump power of 50 W.

Tritium as one of the two fuel components for fusion power plays a special role in any fusion device. Due to its volatile character, radioactivity and easy incorporation as HTO it needs to be contr...

The ITER roughing system provides for both the initial pump-down of the vessel itself and the regular pump-out of the batch-regenerating cryopumps. This system must have a large pumping speed and cope with the radioactive gas tritium at the same time. The present paper shall highlight the results of the ITER roughing train optimization, discuss the modification of a Roots pump for tritium, and present the results of a ferrofluidic seal test and the first tests of a tailor-made tritium-proof Roots pump with inactive gases.

The ELI-Beamlines facility, currently under construction in Prague, Czech Republic, will house multiple high power laser systems with varying pulse energies, pulse durations, and repetition rates. Here we present the status of a high repetition rate beamline currently under construction with target parameters of 20 fs pulse duration, 100 mJ pulse energy, and 1 kHz repetition rate. Specifically we present the Yb:YAG thin disk lasers which are intended to pump picosecond OPCPA, synchronization between pump and signal pulses in the OPCPA, and the first stages of OPCPA.

The physics of the ITER edge and divertor plasma is strongly coupled with the divertor and the fuel cycle design. Owing to the limited space available the design as well as the remote maintenance approach for the ITER divertor are highly optimized to allow maximum space for the divertor plasma. Several auxiliary systems (e.g., in-vessel viewing instruments and glow discharge electrodes) as well as a part of the pumping and fuelling system have to be integrated together with the divertor into the lower level of ITER. Two main options exist for the choice of the plasma facing material in the divertor, i.e. tungsten and CFC. On the basis of already existing R&D results it is likely that the material choice will be mainly determined by physics considerations and material issues (e.g., C-T co-deposition). The requirements for the ITER fuel cycle arise from plasma physics as well as from the envisaged operation scenarios. Owing to the complex dynamic relationship of the fuel cycle subsystems among themselves and with the plasma, codes are employed for their optimization. These interacting issues are elaborated on the latest design status discussed.

We present the results of performance modeling of a diode-pumped solid-state HiLASE laser designed for use in inertial fusion energy power plants. The main amplifier concept is based on a He-gas-cooled multi-slab architecture similar to that employed in Mercury laser system. Our modeling quantifies the reduction of thermally induced phase aberrations and average depolarization in ${\mathrm{Yb}}^{{3+}}$ :YAG slabs by a combination of helium cryogenic cooling and properly designed (doping/width) cladding materials.

The requirements for the ITER divertor design, i.e. power and He ash exhaust, neutral leakage control, lifetime, disruption load resistance and exchange by remote handling, are described in this paper. These requirements and the physics requirements for detached and semi-attached operation result in the vertical target configuration. This is realised by a concept incorporating 60 cassettes carrying the high heat flux components. The armour choice for these components is CFC monoblock in the strike zone near the lower part of the vertical target, and a W brush elsewhere. Cooling is by swirl tubes or hypervapotrons depending on the component. The status of the heat sink and joining technology R and D is given. Finally, the resulting design of the high heat flux components is presented.

We report on a temporal jitter-compensated Yb:YAG thin-disc laser as a pump source for the front-end OPCPA of ELIBeamlines high energy and repetition rate system. The main advantage of using picosecond Yb:YAG thin-disc lasers is that relatively high energies in the kHz repetition rate range can be easily accessed. Although in our case the pump laser is optically synchronized to the OPCPA seeding Ti:Sapph laser, the stability of the OPCPA output gets heavily affected by delay jitter due to a large number of roundtrips in the regenerative amplifier cavity and slight ambient temperature drifts. Since interacting pulses are only ~1.5 ps in duration, an additional active stabilization of the pump path length corresponding to sub-100 fs delay precision must be implemented. In our work we demonstrate a novel design of a jitter stabilization system which employs a cross-correlation setup employing parametric amplification in two perpendicularly oriented nonlinear crystals. A small fraction of the OPCPA seed signal is being locked between cross-polarized and delayed replicas of a pump pulse. The feedback signal for the delay compensation is acquired by coupling the polarization-separated parts of the parametrically amplified signal into two channels of a balanced photodetector. The delay stabilization is achieved mainly by adjusting the cavity length of the regenerative amplifier with a piezo-mounted mirror. The proposed setup allows reducing the temporal jitter of Yb:YAG thin-disc regenerative amplifier to tens of fs RMS and maintaining it over extended periods of time.

A novel frequency synthesis scheme and feed-forward approach is applied directly for stabilization of a sub-MHz frequency comb from a Yb:KGW CPA laser not only reduces the phase noise but also greatly simplifies the stabilization setup.