Search

ELI Beamlines is a rapidly progressing pillar of the pan‐European Extreme Light Infrastructure (ELI) project focusing on the development and deployment of science driven by high‐power lasers for user operations. This work reports the results of a commissioning run of a water‐jet plasma X‐ray source driven by the L1 Allegra laser, outlining the current capabilities and future potential of the system. The L1 Allegra is one of the lasers developed in‐house at ELI Beamlines, designed to be able to reach a pulse energy of 100 mJ at a 1 kHz repetition rate with excellent beam properties. The water‐jet plasma X‐ray source driven by this laser opens opportunities for new pump–probe experiments with sub‐picosecond temporal resolution and inherent synchronization between pump and probe pulses. [ABSTRACT FROM AUTHOR]

A robust and simple method is presented for ensuring constant energy and pointing of a high average power solid state laser on a target. In addition to providing long-term stability, this scheme also eliminates any drifts in energy or pointing resulting from the initial warm-up after a cold start. This is achieved using two separate feedback loops: one loop stabilizes the pointing of the beam external to the amplifier cavity and the other locks the cavity mode to have optimum overlap with the pump spot on the active medium. The key idea of the cavity mode stabilization is to monitor the overlap of the cavity mode and the gain medium with a camera and control it with an actively controlled, intra-cavity mirror. While this method is demonstrated on a thin-disk regenerative amplifier, it can also be applied to a wide variety of solid state laser amplifiers. [ABSTRACT FROM AUTHOR]

We show the laser-driven acceleration of unprecedented, collimated (2 mrad divergence), and quasi-monoenergetic (25% energy spread) electron beams with energy up to 50 MeV at 1 kHz repetition rate. The laser driver is a multi-cycle (15 fs) 1 kHz optical parametric chirped pulse amplification system, operating at 26 mJ (1.7 TW). The scalability of the driver laser technology and the electron beams reported in this work pave the way toward developing high-brilliance x-ray sources for medical imaging and innovative devices for brain cancer treatment and represent a step toward the realization of a kHz GeV electron beamline. [ABSTRACT FROM AUTHOR]

The validation of spectroscopic method for localization of the water plume around a coolant leak in ITER plasma chamber based on the excitation of coolant particles in plasma near wall is presented. The sensitivity of OH hydroxyl and Xe as minor admixtures to cooling water detection in different types of plasma discharges relevant to ITER tested in stellarator L-2M and hollow cathode glow discharge. The limit of sensitivity of water detection in hot plasma using OH* hydroxyl band is estimated as 3×10−5 Pam3 s−1and ∼1×10−6 Pam3 s−1 for Xe. For glow discharge conditions measured sensitivity of OH* detection is equal to 3×10−5 Pam3 s−1. [ABSTRACT FROM AUTHOR]

Abstract: The ITER fuel cycle is designed to handle considerable flow rates of tritium with high flexibility and reliability; experimental work is ongoing to validate these designs. Cryo-pumping systems for torus exhaust and neutral beam injectors have been tested to confirm fast regeneration scenarios and to reduce the accumulation of semi-permanent inventories of tritiated impurities. A 1:1 prototype of the torus exhaust cryo-pump is going to be manufactured and extensively tested. Tritium compatible mechanical pumps are being developed, in which leak rates to the exterior and contact between tritiated gases and lubricating oil have been minimized. Comprehensive integrated tests with the three-step process for torus exhaust processing were carried out. An ITER scale prototype fast delivery, self-assay storage bed has been developed; this component is designed to maximize the ratio of delivery rate to stored inventory and is undergoing testing. An integrated concept for the isotope separation (ISS) and water detritiation (WDS) systems has been developed and is being tested on relevant scale; this will provide an additional decontamination step for the potentially tritiated protium reject from the ISS. Extensive use of computer modeling to study the dynamic behavior of these and other fuel cycle systems is made. [Copyright &y& Elsevier]

The ITER main vacuum system consists of six torus exhaust pumps integrated in the Cryostat through dedicated housings at the building B1 level. The Port Cell area outside the cryopump plug is affected by neutrons streaming through the housing structure and diagnostics penetrations. The aim of the study presented in this paper is to perform a complete assessment of the nuclear responses in the Cryopump Port Cell #12 by means of the MCNP-5 Monte Carlo code in a full 3-D geometry. The results of the neutronic analyses provide guidelines for the design and maintenance of the embedded components, ensuring their structural integrity and proper operation. Radiation transport calculations have been carried out to determine the radiation field inside the Port Cell through 3-D neutrons and gamma maps. Nuclear heating induced by neutrons and photons and the absorbed dose during the ITER lifetime on steel and silicon have been estimated in the Port Cell area, in order to assess the nuclear loads that the diagnostics and related electronic components have to withstand. Furthermore, the impact of the gamma-rays emitted by neutron-activated water circulating in the Primary Heat Transfer System have been evaluated on the Port Cell environment: 3-D maps of the gamma flux, nuclear loads on steel/silicon during plasma operation are provided. [ABSTRACT FROM AUTHOR]

The dynamics of the HO molecule density in a metal gas-discharge chamber filled with low-pressure water vapor or its mixtures with noble gases was investigated by manometric and spectral methods. Regimes both with and without discharge excitation were studied. In the absence of a discharge, the molecule density dynamics is governed by the heterogeneous interaction of molecules with the chamber walls. In the presence of a discharge, in addition to the heterogeneous interaction, fast plasmachemical molecule dissociation also contributes to the initial stage of HO molecule loss. The role of heating of the chamber walls is discussed. [ABSTRACT FROM AUTHOR]

The ITER machine will be equipped with 6 torus Cryopumps (TCP) that are positioned in their housings (TCPH) and integrated into the cryostat walls at B1 level in the port cells. A comprehensive nuclear analysis of the Cryopump Ports #4 and #12 has been carried out by means of the MCNP-5 Monte Carlo code in a full 3-D geometry, providing guidelines for the design of the embedded components. Radiation transport calculations have been performed in order to determine the radiation field inside the Lower Ports, up the Port Cell: 3-D neutrons and gamma maps have been provided in order to evaluate the shielding effectiveness of the TCPHs. Nuclear heating induced by neutron and photons have been estimated on the TCP and TCPH to assess the nuclear loads during plasma operations. The shutdown dose rate in the maintenance area of the Lower Ports has been assessed with the Advanced D1S method to verify the design limits. [ABSTRACT FROM AUTHOR]

A novel method for measuring the number density of water molecules in low-temperature plasma is developed. The absolute intensities of rotational lines of the (0,0) band of the OH( AΣ- XП) transition are used. Lines with sufficiently large rotational quantum numbers referring to the so-called 'hot' group of molecules produced by electron-impact dissociative excitation of water molecules are chosen for measurements. The excitation rate of a process with a known cross section is determined by measuring the parameters of plasma electrons by means of the probe method. The measured number densities of molecules are compared with those in the initial plasma-forming mixture. The time evolution of the particle densities in plasma is investigated. The problems of the sensitivity and applicability of the absolute spectral method are considered. [ABSTRACT FROM AUTHOR]

Abstract: We present simple analytical solutions of coupled wave equations describing chirped pulse parametric amplification under pump depletion. The evolution of the duration and spectrum of amplified pulses in OPA pumped by Gaussian and supergaussian pulses has been investigated both numerically and analytically. Also, the dependence of the energy conversion efficiency from pump to signal was determined for a range of parameter values, and an optimum ratio of signal and pump pulse durations was evaluated. [Copyright &y& Elsevier]

Abstract: The CEA Association is involved, in close collaboration with ENEA, FZK, IPP and UKAEA European Associations, in the first ITER neutral beam (NB) injector and the ITER neutral beam test facility design (EFDA task ref. TW3-THHN-IITF1). A total power of about 50MW will have to be removed in steady state on the neutral beam test facility (NBTF). The main purpose of this task is to make progress with the detailed design of the first ITER NB injector and to start the conceptual design of the ITER NBTF. The general infrastructure layout of a generic site for the NBTF includes the test facility itself equipped with a dedicated beamline vessel [P.L. Zaccaria, et al., Maintenance schemes for the ITER neutral beam test facility, this conference] and integration studies of associated auxiliaries such as cooling plant, cryoplant and forepumping system. [Copyright &y& Elsevier]

Abstract: The ITER neutral beam test facility (NBTF) is planned to be built, after the approval of the ITER construction and the choice of the ITER site, with the agreement of the ITER international team and of the JA and RF participant teams. The key purpose is to progressively increase the performance of the first ITER injector and to demonstrate its reliability at the maximum operation parameters: power delivered to the plasma 16.5MW, beam energy 1MeV, accelerated D− ion current 40A, pulse length 3600s. Several interventions for possible modifications and for maintenance are expected during the early operation of the ITER injector in order to optimise the beam generation, aiming and steering. The maintenance scheme and the related design solutions are therefore a very important aspect to be considered for the NBTF design. The paper describes consistently the many interrelated aspects of the design, such as the optimisation of the vessel and cryopump geometry, in order to get a better maintenance flexibility, an easier man access and a larger access for diagnostic and monitoring. [Copyright &y& Elsevier]