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We demonstrate a method to characterize the beam energy, transverse profile, charge, and dose of a pulsed electron beam generated by a 1 kHz TW laser-plasma accelerator. The method is based on imaging with a scintillating screen in an inhomogeneous, orthogonal magnetic field produced by a wide-gap magnetic dipole. Numerical simulations were developed to reconstruct the electron beam parameters accurately. The method has been experimentally verified and calibrated using a medical LINAC. The energy measurement accuracy in the 6–20 MeV range is proven to be better than 10%. The radiation dose has been calibrated by a water-equivalent phantom, RW3, showing a linear response of the method within 2% in the 0.05–0.5 mGy/pulse range. [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]

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]

In this paper, the authors present the characterization experiments of a 20 fs vacuum ultraviolet beam from a high harmonic generation source. The beam hits a silicon sample and passes a triple reflection gold polarizer located inside an ultrahigh vacuum chamber. The polarizer's Malus curve was obtained; the total acquisition time for each point of the curve was 30 s. This aims to be the first vacuum ultraviolet time-resolved user station dedicated to ellipsometry. The high harmonic beam is generated by a 12 mJ, 1 kHz, 20 fs, in-house-developed laser and detected by a back-illuminated charge-coupled device. [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]

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]

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Experimental determination of the sensitivity of the method for detection of water microleakages in the cooling systems of the plasma vacuum chambers of complex electrophysical devices (such as tokamaks, fuel elements of nuclear reactors, and plasmachemical reactors) is considered. It was shown that the spectroscopic method for detection of water microleakages by using the hydroxyl radiation spectrum makes it possible to detect leakages at a level of 10 Pa m s. The spatial resolution of the method allows one to localize defects with an accuracy of several centimeters. [ABSTRACT FROM AUTHOR]

We report on the implementation of intensity-dependent filter for picosecond pulse temporal cleaning based on an effect of pulse polarization rotation during the unbalanced phase matched second harmonic generation. The pulse contrast enhancement by more than two orders of magnitude and filter transmission of ∼25% has been demonstrated at pulse intensities of <1 GW/cm. A simple and reliable all-solid-state filter scheme was integrated in a two-stage picosecond Nd:YAG regenerative amplifier seeded with pJ-energy femtosecond pulses of the Yb:KGW oscillator, and allowed us to reduce the ASE intensity level down to 1.5×10 with reference to the intensity of main 100 ps and 100 μJ pulse. [ABSTRACT FROM AUTHOR]

Existing methods of leak detection in vacuum chambers were analyzed from the viewpoint of their application to detect microleaks in the tokamak chamber. Microcrack sizes and leak rates most commonly observed during leak testing of fuel elements are presented. A technique for monitoring microcracking in the tokamak chamber was proposed based on laboratory studies. A series of experiments was performed, which confirmed high sensitivity of the proposed method. [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]