Laser Beam Transport Research Articles

Comparative Additional Factor for Diffraction Loss On (TEM01) Mode from That of (TEM00) Mode

Comparative Additional Factor for Diffraction Loss On (TEM01) Mode from That of (TEM00) Mode

Effects of pulse chirp on laser-driven proton acceleration

Optimisation and reproducibility of beams of protons accelerated from laser-solid interactions require accurate control of a wide set of variables, concerning both the laser pulse and the target. Among the former ones, the chirp and temporal shape of the pulse reaching the experimental area may vary because of spectral phase modulations acquired along the laser system and beam transport. Here, we present an experimental study where we investigate the influence of the laser pulse chirp on proton acceleration from ultrathin flat foils (10 and 100 nm thickness), while minimising any asymmetry in the pulse temporal shape. The results show a pm 10% change in the maximum proton energy depending on the sign of the chirp. This effect is most noticeable from 10 nm-thick target foils, suggesting a chirp-dependent influence of relativistic transparency.

Alignment procedure for off-axis-parabolic telescopes in the context of high-intensity laser beam transport.

Off-axis parabolic telescopes are rarely used in high-intensity, high-energy lasers, despite their favorable properties for beam transport such as achromatism, low aberrations and the ability to handle high peak intensities. One of the major reasons for this is the alignment procedure which is commonly viewed as complicated and time consuming. In this article, we revisit off-axis parabolic telescopes in the context of beam transport in high-intensity laser systems and present a corresponding analytical model. Based on that, we propose a suitable setup that enables fast and repeatable alignment for everyday operation.

Design, installation and commissioning of the ELI-Beamlines high-power, high-repetition rate HAPLS laser beam transport system to P3

AbstractThe design and the early commissioning of the ELI-Beamlines laser facility’s 30 J, 30 fs, 10 Hz HAPLS (High-repetition-rate Advanced Petawatt Laser System) beam transport (BT) system to the P3 target chamber are described in detail. It is the world’s first and with 54 m length, the longest distance high average power petawatt (PW) BT system ever built. It connects the HAPLS pulse compressor via the injector periscope with the 4.5 m diameter P3 target chamber of the plasma physics group in hall E3. It is the largest target chamber of the facility and was connected first to the BT system. The major engineering challenges are the required high vibration stability mirror support structures, the high pointing stability optomechanics as well as the required levels for chemical and particle cleanliness of the vacuum vessels to preserve the high laser damage threshold of the dielectrically coated high-power mirrors. A first commissioning experiment at low pulse energy shows the full functionality of the BT system to P3 and the novel experimental infrastructure.

TERESA Target Area at ELI Beamlines

The TERESA (TEstbed for high REpetition-rate Sources of Accelerated particles) target area, recently commissioned with the L3-HAPLS laser at Extreme Light Infrastructure (ELI)-Beamlines, is presented. Its key technological sections (vacuum and control systems, laser parameters and laser beam transport up to the target) are described, along with an overview of the available plasma diagnostics and targetry, tested at relativistic laser intensities. Perspectives of the TERESA laser–plasma experimental area at ELI-Beamlines are briefly discussed.

Single-particle dynamics of microbunching

The mechanism of steady-state microbunching (SSMB) has been proposed [D. F. Ratner and A. W. Chao, Phys. Rev. Lett. 105, 154801 (2010)] to generate high-power coherent radiation at a high repetition rate or in continuous-wave mode using electron storage rings. In this paper, the related single-particle dynamics are theoretically and numerically studied, and important results are presented. The investigated effects are longitudinal quantum radiation excitation, nonlinear momentum compaction, and linear and nonlinear coupling of the transverse and longitudinal motion. Although this analysis is oriented toward SSMB, some of the analyzed effects are also crucial in cases such as coherent harmonic generation, bunch slicing, bunch compression, free-electron laser beam transport lines, and quasi-isochronous rings, which involve precise longitudinal phase-space manipulations.

Optical Properties of Tap Water Purity using He-Ne Laser with Different Power Density

Tap water differs from pure water, it contains more chemical contents arise in drinking water, it effect on health concern only after extended exposure of years, rather than months. The purpose of this article is to study the optical properties of tap water by using different power density from He-Ne laser beam transport through some samples. These samples of water mostly contain NaCl salts and clay .When we increasing concentration and sample length we can observed that decreasing transmittance ,(absorption and extinction) coefficients while the absorbance will be increased .At the 5 cm sample length we observed that tap water has transmittance about 17%, while NaCl (0.7) concentration has 58%,clay solute has 2%, and mixing from (0.7 NaCl and 0.15 clay) concentrations has transmittance 8%, The absorbance and absorption coefficient of tap water is greater than NaCl and less than clay alone and mixing (clay with salt) at the same sample length.

Laser and optical system for laser assisted hydrogen ion beam stripping at SNS

Recently, a high-efficiency laser assisted hydrogen ion (H-) beam stripping was successfully carried out in the Spallation Neutron Source (SNS) accelerator. The experiment was not only an important step toward foil-less H- stripping for charge exchange injection, it also set up a first example of using megawatt ultraviolet (UV) laser source in an operational high power proton accelerator facility. This paper reports in detail the design, installation, and commissioning result of a macro-pulsed multi-megawatt UV laser system and laser beam transport line for the laser stripping experiment.

Effects of different kinds of mitigated pits on transport of laser beam

According to the different kinds of morphology features, 3D grid models of mitigated pits were built, and effects of different kinds of mitigated pits models on transport of laser beam (351 nm) was studied by using scalar diffraction theory and Fast Fourier Transform (FFT) methods. The results indicate that the off-axis downstream intensification of different kinds of mitigated pits, including conic, parabolic and Gaussian, pits, mainly relies on the depth of the mitigated pit. For the off-axis intensification, the maximum intensity increases with deepening depth, and the location of the maximum intensity approaches the output surface of optics with increasing pit depth, and is far away from the output surface of optics with the increasing diameter of mitigated pits. In addition, when the depth and diameter of different kinds of mitigation pits are equal, the parabolic mitigated pits can be the best choice for mitigated morphology. The results of this research indicate that the downstream intensification, which is induced by the mitigated damage pits, can be suppressed by controlling the morphology features of mitigated pits.

Phase Characterization of Multilayer Coatings by Photoemission Measurements

Attosecond science, photolithography, synchrotron, and free electron laser physics are new frontiers research and technological areas, where the properties of the beam play a fundamental role in the light-matter interaction. To fully control the properties of a propagating beam, knowledge and control of the efficiency and phase introduced by the optical components upon reflection is mandatory. In this letter, an original method based on photoemission measurements useful to determine the phase shift upon reflection of extreme ultraviolet multilayer mirrors working in a near Brewster’s condition has been developed. The method has been also successfully applied to test two different innovative samples specifically designed and proposed for the FERMI@ELETTRA free electron laser beam transport system.

High-power fiber lasers for photocathode electron injectors

Many new applications for electron accelerators require high-brightness, high-average power beams, and most rely on photocathode-based electron injectors as a source of electrons. To achieve such a photoinjector, one requires both a high-power laser system to produce the high average current beam, and also a system at reduced repetition rate for electron beam diagnostics to verify high beam brightness. Here we report on two fiber laser systems designed to meet these specific needs, at 50 MHz and 1.3 GHz repetition rate, together with pulse pickers, second harmonic generation, spatiotemporal beam shaping, intensity feedback, and laser beam transport. The performance and flexibility of these laser systems have allowed us to demonstrate electron beam with both low emittance and high average current for the Cornell energy recovery linac.

Optical beam transport to a remote location for low jitter pump-probe experiments with a free electron laser

In this paper we propose a scheme that allows a strong reduction of the timing jitter between the pulses of a free electron laser (FEL) and external laser pulses delivered simultaneously at the FEL experimental stations for pump-probe--type experiments. The technique, applicable to all seeding-based FEL schemes, relies on the free-space optical transport of a portion of the seed laser pulse from its optical table to the experimental stations. The results presented here demonstrate that a carefully designed laser beam transport, incorporating also a transverse beam position stabilization, allows one to keep the timing fluctuations, added by as much as 150 m of free space propagation and a number of beam folding mirrors, to less than 4 femtoseconds rms. By its nature our scheme removes the major common timing jitter sources, so the overall jitter in pump-probe measurements done in this way will be below 10 fs (with a margin to be lowered to below 5 fs), much better than the best results reported previously in the literature amounting to 33 fs rms.

Offner radial group delay compensator for ultra-broadband laser beam transport

Conventional lens-based image relays introduce radial group delay that significantly reduces focal-spot intensity of ultra-broadband short pulses. A direct compensation scheme that can be used with conventional singlet image relays is proposed. The compensation scheme is based on using two negative lenses embedded within an Offner imaging system. The setup allows a single-pass configuration and eliminates the need for polarization switching optics. The performance of this setup is calculated using ray tracing. The compensation improves the spatiotemporal Strehl ratio from 0.02 to 0.97.

Progress on the Femto-Slicing Project at the Synchrotron SOLEIL

The aim of the Femto-Slicing project at SOLEIL is to generate 100 fs X-rays pulses on two beamlines, CRISTAL and TEMPO, for pump-probe experiments in the hard and soft X-rays regions. Two fs lasers are currently in operation on TEMPO and CRISTAL for pump-probe experiments on the ps time scale enabling time resolved photoemission and photodiffraction studies. The Femto-Slicing project is based on the fs laser of the CRISTAL beamline, which can be adjusted to deliver 3 mJ pulses of 30 fs duration at 2.5 kHz. The laser beam will be separated in three branches: one delivering about 2 mJ to the modulator Wiggler and the other ones delivering the remaining energy to the TEMPO and CRISTAL experiments. This layout will yield natural synchronization between IR laser pump and X-ray probe pulses, only affected by jitter associated with beam transport. In this paper, we present the current status of the Femto-Slicing project at SOLEIL, with particular emphasis on the expected performance, and the design and construction of the laser beam transport and the diagnostics implementation.

Vacuum system design for twenty-cell PWT Linac structure

This paper describes the vacuum system design for a 20-cell Plane Wave Transformer (PWT) type LINear ACcelerator (LINAC) structure to obtain a vacuum better than 5×10−8 mbar everywhere inside the linac structure. Specific material out-gassing rate for a 20-cell linac is determined on the basis of vacuum achieved in a similar type of 8-cell linac structure, which is smaller in length, and presently under operation in the Compact Ultrafast TEra-hertz Free Electron Laser (CUTE-FEL) beam transport line at RRCAT.

Chamber Design for the Laser Inertial Fusion Energy (LIFE) Engine

The Laser Inertial Fusion Energy (LIFE) concept is being designed to operate as either a pure fusion or hybrid fusion-fission system. The present work focuses on the pure fusion option. A key component of a LIFE engine is the fusion chamber subsystem. It must absorb the fusion energy, produce fusion fuel to replace that burned in previous targets, and enable both target and laser beam transport to the ignition point. The chamber system also must mitigate target emissions, including ions, x-rays and neutrons and reset itself to enable operation at 10-15 Hz. Finally, the chamber must offer a high level of availability, which implies both a reasonable lifetime and the ability to rapidly replace damaged components. An integrated design that meets all of these requirements is described herein.

Active beam position stabilization of pulsed lasers for long-distance ion profile diagnostics at the Spallation Neutron Source (SNS)

A high peak-power Q-switched laser has been used to monitor the ion beam profiles in the superconducting linac at the Spallation Neutron Source (SNS). The laser beam suffers from position drift due to movement, vibration, or thermal effects on the optical components in the 250-meter long laser beam transport line. We have designed, bench-tested, and implemented a beam position stabilization system by using an Ethernet CMOS camera, computer image processing and analysis, and a piezo-driven mirror platform. The system can respond at frequencies up to 30 Hz with a high position detection accuracy. With the beam stabilization system, we have achieved a laser beam pointing stability within a range of 2 μrad (horizontal) to 4 μrad (vertical), corresponding to beam drifts of only 0.5 mm × 1 mm at the furthest measurement station located 250 meters away from the light source.

The Enhanced Measurements of Laser Micro-jet Processing

In the paper, the enhanced measurements of the laser micro-jet processing are discussed. In fact, within pure water breakdown threshold of laser, the less focal which focused with the appropriate focusing lens and the small nozzle of water chamber enhance the laser power density ,at the same time, the laser beam transport in the wave guided water with the proper total reflection angle. The laser power which depended on the properties of the diameter, the coupling water chamber and the coupling efficiency of the micro-jet and laser beam expect of the properties of laser.

Laser system for high resolution Thomson scattering diagnostics on the COMPASS tokamak

A new Thomson scattering diagnostic has been designed and is currently being installed on the COMPASS tokamak in IPP Prague in the Czech Republic. The requirements for this system are very stringent with approximately 3 mm spatial resolution at the plasma edge. A critical part of this diagnostic is the laser source. To achieve the specified parameters, a multilaser solution is utilized. Two 30 Hz 1.5 J Nd:YAG laser systems, used at the fundamental wavelength of 1064 nm, are located outside the tokamak area at a distance of 20 m from the tokamak. The design of the laser beam transport path is presented. The approach leading to a final choice of optimal focusing optics is given. As well as the beam path to the tokamak, a test path of the same optical length was built. Performance tests of the laser system carried out using the test path are described.

TW Laser system for Thomson scattering X-ray light source at Tsinghua University

A TW (Tera Watt) laser system based on Ti:sapphire mainly for the Tsinghua Thomson scattering X-ray light source (TTX) is being built. Both UV (ultraviolet) laser pulse for driving the photocathode radio-frequency (RF) gun and the IR (infrared) laser pulse as the electron-beam-scattered-light are provided by the system. Efforts have also been made in laser pulse shaping and laser beam transport to optimize the high-brightness electron beam production by the photocathode RF gun.