The extremely high electric fields sustainable by a plasma make the Laser Wakefield Acceleration (LWFA) the most compact technique to generate very highly relativistic electron beams in the GeV regime. The limited repetition rate and low efficiency of this technology has, to date, prevented to unleash its full potential as a unique source for basic research, biomedical applications and high flux sources of secondary radiations as hard X-rays and gamma-rays. In very recent years different works show a new research direction on electron acceleration at 1 kHz repetition rate.
In this talk I will show the laser-driven acceleration of unprecedented, collimated (2 mrad) and quasi-monoenergetic (ΔE/E = 25%) electron beams with energy up to 50 MeV at 1 kHz repetition rate. The laser driver is the in-house developed L1-Allegra multi-cycle (15 fs) 1 kHz OPCPA system, operating at 26 mJ (1.7 TW).
Said innovative results have been achieved in the new Laser Wakefield ALFA platform for user experiments developed at ELI-Beamlines.
The scalability of the driver laser technology and the electron beams reported in this work pave the way towards developing high brilliance X-ray sources for medical imaging, innovative devices for brain cancer treatment and represent a step forward to the realization of a kHz GeV electron beamline.
Allegra laser system is one of the main laser sources of the ELI-Beamlines facility in the Czech Republic. The system is designed to operate at 1 kHz and >100 mJ output with the pulse duration of <15 fs at 820 nm central wavelength. The main role of the laser system includes driving plasma X-ray and high harmonic (HHG) secondary sources at ELI-Beamlines facility. In this submission we present the most recent results on the optimization of high-energy OPCPA amplification stages and discuss the operational performance of the laser system.
The Allegra femtosecond laser system is the main driver for high harmonic and plasma x-ray secondary sources at ELI-Beamlines operating at a 1 kHz rep rate. The system is based on OPCPA technology and consists of seven amplification stages pumped by thin-disk picosecond lasers. It is designed to reach 30 mJ output in the first phase of operation and to be ramped up to 50 mJ by engaging an additional pump laser. The amplified pulse is compressed to sub-20fs by an array of chirped mirrors and higher order dispersion is pre-compensated for by a Dazzler AOPDF in the front-end. In this paper we present the overview of Allegra system and the current status of deployment with a special focus on the high average power OPCPA in vacuum.
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 <15 fs pulses at 1 kHz repetition rate, is up and running. The L2 is a development line employing a 10 J / 10 Hz cryogenic gas-cooled pump laser which has recently been equipped with an advanced cryogenic engine. Operation of the L3-HAPLS system, using a gas-cooled DPSSL pump laser and a Ti:sapphire broadband amplifier, was recently demonstrated at 16 J / 28 fs, at 3.33 Hz rep rate. Finally, the 5 Hz OPCPA front end of the L4 kJ laser is up running and amplification in the Nd:glass large-aperture power amplifiers was demonstrated.
We present an active cavity pointing stabilization system based on a novel method that tracks the cavity mode position directly on the thin disk gain medium itself. Here, the overlap of the lasing cavity with the pump, visible as a depletion within the pumped area, is most crucial to the stability of the laser. Short term stability as well as long term stability are significantly increased enabling day long operation, directly from a cold start of the laser system, without the need for thermalization and manual alignment.
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