Development of a yearlong maintenance-free terawatt Ti:Sapphire laser system with a 3D UV-pulse shaping system for THG

Journal Article · Fri Aug 31 00:00:00 EDT 2007 · Quantum Electronics (Woodbury, N.Y.)

DOI:https://doi.org/10.1070/QE2007V037N08ABEH013564· OSTI ID:21470880

Tomizawa, H; Dewa, H; Hanaki, H ^[1]; Matsui, F ^[2]

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1. Japan Synchrotron Radiation Research Institute, Hyogo (Japan)
2. Industrial Technology Center of Fukui Prefecture, Fukui (Japan)

Laser sources that feature a controlled pulse shape and long-term stability are required in a wide range of scientific fields. We developed a maintenance-free 3D-shaped UV-laser system for the photoinjector (RF gun photocathode) of an X-ray SASE free electron laser (FEL). The laser pulse-energy stability was improved to 0.2%-0.3% (rms, 10 pps, 0.4 TW in femtosecond operation) at the fundamental wavelength and to 0.7%-1.4% at the third-harmonic wavelength. This stability was continuously maintained for five months, 24 hours a day. Such improvement reflects an ability to stabilise the laser system in a humidity-controlled clean room. The pulse-energy stability of a mode-locked femtosecond oscillator was continuously held at 0.3% (p-p) for five months, 24 hours a day. In addition, the ideal spatial and temporal profiles of a shot-by-shot single UV-laser pulse are essential to suppress the emittance of the electron-beam pulse generated by the photocathode of the RF gun. We apply a deformable mirror that automatically shapes the spatial UV-laser profile with a feedback routine, based on a genetic algorithm, and a pulse stacker for temporal shaping at the same time. The 3D shape of the laser pulse is spatially top-hat (flattop) and temporally - a square stacked pulse. We apply the Q-scan method to evaluate the emittance of the electron beam generated by a 3D-shaped laser pulse. By using a 3D-shaped laser pulse of diameter 0.8 mm on the cathode and duration 10 ps (FWHM), we obtain a minimum horizontal normalised emittance of 1.4{pi} mm mrad with beam energy of 26 MeV, holding its net charge to a 0.4 nC pulse{sup -1}. At a higher net charge of 1.0 nC pulse{sup -1}, the minimum beam emittance is 2.3{pi} mm mrad with equivalent diameter and a longer pulse duration of 20 ps (FWHM). In this study, we demonstrate 3D shaping [both temporal (1D) and spatial (2D)] short pulse (5-20ps) laser beam as an ideal light source for yearlong stable generation of a low emittance electron beam with a high charge (1-2 nC pulse{sup -1}). Here, we report the principle and development process of our beam-quality control systems. (selected papers reported at the conference 'laser optics 2006')

• OSTI ID: 21470880
• Journal Information: Quantum Electronics (Woodbury, N.Y.), Vol. 37, Issue 8; Conference: LO'2006: 12. conference on laser optics, St. Petersburg (Russian Federation), 26-30 Jun 2006; Other Information: DOI: 10.1070/QE2007v037n08ABEH013564; ISSN 1063-7818
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
ALGORITHMS
BEAM EMITTANCE
ELECTRON BEAMS
FEEDBACK
FREE ELECTRON LASERS
HARMONIC GENERATION
HUMIDITY
LIGHT SOURCES
MEV RANGE
OSCILLATORS
PHOTOCATHODES
PULSE SHAPERS
PULSES
QUALITY CONTROL
RF SYSTEMS
SAPPHIRE
STABILITY
WAVELENGTHS
X RADIATION
BEAMS
CATHODES
CONTROL
CORUNDUM
ELECTRODES
ELECTROMAGNETIC RADIATION
ELECTRONIC CIRCUITS
ELECTRONIC EQUIPMENT
ENERGY RANGE
EQUIPMENT
FREQUENCY MIXING
IONIZING RADIATIONS
LASERS
LEPTON BEAMS
MATHEMATICAL LOGIC
MINERALS
MOISTURE
OXIDE MINERALS
PARTICLE BEAMS
PULSE CIRCUITS
RADIATION SOURCES
RADIATIONS
SIGNAL CONDITIONERS