The CEnter for Advanced Laser Technologies (CETAL) is a major laser facility installed at the National Institute for Laser, Plasma and Radiation Physics (INFLPR) in Bucharest-Magurele. CETAL is a national project implemented by INFLPR, and realized in collaboration with European partners from the industry.
The CETAL installation of the state-of-the art laser has been completed in June 2013 and the Beam Transportation Line (BTL) in May 2014. The central part of this facility is an ultra-high intensity laser system based on Ti-Sapphire technology which can deliver pulses of 25 Joules of few tens of femtoseconds resulting in up to 1 PW peak powers.
ARDOP has been awarded for the design and realization of the BTL, including the delivery of mechanical and optical parts. The laser will be used to perform cutting edge research in electron and proton acceleration, for generation of X- and γ-rays as well as high harmonics generation and for studying relativistic plasmas.
Beam Transport Line
The Beam Transportation Line (BTL) is designed to transport the beam from the exit of the CETAL compressor vessel to the target interaction chamber (TIC) placed into the bunker. The BTL is 25 m long and made of stainless steel and aluminum assemblies composed of DN250 tubes and turning-boxes of diameter 600 mm (where optics and mounts are placed). Two systems of primary and turbo pumps ensure the BTL to reach a high vacuum of few 10-5 mbar in less than 30 min. The BTL is entirely isolated from the laser facility thanks to the pendulum and gate valves respectively placed at the exit of the compressor and at the entrance of the TIC.
Characteristics of the BTL
The laser is operating at the central wavelength of 810 nm, with a bandwidth of 90 nm. The beam is P-polarized and polarization is maintained until the focusing. The Beam diameter is 160 mm at FWHM. The optical beampath is ensured through 5 folding mirrors 350 x 250 mm2 placed into frames and supported by motorized mounts. The beam is then focused to the target thanks to an off-axis parabolic mirror (OAP) of same dimensions and motorized. The BTL is maintained under high vacuum by the mean of a two systems of primary and turbomolecular pumps which can guarantee a high level of vacuum in a short time. The pointing stability of the beam after 25m of propagation is around 30 µm (PV) and 2 µrad (RMS). The wavefront distortion is better than lambda/45 RMS for each individual mirror and better than lambda/25 RMS for the OAP. The Strehl ratio is better than 70%. The energy transmission is higher than 99% on the range [780-850] nm in P-polarization. The LIDT of the optics is expected to be higher than 0.6 J/cm² @200 fs.
The tubes and turning-boxes are made of either stainless-steel or aluminum in the target room due to activation issues. All the parts are cleaned to reduce the particles contamination levels and compatible with cleanliness level for ultra-intense laser interaction. Tubes are connected to the turning-boxes through welded-membrane bellows so as to compensate the misalignment and ensure the sealing of the system.
The turning-boxes are equipped with breadboards which are decoupled from the pumping system through small bellows.
The local control system of the BTL is ensured by three cabinets. These boxes contain the controllers necessary to actuate the mirrors. The cabinets are linked through optical fiber and can be remotely controlled over Ethernet.