UHI is the most powerful laser at SLIC and one of the two most intense Titanium-Sapphire lasers in France. Since the last scientific council, the UHI facility has undergone 2 major evolutions. The first evolution took place in 2005 and was made jointly by PHI and SLIC groups. It had a dual objective.
The first was to protect the users from harmful radiation generated by the laser-matter interaction at ultra-high intensity. The second aimed at increasing the temporal contrast beyond 109. To achieve these objectives, a new, radiation shielded experimental area was launched for the experiments accommodated at UHI. The UHI compressor is now installed inside the shielded room and, in order to achieve a high temporal contrast on the target, a double plasma mirror set-up (DPM) has been inserted between the compressor and the experimental chamber. In the DPM, the 10TW pulses are focused between 2 anti-reflection coated silica plates distant, from a few millimetres. The plates act as an “intensity-triggered” mirror: the low intensity pedestal is transmitted through the plates whereas the intense part of the pulse is reflected by the plasma generated at the plates’ surface by the leading edge of the main pulse. Using a third-order correlator, we measured a temporal contrast improvement by a factor 104, leading to a contrast on target of 1010 (Figure 3). The transmission of the set-up is 50%. The high temporal contrast allowed to obtain original results in proton acceleration and harmonic generation on solid targets presented in the PHI section of this report.
The second evolution of the UHI laser started mid-2007 and should be completed by the end of 2008. It consists in a major upgrade of the UHI laser mostly made by the Amplitude-Technologies company. The objectives are to increase the peak power up to 100TW while reducing the pulse duration below 25fs and achieving 109 temporal contrast at the input of the DPM.