7-11 June, Endeavours of the Petawatt, Salamanca, Spain

Place: 
Edificio de Físicas (Trilingüe) Physics Building
Plaza de la Merced
37008 Salamanca, Spain
(see Faculty of Sciences homepage)

Organized by CLPU, in collaboration with Laserlab Europe and ELI, and the University of Salamanca. The concluding session was held in connection with the Laserlab network NAUUL.

Endeavours of the Petawatt

Below the Petawatt level, present day laser technology is relatively well established. Certainly, there are many technical difficulties in multi-Terawatt lasers (repetition rate, pulse contrast, beam quality, etc.) requiring further developments, but all of them have found already more or less efficient solutions. Going beyond the Petawatt level, however, is a more difficult task. There are several fundamental issues that pose a serious problem to the realization of multi-PW lasers, needing a joint effort to tackle them. A forum to discuss these problems was the initial idea of the workshop “Endeavors of the Petawatt” organized by CLPU.

The workshop took place at the University of Salamanca from 7 to 11 June 2010, bringing together scientists and industry to analyze the best technical solutions to reach Petawatt and multi-Petawatt laser powers. In order to make the workshop flexible to participants from different fields, each day of the week was dedicated to a particular challenge, namely: gratings and mirrors, pulse contrast, pump lasers, radio-protection & x-rays, and crystals, coatings & cryotechnology.

Each day began with the presentation of the corresponding challenges and current situation of the technology by a number of speakers (from science and the industry). In the afternoon a round table was organized to discuss and propose solutions. Some general talks were also scheduled in order to get acquainted with the most relevant PW systems operative now. The workshop was attended by about 50 people, including speakers and attendees.

Programme:

Monday June 7th, Gratings and mirrors
Due to the power damage thresholds, gratings and mirrors have to be very large and this is an important barrier in price and reliability of the systems. Also the design of the compressors is complicated because of the large sizes of such systems. Possibilities to reduce sizes, increase damage thresholds, and reduce costs with mass production are going to be analysed.

Tuesday June 8th, Pulse contrast
At those huge intensities just a small fraction of the pulse is enough to generate a plasma mirror that reflects the main pulse. Therefore an extremely abrupt turn on of more that ten orders of magnitude in the picosecond domain is required. There are several patents so far to achieve this at the PW level, but to go beyond and enhancement of the contrast is needed.

Wednesday June 9th, Pumping lasers
CPA lasers are laser-pumped lasers. Thus a nanosecond pulse is necessary to pump the chiped pulse amplifiers. Most of the high power Titanium Sapphire lasers are now pumped by the second harmonic of Nd lasers (crystal or glass, depending of the performances), while diode lasers are slowly entering into the game. Optimized candidates for pumping and solutions with the highest possibilities are to be discussed. Pumping lasers are also crucial to increase the repetition rate.

Thursday June 10th, Radioprotection
Optical lasers are for the first time generating radiactivity. Thus radioprotection is a main and new issue in laser facilities. Laser radioprotection has many common points with standard radioprotection but also it has some specific features very peculiar of the extremely short times involved.

Friday June 11th, Crystals and criotechnology
Crystal size is another bottleneck for the construction of PW and multi PW lasers. Big crystals are necessary and their growing is a key issue. We need to discuss up to which point such crystals are necessary and possibilities for alternative options. Cooling of the crystals could be also crucial to increase the repetition rate.

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