LMJ Laser Research Articles

Experimental capabilities of the LMJ-PETAL facility

Recent progress in the experimental capabilities of the LMJ-PETAL laser facility is reviewed. Updates on the indirect-drive D2 implosion experiments and equation-of-state experiments using the LMJ laser are presented, including the commissioning of new plasma diagnostics. Several recent campaigns using the PETAL laser alone are also presented, namely the development of a platform using high-resolution and high-energy X-ray sources for radiography experiments, laser wakefield acceleration studies in the self-modulated regime, and neutron generation using a Target Normal Sheath Accelerated proton beam in a pitcher-catcher configuration.

Thermal analysis of Laser MegaJoule calorimeters

For LMJ applications, an accurate procedure for laser pulse energy measurement is a crucial requirement. In this study, the influence of measurement procedure on LMJ calorimeter uncertainty is experimentally and numerically investigated. To this end, a 3D thermal model is developed and two experimental devices are implemented. The metrological characteristics of both devices are presented. As a first step, the model is validated by crossing numerical and experimental results. Then, the influence of a large number of parameters considered as likely uncertainty sources on calorimeter response is investigated: wavelength, pulse duration, ambient temperature, laser beam shape... The final goal is to define a robust and efficient calibration procedure in order to strongly reduce the uncertainty on LMJ laser pulse measurement.

Single-shot laser driven inertial confinement fusion based on nanosecond and picosecond laser pulses

Nuclear fusion gains of deuterium-tritium (DT) at volume ignition are discussed for the forthcoming conditions of the NIF or LMJ laser pulses in the range of nanosecond duration at direct drive. This turns out to be similar to the expected values known form spark ignition. These conditions should be reached also by single pulse interaction of picosecond pulses using the unique anomaly of nonlinear force driven plasma block acceleration with ps pulses for volume ignition. Total gains of 200 for MJ laser pulses are expected.

Characterization of LIL laser UV focal spot

One way to get the fusion of hydrogen in laboratory consists in heating and compressing a DT fuel capsule by using a laser. To reach this aim requires a new generation of high power laser facility. CEA is developing for this purpose a new 240 laser line facility, the LMJ facility. The LIL which is the prototype of four LMJ laser lines is operational now. In order to confirm the technical choices, a systematic characterization of LIL was carried out. A particular effort has been provided to measure the 3ω high energy laser focal spot (1.5 kJ/700 ps and 5 ns for one beam) and the synchronization of laser beams onto the target, which are key issues for the plasma production. We present the experimental device designed to perform these measures: the SAT 3ω (a 3w laser focal spot analysis system). That diagnostic which is located at the end of the laser lines supplied its first results during the 2004 quadruplet qualification campaigns. We will display and analyze caustic and focal spot results.

New constraints for plasma diagnostics development due to the harsh environment of MJ class lasers (invited)

The design of plasma diagnostics for the future MJ class lasers (LMJ–Laser MégaJoule—in France or NIF—National Ignition Faciliy— in the USA) must take into account the large increased radiation field generated at the target and the effect on the diagnostics components. These facilities will focus up to 1.8 MJ ultraviolet laser light energy into a volume of less than 1 cm3 in a few nanoseconds. This very high power focused onto a small target will generate a large amount of x rays, debris, shrapnel, and nuclear particles (neutrons and gamma rays) if the DT fuel capsules ignite. Ignition targets will produce a million more of 14 MeV neutrons (1019 neutrons) by comparison with the present worldwide most powerful laser neutron source facility at OMEGA. Under these harsh environmental conditions the survivability goal of present diagnostic is not clear and many new studies must be carried out to verify which diagnostic measurement techniques, can be maintained, adapted or must be completely changed. Synergies with similar environment studies conducted for magnetic fusion diagnostic design for ITER facility are considered and must be enhanced.