A high-order harmonic energy Palbociclib cell cycle in the multimicrojoule range for each harmonic order from the 11th to the 17th harmonic was obtained. It was concluded, by analyzing the target morphology and the plasma composition, that the intense harmonics from the bulk carbon targets originate from the nanoparticles produced during ablation of the carbon-contained target. It was shown earlier that nanoparticles and films of C60 would generate harmonics that are more intense than those obtained from solid targets [9]. The disadvantage of using nanoparticle and film targets is the instability of the harmonics, which considerably vary from shot to shot and even disappear after a few laser shots if the target is not moved. On the contrary, in [8] it was found that carbon bulk targets can generate harmonics, comparable to those from the nanoparticle or C60 plasma targets.

The scanning electron microscope (SEM) image of plasma debris from a carbon target revealed that the plasma plumes contain nanoparticles with sizes varying between 100nm and 300nm. It was therefore suggested that, during the interaction of the heating pulse with the carbon target, nanoparticles are formed in the plasma and are then pumped by the fundamental pulse to induce the generation of harmonics. The harmonic intensity using bulk carbon target remained stable for several minutes, even without moving the target position. By creating the plasma during 5min on the same place of the solid carbon target, the harmonic intensity does not decrease more than 10%, while the one from nanoparticles decreased more than 90% after a few seconds.

It was also noted that, unlike most other solid targets, the highest harmonic order obtained with a carbon target does not exceed 21. According to the cut-off law defined by the three-step model, it was suggested that these harmonics are generated by neutral atoms, rather than ions as in the case of other solid targets.Further developments of both the stability of carbon-containing plasma harmonics and their enhanced yield were reported in [10]. The importance of these parameters is defined by the applicability of converted radiation for various needs. Many efforts have been dedicated to the improvement of these characteristics during the long history of harmonic generation in gases.

The multimicrojoule harmonics have been generated by energy scaling of gas HHG under highly optimized conditions [11, 12], which, however, have basically pushed gas HHG to its limits. Therefore, there is an urgent need to search for methods to generate even more intense harmonics and attosecond Carfilzomib pulses. For these purposes, gas clusters [13] and plasma produced from nanoparticle targets [9, 14] can be used to increase the intensity of harmonics. In the former case, microjoule intense harmonics have been demonstrated in the range of 50�C90nm.