In order to investigate the similarity on thermo-mechanical effects by different pulsed beams, this paper
conducts a comparison study on the blow-off impulse of aluminum target by pulsed ultraviolet laser and
X-ray irradiation. Especially, this paper focuses on the thermo-mechanical effects by pulsed ultraviolet laser
and X-ray (blow-off impulse), and build up the scaling relations of impulse coupling with aluminum target
by the two pulsed beams within a certain range of energy flux. The study shows that, within the energy flux
range of 100~400J/cm<sup>2</sup>, although the mechanisms of blow-off impulse generation of the two pulsed beams
are different, the impulse coupling with aluminum target or impulse coupling coefficients of both X-ray and
laser have similar scaling relations. Among others, the impulse coupling coefficient of X-ray is larger than
that of laser. Based on the comparison of scaling relations, this paper provides the similarity between the
two pulsed beams.
A kind of beam automatic alignment method used for double paths amplification in the electron pumped excimer laser system is demonstrated. In this way, the beams from the amplifiers can be transferred along the designated direction and accordingly irradiate on the target with high stabilization and accuracy. However, owing to nonexistence of natural alignment references in excimer laser amplifiers, two cross-hairs structure is used to align the beams. Here, one crosshair put into the input beam is regarded as the near-field reference while the other put into output beam is regarded as the far-field reference. The two cross-hairs are transmitted onto Charge Coupled Devices (CCD) by image-relaying structures separately. The errors between intersection points of two cross-talk images and centroid coordinates of actual beam are recorded automatically and sent to closed loop feedback control mechanism. Negative feedback keeps running until preset accuracy is reached. On the basis of above-mentioned design, the alignment optical path is built and the software is compiled, whereafter the experiment of double paths automatic alignment in electron pumped excimer laser amplifier is carried through. Meanwhile, the related influencing factors and the alignment precision are analyzed. Experimental results indicate that the alignment system can achieve the aiming direction of automatic aligning beams in short time. The analysis shows that the accuracy of alignment system is 0.63μrad and the beam maximum restoration error is 13.75μm. Furthermore, the bigger distance between the two cross-hairs, the higher precision of the system is. Therefore, the automatic alignment system has been used in angular multiplexing excimer Main Oscillation Power Amplification (MOPA) system and can satisfy the requirement of beam alignment precision on the whole.
A short pulse XeCl laser system is being developed for plasma physics and material science study. Partial spatial
incoherence seed with short pulse is amplified by MOPA chain including three discharge pumped amplifiers and two
electron beam pumped amplifiers for one beam. Final laser output of 5~10J in energy with pulse width of around 10ns
has been achieved, which lays a good foundation for full scale construction.