For verification purposes, different radionuclides-H-3, C-14, Na-22, Al-26, Cl-36, Mn-54, Co-60, Au-195, Ra-226, Ra-228, Th-228, and U-238-were chosen to test all pathways and models. The results generated by the RESRAD-BUILD code (version 3.0) were verified with hand or spreadsheet calculations using equations given in the RESRAD-BUILD manual for different pathways. We find the modified 9010's flat-top profile improves conversion efficiency when used for our applications in crystal nonlinear optics. After double-passing the two amplifier rods the beam suffers some degradation in symmetry and uniformity, but is still much improved compared to the beam obtained using the 9010's original factory configuration. Using this approach we've obtained single-pass energy exceeding 250 mJ with little degradation of the flat-top profile and 950 mJ after double pass amplification. The output of the beam shaper is then double-pass amplified through two amplifier rods with thermally induced focusing compensated by a negative lens before the first pass and by a convex mirror before the second pass. To improve the 9010's beam quality we spatially filter the oscillator beam and remove the resulting Airy rings with an iris, then collimate and magnify the remaining central disk so its diameter is appropriate for input to the refractive shaper. ![]() ![]() When these older laser systems are used for tasks like pumping optical parametric oscillators (OPO's), or for other applications demanding good beam quality, their designs are simply inadequate. These characteristics are largely due to poor beam quality from the oscillator coupled with over-filled amplifier rods, and reflect a design philosophy from the era of organic dye lasers. Structure in its near-field spatial fluence profile is reminiscent of round-aperture diffraction that is superposed with additional hot more ยป spots. While its pulse energy is impressive, its beam quality is typically poor, an all too common characteristic of research-grade Nd:YAG lasers manufactured in the late 1980's and early 1990's. ![]() The Powerlite is a flashlamp-pumped, Q-switched, injection-seeded Nd:YAG laser manufactured in 1993 that delivers 1.6 J at 10 Hz using an oscillator and two 9 mm diameter amplifier rods. We've generated high-quality flat-top spatial profiles from a modified Continuum Powerlite 9010 Nd:YAG laser using the Gaussian-to-flat-top refractive beam shaper available from Newport Corporation.
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