At my first experiments I thought that it is enoough to throw a doubling crystal inside the YAG laser and it will be OK and nothing else matters. Unfortunately, no. In the case of a CW or even a QCW laser matters literary everything. To start with, the lamp power supply must give very smooth DC current with minimal ripple factor, otherwise the lamp in the pumping chamber flickers and the laser beam flickers even worse. This leads to poor light stability and great shortage of lamp's life. So I decided to completely rebuild the lamp power supply. I threw away the main power transformer that had aluminium winding and made a new one with copper winding of appropriate thickness, so it doesn't overheat now. I've added a massive filtering capacitor bank with total ~30000 uF capacitance and two massive chokes that form an LCLC filter. I've rebuilt also arc starting circuits and packed everything in a standard rack case. After the rebuild the power unit can give 35A current for more or less long time without overheating with the ripple factor less than 2%, that allowed me to get a smooth and stable laser beam to work with. At the photos you can see both old and new power units.
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So this went into the case of a spectrum analyzer? Hope it was damaged beyond repair. I remember these from the 1970s and they were expensive back then. Cheap ones sold for $50,000.