30 November 2009

Pre-conditioned flash lamps in place

As for the replacement from old to new flash lamps in the PIV laser, we now had a third batch of lamps to install. Replacing these lamps is a risky business for various reasons, not only the need of climbing the tunnel but also the actual replacing these delicate (easy to break) filaments. And when the fourth (final) lamp was to be inserted - i broke! A word signaling a problem was heard from the tunnel top and it was immediately clear that something had gone wrong. Immediately checking with Litron people, however gave some hope in that it might work with one of the non-conditioned lamps in tandem with a pre-conditioned one. Some more work and then a final test - it worked. So, now we have a laser with a complete set of flash lamps. We now only have to align the thing to optimize the set-up for maximum power output.

07 November 2009

PIV laser gets new flash lamps

As the laser has lately given only about 25 mJ per pulse when set to maximum power, we figured it is perhaps time to change the flash lamps. In our Litron laser there are 4 lamps to replace, and on Friday afternoon we had everything in place, i.e. the lamps, new o-rings, appropriate laser manual and isopropyl alcohol to clean the new lamps. It took some time, and even if the manual explicitly said "do not lose" about 4 particular 3M bolts that was exactly what happened to one of them. It fell to the floor, two bounces was heard and then it was gone, probably it fell to the basement. The lost bolt must have moved a horizontal distance of at least 1 m, while subsequent experiments with a similar bolt showed an average horizontal displacement from the position of first floor contact of about 15 cm! However, we found new stainless steel 3M bolts and could proceed as planned. Also cooling water was renewed and before that we had changed to new filters. So, no we will hopefully get back the strong and clear light sheet that make stereo PIV such a nice method.