>Hi Folks > >Has anyone compared directly air cooled and water cooled lasers for 488 >excitation. I >am thinking of replacing my aging 100mW ILT with a larger water cooled unit. > > > >Simon Monard We just did a quick check of _our_ aging "100mW" ILT (hasn't output 100mW for quite some time now) versus our 1986 Coherent Innova 90 5W water-cooled argon ion laser (plasma tube last refurbished 1996). Using BD's DNA QC Kit (PI-labeld CEN and CTN, and 2 micron beads), we looked at %CV of the singlets (CENs and beads) or G0/G1 peak (CTNs) as a measure of laser performance, since air-cooled lasers reportedly are "noisier" than water-cooled lasers. The ILT actually outperformed the I90 when both were set to output 40 mW of 488 nm light. But, if I remember correctly, that is because our vintage I90 laser does not regulate well below 100 mW output (but newer Coherent models may). Adjusting the I90 to 100 mW produced a CEN %CV less than the ILT (at 40 mW), but the CTN and bead %CVs were still higher. At 200 mW, the I90 had better CEN and CTN %CVs. At 300 mW, the bead %CV was finally better. At 500 mW, all 3 samples' %CVs continued to improve. The FACS Vantage was adjusted for each sample (PMT HV) to place the peak of interest at channel 200 (on a 1024 linear scale). This avoided the bias of using different channels (see previous discussion on Purdue list), but the I90 data did enjoy diminished noise generated by the PMT as a result of lower HV settings. Here are the CTN %CVs (from ModFit): 4.27 (ILT), 6.01 (40mW), 4.48 (100mW), 4.04 (200mW), 4.11 (300mW), 3.88 (500mW) (The I90 may be noisier than normal since I had to switch to 488 nm after 4 years of almost exclusive UV usage.) In fact, previously, the same I90 laser set for 100 mW UV output produced lower %CVs (less than 2.5) using CTNs (from an expired lot, no less) stained with either DAPI or Hoechst 33342... and the I90 was the second laser in a dual-laser setup! Now, what I'd _really_ like to see is a comparison to Coherent's not-yet- released-but-recently-announced-at-ISAC solid-state 488 nm laser. Any word on this laser? Eric /\/\/\_ Eric Van Buren, aa9080@wayne.edu \ \ \ Karmanos Cancer Institute and Immunology & Microbiology \_^_/ Wayne State University, Detroit, Michigan, USA
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